Development, Characterization and Commercial Application of Palm Based Dihydroxystearic Acid and Its Derivatives: an Overview Gregory F

REVIEW Development, Characterization and Commercial Application of Palm Based Dihydroxystearic Acid and Its Derivatives: an Overview Gregory F. L. Koay1, 2, Teong-Guan Chuah1, 3＊ , Sumaiya Zainal-Abidin2, 4, Salmiah Ahmad2, 5 and Thomas S. Y. Choong1 1 Department of Chemical and Environmental Engineering, Universiti Putra Malaysia (43400 UPM Serdang, Selangor Darul Ehsan, MALAYSIA) 2 Advanced Oleochemical Technology Division, Malaysian Palm Oil Board (43650 Bandar Baru Bangi, Selangor Darul Ehsan, MALAYSIA) 3 Institute of Tropical Forest and Forestry Products, Universiti Putra Malaysia (43400 UPM Serdang, Selangor Darul Ehsan, MALAYSIA) 4 Faculty of Chemical and Natural Resources Engineering, Universiti Malaysia Pahang (25000 Kuantan, Pahang Darul Makmur, MALAYSIA) 5 Director General’s Offi ce, Malaysian Rubber Board (50450 Kuala Lumpur, MALAYSIA) Abstract: Hydroxyl fatty acids and their derivatives are of high value due to their wide range of industrial application, including cosmetic, food, personal care and pharmaceutical products. Realizing the importance of hydroxyl fatty acids, and yet due to the absence of the conventional starting raw materials, Malaysia has developed 9,10-dihydroxystearic acid (9,10-DHSA) and its derivatives from locally abundant palm based oils. The aim of this article is to provide a general description of the works that have thus far being done on palm based 9,10-DHSA: starting from its conception and production from commercial grade palm based crude oleic acid via epoxidation and hydrolysis, purification through solvent crystallization and characterization through wet and analytical chemistry, moving on to developmental works done on producing its derivatives through blending, esterifi cation, amidation and polymerization, and completing with applications of 9,10-DHSA and its derivatives, e.g. DHSA-stearates and DHSA-estolides, in commercial products such as soaps, deodorant sticks and shampoos. This article incorporates some of the patent fi led technological knowhow on 9,10-DHSA and its derivatives, and will also point out some of the shortcomings in previously published documents and provide some recommendations for future research works in mitigating these shortcomings.

Key words: dihydroxystearic acid, epoxidation, crystallization, characterization, ternary blending, esteriﬁ cation, amidation, polymerization, commercial application

1 INTRODUCTION 9,12-DHSA, with the CAS number 26248-95-3, 93923-70-7 Dihydroxystearic acid（DHSA）, molecular formula and 25754-87-4 respectively. －1 th C18H36O4, molecular weight（MW）316.476 gmol , is a long DHSA has appeared in literature as early as end 19 and chain fatty acid with IUPAC name dihydroxyoctadecanoic early 20th century. In 1901, Le Sueur1）revealed some of the acid. The name‘ dihydroxy’ indicates that there are two chemical characteristics of DHSA while trying to fuse po- hydroxyl groups present in the molecular structure. There tassium hydroxide on it. Some of the plant based natural are various conﬁ gurations to the positions of these two hy- sources of DHSA include olive and castor oils2, 3）and Sal droxyl groups and a literature search has revealed that fat4）. there are more than 30 different DHSA isomers. However, In Malaysia, due to the absence of the above mentioned most of these isomers are not common, let alone cata- three oils and fats, attempt to source for other means to logued in the authoritative CAS registry. The three most produce DHSA was initiated. Through it R&D efforts, the common of the isomers are 2,18-DHSA, 9,10-DHSA and Malaysian Palm Oil Board（MPOB）has successfully pro-

＊Correspondence to: Teong-Guan Chuah, Department of Chemical and Environmental Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor Darul Ehsan, MALAYSIA Email: [email protected] Accepted December 3, 2010 (received for review October 28, 2010) Journal of Oleo Science ISSN 1345-8957 print / ISSN 1347-3352 online http://www.jstage.jst.go.jp/browse/jos/

237 G. F. L. Koay, T.-G. Chuah, S. Zainal-Abidin et al.

duced the 9,10-DHSA isomer from commercial grade palm tic acid in the presence of hydrogen donor such as water. based crude oleic acid, a low value byproduct of palm oil This process has been patent fi led in Malaysia, Singapore industry. and the United States5－7）. The body of this article is outlined as follow: The production of 9,10-DHSA via peracetic acid route □ Production of 9,10-DHSA was measured up from laboratory to pilot plant scale of 500 □ Purifi cation of 9,10-DHSA kg per batch operation8）. For pilot plant production, per- □ Characteristics of 9,10-DHSA acetic acid was formed in situ in a batch stirred tank reac- □ Characteristics of 9,10-DHSA blends tor（BSTR）（R1）by reacting glacial acetic acid（stored in □ Characteristics of 9,10-DHSA derivatives storage tank T1）and hydrogen peroxide（stored in storage □ Applications of 9,10-DHSA and derivatives tank T2）in the presence of sulphuric acid. The peracetic acid which acted as an oxidizing agent converted the unsaturation in commercial grade palm based crude oleic acid to form an epoxide in a second BSTR（R2）. The epoxide 2 PRODUCTION OF 9,10-DHSA was then hydrolyzed to produce crude 9,10-DHSA in the The 9,10-DHSA isomer was first produced by MPOB same BSTR. The crude 9,10-DHSA was water washed and from C18:1 fraction of commercial grade palm based crude gravity separated from spent acid in a settling tank（T3）. oleic acid5）. This crude oleic acid, of 70～78％ purity（Table Alternatively, commercial grade palm based crude oleic 1）was a low value byproduct during extraction of lauric acid was converted via performic acid route8）. Performic （C12:0）and myristic（C14:0）acids from palm kernel oil and acid was formed in situ in R2 by reacting formic acid palmitic（C16:0）acid from palm oil. The C18:1 fraction con- （stored in T1）and hydrogen peroxide（stored in T2）in the tained the unsaturation needed for epoxidation and hydro- presence of sulphuric acid. The performic acid converted lysis for eventual production of 9,10-DHSA. The epoxida- the unsaturation in commercial grade palm based crude tion and hydrolysis reactions were carried out by reacting oleic acid to form an epoxide in the same reactor, R2. The commercial grade palm based crude oleic acid with perace- hydrolysis, washing and separating steps were similar to those of peracetic acid route. Table 1 Fatty acid composition (FAC) of The comparison of 9,10-DHSA production via two differ- commercial grade palm based ent routes is shown in Table 2 and the process flow dia- crude oleic acid5) gram is shown in Fig. 1. Fatty acid Composition, % C8:0 0.1 – 0.8 C10:0 Trace – 1.2 3 PURIFICATION OF 9,10-DHSA C12:0 0.9 – 2.4 Due to the nature of commercial grade palm based crude C14:0 0.3 – 1.5 oleic acid as precursor of 9,10-DHSA and the processes C16:0 3.1 – 5.5 and chemicals involved during reaction stage, there was a C16:1 0.1 – 0.3 need to purify the resultant crude 9,10-DHSA. The objec- C18:0 1.2 – 7.6 tive was to nullify its potency in causing dermal irritancy as C18:1 71.4 – 78.0 its development was meant for use in cosmetic and person- C18:2 11.8 – 17.3 al care products. The purifi cation of 9,10-DHSA involved（i） C18:3 Trace – 0.6 solvent crystallization,（ii）solvent removal and（iii）drying8）. C20:0 0.1 – 0.5 A two-stage 9,10-DHSA purifi cation operation was fi rst C others To 100 reported8）. The solvent was 80％ isopropyl alcohol（IPA）; IV 87 – 95 crude 9,10-DHSA:solvent mass ratio 1.0:1.0; the crystalliza- AV 180 – 204 tion carried out at 5℃. The first stage crystallization im-

Table 2 Comparison of 9,10-DHSA production via performic- and peracetic- acid routes8) Parameters Peracetic acid route Performic acid route Production yield, % 72.5 96 Production cost Reference 30% cheaper Batch processing time, h 12 10 No. of BSTR required Two, R1 and R2 One, R2

238 J. Oleo Sci. 60, (5) 237-265 (2011) Overview of Palm Based Dihydroxystearic Acid and Its Derivatives

Fig. 1 Simpli ﬁ ed process ﬂ ow diagrams of 9,10-DHSA production via (a) peracetic- and (b) performic- acid routes8)

proved 9,10-DHSA purity from 56.6～58.0％ to 70.9％; the second stage improved to 79.9％. The 9,10-DHSA crystals were then separated from solvent through a mechanical vibrating screen and water washed before being dried. The two stages puriﬁ cation operation was improved to a single stage operation with varying IPA concentrations and solvent ratios, the solvent removed through vacuum ﬁ ltration and the crystals dried thereafter without requiring any washing9）. Carried out at room temperature without temperature disturbances, it raised 9,10-DHSA purity to 86～ 92％. Solvent concentration and ratio contributed in im- proving crystal purity. Similar operation was also carried out using ethanol as solvent with a minor alteration at the Fig. 2 Schematic diagram of a custom fabricated si- 10） drying . Solvent crystallization of 9,10-DHSA was better multaneous batch crystallization unit11-13) when carried out at room temperature as rapid cooling （carried out at 5℃）caused solvent entrainment which compromised resultant crystal purity. unit was used to study effects of various parameters on The establishment of preliminary 9,10-DHSA purifying 9,10-DHSA purification, including solvent types, cooling method has led to the development of a custom fabricated modes, solvent concentrations and ratios. A summary of simultaneous bath crystallization unit（Fig. 2）11－13）. This these effects is shown in Table 3.

239 J. Oleo Sci. 60, (5) 237-265 (2011) G. F. L. Koay, T.-G. Chuah, S. Zainal-Abidin et al.

Table 3 Effects of various parameters on 9,10-DHSA purifi cation8-13) Parameters Siwayanan et al.8) Koay et al.9) Sumaiya et al.10) Koay et al.11) Abidin et al.12) Sumaiya et al.13) Crystallization type Solvent crystallization Solvent crystallization Solvent crystallization Solvent crystallization Solvent crystallization Solvent crystallization Solvent type IPA IPA Ethanol Ethanol and IPA Ethanol Ethanol No. of purifi cation Two One One One One One stages Solvent concentration 80% 60-100% Not specifi ed 90-100% Not specifi ed 90-100% Solvent ratio Not specifi ed 100-150% of crude 100-200% of crude Not specifi ed 100% of crude 100-200% of crude 9,10-DHSA 9,10-DHSA 9,10-DHSA 9,10-DHSA Crystallization period Not specifi ed 12 h 24 h 24 h 12 h 24 h Starting temperature 60℃ 80℃ Not specifi ed 80℃ 65℃ 80℃ Final temperature 5℃ Room temperature Room temperature 20℃ 24-28℃ 20℃ and 5℃ Cooling rate Uncontrolled Uncontrolled Uncontrolled 0.2-0.8℃min-1 0.6℃min-1 0.8℃min-1 Crystallizer type Freezer at 5℃ Conditioned room Conditioned room Custom fabricated Custom fabricated Custom fabricated without convective air without convective air simultaneous batch simultaneous batch simultaneous batch fl ow fl ow; freezer at 5℃ crystallization unit crystallization unit; crystallization unit; conditioned room conditioned room without convective air without convective air fl ow fl ow Mode of solvent Mechanical vibrating Vacuum fi ltration Vacuum fi ltration Vacuum fi ltration Vacuum fi ltration Vacuum fi ltration removal screen Water washing Required Not required Not required Not required Not required Not required Mode of crystal Not specifi ed Mechanical induced Oven dried at 50℃ Oven dried at 50℃ Oven dried at 50℃ Oven dried at 50℃ drying ventilation at room for 48 h for 48 h for 48 h for 48 h temperature for 24 h Purity of crude 56.6-58.0% 69.0% Not specifi ed 68.5% Not specifi ed Not specifi ed 9,10-DHSA Purity of 9,10-DHSA 70.9% (1st stage) 86.6-92.2% 86.8-91.4% 80.2-93.0% 88.2-94.7% 73.3-91.4% crystals 79.9% (2nd stage)

4 CHARACTERISTICS OF 9,10-DHSA Table 4. The solubility of 9,10-DHSA decreased with in- The development of 9,10-DHSA was primarily meant for creasing alcohol chain length（Fig. 5）due to solvent’s in- use in cosmetic and personal care products. Various tests creasing viscosity and decreasing polarity. The critical mi- and analyses, including wet chemistry, Thin Layer Chroma- celle concentration（CMC）for 9,10-DHSA was 0.01％ with tography（TLC）, Gas Chromatography（GC）, Gas Chroma- surface tension 37.0 mNm－（1 Fig. 6）, indicating that it was tography Mass Spectrometry（GCMS）, Nuclear Magnetic suitable for use as surfactant. Resonance（NMR）spectroscopy, Fourier Transform Infra Red（FTIR）spectroscopy, X-Ray Diffraction（XRD）micros- 4.2 Physical characteristics of 9,10-DHSA copy, Scanning Electron Microscopy（SEM）, Differential The size of solvent crystallized 9,10-DHSA crystals was Scanning Calorimetry（DSC）and irritancy tests, were car- affected primarily by cooling modes while the structural ried out on it to determine its chemical, physical and safety agglomeration conﬁ guration by types of solvent9－13）. Higher characteristics. cooling rate caused higher super-saturation through higher temperature gradient, resulting in increased nucleation 4.1 Chemical characteristics of 9,10-DHSA and formation of greater number of relatively smaller Conversion of commercial grade palm based crude oleic 9,10-DHSA crystals. Solvent crystallization of 9,10-DHSA acid to 9,10-DHSA resulted in lower iodine value（IV）and with ethanol resulted in sphere-like（global）crystals while higher hydroxyl value（OHV）14）. Lower IV indicated conver- IPA resulted in plate-like（flaky）crystals（Fig. 7 and Table sion of unsaturated starting material to saturated resultant 5）. All 9,10-DHSA crystals were of triclinic crystal system compound; higher OHV indicated formation of hydroxyl （beta crystal polymorph）（Table 6）. group（s）. FTIR, NMR, GC（Fig. 3a）and TLC（Fig. 3b）con- firmed the resultant compound was a mixture of threo- 4.3 Safety characteristics of 9,10-DHSA 9,10-DHSA（Fig. 4）with other impurities. The properties of Initial evaluation concluded that crude 9,10-DHSA was the starting material and resultant compound are shown in irritating to human skin whereas puriﬁ ed 9,10-DHSA was

240 J. Oleo Sci. 60, (5) 237-265 (2011) Overview of Palm Based Dihydroxystearic Acid and Its Derivatives

Fig. 3b TLC chromatogram of palm based 9,10-DHSA14) (1) oleic acid, (2) erythro-9,10-DHSA, (3) threo-9,10-DHSA, (4) crude 9,10-DHSA, (5) puriﬁ ed 9,10-DHSA

Fig. 3a GC chromatograms of (a) crude- and (b) puri- ﬁ ed- palm based 9,10-DHSA14)

14） not Table 7 . Comprehensive evaluation which included 9) （） Fig. 4 Structure of threo-9,10-DHSA four major irritancy tests was then conducted on puriﬁ ed 9,10-DHSA15）. In vitro ocular irrectection assay, through triglycerides（MCT）-16）and 9,10-DHSA/octyl-DHSA/RBD Irritation Draize Equivalent（IDE）score（Fig. 8a）, conclud- palm kernel olein（RBDPKOL）-MCT- systems17, 18）. The ed 9,10-DHSA had no or only minimal irritation potential. anisotropic region of the mixtures was inspected through In vitro dermal irrectection assay, through Human Irritan- crossed polarizer and conﬁ rmed through polarizing micro- cy Equivalent（HIE）score（Fig. 8b）, concluded 9,10-DHSA scope. was nonirritant. In vivo patch test concluded 9,10-DHSA at 1, 3 and 5％ concentrations did not induce any irritation 5.1 9,10-DHSA/octyl-DHSA/MCT system reactions after 48 and 96 h of patching（Fig. 8c）. Under in The ternary phase blend of 9,10-DHSA/octyl-DHSA/MCT vivo human repeated insult patch test, there was no evi- was completely in a two-phase region（Fig. 9a）16）. At 50％ dence that 9,10-DHSA caused cumulative skin irritation at MCT, 9,10-DHSA:octyl-DHSA 100:0 mass ratio exhibited the induction phase（Fig. 8d）; 9,10-DHSA at 1, 3 and 5％ needle form crystal texture; 9,10-DHSA:octyl-DHSA 0:100 concentrations did not cause contact dermatitis or cumula- mass ratio exhibited spherulite form crystal texture; mix- tive skin irritation and/or sensitization at challenge patch tures of the two forms of crystal textures were observed at phase. other 9,10-DHSA:octyl-DHSA mass ratios（Fig. 9b and Ta- ble 8）. The 9,10-DHSA:octyl-DHSA:MCT 5:45:50 mass ratio was useful in stick formulation.

5 CHARACTERISTICS OF 9,10-DHSA TERNARY 5.2 9,10-DHSA/octyl-DHSA/RBDPKOL-MCT system PHASE BLEND SYSTEMS The ternary phase blend of 9,10-DHSA/octyl-DHSA/RB- Two 9,10-DHSA ternary phase blend systems were po- DPKOL-MCT was prepared similar to 9,10-DHSA/octyl-DH- tentially useful for the formulations of cosmetic and per- SA/MCT system. The ternary phase blend of 9,10-DHSA/ sonal care products: 9,10-DHSA/octyl-DHSA/medium chain octyl-DHSA/RBDPKOL-MCT was completely in a two-

241 J. Oleo Sci. 60, (5) 237-265 (2011) G. F. L. Koay, T.-G. Chuah, S. Zainal-Abidin et al.

Table 4 Properties of oleic acid and 9,10-DHSA14-15) Parameters Palm based oleic acid Crude 9,10-DHSA Purifi ed 9,10-DHSA MW 316 IV 93.8±1.4 10.2±1.6 1.1±0.1 AV 204.0±1.8 179.3±0.4 180.3±1.2 OHV 18.7±0.5 196.0±4.2 309.3±3.9 SAPV 204.5±2.6 178.0±0.2 178.5±1.0 MP Not specifi ed 61.9±1.3 88-92 Physical form Liquid Semisolid (Waxy) solid Colour White to ivory Odour Light Density at 25℃, g mL-1 0.978 Self fl ammability Not self fl ammable Solubility, mg mL-1 Water : insoluble Methanol : 94.39±0.12 Ethanol : soluble Chloroform : 2.56±0.10 Diethyl ether : slightly soluble Pentane : insoluble Hexane : insoluble Toluene : 2.60±0.20 Dimethylformamide : 70.01±0.10 Acetone : 2.70±0.30

Fig. 5 Solubility of 9,10-DHSA in various alcohols14) phase region（Fig. 10a）17, 18）. At 50％ RBDPKOL-MCT, （Table 10）and thermal stability（Fig. 11）of the blend. The 9,10-DHSA:octyl-DHSA 100:0 mass ratio exhibited spheru- 9,10-DHSA:octyl-DHSA of 0:100 to 60:40 mass ratios were lite form crystal texture; 9,10-DHSA:octyl-DHSA 0:100 suitable for cosmetic formulations, with 30:70 mass ratio mass ratio exhibited needle form crystal texture; mixtures preferred over the rest as it was the easiest to penetrate of the two forms of crystal textures were observed at other into the skin without much rubbing. DSC revealed that 9,10-DHSA:octyl-DHSA mass ratios（Fig. 10b and Table 9）. 9,10-DHSA and octyl-DHSA had melting point（MP）range Ismail et al.18）further observed the rheological properties of 73.8～84.4℃ and 53.5～65.9℃ respectively. It is note-

242 J. Oleo Sci. 60, (5) 237-265 (2011) Overview of Palm Based Dihydroxystearic Acid and Its Derivatives

Fig. 6 Graphical plot of surface tension vs. concentration for 9,10-DHSA14)

Fig. 7 SEM micrographs of (a) flaky- and (b) global- structure of 9,10-DHSA agglomerates9,13)

Table 5 Crystal habit of 9,10-DHSA11) Solvent types and Crystal habits / structure of agglomerates concentrations Slow cooling Rapid cooling 100% ethanol Large sphere-like, loosely packed Small sphere-like, loosely packed 90% ethanol Plate-like, well formed, densely packed Large sphere-like, packed 100% IPA Plate-like, slightly well formed, densely packed Plate-like, not very well formed, densely packed 90% IPA Plate-like, very well formed, densely packed Plate-like, well formed, densely packed worthy and for researchers interested in this particular texture; octyl-DHSA alone exhibited spherulite form crys- subject matter to verify that at 50％ RBDPKOL-MCT, the tal texture. Kassim et al.17）and Ismail et al.18）reported that blending of merely 10％ of octyl-DHSA greatly reduces the at 50％ RBDPKOL-MCT, 9,10-DHSA alone exhibited spher- viscosity of 9,10-DHSA. ulite form crystal texture; octyl-DHSA alone exhibited nee- It would be of great academic interest to address the dle form crystal texture. Future research should also scru- fundamentals that led to total inversion in the order of tinize ternary phase blend crystal textures of crystal texture formation. Ismail et al.16）reported that at 9,10-DHSA/octyl-DHSA with different types of oily phase. 50％ MCT, 9,10-DHSA alone exhibited needle form crystal

243 J. Oleo Sci. 60, (5) 237-265 (2011) G. F. L. Koay, T.-G. Chuah, S. Zainal-Abidin et al.

Table 6 XRD readings of 9,10-DHSA11,13) Crude 9,10-DHSA Puriﬁ ed 9,10-DHSA Spacing (Å) Intensity Spacing (Å) Intensity Long spacing Long spacing 9.82 Medium 9.82 Medium 6.48 Weak 6.48 Weak Short spacing Short spacing 5.43 Weak 5.43 Weak 5.05 Medium 5.05 Medium 4.77 Weak 4.77 Weak 4.50 Strong 4.50 Strong 4.24 Weak 4.24 Weak 4.07 Strong 4.07 Strong 3.88 Weak 3.88 Weak 3.58 Strong 3.58 Strong 2.85 Weak 2.85 Weak Polymorphic form: strong β (and possibility of weak β’)

Table 7 Irritancy test score of 9,10-DHSA14) Samples Dose, mg Irritancy score Irritancy classiﬁ cation Crude 9,10-DHSA 25 0.62 Nonirritant 50 3.08 Irritant 75 3.81 Irritant 100 >4.00 Irritant 125 >4.00 Irritant Puriﬁ ed 9,10-DHSA 25 0.25 Nonirritant 50 0.40 Nonirritant 75 0.30 Nonirritant 100 0.21 Nonirritant 125 0.29 Nonirritant

6 CHARACTERISTICS OF 9,10-DHSA DERIVATIVES crude esters are presented in Table 11. 6.1 Straight esters from 9,10-DHSA The enzymatic esterifi cation of 9,10-DHSA with various Straight esters from 9,10-DHSA were produced by ester- fatty alcohols with Lipozyme RM IM and Novozym 435 as ifying 9,10-DHSA with various fatty alcohols（octanol, deca- catalysts was affected by（1）organic solvent type,（2）alco- nol, dodecanol, tetradecanol, hexadecanol, octadecanol） hol chain length and（3）substrate mole ratio but not by ini- both in the absence19）and presence20）of catalysts. The es- tial water activity20）（. 1）The conversion to ester（Eqn. 1） terifi cation process in the presence of lipase as catalyst has was higher in organic solvents with log P values［logarithm been patent fi led in the United States21）. In the absence of of partition coeffi cient of solvent in octanol/water system］ catalysts19）, FTIR（Fig. 12）revealed that hydroxyl groups from 2.0 to 4.0（Table 12）. Both enzymes were inactive in and overall structure of 9,10-DHSA were retained and un- dimethylformamide.（2）Alcohol chain lengths affected ini- affected by esterifi cation. The yield（80～96％, determined tial but not ultimate reaction rates and time-course of reac- through Eqn. 1）of reaction was optimized at 180℃（Fig. tions were quite similar（with the exception of octadecanol, 13a）, 9,10-DHSA:alcohol 1:2 mole ratio and reaction time due to its insolubility）（Fig. 14）（. 3）Both Lipozyme RM IM 420 min（Fig. 13b）. The initial rate of esterifi cation was af- and Novozym 435 showed higher conversion when sub- fected by mole ratios of reactants but varied mildly by fatty strate: DHSA mole ratio increased from 0.0 to 2.0（Fig. 15）. alcohol chain lengths. The physical properties of resultant The enzymes’ activities were not inhibited by excess alco-

244 J. Oleo Sci. 60, (5) 237-265 (2011) Overview of Palm Based Dihydroxystearic Acid and Its Derivatives

Fig. 9a Ternary phase diagram of 9,10-DHSA/octyl- DHSA/MCT at 85°C16)

Fig. 9b Crystal textures of 9,10-DHSA/octyl-DHSA at 25°C with 50% MCT, magniﬁ cation 100×16)

（Vo）was affected by enzyme concentration（Vo increased when Lipozyme RM IM concentration increased from 0 to －1 20 mg mL ）（Fig. 16a）and reaction temperature（Vo increased when temperature increased from 30 to 50ºC（）Fig. 16b）but not by treatment imposed on enzyme（Table 13）23）. The reaction followed Michaelis-Menten type kinetics. Fig. 8 Safety characteristics of 9,10-DHSA: (a) in vitro Mechanism wise, Lipozyme RM IM initially formed a non- ocular irritation potential, (b) in vitro dermal covalent enzyme-9,10-DHSA complex. It was then trans- irritation potential, (c) in vivo patch test score formed by a unimolecular isomerization reaction to acyl- and (d) in vivo human repeated insult patch test enzyme intermediate with concomitant release of water. score15) The modifi ed enzyme then reacted with octanol to form a modifi ed enzyme-octanol complex. It was also isomerized by a unimolecular reaction to an enzyme-octyl-DHSA com- hol. plex which then yielded the product octyl-DHSA and free enzyme（Scheme 2）. The kinetic parameters were ob- 6.2 Octyl-DHSA from 9,10-DHSA tained according to Michaelis-Menten model（Eqn. 2）. The With Lipozyme RM IM as catalyst, esterification of Michaelis-Menten constants for DHSA and octanol were 1.3 9,10-DHSA with octanol（Scheme 1）yielded 95％ octyl di- and 0.7 mol L－1 respectively while the maximum esterifi ca- 22）－1 －1 23） hydroxystearate（octyl-DHSA） . The initial reaction rate tion rate（Vmax）was 1 μmol min mg catalyst .

245 J. Oleo Sci. 60, (5) 237-265 (2011) G. F. L. Koay, T.-G. Chuah, S. Zainal-Abidin et al.

Table 8 Crystal textures of 9,10-DHSA/octyl-DHSA at 25°C with 50% MCT16) 9,10-DHSA:octyl-DHSA Textures/Description Corresponding Fig. 9b 100:0 Needles, less densely packed (a) 90:10, 80:20, 70:30, 60:40, 50:50, 40:60, 30:70 Needles, densely packed (b) 20:80 Small spherulites, densely packed, less packed needles (c) 10:90 Small spherulites, densely packed (d) 0:100 Large spherulites, densely packed (e)

Fig. 10b Crystal textures of 9,10-DHSA/octyl-DHSA Fig. 10a Ternary phase diagram of 9,10-DHSA/octyl- at 25°C with 50% RBDPKOL-MCT, magniﬁ - DHSA/RBDPKOL-MCT at 85°C17-18) cation 100×17-18)

Table 9 Crystal textures of 9,10-DHSA/octyl-DHSA at 25°C with 50% RBDPKOL-MCT17-18)

9,10-DHSA:octyl-DHSA Corresponding Textures/Description Kassim et al.17) Ismail et al.18) Fig. 10b 0:100 0:100 Needles, less densely packed (a) 10:90, 20:80, 30:70, 40:60, 50:50, 60:40 10:90, 20:80 Needles, densely packed (b) Small spherulites, densely packed, less 70:30, 80:20 30:70, 40:60, 50:50, 60:40, 70:30, 80:20 (c) packed needles 90:10 90:10 Small spherulites, densely packed (d) 100:0 100:0 Large spherulites, densely packed (e)

Lipozyme RM IM lipase catalyzed esterification of to C3 and constant at higher chain lengths（Fig. 18）. Octyl- 9,10-DHSA to octyl-DHSA resulted in lower acid value DHSA had HIE score below 0.90, which was nonirritant （AV）, saponification value（SAPV）and OHV22）. Lower AV （Table 15）and thus compatible with human skin and po- indicated formation of ester compound; lower SAPV and tentially useful in cosmetic and personal care products. OHV indicated increased product MW. TLC（Fig. 17a）, With Lipozyme TL IM as catalyst, esterification of FTIR, GC（Fig. 17b）, GCMS（Fig. 17c）and NMR confi rmed 9,10-DHSA with octanol yielded 89.7％ octyl-DHSA24）. The the resultant compound was a mixture of octyl-DHSA with conversion（determined through Eqn. 3）of 9,10-DHSA to other impurities. The properties of starting material and octyl-DHSA with different biocatalysts is presented in Ta- resultant compound are shown in Table 14. Not contradic- ble 16. Laboratory scale（250 mL batch）esterifi cation was tory with a later result by Ismail et al.18）, Awang et al.22）re- optimized at 3 h reaction time（Fig. 19a）, 10％ enzyme ported octyl-DHSA with MP range of 63.70～69.91℃（Fig. concentration（Fig. 20a）and 40℃ reaction temperature 17d）. Crude octyl-DHSA was more soluble in alcohol（due （Fig. 21a）. Awang et al.25）reported that large scale（fi ve li- to the presence of excess octanol）while its overall solubili- ter batch）esterifi cation was optimized at 60 min reaction ty increased with increasing alcohol chain length from C1 time, 40～50℃ reaction temperature（Fig. 19b）, 10％ en-

246 J. Oleo Sci. 60, (5) 237-265 (2011) Overview of Palm Based Dihydroxystearic Acid and Its Derivatives

Table 10 Viscosity and thixoropy values of 9,10-DHSA/octyl-DHSA at 25°C with 50% RBDPKOL- MCT18) 9,10-DHSA:octyl-DHSA Viscosity at shear rate 737s-1, Pa Thixoropy at shear rate 3000s-1, Pa 0:100 0.0158 32 10:90 0.0154 32 20:80 0.0172 32 30:70 0.0173 30 40:60 0.0185 36 50:50 0.0189 34 60:40 0.0212 32 70:30 0.0364 45 80:20 0.0955 50 90:10 0.0453 60 100:0 118000* 75

Fig. 11 DSC melting thermograms of (a) 9,10-DHSA Fig. 12 Typical FTIR spectrums of (a) 9,10-DHSA and and (b) octyl-DHSA18) (b) straight esters from 9,10-DHSA19)

247 J. Oleo Sci. 60, (5) 237-265 (2011) G. F. L. Koay, T.-G. Chuah, S. Zainal-Abidin et al.

［（B－A）×100］ 22）. Under vacuum, three cycles of recycling yielded in % esteriﬁ cation = ％ Eqn. 1 B each cycle more than 90％ conversion after 60 min reac- Where tion time; under non-vacuum, the initial activities were A = free fatty acid remaining in the sample comparable to those under vacuum but the overall conver- B = free fatty acid in the unreacted sample sion did not exceed 90％（Fig. 22）. It is interesting though to note that literature search has turned up with negative result on the Michaelis-Menten constant of DHSA for Lipozyme TL IM. This knowledge should be of particular interest especially for researchers in the biological, biochemical and oleochemical related ﬁ elds.

6.3 Monoglycerides from 9,10-DHSA The monoglycerides from 9,10-DHSA was synthesized by reacting 9,10-DHSA with glycerol in the presence of cata- lysts26）. FTIR（Fig. 23a）and GC（Fig. 23b）revealed the product was a mix of monoglycerides of 9,10-DHSA（MG- DHSA）, isomeric and diastereoisomeric diglycerides of 9,10-DHSA（DGDHSA）, with lower AV and SAPV compared to 9,10-DHSA（Table 17）. The product AV decreased over time（Fig. 24a）and was lower at higher reaction temperature（Table 18）and catalyst concentration（Table 19）. Higher initial reaction rate was achieved with sulphuric acid as catalyst（compared to p-TSA and sodium bisul- phate）but the final MGDHSA yield was comparable（Fig. 24b）. However, higher acid（catalysts）concentration caused higher degree of unwanted polymerization and decreased formation of desired MGDHSA, as in the case of 1.0 ～2.0％ catalyst. Regrettably, the optimum parameters to maximize MGDHSA yield were not emphasized on. Awang et al.27）reported that MGDHSA had HIE score below 0.90, which was nonirritant（Table 20）. The biodegrad- Fig. 13 Effects of (a) temperature and (b) reaction ability and ecotoxicity of MGDHSA were evaluated using time on acid value during the esterifi cation of OECD 301D closed bottle test and OECD 302 fish acute 19) 9,10-DHSA toxicity test respectively. MGDHSA was readily biodegradable（degraded by more than 60％ in 20 days）（Fig. 25）and was non toxic to aquatic environment（toxicity value more zyme concentration（Fig. 20b）and 400 rpm agitation rate than 100mg L－1）. MGDHSA was compatible with various （Fig. 21b）using a three bladed propeller. The conversions cosmetic oils: octyl dodecanol, isopropyl myristate, isopro- achieved were 94.1, 92.9 and 91.7％ for three-, two- and pyl palmitate and castor oil at room temperature; MCT, four- bladed propellers respectively. Awang et al.24）and mineral oil and cyclomethicone at elevated temperature Awang et al.25）reported that Lipozyme TL IM retained 70％（Table 21）. The emulsifi cation power of MGDHSA was cal- of initial activity after eight and five cycles recycling for culated based on degree of separation（Eqn. 4）. Oil（MCT）/ laboratory- and large-scale esterifi cation respectively（Fig. water emulsion systems containing more than 1 wt ％ MG-

Table 11 Physical properties of straight esters from 9,10-DHSA19) Straight esters from 9,10-DHSA Characteristics C8-OH C10-OH C12-OH C14-OH C16-OH C18-OH SMP 35.1 40.8 44.3 48.6 53.0 57.8 IV 15.8 13.3 11.9 11.0 10.9 10.2 SAPV 183.0 178.0 166.0 149.0 142.0 131.0

248 J. Oleo Sci. 60, (5) 237-265 (2011) Overview of Palm Based Dihydroxystearic Acid and Its Derivatives

Table 12 Effects of organic solvent type on enzymatic esteriﬁ cation of 9,10-DHSA with octanol20) % esteriﬁ cation Solvents Log P Lipozyme RM IM Novozym 435 Dimethylformamide －0.1 0.0±0.7 3.4±1.0 Acetone －0.23 69.2±0.4 75.7±1.3 Diethyl ether 0.85 74.4±0.6 77.6±2.7 Chloroform 2.0 77.6±1.8 79.5±0.2 Toluene 2.5 80.4±0.5 87.6±0.6 Pentane 3.0 81.9±0.6 81.2±1.2 Hexane 3.5 80.7±0.4 82.9±1.3 Heptane 4.0 79.0±1.0 79.9±0.3 Octane 4.5 72.9±1.9 77.5±0.8 Nonane 5.1 69.8±1.4 72.0±0.5 Decane 5.6 68.1±0.9 67.1±2.6 Dodecane 6.6 63.5±0.5 64.6±0.3 Hexadecane 8.8 54.1±0.9 51.7±0.7

Fig. 14 Conversion of 9,10-DHSA with various fatty alcohols as a function of time20) Fig. 15 Effects of substrate (octanol):9,10-DHSA Octanol ( ), decanol ( ), dodecanol ( ), tet- △ ■ ▲ mole ratio on enzymatic esterification of radecanol ( ), hexadecanol ( ), octadecanol 20) ○ ◇ 9,10-DHSA (●) Lipozyme RM IM (♦), Novozym 435 (■)

Scheme 1 The enzymatic esteriﬁ cation synthesis of octyl-DHSA23)

DHSA were stable at room temperature after seven days were produced by reacting 9,10-DHSA with alkanolamines storage; systems containing more than 2 wt％ were stable （Scheme 3）at elevated temperature28）. Conversion yield at 45℃ after seven days storage（Table 22）. With MGDHSA for DHSA-ethanolamide and DHSA-propanolamide was 98 as emulsiﬁ er, emulsions with higher water content showed and 95％ respectively（Fig. 27）. The resultant products higher stability（Fig. 26）. were characterized through FTIR, GC（Fig. 28a）and NMR （Fig. 28b）. The conversion increased with increasing reac- 6.4 Alkanolamides from 9,10-DHSA tion temperature. Reaction temperatures below 150℃ tend Alkanolamides from 9,10-DHSA（DHSA-alkanolamides） to yield undesirable mixtures of amine soap, esteramide,

249 J. Oleo Sci. 60, (5) 237-265 (2011) G. F. L. Koay, T.-G. Chuah, S. Zainal-Abidin et al.

1 K K 1 = 1＋ m（DHSA）＋ m（Oct）・ Eqn. 2 Vo ［［DHSA］［OCT］］ Vmax Where

Km（DHSA）, Michaelis-Menten constant for DHSA

Km（Oct）, Michaelis-Menten constant for octanol

Vo, initial esteriﬁ cation reaction rate

Vmax, maximum esteriﬁ cation reaction rate ［DHSA］, initial concentration of DHSA ［OCT］, initial concentration of octanol

Fig. 16 Effects of (a) Lipozyme RM IM concentration and (b) reaction temperature on initial reaction rate23) Fig. 17a TLC chromatogram of (1) octanol, (2) 9,10-DHSA and (3) crude octyl-DHSA22) (A) octyl-DHSA, (B) unreacted octanol, (C) unreacted 9,10-DHSA

Table 13 Effects of treatment imposed on Lipozyme RM IM on initial reaction rate23)

-1 -1 Treatment on Lipozyme RM IM Initial reaction rate (Vo), μmol min mg catalyst Untreated Lipozyme RM IM 2.9 Heated Lipozyme RM IM 2.9 (heated at 50℃ for 4 h) Incubated Lipozyme RM IM 2.8 (incubated in hexane at 50℃ for 4 h)

Scheme 2 Mechanism of enzymatic esterifi cation synthesis of octyl-DHSA23) E, enzyme; DHSA, 9,10-dihydroxystearic acid; OCT, octanol; DHSA-E, enzyme-DHSA complex; E*, modifi ed enzyme; W, water; E*-W, modifi ed enzyme-water complex; E*-OCT, modifi ed enzyme-octanol complex; E.DHSAO, enzyme- octyl-DHSA complex; DHSAO, octyl-DHSA

250 J. Oleo Sci. 60, (5) 237-265 (2011) Overview of Palm Based Dihydroxystearic Acid and Its Derivatives

Fig. 17b GC chromatogram of octyl-DHSA from 9,10-DHSA22) Measurement conditions: after derivatiza- tion with N,O-bistrimethylsilyl accetamide; HP-5 non polar column [Hewlett-Packard, (5%-phenyl)-methylpolysiloxane, 0.25mm × 30m × 0.25μm] with helium as carrier gas; oven: 150°C for 1min, 150-290°C at 10° Cmin-1, 290°C for 30min

Fig. 17d DSC melting thermograms of (a) crude and (b) 22) Fig. 17c Octyl-DHSA (a) general MS- and (b) electron puriﬁ ed octyl-DHSA impact GCMS- fragmentation patterns22) alkanolamide and aminoester. The properties of DHSA-al- and readily biodegradable（60％ degraded in 20 days）（Fig. kanolamides are shown in Table 23. The CMC was 0.005％ 31）. with surface tension 35 and 39 mNm－1 for DHSA-ethanolamide and DHSA-propanolamide respectively（Fig. 29）with 6.5 Estolides from 9,10-DHSA the former having better foaming power and stability（Fig. Estolides from 9,10-DHSA（DHSA-estolides）were pre- 30）. Both DHSA-alkanolamides were nonirritant（Table 24） pared through intermolecular esteriﬁ cation（IE）as per the

Table 14 Properties of 9,10-DHSA and octyl-DHSA14, 15, 22) Parameters 9,10-DHSA Crude octyl-DHSA Puriﬁ ed octyl-DHSA AV 180.3±1.2 7.9±0.8 1.8±0.1 OHV 309.3±3.9 223.9±4.6 246.1±3.5 SAPV 178.5±1.0 140.5±0.5 138.5±0.7 IV 1.1±0.2 6.0±0.1 0.3±0.1 MP 90.6±0.9 59.0±0.1 69.8±0.2

251 J. Oleo Sci. 60, (5) 237-265 (2011) G. F. L. Koay, T.-G. Chuah, S. Zainal-Abidin et al.

Fig. 19a Time course laboratory scale formation of octyl-DHSA catalyzed by Lipozyme TL IM (♦) and RM IM (×)24) Fig. 18 Solubility of crude and puriﬁ ed octyl-DHSA in alcohol of various chain lengths22)

Table 15 Irritancy test score of octyl-DHSA22) Irritancy score (DHSA:octanol) Irritancy Dose, mg 1.0:1.0 1.0:1.5 1.0:2.0 classiﬁ cation 50 0.28 0.22 0.00 Nonirritant 75 0.25 0.28 0.05 Nonirritant 100 0.37 0.29 0.16 Nonirritant 125 0.60 0.33 0.25 Nonirritant

（M －M ） % conversion = 0 t ×100％ Eqn. 3 ［ M0－Mb ］ Where M = moles of NaOH consumed by titration of mixture at o Fig. 19b Time course large scale formation of octyl- beginning of reaction DHSA catalyzed by Lipozyme TL IM at vari- Mt = moles of NaOH consumed by tritration of mixture at 25) end of reaction ous reaction temperatures

Mb = moles of NaOH consumed by tritration of mixture without fatty acid

Table 16 Conversion of 9,10-DHSA to octyl- DHSA using different immobilized enzymes24) Enzymes % esteriﬁ cation Lipozyme TL IM 89.7 Lipozyme RM IM 92.3 Novozym 435 95.1

29） technology patent filed in Malaysia . During the IE pro- Fig. 20a Effects of enzyme concentration on laboratory cess, hydroxyl and carboxyl groups in 9,10-DHSA inter-re- scale esteriﬁ cation of 9,10-DHSA with octa- acted and polymerized to yield DHSA-estolides（Scheme nol24) 4）30）. One carbonyl ester transmission peak was observed Lipozyme TL IM (♦), Lipozyme RM IM (×) for DHSA-estolides obtained after 2 h reaction; two peaks were observed after 4 h. This suggested that DHSA-es-

252 J. Oleo Sci. 60, (5) 237-265 (2011) Overview of Palm Based Dihydroxystearic Acid and Its Derivatives

Fig. 20b Effects of enzyme concentration on large scale esteriﬁ cation of 9,10-DHSA with octa- nol25)

Fig. 21 Effects of (a) reaction temperature and (b) agitation speed on esterification of 9,10-DHSA with octanol24, 25) Lipozyme TL IM (♦), Lipozyme RM IM (×) Fig. 22 Reusability performance of Lipozyme TL IM on esteriﬁ cation of 9,10-DHSA with octanol: (a) laboratory- and (b) large- scale; (c) vacuum- and (d) non-vacuum condition24, 25)

253 J. Oleo Sci. 60, (5) 237-265 (2011) G. F. L. Koay, T.-G. Chuah, S. Zainal-Abidin et al.

Fig. 23a FTIR spectrum of reaction product between 9,10-DHSA and glycerol26) Fig. 24a Effects of reaction time on acid value and MGDHSA composition26)

Fig. 23b GC spectrum of reaction product between 9,10-DHSA and glycerol26)

tolides with more than one ester linkage formed after 2 h reaction（Fig. 32）. The properties of DHSA-estolides are Fig. 24b Effects of catalyst type on acid value and shown in Table 25. The IV of DHSA-estolides increased MGDHSA composition26)

with time due to replacement of hydroxyl groups by iodine. H2SO4 ( ), NaHSO4 ( ), p-TSA ( ) The Neutralization Equivalent（NE）and Estolide Number （EN）were calculated based on Eqn. 5 and Eqn. 6 respec- based on end-group analyses（AV and SAPV）were in good tively. The averaged MW of DHSA-estolides calculated correlation with theoretical MW. As IE proceeded, MW of

Table 17 Properties of starting materials and crude reaction product26) Parameters Glycerol 9,10-DHSA Crude reaction product AV Not determined 178.7 53.5 OHV 1612.4 317.2 322.7 SAPV 0.0 183.9 141.2 MP Liquid at room temperature 90.6-91.3 67.5-69.1

Table 18 Effects of reaction temperature on properties and composition of reaction product26)

Temperature, ℃ AV IV MGDHSA, % DGDHSA, % 100 137.37 1.56 11.84 1.04 120 109.40 1.84 18.19 1.64 150 67.97 2.31 43.55 8.90 180 9.71 2.78 72.91 12.39

254 J. Oleo Sci. 60, (5) 237-265 (2011) Overview of Palm Based Dihydroxystearic Acid and Its Derivatives

Table 19 Effects of catalyst concentration on properties and composition of reaction product26) Catalyst, % AV IV MGDHSA, % DGDHSA, % 0.0 99.94 2.43 36.90 8.99 0.2 69.84 2.42 43.72 10.25 0.4 64.19 2.84 43.50 10.96 0.6 58.67 2.67 41.90 10.58 0.8 55.78 3.59 40.61 12.35 1.0 18.01 8.11 21.25 0.00 2.0 8.09 14.72 0.00 0.00

Table 20 Irritancy test score of MGDHSA27) Concentration, μL Irritancy score Irritancy classiﬁ cation 50 0.12 Nonirritant 75 0.19 Nonirritant 100 0.18 Nonirritant 125 0.31 Nonirritant

（top volume, mL） % separation = ×100％ Eqn. 4 （total volume, mL）

7 APPLICATIONS OF 9,10-DHSA AND DERIVATIVES IN COMMERICAL PRODUCTS Palm based 9,10-DHSA was developed for the intended and eventual application in cosmetic and personal care Fig. 25 Biodegradation proﬁ le of MGDHSA27) products. Over the years, 9,10-DHSA has established its Note: MGDHSA biodegraded by more than role as cosmetic ingredient, surfactant, foam improver, 60% in 20 days; beyond that, it appears that emulsiﬁ er and many more15－16, 18, 27－28）. Among some prod- extrapolation was carried out as the final bio- ucts that have successfully incorporated 9,10-DHSA and/or degradation exceeded 100% its derivatives in their formulations included soaps, deodorant sticks and shampoos31－34）. DHSA-estolides increased and the state changed from solid to paste and then to wax. 7.1 Sodium soap from 9,10-DHSA Sodium soap was prepared by reacting 9,10-DHSA with 50％ sodium hydroxide solution31）. According to Ahmad et al.32）, the sodium soap prepared was of clear bar type with

Table 21 Compatibility of MGDHSA with various cosmetic oils27) Cosmetic oils Dissolving temperature,℃ Appearance at room temperature MCT 74 Translucent Octyl dodecanol 52 Clear Isopropyl myristate 58 Clear Isopropyl palmitate 56 Clear Mineral oil 76 Separation Cyclomethicone 76 Sediment Castor oil 52 Clear

255 J. Oleo Sci. 60, (5) 237-265 (2011) G. F. L. Koay, T.-G. Chuah, S. Zainal-Abidin et al.

Table 22 Effects of MGDHSA concentration on oil/water emulsion stability after seven days storage27)

MGDHSA, % % separation at room temperature % separation at 45℃ 12032 20 4 30 0 50 0

Fig. 27 Effects of reaction time on amidation between 9,10-DHSA and alkanolamines28) DHSA-ethanolamide (♦), DHSA-propanolamide (▲)

foam formation was comparable to that of sulphonated Fig. 26 Stability of oil/water emulsion systems of vari- methyl ester（SME）and outperformed that of stearic acid ous phase ratios with 2wt% MGDHSA after soap in both normal and hard water（Fig. 33b）; the foam 7 days storage at room temperature and at 45 stability of SME was superior to that of 9,10-DHSA sodium 27) °C soap in hard water（Fig. 34）. The detergency（determined through ％ soil removal, Eqn. 8）of 9,10-DHSA sodium soap transparency index value range 0.92～0.94（transparency was comparable to other soaps at room temperature but value for glass is 1.00）. The soap with NaOH:DHSA 1.5 the performance deteriorated at elevated temperatures mole ratio gave highest total fatty matter（TFM）and ac- （Fig. 35）. The CMC for 9,10-DHSA sodium soap was 0.01％ ceptable free caustic alkalinity（Eqn. 7（）Table 26）while 1.5 with surface tension 42 mNm－（1 Fig. 36）. The 9,10-DHSA to 3.0 mole ratios gave good foam stability（expressed as sodium soap biodegraded more than 60％ in 28 days（sodi- ratio of foam volume of 5.5- to that of 0.5- min of vigorous um acetate as reference）（Fig. 37）. The wetting power of whipping, V5/V0）（Fig. 33a）. The 9,10-DHSA sodium soap 9,10-DHSA sodium soap was comparable to that of SME

Scheme 3 Reaction between 9,10-DHSA and ethanolamine to produce DHSA-ethanolamide28) 256 J. Oleo Sci. 60, (5) 237-265 (2011) Overview of Palm Based Dihydroxystearic Acid and Its Derivatives

Fig. 28b 13C-NMR spectrum of purified DHSA-etha- nolamide28)

duced corrosiveness of distilled water from 0.1 to 0.002 mmyr－（1 Fig. 39）.

7.2 Deodorant stick from Na-DHSA Deodorant stick from sodium dihydroxystearate（Na-DH- SA）was developed using 9,10-DHSA/propylene glycol（PG） /sodium hydroxide ternary blend of 55:5:40 mass ratio33）. This blend exhibited liquid crystalline Maltase cross structure（Fig. 40）. Minute quantity of humectants, perfume and antimicrobial agent were added as part of the stick formulation. Appearance of the deodorant stick ranged from opaque to transparent to translucent, depending on crys- Fig. 28a GC chromatograms of DHSA-alkanoamides: talline network structure formation. The hardness Fig. (a) DHSA-ethanolamide and (b) DHSA- （ 41a）, softening point（Fig. 41b）and disintegration time propanolamide28) （Fig. 41c）of Na-DHSA deodorant sticks（D4-antimicrobial active and perfumed, D5-antimicrobial active, D6-per- （Fig. 38）. 9,10-DHSA sodium soap displayed good corro- fumed, D7-without antimicrobial agent nor perfumed）were sion inhibitor properties. At 100 ppm concentration, it re- comparable to those of commercial sodium stearate based

Table 23 Properties of DHSA-alkanolamides28) Parameters Mono DHSA-ethanolamide Mono DHSA-propanolamide Colour Yellowish Yellowish AV 1.05 2.18 OHV 281.25 267.71 MP 83-85 84.86

Ecotoxicity, LC50 22.63 22.63 Solubility Soluble in water Soluble in water

257 J. Oleo Sci. 60, (5) 237-265 (2011) G. F. L. Koay, T.-G. Chuah, S. Zainal-Abidin et al.

Table 24 Irritancy test score of DHSA-alkanolamides28) Samples Dose, mg Irritancy score Irritancy classiﬁ cation DHSA-ethanolamide 50 0.76 Nonirritant 75 0.78 Nonirritant 100 0.70 Nonirritant 125 0.68 Nonirritant DHSA-propanolamide 50 0.50 Nonirritant 75 0.68 Nonirritant 100 0.79 Nonirritant 125 0.77 Nonirritant

Fig. 29 Graphical plot of surface tension vs. concentration for DHSA-alkanolamides28)

deodorant sticks（labeled C1 and C2）and were stable upon one month storage. Short integration time rendered Na- DHSA deodorant stick suitable for medicated type applications. The storage stability（upon three months storage at 28 and 45℃）even outperformed one commercial sample which contained alcohol（Table 27）. The pH of the Na-DH- SA deodorant stick varied from 9.5 to 10.5（Fig. 41d）, suitable for human skin and nonirritating upon application. The deodorant stick inhibited microbial growth（bacteria on mannitol agar and mold/fungus/yeast on saboroud dextrose agar）up to 8 h, outperforming commercial samples （Fig. 42）. Fig. 30 Foam volume and stability of DHSA- alkanol- It should be noted, nonetheless, that Ismail et al（. 2006） amides: (a) DHSA-ethanolamide and (b) DH- 28) had presented the formulae of deodorant stick erroneously SA-propanolamide in part of the text（methods in preparation of deodorant sticks and discussion on deodorant stick formulations）, causing ambiguity and thus hampering efforts to replicate braic representations‘ Y’ and‘ Z’, etc.）of the same paper the results. The labeling of liquid crystalline structure in were also not clearly defined and presented. Future re- Fig. 2 and part of the deodorant stick formulations pre- search could scrutinize effects and optimal composition of sented in Table 3（e.g. unit of measure, signiﬁ cance of alge- solubilisant gamma 2428 in deodorant stick and further ex-

258 J. Oleo Sci. 60, (5) 237-265 (2011) Overview of Palm Based Dihydroxystearic Acid and Its Derivatives

Fig. 32 FTIR spectra of DHSA-estolides from various reaction times30) Fig. 31 Biodegradation profile of DHSA-alkanol- 28) amides （1000×56.1） Neutralization equivalent, NE = Eqn. 5 acid value

（NE－316.47） Estolide number, EN= Eqn. 6 316.47

0.4V % free caustic alkalinity= Eqn. 7 W Where V = volume of 0.1N HCl, mL W = weight of sample, g

diestolide）（Table 28）were incorporated into shampoo formulation（Table 29）and its performance was benchmarked against commercial shampoo in terms of viscosity, foaming Scheme 4 Intermolecular esteriﬁ cation of 9,10-DHSA power and stability, detergency（Eqn. 8）and comb-ability followed by dehydration to produce DHSA- （Eqn. 9）34）. The characteristics of DHSA-estolides formu- 30) estolides lated- and commercial- shampoos are shown in Table 30. DHSA-estolides formulated shampoo had higher viscosity plore potential of Na-DHSA in medicated deodorant stick. than commercial ones（suggesting they were suitable as A study on crystalline habit, morphology and network viscosity builder in shampoo）（Fig. 43a）and superior in structure formation relationship with final appearance of terms of foaming power and stability（Fig. 43b）. DHSA-es- end merchandise should be of interest too. tolides slowed coalescence of foams by strengthening the film at the air/water interface in matrix of bubbles. The 7.3 Shampoo from DHSA-estolides foams generated were more compact and uniform, making DHSA-estolides（containing only monoestolide and them nicer, richer and denser. The detergency（conducted

Table 25 Chemical properties, NE, EN and MW of 9,10-DHSA and DHSA-estolides30)

Reaction Chemical properties End-group analysis based MW Theoretical Samples NE EN Description time, h AV SAPV OHV IV AV SAPV OHV MW DHSA 0 176.28 172.08 260.05 3.74 n/a n/a n/a 318.30 326.06 431.53 316.00 DHSA-E2h 2 92.62 209.71 174.57 7.41 605.80 0.91 Monoestolide 605.80 535.12 964.25 614.00 DHSA-E4h 4 67.91 211.54 168.72 7.62 826.24 1.61 Diestolide 756.91 795.74 1445.00 912.00 DHSA-E6h 6 41.70 210.00 155.32 7.73 1345.56 3.25 Triestolide 1345.56 1345.74 1944.55 1216.00 DHSA-E8h 8 29.42 201.02 115.42 9.29 1907.20 5.03 Pentaestolide 1907.20 1674.75 ND 1809.00

259 J. Oleo Sci. 60, (5) 237-265 (2011) G. F. L. Koay, T.-G. Chuah, S. Zainal-Abidin et al.

Table 26 Properties of 9,10-DHSA sodium soap31) NaOH:9,10-DHSA mole ratios pH Free caustic alkalinity, % TFM 8.0:1.0 11.28 20.28 45.98 4.0:1.0 10.97 12.87 66.46 3.0:1.0 10.54 5.94 71.64 2.0:1.0 10.04 1.51 70.99 1.5:1.0 9.63 0.37 92.87 1.0:1.0 7.91 0.05 87.08

Fig. 33a Foam volume of 9,10-DHSA sodium soap produced from various NaOH:DHSA mole ratios after 0.5- and 5.5- minutes of vigorous whipping31) A (8:1), B (4:1), C (3:1), D (2:1), E (1.5:1), F (1:1)

Fig. 34a Foam stability of 9,10-DHSA sodium soap (◇), stearic acid soap (□) and SME (△) in (a) absence of Ca2+ ions and (b) 200ppm of Ca2+ ions31)

Fig. 33b Foam volume of 9,10-DHSA sodium soap Fig. 34b Foam stability of 9,10-DHSA sodium soap (◇), stearic acid soap (□) and SME (△) in (◇) and SME (△) in different concentrations 31) (a) absence of Ca2+ ions and (b) 200ppm of of hard water Ca2+ ions31)

260 J. Oleo Sci. 60, (5) 237-265 (2011) Overview of Palm Based Dihydroxystearic Acid and Its Derivatives

（AW－BW） % soil removal = ×100％ Eqn. 8 ［（OC－BW）］ Where AW = refl ectance of soil cloth after washing BW = refl ectance of soil cloth before washing OC = refl ectance of original cloth

Fig. 37 Biodegradation profile of 9,10-DHSA sodium soap31)

Fig. 35 Detergency of soaps in various water hardness 31) at (a) room temperature and (b) 45°C Fig. 38 Wetting power of soaps31) C18 – stearic acid soap, 12-H.S.A. – 12-hy- DHSA – 9,10-DHSA sodium soap, SME – droxystearic acid soap, DHSA – 9,10-DHSA palm stearin SME, C18 – stearic acid soap, sodium soap, C18-SME – stearic acid SME, 12-H.S.A. – 12-hydroxystearic acid soap SME – palm stearin SME

Fig. 36 Surface tension of soaps as a function of con- Fig. 39 Corrosion rate by 9,10-DHSA sodium soap as centration31) a function of concentration31) 9,10-DHSA sodium soap (♦), stearic acid soap (■), SME (▲) on standard fabric coated with synthetic sebum）of DHSA- monoestolide formulated shampoo outperformed commercial shampoo in both normal and hard water; DHSA- diestolide formulated shampoo outperformed commercial

261 J. Oleo Sci. 60, (5) 237-265 (2011) G. F. L. Koay, T.-G. Chuah, S. Zainal-Abidin et al.

Table 27 Storage stability of Na-DHSA deodorant sticks after three months33) Storage temperature Code 28℃ 45℃ D4 Stable Stable D5 Stable Stable D6 Stable Stable D7 Stable Stable C1 Unstable Unstable Fig. 40 Ternary phase diagram of 9,10-DHSA/PG/ C2 Stable Stable NaOH at 80°C33)

Fig. 42 Growth rate of (a) bacteria on mannitol agar and (b) fungus and yeast on sabaroud dextrose agar for Na-DHSA deodorant sticks33)

shampoo in hard water（Fig. 43c）. Under dry condition, DHSA-estolides formulated shampoo showed comparable comb-ability property to commercial ones（Fig. 43d）, indi- Fig. 41 Na-DHSA deodorant sticks: (a) hardness, (b) cating that DHSA-estolides were suitable as conditioning softening point, (c) disintegration time and (d) agent in shampoo formulation. pH33)

262 J. Oleo Sci. 60, (5) 237-265 (2011) Overview of Palm Based Dihydroxystearic Acid and Its Derivatives

Table 28 Compatibility of DHSA-estolides as ingredient for shampoo formulation34) Stability after 24 h storage at room DHSA-estolides temperature DHSA-monoestolide Stable DHSA-diestolide Stable DHSA-triestolide Separated into 2 layers DHSA-pentaestolide Separated into 2 layers Control Stable

Table 29 DHSA-estolides formulated sham- poo34) Ingredients % weight Sodium laureth sulphate 8.0 Cocamide DEA 5.0 PEG-7 glyceryl cocoate 1.0 EDTA 0.05 Sodium laureth 2.0 DHSA-estolides 2.0 Perfume 0.1 Preservative 0.1 Citric acid/NaOH To pH5.5 Deionized water To 100

（JB－JA） Combing force, % = ×100 Eqn. 9 ［ JB ］ Where JA = combing force of hair after shampooing JB = combing force of hair before shampooing Fig. 43 Characteristics of DHSA-estolides formu- 8 SUMMARY lated-, control- and commercial- shampoos: (a) 9,10-DHSA was successfully prepared through epoxida- viscosity, (b) foaming power and stability, (c) tion of commercial grade palm based crude oleic acid via detergency in various water hardness at room peracetic- and performic- acid routes. The puriﬁ cation of temperature and (d) reduction in combing force 9,10-DHSA through solvent crystallization using ethanol for dry hair34)

Table 30 Characteristics of DHSA-estolides formulated- and commercial- sham- poos34) DHSA-estolides Tests Control Commercial shampoo formulated shampoo Clarity Clear Opaque, pearly Opaque, pearly Foam volume, mL 330 345-365 315 Foam type Loose, airy Rich, dense, creamy Rich, dense, creamy Surface tension, nNm-1 37.1 35.8-36.2 36.5 Wetting time, s 140 138-141 140 pH 5.5 5.5-5.7 5.6

263 J. Oleo Sci. 60, (5) 237-265 (2011) G. F. L. Koay, T.-G. Chuah, S. Zainal-Abidin et al.

Table 31 Summary on development and technological advancement of palm based 9,10-DHSA and its immediate derivatives

Incorporation in No. Primary feed Primary process Primary/desired product commercial products 1a. Oleic acid + Peracetic acid Epoxidation Crude 9,10-DHSA － 1b. Oleic acid + Performic acid Epoxidation Crude 9,10-DHSA － 2 Crude 9,10-DHSA Crystallization Purifi ed 9,10-DHSA DHSA-sodium soaps Octyl-DHSA 9,10-DHSA ternary phase 3a. 9,10-DHSA + Ternary phase blending － MCT blend system Octyl-DHSA 9,10-DHSA ternary phase 3b. 9,10-DHSA + Ternary phase blending － RBDPKOL-MCT blend system Propylene glycol Ternary phase blending 3c. 9,10-DHSA + Sodium dihydroxystearate DHSA-deodorant sticks Sodium hydroxide Chemical esterifi cation 4a. 9,10-DHSA + Straight alcohols Enzymatic esterifi cation DHSA-esters － 4b. 9,10-DHSA + Octanol Enzymatic esterifi cation Octyl-DHSA － 4c. 9,10-DHSA + Glycerol Chemical esterifi cation DHSA-monoglyceride － 5 9,10-DHSA + Alkanolamines Amidation DHSA-alkanolamides － Intermolecular esterifi cation 6 9,10-DHSA DHSA-estolides DHSA-shampoos Polymerization

and propanol had been carried out comprehensively. How- hydroxystearic acid, m.p.’s 132° and 95°. J. Chem. ever, dynamic evolution of the crystalline formation is not Soc., Resumed, 387-391（1942）. fully understood. The characteristics of 9,10-DHSA was 4） Reddy, S. Y.; Prabhakar, J. V. Effect of triglyceride con- studied quite comprehensively though it would be of aca- taining 9,10-dihydroxystearic acid on the solidiﬁ cation demic interest and value to compare characteristics of properties of Sal（Shorea robusta）fat. J. Am. Oil 9,10-DHSA of different sources and/or starting raw materi- Chem. Soc. 62, 1126-1130（1985）. als. The crystal structure/texture of 9,10-DHSA phase 5） Awang, R.; Ahmad, S.; Kang, Y. B. Preparation of dihy- blends should be restudied as there arose serious disparity. droxy fatty acid from oleic acid. Malaysian Pat., Substantial study was done on one 9,10-DHSA derivative- PI9804456（1998）. octyl-DHSA-and more similar works should be done on 6） Awang, R.; Ahmad, S.; Beng, K. Y. Preparation of dihy- other derivatives（Table 31）, especially those that prelimi- droxy compound from unsaturated materials. Singa- nary works had been established. To date, 9,10-DHSA and pore Pat., 86353（2002）. its derivatives had been incorporated into at least three 7） Ahmad, S.; Hoong, S. S.; Sattar, M. N.; Yusof, Y. A.; types of commercial products-soap, deodorant stick and Hassan, H. A.; Awang, R. Palm-based hydroxyl fatty shampoo-but its potential should be beyond these and acid. US Pat., US7560578B2（2009）. more R&D works should be carried out to explore them. 8） Siwayanan, P.; Shaari, N. Z. K.; Maurad, Z.; Aziz, H. A.; Hassan, H. A.; Ahmad, S.; Awang, R. Scale-up production and puriﬁ cation of palm oil-based dihydroxystearic acid（DHSA）. in Proc. 18th SOMChE, pp. 294-300 References （2004）. 1） Le Sueur, H. R. CXXXVIII.-The products of the action 9） Koay, G. F. L.; Abdullah, L. C.; Yunus, R.; Choong, S. Y. of fused potassium hydroxide on dihydroxystearic T.; Siwayanan, P.; Salmiah, A. Crystallization of dihy- acid. J. Chem. Soc., Trans. 79, 1313-1324（1901）. droxystearic acid（DHSA）produced from commercial 2） Lapworth, A.; Mottram, E. N. CCXIV.-Oxidation prod- grade palm oil based crude oleic acid employing iso- ucts of oleic acid. Part I. Conversion of oleic acid into propyl alcohol as solvent. Int. J. Eng. Technol. 3, dihydroxystearic acid and the determination of the 115-124（2006）. higher saturated acids in mixed acids from natural 10） Sumaiya, Z. A.; Koay, G. F. L.; Chuah, T. G.; Parthiban, sources. J. Chem. Soc., Trans. 127, 1628-1631 S.; Robiah, Y.; Salmiah, A.; Choong, T. S. Y. Effect of （1925）. cooling modes on solvent crystallization of palm oil 3） King, G. The dihydroxystearic acid of castor oil: its based dihydroxystearic acid using ethanol. J. Appl. constitution and structural relationship to the 9:10-di- Sci. 7, 2222-2225（2007）.

264 J. Oleo Sci. 60, (5) 237-265 (2011) Overview of Palm Based Dihydroxystearic Acid and Its Derivatives

11） Koay, G. F. L.; Guan, C. T.; Zainal-Abidin, S.; Ahmad, S.; catalyzed synthesis and characterization of octyl dihy- Choong, T. S. Y. Habit and morphology study on the droxystearate from palm-based dihydroxystearic acid. palm-based 9,10-dihydroxystearic acid（DHSA）crys- J. Oleo Sci. 52, 7-14（2003）. tals. Mater. Chem. Phys. 114, 14-17（2009）. 23） Awang, R.; Basri, M.; Ahmad, S.; Salleh, A. B. Lipase- 12） Abidin, S. Z.; Ling, G. K. F.; Abdullah, L. C.; Ahmad, S.; catalyzed esteriﬁ cation of palm-based 9,10-dihydroxy- Yunus, R.; Choong, T. S. Y. Effects of temperature and stearic acid and 1-octanol in hexane-a kinetic study. cooling modes on yield, purity and particle size distri- Biotechnol. Lett. 26, 11-14（2004）. bution of dihydroxystearic acid crystals. Eur. J. Sci. 24） Awang, R.; Basri, M.; Ahmad, S.; Salleh, A. B. Thermo- Res. 33, 471-479（2009）. myces lanuginosus lipase-catalyzed esteriﬁ cation of 13） Sumaiya, Z. A.; Chuah, A. L.; Koay, G. F. L.; Salmiah, A.; 9,10-dihydroxystearic acid and monohydric alcohol. J. Choong, T. S. Y. Effect of solvent concentration and Oleo Sci. 54, 305-309（2005）. cooling modes on morphology, particle size distribu- 25） Awang, R.; Basri, M.; Ahmad, S.; Salleh, A. B. Large tion, and yield of dihydroxystearic acid（DHSA）crys- scale production of octyl-9,10-dihydroxystearate by tals. Part. Sci. Technol. 28, 236-246（2010）. immobilized lipase. J. Oil Palm Res. 19, 393-397 14） Awang, R.; Ahmad, S.; Kang, Y. B.; Ismail, R. Charac- （2007）. terization of dihydroxystearic acid from palm oleic 26） Awang, R.; Ahmad, S.; Ibrahim, M. F. W.; Yunus, W. M. Z. acid. J. Am. Oil Chem. Soc. 78, 1249-1252（2001）. W. Synthesis of monoglycerides from dihydroxystearic 15） Aldrin, A. H. Z.; Ismail, R.; Ahmad, S. Safety evaluation acid: effect of reaction parameters. Malaysian J. for dermal and ocular irritation of palm dihydroxyste- Chem. 6, 13-19（2004）. aric acid as a cosmetic ingredient. J. Oil Palm Res. 27） Awang, R.; Hau, L. T.; Ibrahim, M. F. W.; Basri, M.; Ah- 17, 160-167（2005）. mad, S. Monoglycerides from 9,10-dihydroxystearic 16） Ismail, Z.; Sopian, M. H.; Awang, R.; Ahmad, S.; Kas- acid for the cosmetic industry. J. Oil Palm Res. 21, sim, A. Ternary phase behaviour of dihydroxystearic 636-641（2009）. acid/octyl dihydroxystearate/medium chain triglycer- 28） Awang, R.; Whye, C. K.; Basri, M.; Ismail, R.; Ghazali, R.; ides. J. Dispersion Sci. Technol. 25, 759-761（2004）. Ahmad, S. Alkanolamides from 9,10-dihydroxystearic 17） Kassim, A.; Nadarajan, R.; Ismail, Z.; Desa, M. Z.; Shar- acid. J. Oil Palm Res. 18, 231-238（2006）. if, A. M.; Kuang, D., Haron, M. J. Morphological studies 29） Awang, R.; Ahmad, S.; Azizan, A. N.; Yunus, W. M. Z. W. of DHSA/DHSA-octyl ester/RBD palm kernel olein/me- A process for producing estolides. Malaysian Pat., dium chain triglycerides system. Malaysian J. Anal. PI20050185（2005）. Sci. 11, 331-335（2007）. 30） Awang, R.; Azizan, A. N.; Ahmad, S.; Yunus, W. M. Z. W. 18） Ismail, Z.; Nadarajan, R.; Kassim, A.; Desa, M. Z. Selec- Characterization of estolides from dihydroxystearic tion of polymorphic structure in dihydroxystearic acid. J. Oil Palm Res. 19, 350-355（2007）. acid/octyl dihydroxystearate/RBD palm kernel olein & 31） Awang, R.; Ahmad, S.; Ghazali, R. Properties of sodium medium chain triglycerides in cosmetic and personal soap derived from palm-based dihydroxystearic acid. care formulation. J. Dispersion Sci. Technol. 28, J. Oil Palm Res. 13, 33-38（2001）. 261-265（2008）. 32） Ahmad, N.; Kian, Y. S.; Hassan, H. A. DHSA-transpar- 19） Roila, A.; Salmiah, A. Synthesis and characterization of ency improver in clear bar soap. MPOB Information ester from dihydroxystearic acid. J. Oil Palm Res. 12, Series TT No. 393（2008）. 81-85（2000）. 33） Ismail, Z.; Ahmad, S.; Ismail, R. The advantages of 20） Awang, R.; Basri, M.; Ahmad, S.; Salleh, A. B. Enzy- palm-based dihydroxy stearate in deodorant sticks. J. matic esterification of dihydroxystearic acid. J. Am. Dispersion Sci. Technol. 27, 463-467（2006）. Oil Chem. Soc. 77, 609-612（2000）. 34） Awang, R.; Azizan, A. N.; Ahmad, S.; Yunus, W. M. Z. W.; 21） Awang, R.; Ahmad, S.; Basri, M.; Salleh, A. B. Process Ahmad, N. Palm-based estolide as an ingredient in for producing wax ester from dihydroxy fatty acid. US shampoo: a preliminary study. J. Oil Palm Res. 19, Pat., US7125694B2（2006）. 416-420（2007）. 22） Awang, R.; Basri, M.; Ahmad, S.; Salleh, A. B. Enzyme-

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