Chemical Composition and Antioxidant Potentials of Kigelia Pinnata Root Oil and Extracts
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EXCLI Journal 2011;10:264-273 – ISSN 1611-2156 Received: October 24, 2011, accepted: November 23, 2011, published: November 30, 2011 Original article: CHEMICAL COMPOSITION AND ANTIOXIDANT POTENTIALS OF KIGELIA PINNATA ROOT OIL AND EXTRACTS Olubunmi Atolani*1, Stephen O. Adeyemi 1, Essiet Akpan1, Charles B. Adeosun1, Gabriel A. Olatunji2 1 Atolani Olubunmi, Department of Chemical Sciences, Redeemer’s University, P.M.B. 3005, Redemption Camp, Mowe, Ogun State, Nigeria 2 Department of Chemistry, University of Ilorin, P.M.B. 1515, Ilorin, Nigeria * corresponding author E-mail: [email protected]; Tel; +2348034467136 ABSTRACT The chemical composition of Kigelia pinnata root oil extracted with n-hexane was analyzed by GC/GCMS. The antioxidant potential of the oil was compared to that of ethyl acetate and methanol extracts of the root. UV and IR spectroscopic techniques were used to carry out par- tial characterization of the oil and extracts. The free radical scavenging activity by spectro- photometric assay on the reduction of 1,1-diphenyl-2-picrylhydrazyl (DPPH) was examined while the total antioxidant activity (TAA) and relative antioxidant activity (RAA) were com- pared with standard antioxidant, α-tocopherol. The antioxidant activity (which correlated with the total phenolic content of the extracts) was assumed to be from the total phenolic content of the extracts. TAA was found to be higher in methanol extract (at 0.25 mg/mL). We hereby report for the first time the major component of the oil from the root of Kigelia pinnata to be elaidic acid (56.12 %). It is a reported toxicant which thereby underscores the risk in the use of the plant in traditional therapies. Keywords: Antioxidant, Kigelia pinnata, GC-MS, Free radical, α-tocopherol INTRODUCTION involved in the pathogenesis of aging and many degenerative diseases such as cardio- Antioxidant compounds are abundantly vascular diseases and cancers (Virgili and available in plants and play an important Scaccini, 2003; Kris-Etherton et al., 2004). role in scavenging free radicals, thus pro- Numerous epidemiological studies have viding protection to humans against oxida- suggested a protective role of food poly- tive DNA damage (Ponnan et al., 2006). phenols on human health (Arts and Holl- Although an excess of Reactive Oxygen man, 2005). Recent studies have, however, Species, ROS (oxidative stress) can result stressed that the mechanisms of biological in non-controlled oxidation and damage of actions of polyphenols go beyond their cellular structures such as DNA, protein ROS scavenging and metal chelating prop- and membrane lipids. It is believed that the erties (Halliwell et al., 2005) but may also presence of ROS is essential in cells as they offer indirect protection by activating en- can act as key signaling molecules for the dogenous defense systems and by modulat- activation of the stress-responses and de- ing cellular signaling processes (Yang et fense pathways (Halliwell, 2006; Foyer and al., 2001; Feng et al., 2005). Noctor, 2005). In humans, the plant poly- Kigelia africana (Lam.) Benth. belongs phenols consumed through the diet are con- to the family of Bignoniaceae and has a sidered as effective protective agents wide geographical distribution in west and against the ROS, which are known to be 264 EXCLI Journal 2011;10:264-273 – ISSN 1611-2156 Received: October 24, 2011, accepted: November 23, 2011, published: November 30, 2011 central Africa. The tree grows on river- LUT/3525 at the Herbarium of Botany De- banks, wet areas along streams and on flood partment at the University of Lagos, Lagos, plains of Nigeria, Cameroon, Kenya, Nigeria. The root material was air dried and Guinea and Senegal. It can also be found in pulverized. open woodland from KwaZulu-Natal to Tanzania, Chad, Eritrea, South Africa and Chemicals Namibia (Ogbeche et al., 2002; Abioye et Gallic acid, α-Tocopherol, 1,1-diphe- al., 2003). The tree is widely grown as an nyl-2-picrylhydrazyl (DPPH) were obtained ornamental plant in tropical regions for its from Sigma-Aldrich (Germany), Folin- decorative flowers and unusual fruit that Ciocalteu, reagent, Na2CO3, aluminium conceived the name ‘sausage tree’ (Roodt, chloride, potassium acetate, phosphate buf- 1992). fer, K3Fe(CN)6, trichloroacetic, acid (TCA), The Bignoniaceae family is noted for ferric chloride, HCl, Dragendorff's reagent, the occurrence of iridoids, naphtho- potassium persulphate were obtained from quinones, flavonoids, terpenes, tannins, the chemical store of the Chemical Sciences steroids, coumarins, saponins and caffeic Department of the Redeemer’s University, acid in the fruits, stem, leaves and roots Nigeria, while bismuth nitrate, hexane, (Akunyili and Houghton, 1993; Houghton ethyl acetate and methanol were obtained et al., 1994; Moiden et al., 1999; Weiss et from the Chemistry Department of the Uni- al., 2000; Picerno et al., 2005; Bharti et al., versity of Ilorin, Ilorin, Nigeria. Solvents 2006; Asekun et al., 2007; Owolabi and were re-distilled before use. Omogbai, 2007). Though a large number of plants Instruments worldwide show strong antioxidant activi- A Gas Chromatography-Mass Spectros- ties (Baratto et al., 2003; Katalynic et al., copy, GC-MS system, GCMS-QP 2010 2006), there is no report to our knowledge PLUS (Shimadzu Japan) interfaced with a on the antioxidant properties of the root of finigan MAT ion trap detector ion source this plant in any experimental protocol. In Temperature, was used with the following view of this, we have investigated the in settings; 200 °C, interfaced Temp., 250 °C, vitro antioxidant effect of these extracts by solvent cut time; 2.50 min; relative detector DPPH assay and examined the phytochemi- mode, ACQ mode; Scan; start time – end cals in each extract. The plant root was se- time; 3.00 min – 46.00 min, event time, lected for the study because of the reported 0.50 sec; scan speed, 1428. Identification of phytochemicals which include iridoids, the volatile component was carried out us- naphthoquinones and coumarins among ing the peak enrichment technique of refer- others. The present study provides basic ence compounds and as final confirmation data on the natural antioxidant potential of of the peak identification by GC-MS, their Kigelia pinnata root for the food, pharma- spectral data were compared with those of ceutical or cosmetic industries, and also of- NIST library mass spectra. The infra red fers scientific reference for the large scale spectrum was recorded on a Shimadzu usage and exploitation of Kigelia pinnata as (8400s) Fourier Transform-Infrared Spec- a vital resource. troscopy (FT-IR) Spectrum spectropho- tometer using KBr pellets; UV spectra were EXPERIMENTAL recorded using Shimadzu (1600s) Spectro- photometer. Material and methods Root of mature growing Kigelia pinnata tree was obtained from Abeokuta metropo- Preparation of extract lis in Ogun state Nigeria during the dry sea- The scheme for the extraction is shown son and was taxonomically authenticated in Figure 1. The pulverized plant material and documented with the Voucher number weighing (420 g) was extracted exhaus- tively with n-hexane at room temperature 265 EXCLI Journal 2011;10:264-273 – ISSN 1611-2156 Received: October 24, 2011, accepted: November 23, 2011, published: November 30, 2011 for five days. The extract was decanted, fil- the method of (Ebrahimzadeh et al., 2008a, tered and concentrated under reduced pres- b). To 0.5 mL of each sample (two repli- sure using rotary evaporator to afford cates) of plant extract methanol solution 344 mg of a yellow oil which was coded (1 mg/mL) was added 2.5 mL of 10 % Fo- KPRH. The remaining plant material was lin-Ciocalteu reagent and 2 mL of Na2CO3 subsequently extracted with ethyl acetate (2 % w/v). The resulting mixture was incu- for five days. The ethyl acetate-extract was bated at 50 °C for 30 minutes. The absorb- decanted, filtered using a Whatman No.1 ance of the samples was measured at filter paper and concentrated in vacuo to 765 nm using UV/visible spectrophotome- yield 1.55 g of a reddish-brown extract ter. Concentrations for the extracts were coded KPRE. Finally, the remaining ex- extrapolated from a calibration curve of tracted plant material was extracted again gallic acid using the formula y = 0.646x. for five days with methanol. The methanol- Results were expressed as milligrams of extract was decanted, filtered and concen- gallic acid equivalent/gram of powder dis- trated in vacuo to yield 20.50 g thick black- solved in methanol. ish syrup coded KPRM. The extracts were stored in a cool dark place until further Determination of reducing power analysis. The reducing powers of the extracts KPR (420 g) were evaluated according to the method of Hexane Oyaizu (1986). The mixture containing 2.5 ml of 0.2 M phosphate buffer (pH 6.6) and 2.5 ml of K3Fe(CN)6 (1 % w/v) was KPRH (344 mg) PLANT MATERIAL added to 1.0 ml of the extract dissolved in Ethyl acetate distilled water. The resulting mixture was incubated at 50 °C for 20 min, followed by the addition of 2.5 ml of TCA (10 % w/v). KPRE (1.55 g) PLANT MATERIAL The mixture was centrifuged at 3000 g for Methanol 10 min to collect the upper layer of the so- lution (2.5 ml), mixed with distilled water (2.5 ml) and 0.5 ml of FeCl3 (0.1 %, w/v). KPRM (20.50 g) PLANT MATERIAL The absorbance was then measured at 700 nm against reference blank. Higher ab- Figure 1: Extraction schematics sorbance of the reaction mixture indicates higher reductive potential. Phytochemical screening of the plant ex- tracts Estimation of antioxidant activity A small portion of the dry extract was The antioxidant acivity was measured used for the phytochemical screening for using DPPH assay. This spectrophotometric compounds including tannins, phlobatan- assay uses the stable radical 1,1-diphenyl-1- nins, flavonoids, terpenoids, alkaloids, car- picrylhydrazyl (DPPH) as a reagent (Ama- diac glycosides, anthraquinone, saponins, rowicz et al., 2004).