23 Evaluation of Potential Application for Sunt Pod Extracts (Acacia Nilotica) in Leather Tanning by A. I. Nasr,1* H. Mueller,2* M. M. Abdelsalam,3 A. H. Azzam,1 C. Jungandreas2 and W. Poppitz4 1Department of Wool Production and Technology, Desert Research Center Mathaf El-Matarya St. 1, P.O. Box: 11753-Matariya, Cairo, Egypt. 2Institute of Textile and Leather Technology, University of Applied Sciences Zwickau Klinkhardtstrasse 30, 08468 Reichenbach, Germany. 3Department of Animal Production, Faculty of Agriculture, Alexandria, Egypt. 4Institute of Inorganic and Analytic Chemistry, Friedrich-Schiller-University, Humboldtstrasse 8, 07743 Jena, Germany. Abstract weight polyphenolic compounds rich in phenolic groups. Industrially, tannins are used in the production of leather, The current investigation was carried out to evaluate the adhesive material, dyestuff and ink. Also, due to their astringent efficiency of using sunt, Acacia nilotica, pods extract in leather properties, tannins are used as medicinal materials which tanning. Skins from 16 Barki rams aged 12-18 months were promote rapid healing and formation of new tissues on wounds 1 cured and prepared for tanning using sunt pod extract. The and inflamed mucosa. sunt pods were collected and dried at 25 °C for 5 days. st Thereafter, the dried pods were ground by a 0.3 mm fineness New tannages for the 21 century are aiming to decrease the grinder and were further subjected to the extraction procedure. tanning pollution effect by using environmental-friendly tanning procedures. In this regard, vegetable tanning is Three chemical additives, namely NaOH, Na2SO3 and Na2CO3 were used for the extraction at 70 and 90oC. The influences of considered one of the recent tanning techniques used worldwide. both types of chemical additive and extraction temperature on However, the currently available vegetable tanning agents are 2 extraction yield were determined. The extract characteristics insufficient to tan the current supply of hides. Therefore, the in terms of stiasny number, hide powder, tannins, non-tannins leather industry in Egypt relies mainly on chrome tanning, as and total phenol contents were also analyzed. The results well on mimosa or quebracho tannin extracts. showed that increasing extraction temperature increased (P<0.05) extraction yield and improved the quality of the In Egypt there are many indigenous and exotic plant species, extract regardless of chemical additive type. Meanwhile, the which contain variable concentrations of tannins. Some of these extraction using either Na SO in aqueous solution or by water plants have been analyzed, although no systematic screening has 2 3 3 at 90°C yielded the best extract characteristics. The elevated been completed. Acacia nilotica (Sunt in Arabic) is a member of 4 concentrations of condensed and hydrolysable tannins the subfamily Mimosaoideae of Leguminous trees. The tree is obtained in our results point to the possibility of utilizing sunt characterized by the long white spines, yellow head inflorescence 5 pod extract in tanning or re-tanning of leather rather than and the gray necklace-like pods. It has multiple uses in Africa 3 using traditional tanning reagents. and many Arab countries because it is abundant. Sunt is traditionally used for tanning in tropical Africa in a primitive way, and is one of the most important tanning materials in Introduction Northern India.6,7 Although both pods and bark of Acacia nilotica contain high concentrations of tannins, the tannin The term “tannin” was first introduced in 1796 and came from percent using pods extract is more efficient than that extracted 3,5,6,8,9 the use of these compounds in tanneries. Tannins containing from the bark, and ranges from 26 - 70%. plant extracts have been used to process animal skin into leather since ancient times. Tannins are water-soluble high molecular * Corresponding authors e-mail: [email protected], [email protected] Manuscript received April 24, 2016, accepted for publication September 11, 2016. JALCA, VOL. 112, 2017 Sunt Pod (Acacia Nilotica) Extracts 24 Extraction solvent, temperature, time and alkaline additives are after adding different chemical additives.11,13 A 2-L Pyrex glass important factors when extracting phenolic compounds, due to reactor integrated with mechanical stirring and automatic their impact on both extraction yield and extract quality.10-14 temperature control was used for extraction. The solid / liquid However, sulfitation is one of the oldest techniques used for ratio was maintained constant at 1/10 (w/w). The extraction extraction of tanning reagents, increasing the extraction yield of procedure was conducted either by water only or after adding tannins with improved solubility and lower viscosity.14 The use sodium hydroxide, sodium sulfite or sodium carbonate in of solvents other than water on an industrial scale can be aqueous solution to 0.25% dry plant material weight. The problematic especially in the areas of pollution, recycling and extraction temperatures were set at 70 and 90°C. Ground cost.12,13 material and water were mixed at room temperature, heated and, once the selected temperature was attained, the chemical Generally in vegetable tanning raw materials, the low-molecular additive was added and contact timing started. After one hour tanning substances are converted into higher condensed the warm suspension was vacuum filtered, whereas the solid products when plant life stops. Therefore, either extraction with residue was washed with water. The extracts, together with the water only or after adding small quantities of sulfites enough to first water washings, were further dried in an oven at 70°C. The yield weakly acid or even weakly alkaline extracted liquors is extraction yield was calculated as the percent of weight loss of hampered. Alkali or more substantial quantities of sulfites in the starting raw material. weakly acid or alkaline medium dissolve the high-molecular tanning materials. This may result in a reduction of the Total Phenol and Tannins Content molecular size or their sulfonation. Therefore the alkaline Total phenol content was determined by the Folin–Ciocalteu extraction is a more gentle way than any violent processes, such method.17 Briefly, 0.5 mL of an aqueous solution of the extract, as, extraction under pressure. Moreover, sulfite-alkali mixtures 2.5 ml of Folin–Ciocalteu reactive, previously diluted with for example sodium sulfite and sodium hydroxide, are used to water (1:10, v/v) and 2mL of a 75 g/l sodium carbonate aqueous improve the extraction conditions for a reaction between the solution were added. The mixture was kept at 50°C for five sulfite and the tanning materials.15 On the other hand according minutes and, after cooling, the optical density was measured at to literature16 when extracting the bark with weak alkaline 720 nm. The phenols content was calculated as a tannic acid solutions or in the presence of sulfite and bisulfite, the pyran equivalent (TAE) from the calibration curve of tannic acid rings of polyphenols are partly cleaved with the formation of standard solutions (2–40 g/ml) and expressed as g TAE/100 g carboxylic groups and sulfonic acids. Therefore, the solubility of of extract based on dry basis. Polyvinylpolypyrrolidone (PVPP) phlobaphens increases considerably. was used to bind tannin-phenolics for measurement of tannins, then non-tannins were determined and tannins were The current investigation aimed to evaluate the possibility of calculated. using Acacia nilotica pods extract, obtained by different reagents at different temperatures, in leather tanning. The extract Hide Powder Test characteristics in terms of stiasny number, hide powder, tannin, Samples (400 mg) of each extract were dissolved in 100 ml of non-tannins and total phenol contents were also analyzed. distilled water. Slightly chromated, previously dried hide- powder (3 g) was added and the mixture was stirred for one hour at an ambient temperature. The suspension was filtered Experimental without a vacuum through a sintered glass filter. The weight gain of the hide-powder was expressed as a percentage of the Raw Material initial weight of the starting material.13 Sunt pods were collected from Shalatin region in south of Egypt, and were directly transported to Mariout Research Stiasny Number Station in Alexandria, where they were dried at 25±2°C for five Samples (100 mg) of each extract were dissolved in 10 ml of days in an open and shaded place without using any thermal distilled water. 1 ml of 10M HCl and 2 ml of formaldehyde drying methods. Thereafter, the dried sunt pods were ground (37%) were added and the mixture heated under reflux for 30 by a 0.3 mm fineness grinder and stored in paper bags until minutes. The reaction mixture was filtered through a sintered extraction. glass filter while hot. The precipitate was washed with hot water (5x 10 ml) and dried. The yield of tannin was expressed Extraction Procedure and Experimental Design as a percentage of the initial weight of the starting material.13 Extraction steps were performed in the chemical laboratory of the Institute of Textile and Leather Technology, Reichenbach, Fourier Transform Infrared Spectrometry (FTIR) Germany. Moisture was determined in the ground material, The Bruker alpha FT-IR Spectrometer was used to analyze the then extraction steps were done using either hot water only or changes in the chemical structure of the different plant JALCA, VOL. 112, 2017 25 Sunt Pod (Acacia Nilotica) Extracts material extracts. Low quantities of the extracts were used in Result and Discussions the solid phase and scanned directly on the instrument stage by diamond ATR equipment. The data presented in Table I shows the results obtained for extraction yield and extract properties for sunt pods. The Mass Spectroscopy (MS) highest extraction yield was obtained using NaOH and Na2SO3 One gram of the water extracts was sent to the Institute of aqueous solutions (61.37%), while the lowest was obtained by Inorganic and Analytical Chemistry, Jena, Germany.