CHARACTERIZATION OF TANNIN EXTRACTED FROM BARK OF ACACIA PLANT RESEARCH DONE BY JAMES MUNENE SCH/B/01-02167/2019 DEPT OF PURE AND APPLIED CHEMISTRY SUPERVISED BY: DR JOSEPH OWINO INTRODUCTION • Acacia xanthophloea is a medium sized tree with spreading branches and a smooth greenish yellow bark, belong to the fabaceae family. • Tannins are obtained from renewal sources i.e secondary metabolism of plants and mostly found in barks, seeds and roots • Tannins are mainly classified into two i) condensed tannins - comprises flavonoids without a sugar core ii) Hydrolyzable tannins -comprises of ellagic and gallic acids with glucose as the sugar core. • polar solvents such as water, methanol and ethanol are best for tannin extraction. BACKGROUND • During the first and second industrial revolutions, tannin was mostly used for tanning skin into leather • But gradual human revolution enhanced use of synthetic alternatives in the leather industry and other fields • This has led to high cost of industrial waste water treatment • Industries need to find alternative natural sources for their raw materials OBJECTIVE • To extract tannin from acacia bark, characterize it and determine it reaction with proteins RESEARCH QUESTIONS • can tannin be extracted from the bark of acacia plant? • is the prepared tannin sample volatile? • what are the main applications of tannin? METHODOLOGY • EXTRACTION OF TANNIN • Sample collection and preparation The acacia bark sample was collected from menegai Nakuru • The bark was thoroughly cleaned and then air dried for five days. • it was cut into small pieces and crushed by mortal to obtain a powder • The powder was parked in thimbles and Soxhlet apparatus was be set up for extraction for 4 hours employing ethanol as the solvent • Sample concentration The crude extract was taken to rotary evaporator for concentration. CHARACTERIZING THE TANNIN ferric chloride test 5ml of sample extract was placed in a test tube and aqueous iron (iii) chloride added drop wise while shaking and color changed to blue black ferrous chloride test results Match stick test A match stick was dipped in the aqueous tannin extract, dried near the burner, and was moistened with conc HCl. On warming near the flame, the matchstick wood turned pink due to the formation of phloroglucinol. match stick after warming near a flame Egg albumin precipitation Albumin was attained from an egg after gently separating it from the York The egg albumin, 5ml was placed in a test tube and the sample extract was added gently while shaking and a white precipitate was formed. Cotton fabric test A small piece of cotton wool was soaked in 20% HCl, rinsed with distilled water, and placed in the solution of tannin for 5 minutes. The cotton piece was washed with distilled water and kept in a solution of ferrous sulfate. Brown and blue-black color was produced. DISCUSSION • metal-tannin complex (coagulat) are used for treatment of waste water to remove pollutants including turbidity, colorants and suspended solids. • Tannin solution is used as corrosion inhibitor. Tannins also posses high mechanical strength and weather resistance and are utilized as primary resins • Egg albumin precipitation by tannin is the idea employed in leather processing for converting skin into leather by treating it with acidic medium. • cotton fabric, tannin dyeing characteristics. CONCLUSION • soxhlet extraction displayed good result at reduced extraction time • Bark of acacia xanthophloea was identified as source of tannins • Hydrolysable tannins were in more percentage than condensed tannins REFERENCES 1. Heidman. G,., 1993. Bark extract in adhesives.., 53,p. 111. 2. Miekeley, A., 2012. Action of acid on tanned leather. Collegium 786, 456–463. 3. Narayanamurti, D., Das, N.R., 2018. Tanninformaldehyd-kleber. Kunststoffe 48, 459– 462.
