Study on extraction,purification and antioxidant activity of tannins of Eucalyptus Citriodora bark

Extracted tannin from Eucalyptus Citriodora bark by solvent method. The crude extract of tannin was purified by macroporous resin adsorption. And the total antioxidant activity, the ability of removal DPPH· and ·OH radical of different samples were examined. The optimum extraction conditions of tannin from Eucalyptus Citriodora bark were as follow:extraction temperature was 60℃, extraction time was 150 min, the ethanol volume fraction was 40% and the solid-liquid ratio was 1:50. The optimum adsorption and separation for the crude extract on HPD826 macroporous resin were as follow:the feed concentration of 1.33 mg/mL with flow rate of 1.0 mL/min, the desorption solvent was 50% ethanol with flow rate of 1.0 mL/min. The purified of the ethyl acetate extract, macroporous resin purification substance, ethyl acetate residue purified by macroporous resin, ethyl acetate extracts purified by macroporous resin were 39.91%, 47.97%, 72.43% and 76.90%;the total antioxidant activity of ethyl acetate extract was the highest, 116.88% for tannins. when the mass concentration was 10 μg/mL, the clearance rate for tannin to DPPH· in all different concentration was the highest. the clearance rate were 62.53%、65.11%、58.80%、69.37%、79.63%, the clearance rate for tannin to ·OH in all different concentration was the highest, the clearance rate were 83.08%、70.55%、77.53%、65.37%、77.46% when the mass concentration was 0.01 mg/mL.The results showed that the antioxidant capacity of ethyl acetate extract, macroporous resin purification substance, ethyl acetate extracts purified by macroporous resin and crude extract were stronger than ethyl acetate residue purified by macroporous resin.