Preparative Isolation And Purification Of Flavone Compounds From Bamboo Leaves And Examination Of Antioxidant Activity

Flavonoids from bamboo leaves has multiple biological effects, such as anti-free radical, anti-oxidation, anti-aging, anti-fatigue, anti-bacteria, anti-virus, and prevention of cardiovascular-diseases. The aim of this dissertation is to establish a practical method for-the isolation and purification of flavone compounds from bamboo leaves and examination of the antioxidant activity.First, the Box-Behnken design combined with response surface methodology was used to optimize the organic solvents extraction and aqueous two-phase extraction conditions of flavonoids of bamboo leaves. The optimum solvent extraction conditions were as follows:(n-butyl alcohol/ethyl acetate(9:1))/crude extract solution/acetic acid=3.1:1:0.1, extraction time 15 min, temperature 70℃. Under this condition, the purity is 36.9%, and extraction rate is 91.3%. The optimum aqueous two-phase extraction condition were prepared by 31%PEG 400 and 11% (NH4)2 SO4, pH value 3.9, NaCl 0.7%, temperature 20℃and crude extract solution 51.5%. Under this condition, the extraction rate is 97.8%. Comparative economic benefits of two extraction methods, organic solvents extraction method is more appropriate for industrialization.Then, the separation and enrichment of flavonoids from bamboo leaves were studied on ten macroporous resins. The performance of flavonoids from bamboo leaves on macroporous resins was compared according to their-adsorption and desorption properties. H103 provided a much higher-adsorption capacity for flavonoids from bamboo leaves than other-resins, and its adsorption data fitted well to the Langmuir-and Freundlich isotherm. In order to optimize parameters of separation, dynamic adsorption and desorption experiments were carried out on the columns packed with H103 resin. The optimal conditions were:16mg·mL-1 crude extract solutions at the flow rate 1mL·min-1; the optimal solution for-the adsorption was water with 1BV,20% ethanol with 1BV and 20% ethanol with 4BV at the flow rate of 1.0 mL·min-1. The purity of flavonoids was 77.7%.Last, the antioxidant activity of total flavonoids from bamboo leaves was determined by three assays. The results showed that flavonoids from bamboo leaves have very strong scavenging capabilities for-superoxide anion and DPPH free radical, the low purity's EC5o values are 11.7μg·mL-1 and 18.3μg·mL-1 respectively, and are approximately 1.2 times and 3.4 times as much as that of vitamin C respectively, the high purity's EC50 values are 10.4μg·mL-1 and 15.1μg·mL-1 respectively, and are approximately 1.1 times and 2.8 times as much as that of vitamin C respectively. The scavenging capability of bamboo leaves flavonoids for·hydroxyl radical is stronger-than that of vitamin C, weaker-than tea polyphenol, and the low purity's EC50 is 0.58 mg-mL-1, the high purity's EC50 is 0.54mg·mL-1.