Optimization of Purification of Flavonoids from Aloes Leaves with Macroporous Resin and Comparison of Antioxidant Capacity of Crude and Purified Flavonoids

The purification of flavonoids extracted from aloes leaves by macroporous resin and its antioxidant activity were studied. Based on the static and dynamic experiments,the influence of resin type,crude extract concentration,eluent,loading flow rate and elution flow rate on the adsorption and desorption properties of flavonoids from aloes leaves were investigated to determine the optimal purification conditions. Comparison of antioxidant activity of crude and purified flavonoids from aloes leaves was evaluated by three different methods which were hydroxyl,DPPH and ABTS free radical scavenging assay.NKA-9 was the most suitable type of macroporous resin and the optimum conditions were as follows:The optimal purification conditions were as follows:5.0 mg/mL sample concentration was applied to the column at flow rate of 1.5 mg/mL,and 70%(v/v)alcohol was used to elution with eluanting velocity of 2.0 mL/min. Under these conditions,the purity of flavonoid extracted from aloes leaves increased to 76.58%±3.46%. The IC₅₀ of the final purified product for scavenging hydroxyl,DPPH and ABTS and free radicals were(0.120±0.008),(0.016±0.009),(0.042±0.002) mg/mL respectively,they were much lower than the corresponding results which showed(0.300±0.015),(0.170±0.008),(0.160±0.009) mg/mL of crude flavonoids. The results suggested that the flavonoids from aloes leaves revealed strong antioxidant activity before and after purification,and the antioxidant activity was much stronger after purification. NKA-9 macroporous resin was suitable for separation and purification of flavonoids from aloes leaves.