Study On Extraction And Purification Of Flavonoids From Purple Sweet Potato And The Anti-oxidation Activity

Flavonoids were extracted from purple sweet potato with microwave-assisted method.The effection of extract concentration,ratio of solid/solvent(w/v),microwave reaction time and reaction temperature on the percentage of flavonoids extraction were investigated with L₉(3⁴) orthogonal experimental design. The best conditions forprocedure were extracting for 35 min at 80℃with 20 times of 70% ethanol.Theflavonoids extracted from purple sweet potato by MAE were 1.55% and compared with reflux extraction, microwave-assisted extraction had better performance.The extract was purified by macroporous adsorption resin,four types of macro-porous adsorption resins including D101, NKA-9,AB-8,NKA-â…¡were tested to purify flavonoids. Evaluated by static saturated adsorption ability and elution percentage,AB-8 was thought to be the most suitable type of macroporous adsorption resin. Evaluated by recovery,the influence of concentration of sample,pH,concentration of eluant and flow rate of elution had been investigated by orthogonal experimental design. Analysis of range and analysis of variance were used to determine the optimal parameters of the purification process,the results were:0.81 mg·mL^-1 as the concentration of sample, 2 as the pH value of washing , 70% ethanol aqueous solution as the eluant and 2 mL·min^-1 as the flow rate of elution. The anti-oxidation activity of the extract was evaluated by using methods of DPPH·,pyrogalIol autoxidation and phenanthroline with V_C as reference substance. The study showed that the anti-oxidation activity of the extract was stronger than that of V_C on O·₂^- and·OH, IC₅₀ were 0.0374 mg·mL^-1 and 0.105 mg·mL^-1 ; but it was weaker on DPPH·, IC₅₀ was 0.0204 mg·mL^-1.HPLC and Infrared Spectroscopy were used to analyze the components and structures of flavonoids and gave us more information about them.