Anti-obesity and antioxidant activity of dietary flavonoids from Dioscorea steriscus tubers

Objective: To investigate antioxidant and anti-obesity activity of flavonoids extracted by solvent cold percolation and preparative thin liquid chromatography from Dioscorea steriscus tubers. Methods: 1-diphenyl-2-picrylhydrazyl (DPPH) antiradical activity was employed to investigate antioxidant activity while chromogenic method was used to determine alpha amylase inhibition activity and spectrophotometric methods using triolein as a substrate was used to investigate lipase activity. Results: Thin liquid chromatography profiling revealed eight different flavonoid types. Ethyl acetate extract yielded two types, Rf values 0.38 and 0.40; chloroform extract also yielded two types Rf values 0.06 and 0.51, while ethanol extract yielded four types with Rf values 0.16, 0.33, 0.65 and 0.96. All the extracted flavonoids exhibited antioxidant activity with ethanol extracts exhibiting the greatest antiradical activity. The order of enzyme inhibition capacity was ethyl acetate<chloroform<ethanol. Ethanol extract exhibited significantly greater anti-obesity activity as compared to herbex, a commercially anti-obesity medication sold in drug stores. Anti-α amylase activity and anti-lipase activity for herbex was (78.38依0.02)% and (76.07依0.09)% respectively, while that for ethanolic extract (Rf=0.96) was (93.66依0.00)% and (95.88依0.13)%. Conclusions: Results of the present study show that Dioscorea steriscus consists of bioactive compounds that can act as lipase and α-amylase inhibitors and therefore can be useful for the development of functional foods against obesity. It can also be used as a source of lead compounds for designing new ant-obesity therapeuticals.