Antioxidant activity of different extracts of lotus (Nelumbo nuficera Gaertn) rhizome by gradient solvent extraction

In vitro antioxidant activity of extracts of lotus rhizome with different solvent by gradient extraction was determined. The extraction yield and total phenolic content of extracts were determined. 1,1-diphenyl-2-picrylhydrazyl hydrate (DPPH) radical scavenging assay and β-carotene-linoleic acid assay were conducted to assess the antioxidant activity of the extracts. Results showed that the yield of butanol extract was the highest. The order of total phenolic content in different extracts was as follows: water extract < petroleum ether extract < chloroform extract < butanol extract < ethyl acetate extract, the same with that of the DPPH scavenging activity. The total phenolic content was significantly correlated with DPPH scavenging activity (R2 = 0.9363). All extracts, except water extract with too poor antioxidant activity, showed obvious antioxidant activity against β-carotene-linoleic acid, and the antioxidant activity of butanol extract was significantly lower than others. There was no significant correlation between the antioxidant activity against β-carotene-linoleic acid and the total phenolic content (R2 =0.1995).