Abstract:

The contents of extractable condensed tannins(ECT) in Cercis chinensis, Cercis gigantea leaves and pods were determined. The chemical structure were analyzed by nuclear magnetic resonance(NMR) combined with reversed-phase high performance liquid chromatography-mass spectrometry(RP-HPLC-MS), and the antioxidant activities were determined by DPPH scavenging assay and ferric reducing/antioxidant power(FRAP) assay. The results showed that the mass fractions of tannins in C. chinensis, C. glabra leaves and pods were 151.56, 96.75 and 198.12 mg/g, respectively. The structural units of flavan-3-ols which constituted three condensed tannins, were mainly procyanidin and prodelphidin, and there were galloacylated structures at the C3 position in their structural unit. All three condensed tannins had certain antioxidant activity. The median inhibitory concentration(IC₅₀) values of the three condensed tannins for scavenging DPPH free radicals(DPPH·) were 67.02-97.70 mg/L, which were all higher than that of positive control BHA. The FRAP values of three condensed tannins was 3.51-5.56 mmol/g at the mass fraction of 125 mg/L, which were lower than the positive control BHA(6.51 mmol/g). Among them, the tannins of C. chinensis leaves showed excellent antioxidant activity, and its IC₅₀ values of clearance rate of DPPH· was 67.02 mg/L, which was better than the positive control Vc(76.65 mg/L). Meanwhile, its FRAP value was 5.56 mmol/L.

Key words: Cercis chinensis, Cercis gigantea, condensed tannin, ¹³C NMR, RP-HPLC, antioxidant activity