Antioxidant Activity of Chemical Constituents Isolated from Pithecellobium clypearia

Phytochemical investigation of the aqueous extract of Pithecellobium clypearia afforded one n ovel compound, clypearoside A(1), and one new stereoisomer , (-)-(2S,3S)-epigallocatechin-7-gallate(2) and four known ones (3-6). Their structures were elucidated on the basis of spectroscopic data, especially 2D NMR, HRESIMS and ECD spectra. Compounds 2-4 showed strong activity against DPPH (diphenylpicrylhydrazyl) and ABTS (2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonate) with an IC 50 value of 11.9-13.2 μg/mL (DPPH) and 4.5-6.4 μg/mL (ABTS).