Apocynins A-D : New Phenylpropanoid-substituted Flavan-3-ols Isolated from Leaves of Apocynum venetum (Luobuma-Ye)

Abstract

Four new phenylpropanoid-substituted flavan-3-ols called apocynins A-D (1-4) have been isolated from the leaves of Apocynum venetum (Apocynaceae), together with two known phenylpropanoid-substituted flavan-3-ols, catechin-[8, 7-e]-4α-(3, 4-dihydroxyphenyl)-dihydro-2(3H)-pyranone (5) and cinchonain I1 (6), and four known flavan-3-ols, (-)-epicatechin, (+)-catechin, (-)epigallocatechin, and (+)-gallocatechin. Their structures were elucidated on the basis of spectral analysis, including 2D NMR and CD spectra. They showed hepatoprotective activity against D-galactosamine (D-GaIN)/tumor necrosis factor-α(TNF-α)-induced cell death in primary cultured mouse hepatocytes.