Lignans from the fruits of the red pepper (Capsicum annuum L.) and their antioxidant effects.

The fruits of Capsicum annuum were extracted using 80% aqueous MeOH, and fractionated using EtOAc and water. Repeated column chromatography using silica gel, octadecyl silica gel, and Sephadex LH-20 for the EtOAc fraction led to the isolation of a new lignan glycoside and a known one, icariside E(5). From the results of spectroscopic data, including EIMS, FABMS, UV, IR, (1)H and (13)C-NMR, DEPT, and 2D-NMR (COSY, HSQC, HMBC), the chemical structure of the new lignan glycoside was determined as (8R)-isodehydrodiconiferyl alcohol-4'-O-(6''-vanilloyl)-beta-D-glucopyranoside named vanilloylicariside E(5). All isolated compounds were tested for antioxidant activities using 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. Icariside E(5) (2) and (8R)-Isodehydrodiconiferyl alcohol (3) exhibited a strong scavenging effect on DPPH (2: IC(50)=42.1 microM, 3: IC(50)=4.5 microM).