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 E5. From the results of spectroscopic data, including EIMS, FABMS, UV, IR, 1H and 13C-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)-β-D-glucopyranoside named vanilloylicariside E5. All isolated compounds were tested for antioxidant activities using 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. Icariside E5 (2) and (8R)-Isodehydrodiconiferyl alcohol (3) exhibited a strong scavenging effect on DPPH (2: IC50=42.1 µM, 3: IC50=4.5 µM).