A-type doubly linked proanthocyanidin trimer and other metabolites from Canthium venosum fruits, and their biological activities

Abstract

Phytochemical investigation of Canthium venosum fruits led to the isolation of a new doubly linked A-type proanthocyanidin trimer: epicatechin-(2β→O→7, 4β →8)-catechin-(5→O→2β, 6→4β)-epicatechin [venosumtannin A-1 (1)], along with twenty known compounds 2-21. Allyl (9a) and acetyl (9b) derivatives of 9 were prepared. The structures of compounds were established using comprehensive spectroscopic analysis including 1D NMR, 2D NMR (COSY, HMQC, HMBC, and NOESY) and circular dichroism (CD), and by comparison with the corresponding literature data. The antioxidant, cytotoxic, acetylcholinesterase and antibacterial activities of some of the isolated compounds were investigated. In the acetylcholinesterase inhibitory activity test, compounds 2 and 9 (IC50: 0.03 ± 1.22 × 10−3 and 0.04 ± 1.23 × 10−3μM) were more active than the references (eserine and tacrine; IC50: 0.77 ± 1.84 × 10−3 and 0.15 ± 1.04 × 10−3 μM respectively).