Cholinesterase inhibiting withanolides from Withania somnifera

Abstract

A total of two new (1, 2) and four known (3-6) withanolides were isolated from the whole plant of Withania somnifera. Their structures were elucidated on the basis of spectroscopic techniques and were characterized as 6α,7α-epoxy-3β,5α,20β-trihydroxy-1-oxowitha-24- enolide (1), 5β,6β-epoxy-4β,17α,27-trihydroxy-1-oxowitha-2, 24-dienolide (2), withaferin-A (3), 2,3-dihydrowithaferin-A (4), 6α,7α-epoxy-5α,20β-dihydroxy-1-oxowitha-2,24-dienolide (5), and 5β,6β-epoxy-4β-hydroxy-1-oxowitha-2,14,24-trienolide (6), respectively. Compounds 2, 3, 5, and 6 displayed inhibitory potential against butyrylcholinesterase, but only compounds 3, 4, and 6 were found to be active against acetylcholinesterase. © 2004 Pharmaceutical Society of Japan.