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ChemInform Abstract: Five New Withanolides from Withania coagulans.
Since the isolation of the first withanolides in the mid-1960s, over 600 new members of this group of compounds have been described, with most from genera of the plant family Solanaceae. The basic structure of withaferin A, a C28 ergostane with a modified side chain forming a δ-lactone between carbons 22 and 26, was considered for many years the basic template for the withanolides. Nowadays, a considerable number of related structures are also considered part of the withanolide class; among them are those containing γ-lactones in the side chain that have come to be at least as common as the δ-lactones. The reduced versions (γ and δ-lactols) are also known. Further structural variations include modified skeletons (including C27 compounds), aromatic rings and additional rings, which may coexist in a single plant species. Seasonal and geographical variations have also been described in the concentration levels and types of withanolides that may occur, especially in the Jaborosa and Salpichroa genera, and biogenetic relationships among those withanolides may be inferred from the structural variations detected. Withania is the parent genus of the withanolides and a special section is devoted to the new structures isolated from species in this genus. Following this, all other new structures are grouped by structural types.
Phytochemical studies on the aerial parts of Withania somnifera L. Dunal. (Solanaceae) led to the isolation of a chlorinated steroidal lactone (27-acetoxy-4β,6α-dihydroxy-5β-chloro-1-oxowitha-2,24-dienolide), a diepoxy withanolide (5β,6β,14α,15α-diepoxy-4β,27-dihydroxy-1-oxowitha-2,24-dienolide), and withaferin A. Their structures were elucidated by using spectroscopic techniques. All three compounds exhibited a growth inhibition and cytotoxic activity against human lung cancer cell line (NCI-H460), with withaferin A being the most potent (GI(50)=0.18 μg/mL and LC(50)=0.45 μg/mL) among three compounds tested.
Phytochemical studies on the whole plant of Withania coagulans have resulted in the isolation of five new withanolides, namely coagulins H, I, J, K and L (1-5). Their structures have been established as (17S,20S,22R)-5α6β,14α,15α,17,20-hexahydroxy-1-oxowitha- 2,24-dienolide (1), (14R,17S, 20S,22R)-5α6β,17-trihydroxy-14,20-epoxy-1-oxowitha-2,24-dienolide(2), (14R, 17R,20R,22R)-3β,27-dihydroxy-14,20-epoxy-1-oxowitha-5,24-dienolide (3), (14R,17R,20R,22R)-14,20-epoxy-3β-(O-β-D-glucopyranosyl)-1-oxowitha-5, 24-dienolide (4) and (14R,17S,20S,22R)-14,17,20-trihydroxy-3β-(O-β-D-glucopyranosyl)-1- oxowitha-5,24-dienolide (5), respectively on the basis of spectroscopic techniques.