| Abstract
| - Two Dunaliabrachyacantha specimens collected at different locations in Argentina were investigatedseparately. The 18,20-hemiacetal-type withanolides (17S,20R,22R,24S,25R)-4β-acetyloxy-5β,6β:18,20-diepoxy-18-hydroxy-1-oxowitha-2-enolide (1) and (17S,20R,22R)-4β-acetyloxy-5β,6β:18,20-diepoxy-18-hydroxy-1-oxowitha-2,24-dienolide (2) were isolated from the first collection, both as mixtures epimericat C-18. The second collection contained instead (17R,20S,22R)-5β,6β-epoxy-4β,16α-dihydroxy-1-oxowitha-2,24-dienolide (3); (17R,20S,22R)-5β,6β-epoxy-4β,18-dihydroxy-1-oxowitha-2,24-dienolide (4), and (17R,20S,22R)-5β,6β-epoxy-4β,16α-dihydroxy-1,18-dioxowitha-2,24-dienolide (5). All five new withanolides (1−5) bear an A and B ring substitution pattern similar to that of withaferin A, and their structural elucidationwas achieved by spectroscopic techniques.
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