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Cholinesterase-inhibiting withanolides from Ajuga bracteosa
1International Centre for Chemical Sciences, H.E.J. Research Institute of Chemistry, University of Karachi, Karachi-75270, Pakistan.
Abstract:
Three new withanolides, bracteosin A (= (22R)-5beta,6beta : 22,26-diepoxy-4beta,28-dihydroxy-3beta-methoxyergost-24-ene-1,26-dione; 1), bracteosin B (= (22R)-5beta,6beta : 22,26-diepoxy-4beta,28-dihydroxy-3beta-methoxy-1,26-dioxoergost-24-en-19-oic acid; 2), and bracteosin C (= (22R)-22,26-epoxy-4beta,6beta,27-trihydroxy-3beta-methoxyergost-24-ene-1,26-dione; 3), have been isolated from the whole plants of Ajuga bracteosa. Their structures were deduced by spectral analysis, including 1D- and 2D-NMR techniques. In addition, dihydroclerodin-1, clerodinin A, lupulin A, and dihydroajugapitin have also been isolated for the first time from this species. Compounds 1-3 exhibited evident inhibitory potential against cholinesterase enzymes in a concentration-dependent fashion.
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