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Reciprocal crossbreeding between Withania somnifera chemotype III (Israel) and chemotype Indian I (Delhi) were performed. The F1 offspring of this cross was characterized by significant changes in the main steroidal lactone constituents of the parent plants. From the withaferin A (9) and the withanone (2) both present as major constituents in the parent Indian I, the former had disappeared in the hybrid and was replaced by withanolide D (10), whereas the latter was still present, though in about one third of the original quantity. It was accompanied by 17-deoxy-20-hydroxy withanone (2) and by withanolide T (1); the enzymatic system leading to hydroxylation at C20 (20αF-OH) has a dominant character. Two new withanolides have been isolated from this F1 offspring, namely withanolide T (1) (20αF-hydroxy withanone) and withanolide U (5) (4β-hydroxy-withanolide G). The structures assigned to these two new compounds are based on spectral evidence (NMR, IR and UV) and analysis of their fragmentation under electron impact. |
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