Ring A structural modified derivatives of withaferin A and the evaluation of their cytotoxic potential

► Regio-/stereoselective Michael addition to ring A of withaferin-A. ► Structural modification along ring A has profound effect on in vitro cytotoxicity. ► Nature of the substituent at C-3 is the determining factor for cytotoxicity. ► 3-Azido analogue exhibited 35-fold increase (IC50 = 0.02-1.9 μM) in cytotoxicity.