Pregnane steroids and steroid glycosides with multidrug resistance reversal activity from Marsdenia tenacissima

ABSTRACT Twenty compounds comprising four pregnane steroids ( 2 – 4 & 20 ) and 16 pregnane glycosides ( 1 & 5 – 19 ) have been obtained from the ethanol extract of the roots of a Dai ethnological herb, Marsdenia tenacissima . Their structures were characterized on the basis of comprehensive spectroscopic analyses with 17 ones ( 1 – 17 ) being reported for the first time, including the rare cases ( 2 & 3 ) of free C 21 steroids with 17α-acetyl substitution, compounds 4 – 7 bearing an unusual 14α-OH, and the first examples with simultaneous 14α-OH/17α-acetyl substitution ( 7 ) and glycosylation at C-12 position ( 10 & 11 ). An empirical rule for the identification of C-17 configuration, in C 21 steroids incorporating the marsdenin constitution structure, was also proposed. All the isolates, along with an array of previously reported analogues in our compound library, were screened for their chemo-reversal ability against P-glycoprotein (P-gp)-mediated multidrug resistance (MDR) in MCF-7/ADR cell line, and six compounds exhibited moderate MDR reversal activity with reversal folds ranging from 1.92 to 4.44.