Seven undescribed steroidal glycosides with CYP3A4 inhibitory activity from the stems of Marsdenia tenacissima.

Seven undescribed steroidal glycosides (compounds 1-7) and nine known glycosides (compounds 8-16) were isolated from the ethyl acetate fraction of Marsdenia tenacissima, which is frequently utilized as an adjunctive treatment alongside conventional chemotherapy for various solid tumors in clinical practice in China. All of these compounds are naturally occurring polyoxypregnane glycosides, except for compound 5, which possesses a unique aglycone skeleton with a conjugated moiety. The structural elucidation of these compounds was achieved through comprehensive spectroscopic analysis and electronic circular dichroism (ECD) calculations. An integrated strategy combining network pharmacology and molecular docking revealed that cytochrome P450 3A4 (CYP3A4) is closely associated with multidrug resistance. The inhibition activities of cytochrome P450 enzymes were assessed using a cocktail-probe assay, and the inhibition of CYP3A4 was further validated using a single-substrate assay in pooled human liver microsomes. All isolated compounds exhibited statistically significant inhibitory effects on CYP3A4 enzymatic activity. The steroidal glycosides derived from M. tenacissima are expected to serve as novel inhibitors of CYP3A4, thereby enhancing the therapeutic efficacy of chemotherapeutic agents that are substrates of this enzyme.