Cytotoxic pregnane glycosides from <i>Monolluma quadrangula</i> (Forssk.)

<i>Monolluma quadrangula</i> (Forssk.) is a medicinal succulent plant belonging to the family Apocynaceae. The phytochemical examination of <i>M. quadrangula</i> methanolic extract resulted in isolation of three unique new pregnane glycosides, quadrangulosides G-I (<b>1-3</b>), their structures were elucidated utilising 1D, 2D NMR and ESI MS spectral studies. Pure sixteen isolated pregnane glycosides from <i>M. quadrangula</i> were tested for cytotoxicity against breast cancer cell lines (MCF-7) and colon cancer cell lines (HCT-116), using MTT assay and doxorubicin as a positive control. From these compounds russelioside B and quadranguloside E displayed the most potent cytotoxic effect with IC₅₀ values of 0.18, 0.22 μM and 0.56 and 0.12 μM, respectively.