Sutherlandiosides E−K: Further cycloartane glycosides from Sutherlandia frutescens

A further chemical investigation of the butanol extract of leaves from the South African medicinal plant Sutherlandia frutescens led to the isolation of eight previously unreported saponins (1−8), together with the known sutherlandiosides A−D. Their structures were established by spectroscopic (1D and 2D NMR) analyses, CD, optical rotation, mass spectrometry, as well as chemical conversions. The isolates were screened for their cytotoxic activity against the MCF-7 human breast cancer cell line, although no significant activity was observed. In addition to the chemophenetic markers for this genus, i.e. the cycloartane glycosides, the present work also reports on the first isolation of an oleanan-type saponin from the Sutherlandia genus, forming an important fingerprint for the chemical composition of the plant.