Zeinosides A-D: pregnane glycosides from Caralluma adenensis

Four undescribed pregnane glycosides, zeinosides A-D, were isolated from the methanolic extract of Caralluma adenensis (Family Apocyanaceae). This plant is native to Yemen and traditionally used for its antidiabetic, anti-ulcer, anti-inflammatory, antiparasitic, and antipyretic properties. The structures of these compounds were elucidated using comprehensive spectroscopic techniques, including 1D and 2D NMR, LC-ESI-IT-TOF-MS, and IR spectroscopy. The structures of zeinosides A-D are determined as a polyhydroxylated C-21 steroidal skeleton with benzoyl esters at C-15 and/or C-20, except for zeinoside C, which has a ketone at C-20. The sugar moieties consist of β-d-digitalose and β-d-glucose units, with zeinoside A containing two sugars and zeinosides B-D each bearing three. The stereochemistry was determined through NOESY correlations and comparison with literature data. These findings add to the chemical diversity of the Caralluma genus and suggest that zeinosides A-D could be promising candidates for future studies, potentially supporting the plant's traditional uses in medicine.