Zeinosides A–D: pregnane glycosides from Caralluma adenensis

Abstract

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.