New steroidal glycoside of allium cyrilіlii racemes

Abstract

Steroidal glycosides are the vast class of natural compounds from the group of saponins that attract attention of researchers due to the wide spectrum of their biological activity and ecological safety. Plants from Allium genus growing in the Crimea are promising as to search of species with saponins. As a result of research of steroidal glycosides of Allium cyrillii Ten. racemes a new spirostanol glycoside has been isolated. The 1H- and 13C-NMR spectral data testify that this compound is a derivative of spirostan series. After acidic hydrolysis with the help of TLC only glucose has been identified by comparing to the samples of monosaccharides known beforehand. The chemical shifts of all protons of the carbohydrate residue have been determined by means of combination of two-dimensional TOCSY and COSY spectra. The 13C-chemical shifts of signals of their corresponding atoms are simply taken by means of the HSQC spectrum. The hydroxy groups position at C-2 and C-6 atoms of aglycone have been determined by the analysis of chemical shifts of C-atom signal comparing to the literary data for unsubstituted for aglycon parts and taking into account considerable positive α-effects of hydroxylation and little, usually negative, β-effects. Analysis of NMR 13C spectra of the compound isolated and 24 hydroxy derivative has shown that the signal of C-24 undergoes paramagnetic displacement in +10.8 ppm. The strong field change of signals of C-23 and C-25 also takes place. Correlation between the signal of the anomeric proton of glucose and C-24 aglycone in the HMBC spectrum confirms the site of addition of the glucose residue to aglycone. Thus, the glycoside isolated from Allium cyrillii racemes is (24S,25S)-5α-spirostan-2α,3β,6β,24-tetraol-24-O-β-D-glucopyranoside and it is a new compound.