Analysis of Flavones C-Glycosides and and Stepwise Hydrolysis of Their Acetates in the Leaves of Rubus Chamaemorus L.

Abstract

The C-glycoside embinin and its mono- and diacetate derivatives have immunotropic and cardiotonic activity, which makes the search for plants that contain them interesting. Embinin and its acetate derivatives were previously isolated only from some plants of the genus Iris, the habitat and growing conditions of which are very different from those of the genus Rubus. As a result of the study, the structure of seven C-glycosides, embinin derivatives, isolated from the leaves of Rubus chamaemorus L. (Rosaceae) was established. Using HR-ESI-MS, HPLC-MS, as well as one- and two-dimensional NMR spectroscopy, the structure of three substances isolated in individual form was established: embinin (1) and its diacetyl derivatives – 2''',3'''-diacetylembinin (5) and 3''',4'''-diacetylembinin (7). The method of stepwise hydrolysis of C-glycoside acetate residues proposed in this study, followed by HPLC analysis of the resulting hydrolysis products, made it possible to establish the structure of minor flavone C-glycosides contained in the leaves of Rubus chamaemorus L.: 2'''-acetylembinin (2), 3'''-acetylembinin (3), 4'''-acetylembinin (4) and 2''',4'''-diacetylembinin (6). All these compounds were found in the leaves of Rubus chamaemorus L. for the first time. The C-glycosides - embinin and its acetate derivatives are rare metabolites of higher plants, the presence of which is determined by the peculiarity of their physiology, and the biological activity determines the prospects for medical use.