Alkaloid subfractions of Buxus sempervirens L. leaves with strong in vitro activity against Trypanosoma brucei rhodesiense

Abstract

Buxus sempervirens L. is very rich in triterpene-alkaloids of different types. The 9β-19-cyclo-5α-pregnanes and (9-(10→19))abeo-5α-pregnanes with variable substitution patterns are described in literature as characteristic for B. sempervirens L. [1, 2]. In a previous study we reported on the antiplasmodial activity of a CH2Cl2 extract from the leaves and isolated as the main responsible alkaloid O-tigloylcyclovirobuxeine B [3]. In the course of this investigation, we also found specific antitrypanosomal activity in some subfractions obtained by ESI-MS/MS guided 'spiral coil-countercurrent chromatography' [3]. Their antitrypanosomal IC50 values of the tested fractions, along with their cytotoxicity and selectivity indices, are reported in Table 1. Characterization of the complex pattern of triterpene-alkaloids in the fractions with a high antitrypanosomal activity and selectivity was performed by UHPLC/+ESI-QTOF MS analyses. The aim of this study is to identify the compounds with a selective antitrypanosomal activity. Especially subfraction E9 with an IC50 of 0.18 µg/mL and a good selectivity index of 26.2 is remarkable in comparison with the neighboring fractions 146 and E53, from which it differs conspicuously by the occurrence of compounds with elemental formulas of C24H35N (337 m/z), C26H44N2 (384 m/z), C25H41NO (371 m/z) and C35H48N2O3 (544 m/z). Isolation, identification and testing of these alkaloids with hitherto unknown antitrypanosomal activity is in progress.