Alkaloids, flavanones and other compounds new to Goldenseal (Hydrastis canadensis)

Abstract

Hydrastis canadensis L. (Ranunculaceae), commonly known as goldenseal, is used in traditional and modern herbal medicine to treat a variety of conditions including digestive problems and infections. Previous studies from our laboratory have indicated that leaf extracts from this botanical possess antimicrobial effects against the pathogenic bacterium Staphylococcus aureus. The goal of these studies was to identify chemical components of these extracts. Goldenseal leaves were homogenized and percolated in MeOH overnight, and the MeOH extract was concentrated in vacuo. The aqueous methanol layer was partitioned with hexane followed by ethyl acetate. Normal-phase flash chromatography yielded eight major primary fractions (FI-FVIII). Fraction II, III and IV was subjected to an additional stage of preparative HPLC, and these fractions yielded several known compounds previously not reported as constituents of goldenseal, two flavanones (1-2), one isoquinolone alkaloid (3), an isoindolobenzazepine alkaloid (4), and a spiro compound (5). Additionally, fraction FII afforded a new chromenone (6) and fraction IV a new methoxycarbonylbenzoic acid (7). The structures of the isolates were established by spectrometric and spectroscopic methods. Compound 1 demonstrated efflux pump inhibitory activity against Staphylococcus aureus.