A new tropane alkaloid and other metabolites from Erythroxylum macrocalyx (Erythroxylaceae) and their antiproliferative activities

Abstract

Abstract A new tropane alkaloid 7β-acetoxy-6β-benzoyloxy-3α-hydroxytropane (1) was isolated from the twigs of Erythroxylum macrocalyx Mart. (Erythroxylaceae), along with the known substances: 6β,7β-dibenzoyloxy-3α-hydroxytropane (2), 6β,7β-dihydroxy-3α-(phenylacetoxy)tropane (3), 3α-benzoyloxy-6β,7β-dihydroxytropane (4), 6β-benzoyloxy-3α-(4-hydroxy-3,5-dimetoxybenzoyloxy)tropane (5), ombuin-3-rutinoside-5-glucoside (6), lupeol (7), taraxerol (8) and lupenone (9). Compounds 1 and 2 were also isolated from the leaves. The structures were established by analyses of 1D- and 2D-NMR and MS data, as well as by comparison with literature data for known compounds. The structure of 2 was also supported by X-ray crystallography analyses. The compounds were evaluated in vitro for their antibacterial and antiproliferative activities. Compound 5 showed high antiproliferative activity on liver hepatocellular carcinoma cells (HepG2) with IC50 value of 3.66 μg mL−1 (8.29 μmol L-1), but no cytotoxic effect (IC50 > 25 μg mL-1) on human lymphoblast cell line. This study reveals the potential use of 5 as prototype for the synthesis of new antiproliferative agents.