Constituents of Leonotis leonurus flowering tops

Phytochemical investigation of flowering tops of Leonotis leonurus, yielded a new diterpene ester, 1,2,3-trihydroxy-3,7,11,15-tetramethylhexadecan-1-yl-palmitate along with five known metabolites. The structures of all compounds were determined by spectroscopic methods including 1D- and 2D NMR spectroscopy. All the isolated compounds were evaluated for antimalarial, cytotoxicity and for antimicrobial activities. Antimalarial activity for luteolin 7-O-beta-D-glucopyranoside (4) (IC50 = 2.2 mu g/mL for the D6 clone and 1.8 mu g/mL for the W2 clone) was observed. Chloroquine and artemisinin were used as positive controls which showed IC50 of 0.016 and 0.0048 mu g/mL for the D6 clone, respectively, and IC50 of 0.14 and 0.0047 mu g/mL for the W2 clone, respectively. None of the compounds were cytotoxic to Vero cells up to a concentration of 4.76 mu g/mL. (C) 2009 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved.