New Glycosides and Trypanocidal Metabolites from Vangueria edulis.

A new iridoid glucoside, 10-methoxy apodanthoside (1), and a new monoterpene glycoside, (3S,6S)-cis linalool-3,7-oxide O-β-D-glucopyranosyl-(1"-->5')-β-D- xylofuranoside (2), were isolated from V. edulis (Rubiaceae), along with eighteen known compounds (3-20), including monoterpenes, iridoid glycosides, and a lignin, which were encountered for the first time in the genus Vangueria,. The structural elucidation of the isolates was based on the analysis of spectroscopic (1D and 2D NMR) and HR-ESI-MS data. Detailed stereochemical studies of 1 and related iridoid glucosides (compounds 3, 4 and 8) were made by matching the calculated ECD peaks with the experimental ones. All isolates were tested for their antiprotozoal, antifungal, and antiplasmodial activities. Compounds 9, 15 and 16 showed good trypanocidal activities against Trypanosoma brucei brucei with IC50 values of 8.18, 9.02 and 7.80 µg/mL, respectively and IC90 values of > 10, > 10 and 9.76 µg/mL, respectively. Compound 16 showed a moderate activity against Candida glabrata with an IC50 value of 8.66 µg/mL. Compound 20 showed a weak antiplasmodial activity against chloroquine-sensitive (D6) and resistant (W2) Plasmodium falciparum with IC50 values of 3.29 (SI, > 1.4) and 4.53 (SI, > 1) µg/mL, respectively.