Antiprotozoal activity of Melampyrum arvense and its metabolites.

An activity guided isolation of the H(2)O subextract of the crude extract of Melampyrum arvense L. afforded iridoid glucosides: aucubin (1), melampyroside (2), mussaenoside (3), mussaenosidic acid (4), 8-epi-loganin (5); flavonoids: apigenin (6), luteolin (7), luteolin 7-O-β-glucopyranoside (8); a lignan glycoside dehydrodiconiferyl alcohol 9-O-β-glucopyranoside (9); and benzoic acid (10). β-Sitosterol (11) and a fatty acid mixture (12) were identified as the active principles of the CHCl(3) subextract. The structures of the isolates were elucidated by spectroscopic methods, while the composition of 12 was identified by GC-MS after methylation. Luteolin (7) appeared as the most active compound against Trypanosoma brucei rhodesiense and Leishmania donovani (IC(50) values 3.8 and 3.0 μg/mL). Luteolin 7-O-β-glucopyranoside (8) displayed the best antiplasmodial activity against Plasmodium falciparum (IC(50) value 2.9 μg/mL). This is the first detailed phytochemical study on Turkish M. arvense and the first report of the antiprotozoal effect of Melampyrum species and its constituents.