Trypanocidal Activity of 2,5-Diphenyloxazoles Isolated from the Roots of Oxytropis lanata

Eleven 2,5-diphenyloxazole derivatives (1–11), together with six known isoflavonoid derivatives, were isolated from the roots of Oxytropis lanata. The 2,5-diphenyloxazole (1) obtained proved to be identical to a standard sample used as a scintillator and liquid laser dye. The other oxazole derivatives isolated were found to have one to four hydroxy and/or O-methyl groups in their phenyl rings. Seven of the oxazole derivatives obtained are new (3–9). The inhibitory activity of the isolated compounds was evaluated against Trypanosoma congolense, the causative agent of African trypanosomosis in animals. Oxazoles with di- and trihydroxy groups showed trypanocidal activity, and 2-(2′,3′-dihydroxyphenyl)-5-(2″-hydroxyphenyl)oxazole (4) exhibited the most potent inhibitory activity (IC50 1.0 μM).