A series of 4, 5-diaryl-1H-imidazole-2 (3H)-thione was synthesized and their inhibitory potency against soybean 15-lipoxygenase and free radical scavenging activities were determined. Compound 11 showed the best IC50 for 15-LOX inhibition (IC50= 4.7 μM) and free radical scavenging activity (IC50= 14μM). Methylation of SH at C2 position of imidazole has dramatically decreased the 15-LOX inhibition and radical scavenging activity as it can ...