Relationship between cytotoxic activity and radical intensity of isoflavones from Sophora species

Among 11 isoflavones tested, genistein [YS13] produced higher cytotoxic act ivity against human oral tumor cell lines (HSC-2, HSG) than against normal cells (human gingival fibroblast, HGF), suggesting its tumor-specific actio n. Electron spin resonance (ESR) spectroscopy showed that YS13 did not prod uce radical, nor scavenged O-2. (-), generated by hypoxanthine-xanthine oxi dase reaction system, suggesting that radical-mediated oxidation mechanism is not be involved in the YS13-induced cytotoxicity. Addition of one prenyl group produced YS18 and YS19 with higher anti-Helicobacter pylori activity . Addition of two prenyl groups produced YS21 with the highest cytotoxic ac tivity but lower tumor-specificity. Since YS21 produced the highest amount of radical and most efficiently scavenged O-2. (-), this compound may induc e cytotoxicity by radical-mediated oxidation mechanism. All isoflavones fai led to induce anti-human immunodeficiency virus (HIV) activity. These data suggest the medicinal efficacy of isoflavones.