Content of luteolin and luteolin-7-О-glucoside from the leaves of Vernonia amygdalinaDel., and synergistic inhibitory effect with cisplatin on nasopharyngeal carcinoma cells

This study describes the quantification of luteolin and luteolin-7-О-glucoside in methanol leaf extract of Vernonia amygdalinaby HPLC method. Dried powdered leaves were extracted with methanol at 40 °C for 6 h and freeze-dried. The freeze-dried sample was then analyzed by HPLC. The content of luteolin was lesser than luteolin-7-O-glucoside in the extract. The extract and the bioactive compounds were screened for inhibitory effects on nasopharyngeal carcinoma cells. Flow-cytometry and high content analysis were performed to detect luteolin-induced apoptosis. The effects of combining luteolin and cisplatin on cultured cells were explored. Luteolin produced a dose-dependent inhibition of all cell lines tested. Flow cytometry analysis revealed that luteolin did not induce apoptosis. Simultaneous combinations of luteolin and cisplatin produced synergistic effects, suggesting that the dosage of cisplatin required to treat NPC could be reduced with the addition of luteolin; sequentially lessening the risk of cisplatin-associated toxicity.