Comparison of Lipoxygenase, Cyclooxygenase, Xanthine Oxidase Inhibitory Effects and Cytotoxic Activities of Selected Flavonoids

Abstract

This study aimed to evaluate and compare lipoxygenase (LOX), cyclooxygenase (COX), xanthine oxidase (XO) inhibitory effects and cytotoxic activities of selected flavonoids in vitro. The antioxidant and cytotoxic activities had been investigated using ultraviolet spectrophotometry, MTT assay, RT-PCR, and flow cytometry. The results showed that luteolin, luteoloside and quercetin exhibited better inhibition on XOD and LOX enzymes. In addition, all the selected flavonoid glycosides showed no significant cytotoxicity, but diosmetin, luteolin, apigenin and quercetin expressed significant cell toxicity. Meanwhile, these four flavonoids also showed better inhibition on COX-2 mRNA expression and apoptosis-inducing effect. In conclusion, this study suggests that these anti-tumor flavonoids possess anti-inflammatory and anti-oxidative properties, which are associated with their direct inhibition of XO and LOX activities and down-regulation of COX-2 transcription.