Synergistic antioxidant action of Phikud Navakot ameliorates hydrogen peroxide-induced stress in human endothelial cells

BACKGROUND Phikud Navakot (PN), a combination of nine herbs, has been used traditionally in Thai medicinal formulas to relieve circulatory disorder. The present study aimed to compare the synergistic antioxidant efficacy and toxicity of the hydroethanolic and water extracts of PN at cellular level. METHODS PN and its nine herbs were extracted with either 50% ethanol or water. All extracts were tested for in vitro antioxidant potential using standard antioxidant assays. Evaluation of cytotoxicity, genotoxicity, and intracellular reactive oxygen species were performed using human endothelial ECV304 cells. RESULTS Antioxidant assays in cell-free systems showed that the hydroethanolic extract of PN scavenged superoxide, hydroxyl, nitric oxide radicals, and hydrogen peroxide more effectively than its water extract. Combination indices were calculated to show that the ingredients of the hydroethanolic extract acted synergistically to exhibit antioxidant activities against all tested radicals, whereas, in the case of water extract, this effect was observed only against 2,2-diphenyl-1-picrylhydrazyl, superoxide, and hydroxyl radicals. A cell-based assay also revealed that the hydroethanolic extract concentration-dependently attenuated hydrogen peroxide-induced stress more effectively than the water extract. At the antioxidant and cytotoxic concentrations of both extracts, no genotoxicity was found. CONCLUSION Our findings demonstrate that the synergistic antioxidant action of PN ameliorates endothelial stress, which may provide some clues for understanding the traditional use of PN for the treatment of circulatory disorder. Additionally, the selection of a suitable solvent for the extraction of PN herbal combination is essential for maximal efficacy and safety.