The effect of Tropaeolum majus L. on bacterial infections and in vitro efficacy on apoptosis and DNA lesions in hyperosmotic stress.

Tropaeolum majus L. (T. majus) or nasturtium is a medicinal plant widespread in the areas with temperate climate, commonly used in culinary and in traditional medicine due to therapeutic properties. In the last few years, various effects of the flowers and leaves of this plant have been studied, but their benefits are not fully known. The aim of the study was to identify the phenolic compounds from T. majus edible flowers in relation with its antioxidant capacity and the antimicrobial activity against different bacteria and Candida albicans. In addition, the impact of natural extract on oxidative stress, inflammation and apoptosis was analysed on human umbilical vein endothelial cells (HUVECs) exposed to normotonic and hypertonic conditions. The major phenolic acids, identified by HPLC-RP with UV detection, were gallic acid, caffeic acid and p-coumaric and predominant flavonoids were quercetin, epicatechin and luteolin. The both fractions of T. majus were rich sources of polyphenols with marked antioxidant activity, evidenced by TEAC or DPPH methods. The extract exhibited a week antibacterial effect on some strains of streptococcus, without antifungal or antibacterial effect on gram negative bacteria. T. majus extract increased the p53 and Bcl-2 expressions and diminished the DNA lesions indicating the protective and antiapoptotic effects in vitro, on endothelial cells exposed to hyperosmotic stress. These experimental findings suggest that T. majus can exert some protection against bacterial infections and reduce apoptosis and DNA lesions in hypertonic conditions.