Activity: Talk or presentation › Oral presentation
Polyphenols are natural compounds, regarded to have wide range of health beneficial effects. Nevertheless, their mode of action still remains equivocal. Polyphenols are considered to be strong antioxidants on account of their chemical structure (presence of hydroxyl and catechol groups). However, they are characterised by poor absorption, rapid degradation and extensive metabolism, resulting in poor bioavailability (~ 1 µM). Therefore, these compounds are unlikely to mediate direct antioxidant activity in vivo. Instead, it is becoming apparent that phenolic compounds can interact with various molecular targets and activate multiple signalling pathways. This study investigated the protective effects of physiologically attainable concentrations of the polyphenol, delphinidin, and its major metabolite gallic acid, in human umbilical vein endothelial cells (HUVECs). Both phenolics offered significant cytoprotection against chemically induced oxidative stress. The effect was hormesic in profile. Low concentrations (≤1 µM) had the most pronounced beneficial effects, whilst concentrations ˃10 µM caused additional cytotoxic effects. Delphinidin and gallic acid generated significant amounts of oxygen-centred radicals, as shown by electron paramagnetic resonance spectrometry and total ROS/Superoxide assay, possibly explaining their cytotoxicity towards HUVECs at high concentrations. Moreover, both phenolic compounds (100 nM and 1µM) were associated with increased intracellular glutathione production. The results confirm that physiologically relevant concentrations of delphinidin and its major metabolite, gallic acid, induce antioxidant benefits in HUVECs via an indirect, xenobiotic mechanism that induces upregulation of endogenous antioxidant capacity, rather than through direct antioxidant effects.