Antioxidant Effects of Quercetin in Human Peripheral Lymphocytes

The antioxidant diet in humans has been increased in our days; such compounds are related with several beneficial effects to health, as prevention of chronic-degenerative diseases. Quercetin, flavonoid very abundant in apples, onions and red wine, has anti-oxidant, anti-inflammatory and anti-proliferative effects in tumoral cells, demonstrated by in vitro experiments. Nevertheless, there are adverse experimental evidences related with DNA damage when cells are induced to high quercetin concentrations, but as well quercetin can increase antioxidant cellular response, activating transcriptional promoters. In the present work we used peripheral human lymphocytes exposed to aglycone quercetin and 3’-O-methylquercetin at a low concentration, similar to the concentration reached in plasma after a quercetin-rich meal, and measured enzyme activity and transcripts of superoxide dismutase, catalase and glutathion-S-transferase.  It was first necessary to separate the lymphocytes from human healthy blood, donated by the blood bank, after that, cells were incubated at 0.74 µM of the flavonoids for five hours at 37 ºC. A protein extract was obtained, and then enzymatic activities were measured. Gene expression was evaluated by semi-quantitative PCR using cDNA synthesized by reverse transcription from total RNA isolated from cells. The results demonstrate both flavonoids stimulated superoxide dismutase and catalase activity, and increased transcription of these enzymes.