In vitro maturation of bovine oocytes in medium supplemented with quercetin, and its effect on embryonic development

Quercetin is a flavonoid widely found in fruit, vegetables, grains and flowers, with a high concentration in red wine, and has been functionally characterized by its antioxidant activity. For assessment of nuclear maturation and bovine embryo, oocytes were matured for 22h in the presence of quercetin (0.4, 2, 10 and 50 mu M), cysteamine (100 mu M) and in the absence of antioxidants. The matured oocytes were stained with Hoechst to evaluate the in vitro maturation. To assess embryonic development, oocytes were fertilized and cultured in vitro and rates of embryo development were obtained in the seventh day of culture and the percentage of hatching and the number of cells on eighth day embryos. The levels of glutathione (GSH) of the oocytes were measured by fluorescence emission with CMF2HC. The percentage of nuclear maturation (+/- 89%) did not differ between groups. Embryonic development varied between treatments, the percentage of blastocyst was higher (P<0.05) in the groups treated with 0.4, 2, 10 and 50 mu M of quercetin (56.9, 59.5, 53.6 and 49.6%, respectively) and 100 mu M cysteamine (50.4%) compared to the control group (42.3%). Comparing the two antioxidants, quercetin (0.4 to 2 mu M) was superior in embryo production (56.9 and 59.5% respectively) compared with cysteamine (50.4%). The rates of hatched embryos were similar (P>0.05) between groups (+/- 63.0%). The average number of embryo cells was also similar in both groups (+/- 233). The intracellular GSH levels were higher in oocytes matured with cysteamine, but similar between the oocytes treated with quercetin and control. The supplementation of matured in vitro with antioxidants improves blastocyst rates. Quercetin was greater than cysteamine, which in turn was superior to the control. However, GSH levels were higher in oocytes treated only with cysteamine.