Eugenol as a natural antioxidant for porcine in vitro embryo production

Oxidative stress negatively affects oocyte quality and embryo development during in vitro embryo production (IVEP). Plant-derived antioxidants, such as eugenol (EG), have emerged as promising alternatives to mitigate the detrimental impacts of reactive oxygen species (ROS) and enhance IVEP outcomes and embryo quality. This study evaluated EG as a potential antioxidant for porcine oocyte in vitro maturation (IVM) and embryo culture (IVC). In the first experiment, cumulus-oocyte complexes (COCs) were matured in vitro with varying concentrations of EG (0, 10, 20, 30, 40, 60 or 80 μM), and subsequent cleavage, development, morphology and total cell number at the blastocyst stage were assessed. The 60 μM (EG60) concentration was selected for further experiments, as it yielded the highest numerical rate of blastocyst formation and a significantly higher proportion of expanded blastocysts. In the second experiment, IVM medium with EG60 or cysteine (CYS; 100 μg/mL) supported similar blastocyst development rates, although no additive effect was observed when both were combined. Notably, EG60 significantly reduced ROS levels in matured oocytes and produced a numerically higher, hence not statistically significant, rate of hatched blastocysts compared to CYS. Additionally, PTGS1 mRNA abundance in cumulus cells (CCs) was significantly higher in the EG60 group than in the CYS group. Finally, the supplementation of the IVC medium with 80 μM EG reduced ROS levels in blastocysts but did not significantly improve embryo development rates and blastocyst cell number. These findings suggest that eugenol is an effective natural antioxidant for enhancing in vitro embryo production in swine.