Antioxidant effects of Citrus sinensis peel essential oil in a bovine oocyte model

Essential oils are a rich source of bioactive antioxidants that can replace synthetic compounds in cell culture systems. This study aimed to evaluate the antioxidant effects of the Citrus sinensis peel essential oil (EOCS) in a bovine oocyte model on nuclear and cytoplasmic maturation, bioenergetic/oxidative stress, and preimplantation embryonic development of bovine oocytes. Oocytes were divided into five groups: control, synthetic compound (CYS), and 10 (EOCS10), 30 (EOCS30), and 50 mu g/mL (EOCS50) of EOCS. Oocytes were evaluated for cumulus cell expansion, viability, and nuclear and cytoplasmic maturation. Oxidative status was evaluated using reactive oxygen species (ROS), mitochondrial membrane potential (Delta psi m), and glutathione (GSH). Additionally, blastocyst production and quality were evaluated after oocyte artificial activation. Although all antioxidant groups had improved viability, only the CYS, EOCS10, and EOCS30 allowed greater cumulus cell expansion (P < 0.05). EOCS10 and EOCS30 ensured a higher rate of nuclear maturation than EOCS50 (P < 0.05). All groups showed reduced ROS levels compared to that of the control (P < 0.05), but no difference was observed in Delta psi m and GSH (P > 0.05). Although only the control and EOCS10 produced expanded blastocysts, CYS and EOCS10 ensured a greater blastomere number when compared to the control and EOCS50 (P < 0.05). In summary, EOCS10 showed better oocyte maturation rates and embryonic quality. EOCS, in defined concentrations, added to the IVM medium, can be an interesting substitute for a synthetic compound to reduce the damage caused by oxidative stress in bovine oocytes.