Essential oil of Cymbopogon citratus enhances redox balance and supports early embryonic development in bovine oocytes

Oocytes matured in vitro often exhibit reduced developmental competence due to suboptimal culture conditions, in which oxidative imbalance plays a central role. Antioxidant supplementation during in vitro maturation (IVM) may improve oocyte quality. This study evaluated the effects of essential oil of Cymbopogon citratus (EOCC), a source of bioactive antioxidant compounds, on nuclear and cytoplasmic maturation, redox status, and preimplantation development of bovine oocytes. The antioxidant capacity of IVM media was confirmed using DPPH and ABTS assays. Viable oocytes were matured under five conditions: control (no antioxidant), cysteamine (100 µM), EOCC10 (10 µg/mL), EOCC25 (25 µg/mL), and EOCC50 (50 µg/mL). Three experiments were performed. First, maturation was assessed by cumulus cell expansion and viability, first polar body extrusion, metaphase II progression, and mitochondrial distribution. Second, intracellular reactive oxygen species (ROS), glutathione (GSH) levels, and mitochondrial membrane potential (ΔΨm) were evaluated. Third, oocytes matured under optimal EOCC concentrations were subjected to parthenogenetic activation and embryo culture. EOCC dose-dependently increased the antioxidant capacity of the IVM medium. Although nuclear maturation rates were similar among treatments, CYS, EOCC10, and EOCC25 improved cumulus cell viability and cytoplasmic maturation. EOCC10 and EOCC25 reduced ROS and ΔΨm, while antioxidant-treated oocytes showed higher GSH levels than control. EOCC50 increased ROS and adversely affected cytoplasmic maturation; therefore, it was excluded from subsequent analyses. Cleavage rates were unaffected; however, EOCC10 increased blastocyst yield and blastomere numbers, along with reduced embryonic ROS levels. In conclusion, EOCC at 10 µg/mL improves the redox environment and enhances bovine oocytes developmental competence.