Effects of different concentrations of eugenol in maturation medium on bovine oocytes, oxidative status and preimplantation embryos

Context Eugenol is a bioactive compound with defined attributes, including a role in reducing oxidative stress. Therefore, it is an interesting candidate for in vitro embryo production that has an environment that favours the formation of reactive oxygen species. Aim The objective of the study was to evaluate different concentrations of eugenol in bovine oocytes during in vitro maturation to observe the oxidative status and embryonic development. Methods Oocytes were allocated into five groups: control (without antioxidant), 100μM cysteamine, 83μM eugenol (E83), 100μM eugenol and 120μM eugenol. Three experiments were performed with 23 replicates. Oocytes were evaluated for metaphase II, first polar body, cytoplasmic maturation, cumulus cell expansion and viability. Oxidative status was measured by mitochondrial membrane potential, reactive oxygen species and glutathione. Oocytes were artificially activated and cultured in vitro. Key results The presence of eugenol at 83μM improved the metaphase II rate compared with all treatments (P<0.05). E83 and 100μM cysteamine improved first polar body extrusion, cumulus cell expansion, viability and mitochondrial aggregation rates (P<0.05). All antioxidant treatments resulted in increased cytoplasmic maturation and decreased mitochondrial membrane potential (P<0.05). Reactive oxygen species levels decreased, and glutathione levels increased with E83 and 100μM cysteamine treatments (P<0.05). Finally, the E83 group increased the cleavage rates, embryo development, number of expanded blastocysts and number of blastomeres (P<0.05). Conclusions A low concentration of eugenol (83μM) is sufficient to generate a significant effect, attenuating the oxidative status and optimising i n vitro maturation and embryo development. Implications This study provides information of a new natural antioxidant with defined concentration, 83μM eugenol, representing a lower cost alternative capable of improving the efficiency of in vitro embryo production in cattle.