Atividade antioxidante do óleo essencial de syzygium aromaticum l. sobre gametas bovinos

The use of natural antioxidants in culture media may be an alternative to minimize the negative effects of oxidative stress produced by in vitro conditions. In this sense, the essential oil of Syzygium aromaticum (EOSA), has therapeutic properties, including antioxidant activity, and could be used during in vitro maturation (IVM) of bovine oocytes and incubation of bovine spermatozoa. Therefore, the aim was to evaluate the antioxidant activity of EOSA on bovine gametes, specifically its addition (i) during IVM and influence on nuclear maturation, cytoplasmic maturation, viability of cumulus cells, reactive oxygen species (ROS) levels, mitochondrial membrane potential (ΔΨm), and parthenogenetic embryonic development; and (ii) during incubation for 1 and 6 h of epididymal spermatozoa and its influence on sperm quality and ROS levels. Thus, gametes were cultured in media containing the following supplements: EOSA (without antioxidants), EOSA 10 (10 μg/mL of EOSA), EOSA15 (15 μg/mL of EOSA), EOSA20 (20 μg/mL of EOSA) (100 μM of cysteamine, only for oocytes) and Control (only for fresh spermatozoa, immediately evaluated). Thus, regarding the influence of EOSA during IVM, no difference was observed for maturation rates. Nevertheless, EOSA15, EOSA 20 and CYS improved the viability of cumulus cells after IVM, being only the EOSA20 group greater than EOSA0 (P < 0.05). Moreover, although no difference was observed for ROS levels (P > 0.05), oocytes derived from the EOSA15, EOSA20 and CYS groups showed ΔΨm lower than the EOSA0 (P < 0.05) oocytes. Additionally, although no differences was observed for cleavage rates of the parthenogenetically activated oocytes, EOSA20 improved blastocyst rates, both when calculated by the total number of cultured oocytes, and by the total number of cleaved oocytes. Also, these blastocyst rates were different from EOSA0 group and similar to CYS group. As to the quality of the embryos produced, OESA15 and OESA20 groups showed a higher number of blastomeres when compared to OESA0 (P < 0.05). Regarding the influence of EOSA during sperm incubation, no difference was observed for sperm morphology (P > 0.05). Nevertheless, spermatozoa incubated in the presence of EOSA preserved the parameters over time, especially for structural and functional integrity of the plasma membrane, mitochondrial activity, curvilinear velocity and metabolic activity (P < 0.05). Moreover, spermatozoa derived from the EOSA15 group maintained similar results to the control group for medium velocity after 6 h of incubation, functional integrity of the membrane and percentage of damaged membrane and inactive mitochondria (P < 0.05). Also, no difference was observed for ROS levels after incubation. In conclusion, OESA at 20 μg/mL and 15 μg/mL added to media during IVM and sperm incubation, respectively, may be an interesting antioxidant alternative for maintaining the quality of bovine gametes in vitro