Reproductive Toxicity Assessment of Four Portuguese Plant Hydrolates: Effects on Oocyte Maturation and Sperm Viability

Extracts of aromatic medicinal plants have been extensively studied regarding their numerous bioactivities. However, despite being highly used by humans, studies on the safety of these extracts for animal use are scarce. In this study, we aim to contribute to the determination of the safety profile of plant extracts by focusing on the reproductive toxicity of hydrolates (a by-product of essential oils production) of four endogenous Portuguese plants-<i>Cistus ladanifer</i>, <i>Cupressus lusitanica</i>, <i>Helychrisium italicum</i>, and <i>Thymbra capitata</i>-by studying their effects on bovine oocytes and spermatozoa. To achieve our aims, we determined the oocyte maturation and viability rate in the bovine in vitro maturation test (bIVM) and the bovine sperm viability using the eosin-nigrosin test, in the presence of five concentrations of each hydrolate at half-log intervals (% <i>v/v</i> of culture media). We found that hydrolates did not affect oocyte maturation or viability (maximum concentration tested: 0.2%, <i>v</i>/<i>v</i>). Regarding the sperm viability test, we found that <i>T. capitata</i> and <i>C. ladanifer</i> hydrolates impaired sperm viability (<i>p</i> < 0.05) (maximum concentration tested: 0.2%, <i>v</i>/<i>v</i>), in comparison with the negative control. In summary, we found that <i>H. italicum</i> and <i>C. lusitanica</i> hydrolates were safe regarding oocyte maturation, oocyte viability, and sperm viability, being candidates to be included in bovine husbandry as feeding additives.