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

## TL;DR

This study assesses the reproductive safety of four Portuguese plant hydrolates on bovine oocytes and sperm, finding some hydrolates may harm sperm viability.

## Contribution

The study evaluates the reproductive toxicity of four Portuguese plant hydrolates for potential use in bovine husbandry.

## Key findings

- Hydrolates did not affect oocyte maturation or viability at tested concentrations.
- T. capitata and C. ladanifer hydrolates impaired sperm viability.
- H. italicum and C. lusitanica hydrolates were safe for oocyte and sperm viability.

## Abstract

Plant extracts are commonly regarded as safe due to their traditional use in medicine. Furthermore, new products have been arising that use natural ingredients such as plant extracts as supplements for bovine husbandry. However, studies on their reproductive toxicity remain limited. In this study, we aim to assess the reproductive toxicity of plant extracts in order to evaluate their safety to be included as active ingredients for food supplements for animals. We found that endogenous plant extracts showed low toxicity on oocyte maturation, but notably impaired sperm viability. These findings highlight the importance of testing plant extracts before including them in formulations for bovine husbandry.

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—Cistus ladanifer, Cupressus lusitanica, Helychrisium italicum, and Thymbra capitata—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 (% v/v of culture media). We found that hydrolates did not affect oocyte maturation or viability (maximum concentration tested: 0.2%, v/v). Regarding the sperm viability test, we found that T. capitata and C. ladanifer hydrolates impaired sperm viability (p < 0.05) (maximum concentration tested: 0.2%, v/v), in comparison with the negative control. In summary, we found that H. italicum and C. lusitanica hydrolates were safe regarding oocyte maturation, oocyte viability, and sperm viability, being candidates to be included in bovine husbandry as feeding additives.