The effects of Glycyrrhiza flavonoids on sperm quality and oxidative stress during the liquid preservation of boar semen

Context Sperm quality is essential for artificial insemination success, because oxidative stress during in vitro storage impairs boar semen quality. Glycyrrhiza flavonoids (GF), the major bioactive components of licorice, possess antioxidant properties; however, their role in boar semen preservation has not been fully elucidated. Aims This study aimed to evaluate the protective effects of GF on boar sperm during liquid storage at 17°C and 4°C. Methods Four concentrations (3, 15, 75, and 375 μg/mL) of GF were added to the diluent and tested for effects on sperm motility, plasma membrane integrity, mitochondrial activity, activities of antioxidant enzymes (total superoxide dismutase [T-SOD] and catalase [CAT]), and oxidative stress biomarkers (reactive oxygen species [ROS] and malondialdehyde [MDA]). Key results GF at 75 μg/mL and 375 μg/mL significantly preserved sperm motility, plasma membrane integrity and mitochondrial activity on Days 1, 3 and 5 at 17°C. Specifically, at 4°C with these concentrations, sperm motility and plasma membrane integrity were increased on Days 1, 3 and 5, whereas mitochondrial function was enhanced on Day 3. SOD activity was significantly elevated by treatment with 75 μg/mL GF on Days 1 and 5 at both temperatures. Conclusions These findings suggest that optimal GF doses preserve sperm function and attenuate oxidative stress during liquid storage by enhancing enzymatic antioxidant activities, thereby maintaining cellular structural and functional stability. Implications These findings have provided a potential strategy to improve boar semen preservation for artificial insemination.