Redox hormesis in the testis: Bunium incrassatum root extract biphasically modulates testosterone levels and spermatogenesis in male rabbits (Oryctolagus cuniculus)

Abstract

Bunium incrassatum (Apiaceae), whose tuber is traditionally consumed in North Africa as a tonic food reputed to support fertility, had never been assessed for male reproductive function. Twenty-four adult male rabbits assigned to four groups received the CH₂Cl₂/MeOH root extract by daily gavage for 15 days at 0, 50, 100 and 200 mg/kg/day. At 100 mg/kg/day, every indicator of gonadal function improved: serum testosterone rose by 50.4%, superoxide dismutase and glutathione peroxidase activities increased in testicular homogenate while malondialdehyde decreased significantly (−20.0%), seminiferous tubule diameter increased from 249.19 ± 3.01 to 290.68 ± 3.99 µm and germinal epithelium height from 73.30 ± 4.55 to 91.00 ± 3.21 µm, and sperm concentration, motility and viability increased concurrently (p < 0.05). The convergence of four methodologically independent parameter families indicates reinforced gonadal antioxidant defences preserving Leydig cell steroidogenic competence. At 200 mg/kg/day, the testicular redox balance reversed: antioxidant enzymes collapsed, malondialdehyde rose by 70.3%, and the endocrine, tissue and sperm gains were not merely abolished but crossed in the opposite direction. The optimum therefore lies at 100 mg/kg/day, a dose coinciding with the safety ceiling previously established for this extract. Blood glucose, which declined monotonically across the whole dose range, confines this hormetic behaviour to the steroidogenic and germinal compartments. B. incrassatum thus holds genuine reproductive value, inseparable from control of both dose and administered formulation.