Influence of Echeveria gibbiflora DC aqueous crude extract on mouse sperm energy metabolism and calcium-dependent channels

Ethnopharmacology relevance: In traditional Mexican medicine, Echeveria gibbiflora DC has been used as a vaginal post-coital rinse to prevent pregnancy. The aqueous crude extract (OBACE) induces sperm immobilization/agglutination and a hypotonic-like effect, likely attributed to the high concentration of calcium bis-(hydrogen-1-malate) hexahydrate [Ca²⁺ (C₄H₅O₅)₂•6H₂O]. Likewise, OBACE impedes the increase of [Ca²⁺]i during capacitation. Aim of the study: Evaluate the effect of OBACE on sperm energy metabolism and the underlying mechanism of action on sperm-specific channel. Material and methods: In vitro, we quantified the mouse sperm immobilization effect and the antifertility potential of OBACE. The energetic metabolism status was also evaluated by assessing the ATP levels, general mitochondrial activity, mitochondrial membrane potential, and enzymatic activity of three key enzymes of energy metabolism. Furthermore, the effect of the ion efflux of Cl⁻ and K⁺, as well as the pHi, were investigated in order to elucidate which channel is suitable to perform an in silico study. Results: Total and progressive motility notably decreased, as did fertility rates. ATP levels, mitochondrial activity and membrane potential were reduced. Furthermore, the activities of the three enzymes decreased. Neither Cl⁻ or K⁺ channels activities were affected at low concentrations of OBACE; nevertheless, pHi did not alkalinize. Finally, an in silico analysis was performed between the Catsper channel and calcium bis-(hydrogen-1-malate) hexahydrate, which showed a possible blockade of this sperm cation channel. Conclusion: The results were useful to elucidate the effect of OBACE and to propose it as a future male contraceptive.