RESUMO
PURPOSE: Aqueous decoction of Chenopodium album seeds (CAD) was assessed for its sperm-immobilizing and contraceptive efficacy in laboratory mammals. METHOD: Spermicidal efficacy was evaluated in vitro by a modified Sander-Cramer test. The mode of spermicidal action was assessed by (a) supravital and double fluoroprobe staining of sperm, (b) hypoosmotic swelling tests and (c) transmission electron microscopy. Contraceptive efficacy was evaluated by intrauterine and vaginal application of CAD in rats and rabbits, respectively, followed by their mating and evaluation of pregnancy outcomes. RESULTS: The minimum effective concentration of CAD that induced instantaneous immobilization of rat spermatozoa in vitro was 2 mg/mL. The mechanism of CAD action involved disintegration of sperm plasma membrane and dissolution of acrosomal cap causing sperm death. Fertilization of oocytes and establishment of implantation were prevented in the uterine horn that was administered with CAD, while these events occurred unhindered in the untreated contralateral side. In rabbit, intravaginal application of CAD significantly blocked the establishment of pregnancy. CONCLUSION: CAD possesses appreciable spermicidal potential, which may be explored as an effector constituent of vaginal contraceptive.
