RESUMEN
A previous study conducted in our department, showed that 50% ethanolic extract of the roots of Achyranthes aspera possess spermatotoxic effects. Preliminary studies also revealed that the active principle may be a protein. In this study a 58 kDa Achyranthes protein (Ap) was isolated from Achyranthes aspera using standard protocols and their effects on the rat sperm was studied in vitro in comparison with nonoxynol-9 (N-9). The sperm immobilization studies showed that about 150 µg of Ap was able to immobilize sperms completely within seconds at a lower concentration than N-9 (250 µg). The sperm revival test revealed that the spermicidal effect was irreversible. There was also a significant reduction in sperm viability and hypo-osmotic swelling in the Ap-treated and N-9 treated groups in comparison to the control. In the Ap and N-9 treated groups the number of acrosome reacted cells were found to be high and it also caused agglutination of the sperms indicating the loss of intactness of the plasma membrane which was further supported by the significant reduction in the activity of membrane bound 5' nucleotidase and acrosin enzyme. Hence this study showed that the protein isolated from the roots of Achyranthes aspera possess spermicidal activity in vitro and can act as a spermicide similar to that of nonoxynol 9. Ap also possessed spermicidal activity against human sperms in vitro.