Inhibitory Effects of Saponins from Tetrapleura tetraptera on the LH Released by Cultured Rat Pituitary Cells

Abstract

Ethanolic extracts from stem bark of Tetrapleura tetraptera exerted an inhibitory effect on the luteinizing hormone (LH) released by cultured rat pituitary cells. These extracts contained triterpenic saponins, tannins, and flavonoids as estimated through phytochemical screening. Saponins were extracted. They apparently inhibited the luteinizing hormone-releasing hormone (LHRH)-induced LH release, the inhibition level being dose-dependent. Yet, the intracellular LH content remained constant whatever the saponin concentration, which demonstrated a lack of effect on the true release process. Accordingly, an interaction between saponins and LH released into the medium was demonstrated, which led to a decrease in the amount of immunoassayable hormone. This decrease was both time- and dose-dependent. It occurred even in the presence of serum in the medium, which suggests that the inactivation process may occur in vivo. Taken together, these results could explain the anti-gonadotrope properties of T. tetraptera extracts that are used as natural contraceptives in Ivory Coast pharmacopoeia.

Key words

Tetrapleura tetraptera - saponins - pituitary - LH release - cell culture