Acaciaside-B-enriched fraction of Acacia auriculiformis is a prospective spermicide with no mutagenic property

Abstract

As a part of our continued venture to develop a safe and effective spermicide, we have identified a triterpene glycoside (Acaciaside-B (Ac-B))-enriched fraction (Ac-B-en) isolated from the seeds of Acacia auriculiformis and evaluated its spermicidal potential in vitro. Sperm motility was completely inhibited within 20 s at a minimum effective concentration (MEC) of 120 μg/ml. Tests for sperm viability by dual fluoroprobe staining showed the effect to be spermicidal with an EC₅₀ of 35.20 μg/ml. A series of investigations including tests for hypo-osmotic swelling, membrane lipid peroxidation, and electron microscopy document that the spermicidal effect of the fraction involves loss of sperm plasma membrane integrity and dissolution of the acrosomal vesicle – the two most important structural components that play diverse roles in physiological functions of sperm including fertilization. The fraction at 10×MEC exerted no detrimental effects on in vitro growth of Lactobacillus acidophilus, which is considered the major constituent of vaginal microflora that maintains vaginal health. Ames tests performed with different strains of Salmonella typhimurium including TA 97a, 98, 100, and 102, which detect mutagens causing bp substitution or frameshifting at G-C or A-T bp, demonstrate no mutagenic potential of the fraction. Significant spermicidal potential with no possible mutagenic effect and adverse impacts on lactobacilli growth attests to the credential of Ac-B-en as a prospective future spermicide for the development of a safe and effective vaginal contraceptive formulation.