Acacetin and luteolin, the flavones isolated from the whole plant S. lutea, have been investigated for endocrine and contraceptive properties in the pre-implantation stage of pregnancy. Graded doses of these compounds, in gum acacia suspension, by oral administration from day 1 to day 4 of pregnancy showed dose-dependent anti-implantation activity (5-25 mg/kg body weight/day). MED100 was found to be 25 mg/kg body weight in the day 1-4 regimen in rats for both the compounds. In another study, a single oral dose of these compounds (10 mg/kg body weight) on day 1, 2 or 3 of pregnancy prevented 100% implantation. The compounds exhibited estrogenic property at their contraceptive dose level but failed to show antiestrogenic activity.