This study was conducted to assess the potential of St. John's Wort ( Hypericum perforatum ) to prevent obesity and abnormalities in lipid metabolism induced by ovariectomy in a rat model without stimulatory activity on uterus.

Ovariectomized (OVX) rats were treated for 6 weeks with 70% ethanol extracts of Hypericum perforatum [HPEs: whole plant (WHPE) and flower and leaves (FLHPE)], β-estradiol-3-benzoate at a dose of 50 µg/kg/day (E2) or vehicle (distilled water).

As expected, OVX increased body weight gain and adiposity and showed higher food efficacy ratio. OVX also increased the serum cholesterol as well as insulin resistance, while reducing uterus weight and uterine epithelial proliferation rate. HPEs (WHPE and FLHPE) showed estrogen-like effect on body weight gain, adipose tissue weight and food efficacy ratio in OVX rats. HPEs prevented hypercholesterolemia induced by OVX more effectively than E2. E2 increased uterus weight and epithelial proliferation rate in OVX rats, while HPEs maintained them at the level of the sham-operated animals.

Our finding demonstrates that HPEs can be considered as an effective agent to prevent OVX-induced obesity without stimulatory activity on uterus.