Protective effect of plant extract from Onobrychis ebenoides on ovariectomy-induced bone loss in rats

Certain plant extracts have been the object of recent studies due to their mild estrogenic action and their possible potential role in osteoporosis prevention and/or treatment. The present study was undertaken to investigate the possible protective effect of the aqueous solution of the plant Onobrychis ebenoides, with proven in vitro mild estrogenic action, on bone mass loss of the ovariectomized (Ovx) rat experimental model of osteoporosis.

Forty intact female mature (10-month-old) Wistar rats were separated into three groups: Ovx, Ovx plus plant extract (Ph) and sham-operated (control). Ph administration in the drinking water at a dose of 300 mg/kg body weight/day commenced immediately after Ovx. Bone mineral density (BMD) values, percentage change from the baseline measurement and histomorphometry of the tibia, as well as body and uterine weight, were examined and compared between groups.

Comparison of BMD absolute values of the whole tibia of Ovx + Ph and Ovx animals at both 3 and 6 months post-Ovx were highly significant (p < 0.0005), showing a protective effect on treated animals. The extract did not appear to have such a beneficial effect on BMD of the proximal tibia of the treated animals compared to the Ovx animals after 3 months; however, a significant protective effect was observed at 6 months post-Ovx in treated animals compared to the Ovx (p = 0.015). When the % changes from baseline measurement of the whole tibia of Ovx + Ph and controls were compared, there was no significant difference at 3 or 6 months, demonstrating a highly protective effect; the respective comparisons of proximal tibia % changes did not display such protection. Body and uterine weight comparisons showed no significant difference between Ovx and treated rats, whereas, the level of significance for each group compared to controls was p < 0.0005.

The Ph studied showed a highly significant protective effect on BMD of the whole tibia of Ovx rats after 3 and 6 months of treatment, compared to the non-treated animals. Its effect on the proximal tibia was less pronounced, but also statistically significant compared to non-treated rats after 6 months. The lack of significant effect on body and uterine weight is in favor of its selective estrogen receptor modulator-like activity, and merits further studies.