Effects of Rosmarinic Acid and Sinapic Acid on the Skeletal System in Ovariectomized Rats

Background/Objectives: It is believed that some polyphenols, including phenolic acids, may counteract estrogen deficiency-induced bone loss, decreasing oxidative stress. Moreover, some phenolic acids-among others, rosmarinic acid and sinapic acid-have been reported to increase the serum estradiol concentration in rats. The study aimed to investigate the impact of rosmarinic acid and sinapic acid on the skeletal system of rats with estrogen deficiency induced by bilateral ovariectomy. Methods: The study was carried out on mature female rats, divided into sham-operated control rats, ovariectomized (OVX) control rats, and OVX rats treated with estradiol (0.2 mg/kg; positive control), rosmarinic acid (10 and 50 mg/kg), or sinapic acid (5 and 25 mg/kg). The compounds were administered orally for 4 weeks. Serum bone turnover markers, bone mass, mineral and calcium content, macrometric and histomorphometric parameters, as well as mechanical properties were examined. Results: Estrogen deficiency induced osteoporotic changes in ovariectomized control rats, which were slightly counteracted by the administration of estradiol. The phenolic acids slightly counteracted some changes caused by estrogen deficiency, but their administration at higher doses led to further worsening of cancellous bone quality. Conclusions: The results demonstrated that administration of high doses of rosmarinic acid or sinapic acid slightly unfavorably affected the rats' skeletal system under conditions of estrogen deficiency.