Protective effect of Citrus sinensis and Citrus aurantifolia against osteoporosis and their phytochemical constituents

The efficacy of Citrus aurantifolia L. cv. Swingle and Citrus sinensis L. cv. Liucheng against osteoporosis was evaluated in an ovariectomized rat model. Administration of Citrus extracts increased trabecular bone mineral content and bone mineral density of tibia, improved the levels of phosphorus and calcium. The results demonstrated that Citrus extracts reduced bone loss in ovariectomized rats. These findings have prompted the authors to investigate the phytochemical constituents of those plants, collected in Saudi Arabia, for the first time. Eighteen compounds were obtained from both plants and classified into, eight coumarins (1-8), eight flavonoids (9-16) and two sterols analogues (17 and 18). Leaves and peels of C. aurantifolia afforded eleven components, while those of C. sinensis afforded fourteen compounds. Structures of the isolated compounds were deduced by UV, NMR and MS spectra, and comparison with related structures, in which isobergapten (6), marmesin (7), myricetin (11), 4',5,7-trihydroxy-3,6-dimethoxy flavone (12), and quercetin-3-O-robinobioside (14), were reported to first time from Citrus species, Coumarins, flavonoids and sterols from C. aurantifolia and C. sinensis could be responsible for their antiosteoporotic activity and the action mechanism of these constituents needs to be further studied. Therefore, Citrus extracts have the potential to develop a clinically useful antiosteoporotic agent.