The capability of an aqueous methanol extract obtained from the leaves of Feijoa sellowiana Berg. on possible prevention and treatment of osteoporosis has been examined by evaluating its stimulating effect on the two human osteoblastic cell lines HOS58 and SaOS-2. The extract was found to increase significantly the mineralization of cultivated human bone cell, whereby a clear increment (15.3 +/- 2.7%) in von Kossa positive area was determined when administering 25 microg/ml leaf extract. A phytochemical investigation of the extract has demonstrated the high phenolic content and led to the isolation and identification of twenty three of them, among which the new 3-methoxyellagic acid 4-O-beta-glucopyranoside was fully identified. All structures were elucidated on the basis of conventional analytical methods and confirmed by FTMS, 1D- and 2D-NMR data. The new compound was found to cause a significant increase of mineralized area at 20 microg/mL, while at lower concentrations the effect was not significant. However, an increase of the number of mineralized spots (nodules) at all tested concentrations of the compound was observed.