Potential Antiosteoporotic Natural Product Lead Compounds That Inhibit 17β-Hydroxysteroid Dehydrogenase Type 2

17 beta-Hydroxysteroid dehydrogenase type 2 (17 beta-HSD2) converts the active steroid hormones estradiol, testosterone, and 5 alpha-dihydrotestosterone into their weakly active forms estrone, Delta(4)-androstene-3,17-dione, and 5 alpha-androstane-3,17-dione, respectively, thereby regulating cell- and tissue-specific steroid action. As reduced levels of active steroids are associated with compromised bone health and onset of osteoporosis, 17 beta-HSD2 is considered a target for antiosteoporotic treatment. In this study, a pharmacophore model based on 17 beta-HSD2 inhibitors was applied to a virtual screening of various databases containing natural products in order to discover new lead structures from nature. In total, 36 hit molecules were selected for biological evaluation. Of these compounds, 12 inhibited 17 beta-HSD2 with nanomolar to low micromolar IC50 values. The most potent compounds, nordihydroguaiaretic acid (1), IC50 0.38 +/- 0.04 mu M, (-)-dihydroguaiaretic acid (4), IC50 0.94 +/- 0.02 mu M, isoliquiritigenin (6), IC50 0.36 +/- 0.08 mu M, and ethyl vanillate (12), IC50 1.28 +/- 0.26 mu M, showed 8-fold or higher selectivity over 17 beta-HSD1. As some of the identified compounds belong to the same structural class, structure-activity relationships were derived for these molecules. Thus, this study describes new 17 beta-HSD2 inhibitors from nature and provides insights into the binding pocket of 17 beta-HSD2, offering a promising starting point for further research in this area.