Lithocarpic acids O-S, five homo-cycloartane derivatives from the cupules of Lithocarpus polystachyus.

Chemical investigation of the cupules of Lithocarpus polystachyus resulted in the identification of four 3,4-seco-homo-cycloartane and one homo-cycloartane derivatives named lithocarpic acids O-S. Their structures were determined based on extensive 1D/2D NMR, IR, MS spectroscopic analyses and chemical methods. Lithocarpic acid O (1) exhibited inhibitory activities on mouse and human isozymes of 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) with IC50 values of 0.49 and 1.1 µM, respectively.