LC/MS-based Analysis of Bioactive Compounds from the Bark of Betula platyphylla var. japonica and Their Effects on Regulation of Adipocyte and Osteoblast Differentiation

Betula platyphylla var. japonica (Betulaceae), also known as Asian white birch, is an endemic medicinal tree, the bark of which has been used in Chinese traditional medicine for the treatment of various inflammatory diseases. In our continuing search for bioactive compounds from Korean natural resources, a phytochemical investigation of the bark of B. platyphylla var. japonica led to the isolation of 7-oxo-${\beta}$-sitosterol (1) and soyacerebroside I (2) from its ethanol extract as main components by liquid chromatography (LC)/mass spectrometry (MS)-based analysis. The structures of isolates were identified by comparison of $^1H$ and $^{13}C$ nuclear magnetic resonance spectroscopic data and physical data with the previously reported values and LC/MS analyses. To the best of our knowledge, this is the first study to demonstrate that the isolated compounds, 7-oxo-${\beta}$-sitosterol and soyacerebroside I, were isolated in B. platyphylla var. japonica. We examined the effects of the isolates on the regulation of adipocytes and osteoblast differentiation. These isolates (1 and 2) produced fewer lipid droplets compared to the untreated negative control in Oil Red O staining of the mouse mesenchymal stem cell line without altering the amount of alkaline phosphatase staining. The results demonstrated that both compounds showed marginal inhibitory effects on adipocyte differentiation but did not affect osteoblast differentiation.