Isolation of triterpenoids from the stem bark of Albizia julibrissin and their inhibition activity on ACAT-1 and ACAT-2

The dried stem bark of Albizia julibrissin was extracted in 70% aqueous EtOH, and concentrated extracts were partitioned with EtOAc, n-BuOH, and H 2 O, successively. From the EtOAc fraction, three triterpenoids were isolated through repeated silica gel and octadecyl silica gel column chromatography. Based on nuclear magnetic resonance spectrometry (NMR), mass spectrometry, and infrared spectroscopy spectroscopic data, the chemical structures of the compounds were determined to be lupeol (1), betulinic acid (2), and oleanolic acid (3). This was the first report in which compounds 1, 2, and 3 were isolated from the stem bark of A. julibrissin. Since the NMR data for some compounds have been incorrectly or incompletely identified in previous literature, the NMR were revised on the basis of 2-D NMR experiments. Compounds 1, 2, and 3 showed inhibition activity on ACAT-1 with values of 89.3±3.7%, 61.2±3.4%, and 52.5±0.7%, respectively, at a concentration of 50 μg/mL and on ACAT-2 with values of 44.3±2.1%, 55.5±0.3%, and 22.0±2.6%, respectively, at a concentration 50 μg/mL.