Isolation and Characterization of Lupeol from Pterocarpus Osun Leaf Extract

Adeniran OI and Fadeyi AE

Published on: 2024-02-24


Pterocarpus osun, an indigenous plant with traditional therapeutic applications, was macerated with n-hexane, ethyl acetate, and methanol to obtain crude extracts. Extensive phytochemical screening led to the isolation of a white solid compound, lupeol, which was analysed using FTIR, 1D and 2D NMR, HR-LCMS, and by comparison with reference spectral data. 1H NMR showed seven methyl singlet’s at 0.72, 0.77, 0.79, 0.81, 0.82, 0.83 and 0.87 correspond to C-24, C-28, C-25, C-27, C-23, C- 26, and C-30 with two olefinic protons at 4.57 and 4.69 ppm representing the exocyclic double bond. The 13C-NMR spectrum revealed 30 carbon signals, including 7 methyl, 11 methylene, 6 methine, and 6 quaternary carbons, which came up at 78.6 ppm. Around 150.98 ppm (quaternary C) and 109.312 ppm (methylene C), respectively, the olefinic carbons of the exocyclic double bond were noted. These are designated as the C-20 and C-29 double bonds of the lupane-type triterpenoid molecule. 1H-1H COSY spectrum served as confirmation for the accurate designation of each proton. Mass spectrometric (MS) showed that lupeol exhibits a parent ion peak at m/z 427 [M+H] [+]. Lupeol is a well-known triterpenoid with pharmacological properties.