Isolation of Trimer stilbenoids from the bark of Shorea maxwelliana
The stem bark of Shorea maxwelliana King (2.85kg) was collected from reserved forest Jengka, Pahang, Malaysia. Three major trimer stilbenoids have been isolated from acetone extract of the stem bark of Shorea maxwelliana. Sample of S. maxwelliana was macerated in acetone for five times, and the solvent evaporated using rotary evaporator to produce crude acetone extract. The acetone extract (178.90g) was fractionated by a series of solvent partitions into an EtOH soluble phenolic fraction (25.78g). This fraction was repeatedly chromatographed on silica gel columns with Hex-EtOH (1:1) and EtOH, and then with a CHCl3-MeOH gradient of increasing MeOH to provide four fractions (A-D). Fraction A was the n-hexane soluble fraction (12.6g). Fraction B (2.26g) was subjected to silica gel chromatography eluted with CHCl3-MeOH (95:10 to 80:20) to give compound 1 (500mg). Fraction C (9.8g) was subjected to silica gel chromatography eluted with CHCl3-EtOH-MeOH (85:1:0.5) to afford compound 2 (250mg). Compound 3 (185mg) was obtained from fraction D (1.12g) by silica gel chromatography eluted with CHCl3-MeOH (8:2) . The molecular structures of 1, 2 and 3 were determined based on spectroscopic data, including UV, IR, 1H NMR, 13C NMR, 2D NMR and comparison with that reported in the literature. Spectral data of compounds 1, 2 and 3 showed very close similarity to α-viniferin , vaticanol A  and copalliferol A .
Acknowledgement: The authors would like to thank the Ministry of Science, Technology and Innovation, Malaysia (MOSTI) for funding the research grant, Fundamental Research Grant Scheme (FRGS), 600-RMI/FRGS 5/3/Fst (19/2009) and National Science Fellowships (NSF) for financing the study of one of the authors.
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