Khayanolides from African mahogany Khaya senegalensis (Meliaceae): A revision |
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Authors: | Huaping Zhang Don VanDerveer Michael J Wargovich |
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Institution: | a Department of Food Science and Human Nutrition, Clemson University, Clemson, 29634 SC, USA b State Key Laboratory of Drug Research, Institute of Materia Medica, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, PR China c Department of Chemistry, Clemson University, Clemson, 29634 SC, USA d Department of Genetics and Biochemistry, Clemson University, Clemson, 29634 SC, USA e Department of Cell and Molecular Pharmacology, Hollings Cancer Center, Charleston, 29425 SC, USA |
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Abstract: | Five khayanolides (1-O-acetylkhayanolide B 1, khayanolide B 2, khayanolide E 3, 1-O-deacetylkhayanolide E 4, 6-dehydroxylkhayanolide E 5) were isolated from the stem bark of African mahogany Khaya senegalensis (Meliaceae). Their structures and absolute configurations were determined through extensive spectroscopic analyses including MS, NMR, and single-crystal X-ray diffraction experiments. The results established that two previously reported khayanolides, 1α-acetoxy-2β,3α,6,8α,14β-pentahydroxy-4.2.110,30.11,4]-tricyclomeliac-7-oate 6 and 1α,2β,3α,6,8α,14β-hexahydroxy-4.2.110,30.11,4]-tricyclomeliac-7-oate 7, were, in fact, 1-O-acetylkhayanolide B 1 and khayanolide B 2, and that the two reported phragmalin derivatives, methyl 1α-acetoxy-6,8α,14β,30β-tetrahydroxy-3-oxo-3.3.110,2.11,4]-tricyclomeliac-7-oate 8 and methyl 1α,6,8α,14β,30β-pentahydroxy-3-oxo-3.3.110,2.11,4]-tricyclomeliac-7-oate 9, were, in fact, khayanolide E 3 and 1-O-deacetylkhayanolide E 4, respectively. Based on the results from this study and consideration of the biogenetic pathway, the methyl 6-hydroxyangolensate in African mahogany K. senegalensis should have a C-6 S configuration while methyl 6-hydroxyangolensate in genuine mahogany Swietenia species should have a C-6 R configuration. |
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Keywords: | Khaya senegalensis Meliaceae African mahogany Limonoid Khayanolide Structure revision 1-O-acetylkhayanolide B Khayanolide B Khayanolide E 1-O-deacetylkhayanolide E 6-Dehydroxylkhayanolide E Methyl 6-hydroxyangolensate |
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