Abstract
Bioassay-guided fractionation of a leaf extract of G. bracteata has yielded six new prenylxanthones, bractatin (1), isobractatin (2), 1-O-methylbractatin (3), 1-O-methylisobractatin (4), 1-O-methyl-8-methoxy-8,8a-dihydrobractatin (5), and 1-O-methylneobractatin (6). The structures of these compounds have been elucidated by spectroscopic means (NMR, MS), literature data, and X-ray crystallographic analysis of 2. These compounds possess significant cytotoxicity against the KB cell line.
MeSH terms
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Alkyl and Aryl Transferases / antagonists & inhibitors
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Antineoplastic Agents, Phytogenic / isolation & purification*
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Antineoplastic Agents, Phytogenic / pharmacology
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Crystallography, X-Ray
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Enzyme Inhibitors / pharmacology
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Humans
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KB Cells
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Magnetic Resonance Spectroscopy
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Mass Spectrometry
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Plant Leaves / chemistry
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Plants, Medicinal / chemistry*
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Spectrophotometry, Ultraviolet
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Xanthenes / isolation & purification*
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Xanthenes / pharmacology
Substances
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Antineoplastic Agents, Phytogenic
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Enzyme Inhibitors
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Xanthenes
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Alkyl and Aryl Transferases
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p21(ras) farnesyl-protein transferase