Abstract
Four new quercetin-derived oxidation products (1-4) and lunularin-4-O-beta-D-glucoside (5) were isolated from a water extract of onion (Allium cepa) skin, together with 17 other known compounds. Antibacterial assays for the isolated compounds showed that 2-(3,4-dihydroxyphenyl)-4,6-dihydroxy-2-methoxybenzofuran-3-one (1) presented selective activity against Helicobacter pylori strains and 3-(quercetin-8-yl)-2,3-epoxyflavanone (4) showed antibacterial activity against MRSA and H. pylori strains at the same time that it increased susceptibility of MRSA to beta-lactams. Evaluation of antioxidant activity against DPPH for the isolated compounds showed that the new derivative compounds (1-4) and 2,5,7,3',4'-pentahydroxy-3,4-flavandione (6) are more active than quercetin.
MeSH terms
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Anti-Bacterial Agents / isolation & purification
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Anti-Bacterial Agents / pharmacology*
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Antioxidants / isolation & purification
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Antioxidants / pharmacology*
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Bibenzyls / chemistry
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Bibenzyls / isolation & purification
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Biphenyl Compounds
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Disk Diffusion Antimicrobial Tests
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Glucosides / chemistry
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Glucosides / isolation & purification
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Helicobacter pylori / drug effects
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Hydrazines
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Methicillin-Resistant Staphylococcus aureus / drug effects
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Molecular Structure
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Onions / chemistry*
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Phenols / chemistry
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Phenols / isolation & purification
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Picrates
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Plant Extracts / isolation & purification
Substances
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Anti-Bacterial Agents
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Antioxidants
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Bibenzyls
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Biphenyl Compounds
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Glucosides
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Hydrazines
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Phenols
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Picrates
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Plant Extracts
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lunularin-4-O-beta-D-glucoside
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1,1-diphenyl-2-picrylhydrazyl