Abstract
Two new glycosides, 3-hydroxy-5-methoxy-4-methylphenyl beta-D-glucopyranoside (1) and 4-benzoyl-2-C-beta-glucopyranosyl-3,5-dihydroxy-6-methylphenyl beta-D-glucopyranoside (2), together with four known glycosides, 2-endo-beta-D-glucopyranosyloxy-1,8-cineole (3a), 2-exo-beta-D-glucopyranosyloxy-1,8-cineole (3b), roseoside (4), and citroside A (5), were isolated from the methanolic extract of leaves of Melaleuca quinquenervia. Their structures were elucidated on the basis of spectroscopic analysis. Compounds 1, 2a and 3 inhibited contractile response induced by phenylephrine in aortic rings from Sprague-Dawley rats. This inhibition was independent of the endothelium. Compounds 2 and 4 significantly relaxed precontracted aortic rings, in an endothelium-dependent manner. Pretreatment of N(omega)-nitro-L-arginine (L-NNA), a nitric oxide synthase inhibitor, partially attenuated the vasorelaxation induced by both compounds, suggesting that nitric oxide was likely the responsible mediator. The rank-order potency (EC 50 value) of vasorelaxing activities of these compounds is 4 > 2 > 2a > 3 > 1.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Aorta, Thoracic / drug effects
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Disaccharides / chemistry
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Disaccharides / isolation & purification
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Disaccharides / pharmacology*
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Dose-Response Relationship, Drug
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Endothelium, Vascular / physiology
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Glucosides / isolation & purification
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Glucosides / pharmacology
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Glycosides / chemistry
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Glycosides / isolation & purification
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Glycosides / pharmacology*
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Monosaccharides / chemistry
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Monosaccharides / isolation & purification
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Monosaccharides / pharmacology*
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Myrtaceae*
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Nitric Oxide / metabolism
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Nitric Oxide Synthase / antagonists & inhibitors
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Nitroarginine / pharmacology
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Norisoprenoids*
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Phenylephrine / pharmacology
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Plant Extracts / chemistry
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Plant Extracts / pharmacology*
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Plant Leaves / chemistry*
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Rats
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Rats, Sprague-Dawley
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Vasoconstriction / drug effects*
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Vasodilation / drug effects
Substances
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2-endo-glucopyranosyloxy-1,8-cineole
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3-hydroxy-5-methoxy-4-methylphenyl-glucopyranoside
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4-benzoyl-2-C-glucopyranosyl-3,5-dihydroxy-6-methylphenyl-glucopyranoside
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Disaccharides
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Glucosides
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Glycosides
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Monosaccharides
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Norisoprenoids
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Plant Extracts
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roseoside
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Phenylephrine
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Nitroarginine
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Nitric Oxide
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Nitric Oxide Synthase