Antioxidative activities of heterocyclic compounds formed in brewed coffee.
Typical volatile heterocyclic compounds found in brewed coffee extracts-pyrroles, furans, thiophenes, and thiazoles-were examined for antioxidative activity, which was determined by measuring the oxidative conversion of hexanal to hexanoic acid using gas chromatography. 2-Acetylpyrrole, 1-methylpyrrole, and pyrrole inhibited hexanal oxidation by 98, 87, and 78%, respectively, at a concentration of 500 microgram/mL over a period of 30 days. 2-Methylfuran, which inhibited hexanal oxidation by 90% at all concentrations tested (500, 200, and 100 microgram/mL) for a 30-day period, exhibited the greatest activity among furans tested. Similarly, 2-methylthiophene, which inhibited hexanal oxidation by almost 100% at a concentration of 500 microgram/mL over 30 days, exhibited the greatest activity among the thiophenes tested. In general, thiazoles were ineffective antioxidants at all concentrations tested. However, 4,5-dimethylthiazole was able to inhibit hexanal oxidation by 50% at the highest level tested (500 microgram/mL). 2-Acetylpyrrole, 2-methylfuran, and 2-methylthiophene at concentrations of 500, 200, and 100 microgram/mL and furan at a concentration of 500 microgram/mL exhibited antioxidative activities comparable to that of the synthetic antioxidant butylated hydroxytoluene at a concentration of 50 microgram/mL.
Fuster
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MD
Department of Environmental Toxicology, University of California, Davis, California 95616, USA.
Mitchell
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AE
Ochi
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Shibamoto
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D000447:Aldehydes / Q000737:chemistry; D000975:Antioxidants / Q000032:analysis* / Q000737:chemistry; D002208:Caproates / Q000737:chemistry; D002849:Chromatography, Gas; D003069:Coffee / Q000737:chemistry*; D003296:Cooking; D006571:Heterocyclic Compounds / Q000032:analysis* / Q000737:chemistry; D010084:Oxidation-Reduction
D000447:Aldehydes; D000975:Antioxidants; D002208:Caproates; D003069:Coffee; D006571:Heterocyclic Compounds; C037652:hexanoic acid; C010463:n-hexanal