Quantitation of volatiles and nonvolatile acids in an extract from coffee beverages: correlation with antioxidant activity.
The antioxidant activities of a commercial brewed coffee were investigated by measuring malonaldehyde (MA) formation from oxidized cod liver oil using a gas chromatographic method (MA-GC assay) and a thiobarbituric acid method (TBA assay). The highest antioxidant activity obtained by the MA-GC assay was from regular whole brewed coffee (97.8%) at a level of 20%, and the highest antioxidant activity obtained by the TBA assay was from decaffeinated whole brewed coffee (96.6%) at a level of 5%. Among 31 chemicals identified in a dichloromethane extract, guaiacol, ethylguaiacol, and vinylguaiacol exhibited antioxidant activities, which were comparable to that of alpha-tocopherol. Among nine chlorogenic acids (three caffeoylquinic acids, three feruloylquinic acids, and three dicaffeoylquinic acids) identified, 5-caffeoylquinic acid contained the greatest amount both in regular (883.5 microg/mL) and in decaffeinated (1032.6 microg/mL) coffees; it exhibited 24.5% activity by the MA-GC assay and 45.3% activity by the TBA assay at a level of 10 microg/mL. Caffeic and ferulic acids showed moderate antioxidant activities in both assays.
Fujioka
Kazutoshi
K
Department of Environmental Toxicology, University of California, Davis, 95616, USA.
Shibamoto
Takayuki
T
D000146:Acids, Carbocyclic / Q000032:analysis* / Q000494:pharmacology; D000975:Antioxidants / Q000032:analysis*; D002109:Caffeic Acids / Q000032:analysis / Q000494:pharmacology; D002110:Caffeine / Q000032:analysis; D002849:Chromatography, Gas; D003060:Cod Liver Oil / Q000737:chemistry; D003069:Coffee / Q000737:chemistry*; D003373:Coumaric Acids / Q000032:analysis / Q000494:pharmacology; D008315:Malondialdehyde / Q000032:analysis; D010084:Oxidation-Reduction; D017392:Thiobarbituric Acid Reactive Substances / Q000032:analysis; D014835:Volatilization
D000146:Acids, Carbocyclic; D000975:Antioxidants; D002109:Caffeic Acids; D003069:Coffee; D003373:Coumaric Acids; D017392:Thiobarbituric Acid Reactive Substances; D002110:Caffeine; D008315:Malondialdehyde; D003060:Cod Liver Oil; C004999:ferulic acid; C040048:caffeic acid