Antioxidative activities of heterocyclic compounds formed in brewed coffee

Typical volatile heterocyclic compounds found in brewed coffee extracts-pyr roles, furans, thiophenes, and thiazoles-were examined for antioxidative ac tivity which was determined by measuring the oxidative conversion of hexana l to hexanoic acid using gas chromatography. 2-Acetylpyrrole, 1-methylpyrro le, and pyrrole inhibited hexanal oxidation by 98, 87, and 78%, respectivel y, at a concentration of 500 mug/mL over a period of 30 days. 2-Methylfuran , which inhibited hexanal oxidation by 90% at all concentrations tested (50 0, 200, and 100 mug/mL) for a 30-day period, exhibited the greatest activit y among furans tested. Similarly, 2-methylthiophene, which inhibited hexana l oxidation by almost 100% at a concentration of 500 mug/mL over 30 days, e xhibited the greatest activity among the thiophenes tested. In general, thi azoles were ineffective antioxidants at all concentrations tested. However, 4,5-dimethylthiazole was able to inhibit hexanal oxidation by 50% at the h ighest level tested (500 mug/mL). 2-Acetylpyrrole, 2-methylfuran, and 2-met hylthiophene at concentrations of 500, 200, and 100 mug/mL and furan at a c oncentration of 500 mug/mL exhibited antioxidative activities comparable to that of the synthetic antioxidant butylated hydroxytoluene at a concentrat ion of 50 mug/mL.