Evaluation of the antioxidant capacity of limonin, nomilin, and limonin glucoside.
The antioxidant capacity (AOC) of three representative citrus limonoids, limonin, nomilin, and limonin glucoside, was examined by the oxygen radical absorbance capacity (ORAC), Trolox equivalent antioxidant capacity (TEAC), beta-carotene-linoleic acid bleaching, and 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical scavenging assays. Pure compounds and proper negative (cinnamic acid) and positive (2,6-di-tert-butyl-4-methylphenol (BHT) and ascorbic acid) controls were used to remove any ambiguity in interpreting results. In all cases, limonin and nomilin gave results equivalent to those of cinnamic acid, indicating that they do not possess any inherent AOC and should not be considered antioxidants. Similar results were observed for limonin glucoside, with the exception of an anomalous result obtained from the beta-carotene-linoleic acid bleaching assay. Limonin glucoside was deemed not to be an antioxidant on the basis of the three unequivocal assays.
Breksa
Andrew P
AP
Western Regional Research Center, Agricultural Research Service, United States Department of Agriculture, 800 Buchanan Street, Albany, California 94710, USA. apb3@pw.usda.gov
Manners
Gary D
GD
D000975:Antioxidants / Q000494:pharmacology*; D001584:Benzoxepins / Q000494:pharmacology*; D001713:Biphenyl Compounds; D002839:Chromans; D005960:Glucosides / Q000494:pharmacology*; D036701:Limonins / Q000494:pharmacology*; D019787:Linoleic Acid / Q000737:chemistry; D010851:Picrates; D017382:Reactive Oxygen Species / Q000737:chemistry; D019207:beta Carotene / Q000737:chemistry
D000975:Antioxidants; D001584:Benzoxepins; D001713:Biphenyl Compounds; D002839:Chromans; D005960:Glucosides; D036701:Limonins; D010851:Picrates; D017382:Reactive Oxygen Species; D019207:beta Carotene; D019787:Linoleic Acid; C004931:1,1-diphenyl-2-picrylhydrazyl; C059405:nomilin; C001546:limonin; C010643:6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid