Avenanthramides in oats (Avena sativa L.) and structure-antioxidant activity relationships.
Eight avenanthramides, amides of anthranilic acid (1) and 5-hydroxyanthranilic acid (2), respectively, and the four cinnamic acids p-coumaric (p), caffeic (c), ferulic (f), and sinapic (s) acid, were synthesized for identification in oat extracts and for structure-antioxidant activity studies. Three compounds (2p, 2c, and 2f) were found in oat extracts. As assessed by the reactivity toward 1,1-diphenyl-2-picrylhydrazyl (DPPH), all avenanthramides except 1p showed activity. Initially, the antioxidant activity of the avenanthramides decreased in a similar order as for the corresponding cinnamic acids, that is: sinapic > caffeic > ferulic > p-coumaric acid. The avenanthramides derived from 2 were usually slightly more active than those derived from 1. All avenanthramides inhibited azo-initiated peroxidation of linoleic acid. 1c and 1s were initially the most effective compounds. The relative order of antioxidant activities was slightly different for the DPPH and the linoleic acid assays run in methanol and chlorobenzene, respectively.
Bratt
Katarina
K
Institute of Chemistry, Department of Organic Chemistry, Uppsala University, P.O. Box 531, SE-751 21 Uppsala, Sweden.
Sunnerheim
Kerstin
K
Bryngelsson
Susanne
S
Fagerlund
Amelie
A
Engman
Lars
L
Andersson
Rolf E
RE
Dimberg
Lena H
LH
D000577:Amides / Q000032:analysis* / Q000737:chemistry; D000975:Antioxidants / Q000032:analysis* / Q000737:chemistry; D018554:Avena / Q000737:chemistry*; D002109:Caffeic Acids / Q000032:analysis / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D003373:Coumaric Acids / Q000032:analysis / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D010936:Plant Extracts / Q000737:chemistry; D011422:Propionates; D013329:Structure-Activity Relationship; D062367:ortho-Aminobenzoates / Q000032:analysis* / Q000737:chemistry
D000577:Amides; D000975:Antioxidants; D002109:Caffeic Acids; D003373:Coumaric Acids; D010936:Plant Extracts; D011422:Propionates; D062367:ortho-Aminobenzoates; C073734:sinapinic acid; C004999:ferulic acid; C495469:p-coumaric acid; C040048:caffeic acid