High-Performance Liquid Chromatography Determination of Phenolic Constituents in 17 Varieties of Cowpeas
- 7 February 2003
- journal article
- Published by American Chemical Society (ACS) in Journal of Agricultural and Food Chemistry
- Vol. 51 (6), 1623-1627
- https://doi.org/10.1021/jf020867b
Abstract
Seventeen varieties of cowpeas grown in Arkansas were analyzed for their phenolic constituents using high-performance liquid chromatography (HPLC). Protocatechuic acid was identified as the major phenolic acid present in esterified forms. The amount of protocatechuic acid increased from trace−3.6 to 9.3−92.7 mg/100 g of flour in the 17 varieties of cowpeas after hydrolysis. Six other phenolic acids, including, p-hydroxybenzoic acid, caffeic acid, p-coumaric acid, ferulic acid, 2,4-dimethoxybenzoic acid, and cinnamic acid, were also identified. These phenolic acids were evenly distributed mainly in free acid forms at <7 mg/100 g of flour. Total phenolic contents determined using Folin−Ciocalteu's reagent were largely different among the 17 varieties, ranging from 34.6 to 376.6 mg/100 g of flour. A comparison of the HPLC chromatograms of the 17 cowpea phenolics before and after alkali hydrolysis indicated the conversion of a pattern with evenly distributed peaks to one with a single major peak for protocatechuic acid, suggesting that the chromatograms before hydrolysis better represent the identities of the cowpea varieties. Keywords: Cowpea; HPLC; phenolics; protocatechuic acidKeywords
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