High-performance liquid chromatography determination of phenolic constituents in 17 varieties of cowpeas.
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.
Cai
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Department of Food Science, University of Arkansas, Fayetteville 72704, USA.
Hettiarachchy
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Jalaluddin
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D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004951:Esterification; D007887:Fabaceae / Q000737:chemistry*; D006868:Hydrolysis; D062385:Hydroxybenzoates / Q000032:analysis; D007202:Indicators and Reagents; D010636:Phenols / Q000032:analysis*
D062385:Hydroxybenzoates; D007202:Indicators and Reagents; D010636:Phenols; C009091:protocatechuic acid