Comparison of total phenolic content and composition of individual phenolic acids in testae and testa-removed kernels of 15 Valencia-type peanut (Arachis hypogaea L.) genotypes
A successful peanut breeding to obtain genotypes with greater phenolic content requires information on type and content of phenolic compounds in parental peanut genotypes. The aim of this study was to investigate the total phenolic contents and phenolic acid profiles of 15 Valencia-type peanut genotypes both in peanut testae and testa-removed kernels (cotyledons and embryonic axes). Total phenolic content and phenolic acid profiles were analyzed using Folin-Ciocalteu method and high-performance liquid chromatography (HPLC), respectively. The total phenolic contents of testae and testa-removed kernels varied from 2.47 ± 0.96 to 84.53 ± 5.57 and 0.07 ± 0.01 to 0.12 ± 0.01 mg gallic acid equivalent (GAE)/g dry weight, respectively. Testae of KK4 and ICG14710 genotypes had the greatest and least total phenolic content, respectively. The peanut testae with pink color (NM044, NM071, ICG15042 and KK4) had significantly greater phenolic content than those with gray (ICG397 and ICG14710) and yellow (NM001) colors. The present study demonstrates that p-coumaric and vanillic acids were the two predominant phenolic acids in the testae of nearly all peanut genotypes tested, except for KK4 genotype whose predominant phenolic acid in its testa was p-hydroxybenzoic acid. All the testa-removed kernels tested contained significantly greater amount of p-coumaric acid than other identified phenolic acids. These results would be useful for peanut breeding to obtain peanut genotypes with greater phenolic acid and other favorable traits.
Key words: Valencia peanuts, peanut testae, phenolic acids, p-coumaric acid, vanillic acid.