Analysis of the free amino acid content and profile of 129 peach (Prunus persica (L.) Batsch) germplasms using LC-MS/MS without derivatization

Free amino acids (FAAs) are essential for fruit flavor and function. In this study, mature fruits of 129 germplasms grown in China were employed to fully comprehend the variability in the FAA composition of peaches (Prunus persica (L.) Batsch). A brief sample preparation process, based on formic acid/water/methanol extraction, was performed. Using the HSS T3 column, 24 FAAs were successfully separated. These FAAs were analyzed using LC-MS/MS without derivatization. A total of 20 FAAs were detected in peaches. Asparagine was the most abundant FAA (368.04–6090.79 μg/g FW) in peach fruit, followed by aspartic acid (29.00–409.51 μg/g FW), glutamic acid (45.33–290.13 μg/g FW), alanine (22.39–805.21 μg/g FW), glutamine (12.05–322.62 μg/g FW), serine (17.81–323.35 μg/g FW), and threonine (10.9–109.04 μg/g FW). Other proteinaceous amino acids, including arginine, glycine, histidine, isoleucine, leucine, lysine, phenylalanine, proline, tryptophan, tyrosine, valine, cis-4-hydroxy-proline, and a specialized non-proteinaceous amino acid, γ-aminobutyric acid, were identified and quantified in the peach germplasm. By comparing the FAA content of various germplasms, middle- and late- maturing peaches were found to possess more asparagine, proline, and cis-4-hydroxy-proline than early-maturing peaches. These essential results could markedly augment peach breeding programs and provide a comprehensive understanding of the peach germplasm resources.