Determination of free amino acids in five commercial sweetpotato cultivars by hydrophilic interaction liquid chromatography-mass spectrometry

Abstract

A sensitive and rapid method was developed for the determination of free amino acid profiles in sweetpotatoes. The method utilized an ultra-high-performance liquid chromatography system with hydrophilic interaction liquid chromatography (HILIC) separation coupled with tandem mass-spectrometry (MS/MS) detection without the need for chemical derivatization. Separation of 36 amino acid standards was achieved on a silica HILIC column in a single MS/MS run of 19 min. This validated method was applied for the analysis of the free amino acid composition of five commercial sweetpotato cultivars (Covington, Beauregard, Hatteras, Murasaki-29 and O’ Henry) from two planting lots grown in experimental fields. Analysis of variance with Tukey’s test was used to determine the differences in individual free amino acid content among the analyzed samples, and principle component analysis (PCA) was implemented to evaluate the variation in amino acid profiles of different sweetpotato cultivars. Asparagine was the most abundant free amino acid and its content varied significantly among the cultivars (p < 0.05). Fifteen additional amino acids also varied among cultivars and contributed to the differentiation of the genotypes by PCA based on their complete amino acid profiles. The efficient, reliable, sensitive method described herein could be used in quantifying amino acids in food matrices similar to sweetpotatoes.