Abstract: In this study, an ultra-high performance liquid chromatography (UPLC) method was established to analyze the distribution of phenolic acids in aerial parts of 13 sweetpotato varieties. The results showed that addition of 0.2% sodium hydrogen sulfite to the extraction solvent could improve the recovery and stability of caffeic acid (CA) and caffeoylquinic acids (CQAs). Among the tested pretreatment methods, freeze grinding resulted in the highest content of phenolic acids, followed by freeze drying, oven drying, sun drying and homogenization. The UPLC method was fast, stable and highly sensitive with spiked recoveries of 99.5%?103.1%, and precision (expressed as relative standard deviation, RSD) of 0.3%?1.2%. The limit of detection (LOD) and the limit of quantification (LOQ) were 3.6?21.4 and 12.1?71.3 ng/mL, respectively. The contents of total CA and CQAs including CA, 3-CQA, 4-CQA, 5-CQA, 3,4-diCQA, 3,5-diCQA, 4,5-diCQA and 3,4,5-triCQA in the leaves, petioles and stems of sweatpotato ranged from 18.0?44.8, 0.7?11.9, and 0.3?9.7 g/kg dry sample, respectively. The contents of phenolic acids in different sweetpotato varieties were obviously different from each other, with dicaffeoylquinic acids (diCQAs) being the most abundant phenolic acid in all varieties. Moreover, diCQAs were the most abundant in the leaves among the three parts.

Key words: sweetpotato; caffeoylquinic acids; phenolic acids; freeze grinding; drying; ultra-high performance liquid chromatography