Identification and quantification of (dihydro) hydroxycinnamic acids and their conjugates in potato by UHPLC–DAD–ESI-MSn

Hydroxycinnamic acid conjugates (HCAcs) and dihydrohydroxycinamic acid conjugates (DHCAcs) were identified and quantified in potato tuber extracts by UHPLC–DAD–ESI-MSn. The HCAcs and DHCAcs identification took place by screening for product ions and neutral losses in combination with UV spectra. Thirty-nine HCAcs/DHCAcs were detected, including 17 previously reported in potato. HCAs were found unconjugated, linked to hydroxyl-containing compounds including hexose, quinic acid and malic acid, to amino-containing compounds, such as putrescine and octopamine, and to unknown compounds. DHCAs were present linked to spermine, spermidine and to still unidentified compounds. Chlorogenic acid was the most abundant compound (25.43 ± 0.49 mg/g DW) followed by cryptochlorogenic acid (7.31 ± 0.38 mg/g DW), a non-hydrolyzable sinapic acid conjugate (2.80 ± 0.06 mg/g DW) and neochlorogenic acid (2.41 ± 0.10 mg/g DW), in total accounting for 83% (w/w) of the total concentration of HCAs/DHCAs-containing compounds. Quantifications of HCAs released after alkaline hydrolysis matched well with the quantification of the unhydrolyzed molecules. The UHPLC–DAD–ESI-MSn method showed a larger diversity of HCAcs and DHCAcs in potato than described before.