Free and soluble bound phenolic acids in some cruciferous vegetables.

Hydroxybenzoic, and hydroxycinnamic acids of free, glucosidic, and ester forms were obtained separately from fresh leaves of six cruciferous vegetables and analyzed by GC and GC-MS. Three hydroxybenzoic acids (p-hydroxybenzoic, vanillic, and protocatechuic acids) and eight hydroxycinnamic acids (cis-, and trans-isomers of p-coumaric, ferulic, caffeic, and sinapic acids) were identified in all the vegetables used, of which cis-, and trans-sinapic acids were the most prominent and trans-ferulic acid was next abundant in each phenolic acid fraction of the vegetables. The hydroxybenzoic acids were relatively higher in amounts in the glucosidic fractions. On the other hand, most of the hydroxycinnamic acids were found in the alkaline hydrolyzates of each vegetable extract, indicating that the hydroxycinnamic acids are mainly contained as esters.