TLC and HPLC analysis of the phenolic acids in Silphium perfoliatum L. leaves, inflorescences and rhizomes

TLC and HPLC have been used for preliminary evaluation of the phenolic acids occurring in the leaves, inflorescences, and rhizomes of Silphium perfoliatum L. Free phenolic acids and those released after acidic and basic hydrolysis were subjected to chromatographic analysis. Qualitative TLC analysis was performed by one- and two-dimensional ascending development on plates coated with cellulose, polyamide 11 F-254, and silica-gel 60 F-254. Reversed-phase HPLC was performed with photodiode-array detection. Seven phenolic acids were present, in the free and bonded forms, in the raw material studied. Caffeic and protocatechuic acids occurred in all the fractions analyzed. p-Coumaric and p-hydroxybenzoic acids were identified in all the free phenolic acid fractions. Ferulic acid was found in inflorescences and rhizomes and vanillic acid in leaves and inflorescences. After acidic hydrolysis chlorogenic acid was identified in leaves and p-hydroxybenzoic and vanillic acids in inflorescences. After basic hydrolysis phenolic acid fractions isolated from leaves also contained p-coumaric acid; those isolated from inflorescences contained p-coumaric, ferulic and p-hydroxybenzoic acids. It was found that caffeic acid was the most predominant phenolic acid in S. perfoliatum (from 67.8% in the leaves to 94.4% in the rhizomes).