Comparative study of phenolic acids from underground parts of Rheum palmatum L., R. rhaponticum L. and R. undulatum L.

In three species of Rheum L. genus growing in Poland the composition of phenolic acids was determined. By 2D-TLC method the following acids were identified: ellagic, chlorogenic, gallic, protocatechuic, homoprotocatechuic, caffeic, α-resorcilic, p-hydroxyphenylacetic, p-hydroxybenzoic, p-coumaric, syringic, vanillic and ferulic. There are no substantial qualitative differences among the complex of phenolic acids in the investigated species. The RP-HPLC method was used for quanitative determination of phenolic acids. The amount of individual phenolic acids ranged between 2.2 µg/g and 147.8 µg/g in air-dry rhizome. The content of ferulic acid is the highest in all the examined cases. The total amount of the tested phenolic acids in Rheum undulatum L., R. palmatum L., and R. raponticum L. was respectively 346.4 µg/g, 229.8 µg/g, and 195 µg/g.