Phenolic Compounds of Rhodiola algida (Ledeb.) Fisch. & C.A. Mey.: New Glycosides of Herbacetin, HPLC-MS Profile and Organ-Specific Distribution

Abstract

Phenolic compounds of the genus Rhodiola (Crassulaceae) are the subject of numerous studies. Still, most data are dedicated to analyzing roots and rhizomes and, therefore, the metabolites of above-ground organs have been understudied. Rhodiola algida (Ledeb.) Fisch. & C.A. Mey. is a rare and under-investigated species of the genus growing in Altai-Sayan region. As a result of chromatographic separation of the metabolites of R. algida flower extract, 16 known compounds, including gallic acid, herbacetin glycosides, gossypetine, hibiscetin, quercetin, and kaempferol, as well as four new flavonoids (I–IV), were identified. The data of UV, NMR spectroscopy, mass spectrometry, and chemical transformations demonstrated that the new compounds were herbacetin 7-O-β-D-glucopyranoside-8-O-(2′′′-O-β-D-glucopyranosyl)-β-D-glucuronopyranoside (rhodiolgin A, I), herbacetin 3-O-β-D-glucopyranoside-8-O-(2′′′-O-acetyl)-α-L-arabinopyranoside (rhodiolgin B, II), herbacetin 3-O-β-D-glucopyranoside-8-O-(4'''-O-acetyl)-α-L-arabinopyranoside (rhodiolgin C, III), and herbacetin 8-O-(4''-O-acetyl)-β-D-xylopyranoside (rhodiolgin D, IV). The use of liquid chromatography-mass spectrometry allowed the identification of 96 metabolites in R. algida; herbacetin and gossypetin glycosides were the dominant compounds. The qualitative composition and quantitative content of groups and individual compounds in various organs of R. algida were significantly different, indicating an organ-specific feature of the accumulation of phenolic compounds in the plant.