Phenolic compounds in ethanol extracts of different plant organs of Inula oculis-christi L.

Abstract

Inula oculus-christi L. (family Asteraceae), grows naturally in Asia, Central Europe and the Balkan Peninsula. Sesquiterpenoids, flavonoids and phenolics as major secondary metabolites contribute to a variety of biological activities of this perennial species. In this research, an emphasis is given to the analysis of phenolic compounds in ethanol extracts of leaves, flowers, stems, rhizomes, and roots of I. oculus-christi. The content of total phenolics (TPC) and total flavonoids (TFC) in extracts of different plant parts of I. oculus-christi was determined. Significantly high TPC and TFC were observed in extract of flowers, while the extracts of stems and roots had the lowest content of phenolic compounds. UHPLC–LTQ/orbitrap/MS analysis was performed for separation, identification, and quantification of the major phenolic components in I. oculus-christi extracts. A total of 46 compounds detected belong to three structurally distinct groups: 1) hydroxycinnamic acid derivatives (14 compounds); 2) flavonoid glycosides (21 compounds); and 3) flavonoid aglycones (11 compounds). Dominant hydroxycinnamates were derivatives of caffeic acid, esterified with quinic or aldaric acids. The relative abundance of these compounds was higher in extracts of flowers, leaves and rhizomes. From the flavonoid glycoside group, flavone (nepetin, luteolin, apigenin, and chrysoeriol) and flavonol (quercetin, patuletin, kaempferol, isorhamnetin, and 3,3’-dimethylquercetin) derivatives were found in tested samples. Flavonoid aglycones were the most abundant compounds in extracts of flowers. Observed differences in phenolic content highlight the possibility of targeted collection and application of different I. oculus-christi extracts considering previously determined biological activities.