Antioxidant and antimicrobial activities, and phenolic compounds of Inula thapsoides ssp. thapsoides

Abstract

The members of Inula genus are widespread in the world and are used for many disorders by different cultures. Inula species contain terpenic compounds, especially sesquiterpen lactones, flavonoids, glycolipids and anthranilic acid derivatives (1). I. thapsoides (Bieb. ex Willd.) Sprengel which is a rhizomatous perennial herb (45 – 150 cm), has two subspecies in Turkey. In this study, I. thapsoides ssp. thapsoides was investigated for its total phenolic content, antioxidant, antimicrobial potential, and phenolic compound profile (2). Antioxidant activities of water, methanol and ethyl acetate extracts of flowers, leaves and roots of the plant were evaluated by DPPH and ABTS methods. All the extracts showed antioxidant activity in different concentrations. Water extract of leaves and methanol extract of roots expressed strong antioxidant activities with both methods compared to other extracts. Antimicrobial activities of the methanol extracts of flowers, leaves and roots of the plant were determined against S. aureus, E. faecalis, E. coli, P. aeruginosa, C. albicans and C. tropicalis by agar dilution method. All extracts exhibited antibacterial and anticandidal activities with different MIC values ranging from 50 to 200 µg/ml. Root extract was found very active against the investigated microorganisms. As the liable antioxidant and antimicrobial compounds, chlorogenic acid, caffeic acid, rutin, myricetin, quercetin, luteolin and kaempferol were analyzed qualitatively and quantitatively in the plant parts by RP-HPLC. While chlorogenic and caffeic acids were found in all the investigated extracts, myricetin was not determined in the plant. Consequently, investigated phenolics could be responsible for the potent antioxidant and antimicrobial activities of the plant.