Chemical Profile and Biological Properties of Methanolic and Ethanolic Extracts from the Aerial Parts of Inula britannica L. Growing in Central Asia

The genus Inula has been used in folk medicine for centuries; however, the data concerning Inula britannica L. are scarce. This study aimed at investigating the chemical composition of methanolic and ethanolic extracts from the aerial parts of I. britannica collected in Kazakhstan and evaluating their antimicrobial and antioxidant properties, with special attention being paid to polyphenols. The total content of polyphenols and flavonoids in the extracts was determined colorimetrically, while their qualitative and quantitative analyses were conducted using HPLC/ESI-QTOF-MS and RP-HPLC/DAD. Their antioxidant potential was determined using the FRAP and DPPH methods, whereas their antimicrobial activity was determined by the microdilution method towards a panel of reference microorganisms, including pathogens of the human gastrointestinal tract. Chemical analysis demonstrated that the methanolic extract had a higher content of polyphenols (58.02 vs. 43.44 mg GAE/g) and flavonoids (21.69 vs. 13.91 mg QUE/g) than the ethanolic extract. In both extracts, 15 compounds were identified, with the highest contents being those of cynarine (13.96 and 11.68 mg/g) and chlorogenic acid (9.22 and 5.09 mg/g). The DPPH assay showed a higher antioxidant activity of the methanolic extract (19.78 +/- 0.12 mg GAE/g) in comparison to that of the ethanolic extract (15.56 +/- 0.24 mg GAE/g). Similarly, the FRAP method showed that the methanolic extract exerted a much higher antioxidant activity (5.07 +/- 0.18 mmol Fe2+/g) than the ethanolic extract (0.39 +/- 0.01 mmol Fe2+/g). In contrast, both extracts showed similar antimicrobial properties, with the highest activity being that against Helicobacter pylori ATCC 43504 (MIC = 0.125-0.25 mg/mL). This paper presents novel data on I. britannica L., implying its significance as a source of valuable active compounds and being a prerequisite for further biological studies.