Many plant species have a large diversity of secondary metabolites with different biological activities. This study aims to assess the phenolic constituent, enzyme inhibitory and antioxidant activities of the aqueous (water) and methanol extracts of Inula discoidea. The enzyme assays showed effective enzyme inhibition of the methanol extract against acetylcholinesterase (AChE), butyrylcholinesterase (BChE), glutathione S-transferase (GST), and α-glycosidase (α-Gly) enzymes. The IC50 values for AChE, BChE, GST, and α-Gly were found as 38.5 mg/mL, 34.65 mg/mL, 77.0 mg/mL, and 40.76 mg/mL, respectively. Antioxidant properties of the aqueous and methanol extracts of I. discoidea were determined by four well-known in vitro techniques (ABTS, CUPRAC, DPPH, and FRAP methods). The antioxidant values of both water and methanol extracts were found to be better than the standard antioxidants (BHA, BHT, ascorbic acid, and α-tocopherol) in ABTS and CUPRAC methods. According to an updated LC-MS/MS technique analysis, quinic acid (21.08 mg/g), protocatechuic acid (4.49 mg/g), and gallic acid (0.48 mg/g) were found as major phenolic compounds of the plant extract. The binding interactions of major phenolic compounds of I. discoidea with the AChE, BChE, GST, and α-Gly enzymes were investigated by the molecular docking studies.
Keywords: Antioxidant; Enzyme inhibition; Inula discoidea; LC-MS/MS; Molecular docking.
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