Phytochemical profiling of Inula viscosa methanolic extracts and evaluation of their antioxidant, antimicrobial, enzyme-inhibitory activities and in vivo safety

Abstract Inula viscosa is a Mediterranean medicinal plant known for its anti-inflammatory, antimicrobial, and antioxidant properties. This study investigated the phytochemical profile and biological activities of methanolic extracts of I. viscosa collected from Skikda. The extract was rich in phenolics (210.30 ± 15.69 mg GAE/g dry extract), flavonoids (90.19 ± 6.90 mg QE/g dry extract), and tannins (65.65 ± 5.76 mg TAE/g dry extract). Strong antioxidant activity was observed with IC 50 values of 0.69 ± 0.09 mg/mL (DPPH) and 0.63 ± 0.66 mg/mL (ABTS), alongside total antioxidant capacity. HPLC and LC–MS/MS analyses identified major phenolics, including luteolin (4.080 μg/g dry extract, 5.33 %), myricetin (7.94 %), apigenin (0.540 μg/g dry extract, 6.60 %), quercetin (2.300 μg/g dry extract, 0.96 %), and kaempferol (1.560 μg/g dry extract, 4.01 %). The extract exhibited potent α-glucosidase (IC 50 = 15.82 ± 1.29 μg/mL) and α-amylase inhibition (IC 50 = 28.76 ± 0.67 μg/mL), moderate urease inhibition, and weaker acetylcholinesterase inhibition. Antibacterial activity was strongest against Klebsiella pneumoniae and Staphylococcus aureus . A 28-day oral toxicity study (100–300 mg/kg) confirmed safety, enhanced antioxidant defenses, reduced lipid peroxidation, and normalized hepatic and renal biomarkers. These findings support I. viscosa as a promising natural source of bioactive compounds.