New Specific α-Glucosidase Inhibitor Flavonoid from Thymelaea tartonraira Leaves: Structure Elucidation, Biological...

The phytochemical investigation of Thymelaea tartonraira leaves led to the isolation and characterization of six compounds, including one new flavonoid glycoside identified as hypolaetin 8-O-β-D-galactopyranoside (4) along with five known compounds, daphnoretin (1), triumbelletin (2), genkwanin (3), tiliroside (5) and yuankanin (6). Their structures were established based on spectroscopic methods, such as UV, IR, NMR, and HR-ESI-MS. Triumbelletin (2) and tiliroside (5) were isolated for the first time from T. tartonraira leaves. The antioxidant property of all isolated compounds was tested based on DPPH, FRAP and total antioxidant capacity assays. Compound 4 displayed an antioxidant potency more interesting than vitamin C with an IC₅₀ =15.00±0.50 μg/ml, followed by compound 5. Furthermore, the both compounds 4 and 5 were tested for their α-amylase inhibitory activity in-vitro. Compound 4 displayed higher potency to inhibit α-amylase, with an IC₅₀ =46.49±2.32 μg/ml, than compound 5, with an IC₅₀ =184.2±9.2 μg/ml, while the reference compound acarbose presented the highest potency to inhibit α-amylase with an IC₅₀ =0.44±0.022 μg/ml. Compound 4 displayed a strong inhibitory ability of α-glucosidase activity approximately twice more than the reference compound, acarbose, with IC₅₀ values of 60.00±3.00 and 125.00±6.25 μg/ml, respectively. Thus, compound 4 exhibited a specific inhibitory activity for α-glucosidase. The molecular docking studies have supported our findings and suggested that compound 4 has been involved in various binding interactions within the active site of both enzymes α-amylase and α-glucosidase.