phenolic compounds from diarthron iranica: enzymatic and in silico insights into α-amylase inhibitory activity

Background :diarthron iranica (family: thymelaeaceae), a medicinal plant native to iran, contains a variety of beneficial phytochemicals, among which phenolic compounds with a spectrum of health-promoting activities hold a special place. objectives :this study deals with the isolation and identification of the main phenolic compounds from d. iranica and investigates their inhibitory potential against α-amylase, an important enzyme in glucose metabolism, using in silico and in vitro approaches. methods :the purification procedure was accomplished employing chromatographic methods, including thin-layer chromatography (tlc), medium-pressure liquid chromatography (mplc), and high-performance liquid chromatography (hplc). the structures were determined using spectroscopic techniques: nmr (1h, 13c, dept), mass spectrometry (ms), and uv-vis spectroscopy. the in vitro α-amylase inhibition was performed in triplicate across seven concentrations (0.30 - 2.80 mg/ml) using the dns colorimetric method. molecular docking simulations were conducted using autodock 4.2, with ten conformations generated per ligand. results :several phenolic derivatives, including 5-[(β)-d-xylopyranoside-(1'''→6'')-β-d-glucopyranoside] 7-methoxy apigenin (yuankanin, 1), 6'-methoxy-7'-hydroxy-3'-o-7-bicoumarin (daphnoretin, 2), 4,4'-dihydroxy-3,3'-dimethoxy-7, 9':7', 9-diepoxylignan known as pinoresinol (3), and kusunokinin (4) with 3',4'-dimethoxy-3,4-methylenedioxydibenzyl butyrolactone structure were isolated and identified. in an α-amylase inhibition assay, compounds 1 and 3 exhibited moderate inhibitory activity with ic50 values of 1.32 mg/ml and 1.81 mg/ml, respectively, compared to the reference compound luteolin (ic50 = 0.63 mg/ml), indicating effective but relatively weaker inhibition. compound 2 demonstrated the strongest inhibitory activity with an ic50 value of 0.71 mg/ml, surpassing compounds 1 and 3. molecular docking studies revealed that compound 1 had a superior binding free energy of -7.13 kcal/mol, forming stable interactions through hydrogen bonding and van der waals forces within the enzyme's binding site. compound 3 showed a slightly lower binding energy of -6.43 kcal/mol with fewer stabilizing interactions. however, compound 2 demonstrated poor performance in the docking assay, despite its potent inhibitory activity in the α-amylase assay. conclusions :the phytochemical analysis carried out on the aerial parts of d. iranica yielded the identification and characterization of four phenolic compounds, including a methoxy apigenin glycoside (1), one bicoumarin (2), and two lignans (3-4). molecular docking studies indicated that compound 1 exhibited superior inhibitory potential compared to compound 3, with stable interactions in the enzyme's binding site. in α-amylase inhibitory assays, these compounds displayed varying levels of activity, with compound 2 showing the highest potency (ic50 = 0.71 mg/ml), followed by compounds 1 (ic50 = 1.32 mg/ml) and 3 (ic50 = 1.81 mg/ml). however, all were less effective than the reference compound luteolin (ic50 = 0.63 mg/ml), which demonstrated superior efficacy.