Phytochemical on-line screening and <i>in silico</i> study of <i>Helianthemum confertum</i>: antioxidant activity, DFT, MD simulation, ADME/T analysis, and xanthine oxidase binding

Abstract

Seven components from the methanol extract of the aerial part of the endemic species <i>Helianthemum confertum</i> were isolated and identified for the first time. Investigating this species and its separated components chemical make-up and radical scavenging capacity, was the main goal. Using an online HPLC-ABTS˙⁺ test, ORAC, and TEAC assays, the free radical scavenging capacity of the ethyl acetate extract was assessed. The fractionation of these extracts by CC, TLC, and reverse-phase HPLC was guided by the collected data, which was corroborated by TEAC and ORAC assays. Molecular docking studies, DFT at the B3LYP level, and an examination of the ADME/T predictions of all compounds helped to further clarify the phytochemicals' antioxidant potential. Isolation and identification of all components were confirmed through spectroscopy, which revealed a mixture (50-50%) of <i>para</i>-hydroxybenzoic acid 1 and methyl gallate 2, protocatechuic acid 3, astragalin 4, <i>trans</i>-tiliroside 5, <i>cis</i>-tiliroside 6, contaminated by <i>trans</i>-tiliroside and 3-oxo-α-ionol-β-d-glucopyranoside 7, as well as two new compounds for the genus <i>Helianthemum</i> (2 and 7). With a focus on compounds 1, 2, 3, and 4, the results clearly showed that the extract and the compounds tested from this species had a high antioxidant capacity. Within the xanthine oxidase enzyme's pocket, all of the components tested showed strong and stable binding. In light of these findings, the xanthine oxidase/methyl gallate 2 complex was simulated using the Desmond module of the Schrodinger suite molecular dynamics (MD) for 100 ns. Substantially stable receptor-ligand complexes were observed following 1 ns of MD simulation.