A DFT Analysis on Antioxidant and Antiradical Activities from Anthraquinones Isolated from the Cameroonian Flora

Abstract

The present work is devoted to the exploration antioxidant and antiradical activity of twenty anthraquinones isolated from the Cameroonian flora at B3LYP/6-311++G(d,p) level of theory using the B3LYP/6-31 + G(d,p) geometrical data as geometry optimization starting points. The single electron transfer mechanism has been adopted to examine both biological activities. The classification of the antiradical profile to integrate the electrodonating power (ω−), electroaccepting power (ω+), donor index (Rd) and acceptor index (Ra) has been performed using the donor-acceptor map (DAM). The antioxidant and radical powers of compounds analyzed have been compared to that of two classical vitamins (vitamin C and gallic acid). The stability of each anthraquinone derivative of the molecular library has been developed according to thermodynamic and kinetic concepts. The global reactivity descriptors (GRDs; electrophilicity index (ω), electronegativity (χ), global softness (S), and global hardness (η)) have been used to analyze the reactivity. The topological analysis of optimized structures indicates that the strength of the hydrogen bonds formed is situated between 44.205 and 52.001 kJ/mol. Our B3LYP results reveal that 3-methoxy-1-vismiaquinone (in a configuration without hydrogen bond) exhibits the best antioxidant capacity in gas phase. A comparison between antioxidant performance of molecules examined and that of classical vitamins (gallic acid, caffeic acid, ferulic acid, and ascorbic acid (vitamin C)) displayed the fact that the single electron transfer (SET) mechanism is more prominent for compounds of the molecular library analyzed. In the same vein, the antiradical behaviors of anthraquinone derivatives have shown to be higher than that of gallic acid and vitamin C in gas phase and water. The 5,8-dihydroxy-2-methylantraquinone structure in a configuration bearing one hydrogen bond has been found to be the best antiradical of the series in aqueous solution.

Thiohydantoins as Potential Antioxidant Agents: In vitro and in silico evaluation

“…The global reactivity parameters can provide important information about behavior of chemistry systems. The energies of frontier molecular orbitals, HOMO (E HOMO , highest occupied molecular orbital) and LUMO (E LUMO , lowest unoccupied molecular orbital) energies indicate the tendency of a molecule donate and accepted electrons, respectively [26] . In addition, a small difference between energies of these orbitals (gap HOMO‐LUMO =E LUMO ‐ E HOMO ) indicate a high chemical reactivity and low kinetic stability of the molecule [27] …”

Current Trends in Computational Quantum Chemistry Studies on Antioxidant Radical Scavenging Activity

“… 50 Bader’s Quantum Theory of Atoms in Molecules (QTAIM) can be used to quantify their strength 208 , 209 and thus has been widely applied in antioxidants research. 31 , 58 , 62 , 103 , 122 , 130 Despite the analysis’s complexicity, specialized tools such as the Multiwfn software 210 eases it.…”

“…In the above graph, the electron flow goes from species in the bottom left to species in the top right. When comparing substances, DAM helps to predict which will behave as stronger or weaker oxidizers or reducers, while also accounting for the effects of the environement. , It is good to remember, there is a general trend of increasing electron-donating properties with each subsequent dissociation, so polyanionic species shall generally have lower R d values than neutral of cationic forms. , …”

“…Hydrogen bonds and weak interactions are important in stabilizing radicals or transition states rendering reactions to be more feasible, for example, by lowering BDE values . Bader’s Quantum Theory of Atoms in Molecules (QTAIM) can be used to quantify their strength , and thus has been widely applied in antioxidants research. ,,,,, Despite the analysis’s complexicity, specialized tools such as the Multiwfn software eases it.…”

“…Phytochemicals are plant-derived compounds that are plentiful in many herbs and commonly consumed plants such as beetroot, high in betalains; tea, rich in catechins; or grapefruit, abundant in flavanons . This family can be further subdivided into flavonoids, ,,− ,,− ,− phenolic acids, − lignans, aurones, chalcones, − curcuminoids, , anthocyanidins, − stilbenoids; ,− anthraquinones, − glucosinolates, , alkaloids, , coumarins, terpenes and terpenoids, − and others ,,− ,− (Figure ), all of them being extensively studied with computational quantum chemistry methods, as evidenced by the number of recent scientific findings. Albeit, plants are not the only source of antioxidants substances with promising antiradica...…”