Investigating the antioxidant potential and mechanism of a hydrazide bioactive component of garlic: insights from density functional theory calculations, drug-likeness and molecular docking studies

Glutathione remains one of the most efficient antioxidant compounds in living systems, and the biological abilities of hydrazides have been well documented in literature. This study highlights the phytochemical constituents of garlic and the separation of the bioactive benzoic acid, 4-chloro- 1-(4-methoxyphenyl) hydrazide (BA4C) using gas chromatography-mass spectroscopy (GC-MS) technique. Preliminary phytochemical screening reveals the presence of alkaloids, saponins, flavonoids, tannins, terpenoids, steroids and phenols. Computationally, compound BA4C was optimized using the B3LYP/aug-cc-PVDZ DFT method. Spectroscopic studies of the compound involved analysis of the vibrational FT-IR frequencies and the modes of vibrations. Frontier molecular orbitals analysis records an energy gap of 4.3391 eV; NBO studies reveal that the compound has strong perturbation energies of 246 kcal/mol and 269 kcal/mol among its intramolecular interactions such as π *C12 - C13 to π *C14 - C15 and π *C11 - C16 to π *C14 - C15, respectively. According to the visualization of non-covalent interactions, steric repulsions were observed at the core of the phenyl and benzene rings. However, other regions of the compound depict a significant balance of forces between steric repulsions and van der Waals forces. To significantly deduce the reducing power of compound BA4C, electrons were found to be highly localized at the methoxy and hydrazide moieties significantly implying their propensity to donate electrons to oxidized systems. Furthermore, ADMET analysis reveals that the compound has two hydrogen donors. Most significantly, the compound binds to NADPH dehydrogenase (5V4P) and glutathione reductase (1XAN) with binding energies of - 6.0 kcal/mol and - 8.0 kcal/mol showing considerable favourable binding feasibility as well as forming plural hydrogen bonds with the amino acid residues. Notably, BA4C was bonded at the active site of 1XAN, which implies the ability of the compound for the reduction of oxidized glutathione.

Impact of carboxylate ligation on the C-H activation reactivity of a non-heme Fe(IV)O complex: a computational investigation

A comprehensive DFT investigation has been presented to predict how a carboxylate-rich macrocycle would affect the reactivity of a non-heme Fe(IV)O complex towards C-H activation. The popular non-heme iron oxo complex [FeIV(O)(N4Py)]2+, (N4Py = N,N-(bis(2-pyridyl)methyl)N-bis(2-pyridylmethyl)amine) (1), has been selected here as the primary compound. It is transformed to the compound [FeIV(O)(nBu-P2DA)], where nBu-P2DA = N-(1',1'-bis(2-pyridyl)pentyl)iminodiacetate (2) after the replacement of two pyridine donors of N4Py with carboxylate groups. Two other complexes, namely 3 and 4, have been predicted sequentially substituting nitrogen with the carboxylate groups. Ethylbenzene and dihydrotoluene were chosen as substrates. In terms of C-H activation reactivity, an interesting pattern emerges: as the carboxylate group becomes more equatorially enriched, the reactivity increases, following the trend 1 < 2 < 3 < 4. This also aligns with available experimental reports related to complexes 1 and 2. Fe(IV)O complexes exhibit two-state reactivity (triplet and quintet), whereas the quintet state is more favourable due to the stabilization of the transition states through exchange interactions involving a greater number of unpaired electrons. A detailed analysis of the factors influencing reactivity has been performed, including distortion energy (which decreases for the transition state with the addition of carboxylate groups), the triplet-quintet oxidant energy gap (which consistently decreases as carboxylate group enrichment increases), steric factors, and quantum mechanical tunneling. This investigation provides a detailed explanation of the observed outcomes and predicts the higher reactivity of carboxylate-enriched Fe(IV)O complexes. After potential experimental verification, this could lead to the development of new, optimal catalysts for C-H activation.

High-valent nonheme Fe(IV)O/Ru(IV)O complexes catalyze C-H activation reactivity and hydrogen tunneling: a comparative DFT investigation

A comprehensive density functional theory investigation has been presented towards the comparison of the C-H activation reactivity between high-valent iron-oxo and ruthenium-oxo complexes. A total of four compounds, e.g., [Ru(IV)O(tpy-dcbpy)] (1), [Fe(IV)O(tpy-dcbpy)] (1'), [Ru(IV)O(TMCS)] (2), and [Fe(IV)O(TMCS)] (2'), have been considered for this investigation. The macrocyclic ligand framework tpy(dcbpy) implies tpy = 2,2':6',2''-terpyridine, dcbpy = 5,5'-dicarboxy-2,2'-bipyridine, and TMCS is TMC with an axially tethered -SCH2CH2 group. Compounds 1 and 2' are experimentally synthesized standard complexes with Ru and Fe, whereas compounds 1' and 2 were considered to keep the macrocycle intact when switching the central metal atom. Three reactants including benzyl alcohol, ethyl benzene, and dihydroanthracene were selected as substrates for C-H activation. It is noteworthy to mention that Fe(IV)O complexes exhibit higher reactivity than those of their Ru(IV)O counterparts. Furthermore, regardless of the central metal, the complex featuring a tpy-dcbpy macrocycle demonstrates higher reactivity than that of TMCS. Here, a thorough analysis of the reactivity-controlling characteristics-such as spin state, steric factor, distortion energy, energy of the electron acceptor orbital, and quantum mechanical tunneling-was conducted. Fe(IV)O exhibits the exchanged enhanced two-state-reactivity with the quintet reactive state, whereas Ru(IV)O has only a triplet reactive state. Both the distortion energy and acceptor orbital energy are low in the case of Fe(IV)O supporting its higher reactivity. All the investigated C-H activation processes involve a significant contribution from hydrogen tunneling, which is more pronounced in the case of Ru, although it cannot alter the reactivity pattern. Furthermore, it has also been found that, independent of the central metal, aliphatic hydroxylation is always preferable to aromatic hydroxylation. Overall, this work is successful in establishing and investigating the cause of enzymes' natural preference for Fe over Ru as a cofactor for C-H activation enzymes.

Effect of Substituent on C-H Activation Catalysed by a nonheme Fe(IV)O Complex: A Computational Investigation of Reactivity and Hydrogen Tunneling

A density functional theory investigation has been presented here to address the C-H activation reactivity and the influence of quantum mechanical tunneling catalyzed by a non-heme iron(IV)-Oxo complex viz. [FeIVOdpaq-X]+...