Mechanistic and Kinetic Studies of the Radical Scavenging Activity of 5-O-Methylnorbergenin: Theoretical and Experimental Insights

The scavenging mechanism of hydrazone compounds towards HOO˙ and CH3OO˙ radicals: a computational mechanistic and kinetic study

In this study, a detailed DFT investigation was conducted to systematically analyze the scavenging activity of six hydrazone compounds (1-6) against HOO˙ and CH3OO˙ radicals. Three mechanistic pathways were explored: hydrogen atom transfer (HAT), single electron transfer followed by proton transfer (SETPT), and sequential proton loss electron transfer (SPLET). These mechanisms were evaluated based on thermodynamic parameters, including bond dissociation enthalpy (BDE), ionization potential (IP), proton dissociation enthalpy (PDE), proton affinity (PA), and electron transfer enthalpy (ETE) in the gas phase, water, and pentyl ethanoate. HAT was identified as the most favorable mechanism in the gas phase, while SPLET was preferred in water. Among the studied compounds, compound 2 showed the highest rate constants for HOO˙ scavenging following the HAT mechanism in the gas phase observed at the O2'-H bond with a k Eck value of 6.02 × 104 M-1 s-1. For CH3OO˙ scavenging, the same compound exhibited the highest rate constants at the N8-H (9.03 × 104 M-1 s-1) and O2'-H (7.22 × 104 M-1 s-1) sites. The calculated overall rate constant values of compound 2 are k overall (HOO˙) = 6.86 × 104 M-1 s-1 and k overall (CH3OO˙) = 1.63 × 105 M-1 s-1. These results suggest that compound 2 exhibits antioxidant activities comparable to butylated hydroxyanisole (BHA), consistent with experimental findings, indicating its potential as an effective scavenger of hydroperoxyl and methoxy peroxyl radicals. In aqueous solution, the anionic form of compound 2 showed the greatest HOO˙ and CH3OO˙ radical scavenging activity among all of the studied compounds with rate constants of k app = 1.8 × 107 M-1 s-1 and k app = 3.3 × 106 M-1 s-1, respectively. Compared with some typical antioxidants such as rubiadin, natural fraxin, and natural anthraquinones, compound 2 showed higher HOO˙ and CH3OO˙ radical scavenging activity in water. Thus, compound 2 is a promising antioxidant in aqueous physiological environments.

Optimization of the Search for Neuroprotectors among Bioflavonoids

For the first time, to optimize the creation of new neuroprotective agents based on bioflavonoids, we applied information technologies; these include docking analysis to calculate the binding of candidate molecules to the pharmacological target protein transthyretin as well as a program of virtual screening of NO scavengers. As a result of this approach, the substance catechin was isolated from candidate molecules-quercetin, catechin, Epicatechin gallate, Epicatechin, Procyanidin B1, Procyanidin B2, Procyanidin B3, and Catechin-3-gallate-according to docking analysis. As a result of virtual screening, catechin was identified as a potential NO scavenger (55.15% prediction). The results of the prediction were confirmed by in vitro experiments. Course administration of catechin to animals with experimental multiple sclerosis (MS) against the background of methylprednisolone administration completely eliminated lethal cases, reduced the number of diseased animals by 20% as well as prevented the development of severe neurological symptoms by 20% (compared to the methylprednisolone group) and by 60% compared to the control group. Course administration of catechin with methylprednisolone leads to a decrease in the neurodegradation markers in the cytosol of rats, with EAE: NSE by 37% and S-100 by 54.8%. The combined administration of methylprednisolone significantly exceeds the combination of methylprednisolone with the reference drug mexidol by the degree of NSE reduction. The obtained results indicate a significant neuroprotective effect of ocular combinations of methylprednisolone and catechin. The above-mentioned confirms the correctness of the bioflavonoid selection with the help of a virtual screening program.

Mechanistic Insights into the Antioxidant and Pro-oxidant Activities of Bromophenols from Marine Algae: A DFT Investigation

Marine algae are a rich source of aromatic secondary metabolites, with bromophenols (BPs) receiving particular attention due to their health benefits. Despite extensive research on BPs, the understanding of their antioxidant potential, as well as their mechanisms of action at the molecular level, remains incomplete. This study utilized density functional theory (DFT) to systematically elucidate the antioxidant and pro-oxidant mechanisms of the main BP scaffolds under physiological conditions. It was found that BPs exhibit potent antioxidant capacity in both polar and lipid environments. In lipid media, the formal hydrogen transfer mechanism has been identified as the exclusive antiradical pathway. The position of bromine atoms significantly influenced the activity, particularly in scaffolds containing one hydroxyl group. However, no significant effect was observed in scaffolds with two hydroxyl groups. In water, monodeprotonated BPs showed key radical scavenging activity, with different mechanisms favored depending on the configuration of the hydroxyl groups. Additionally, BPs, particularly those bearing a catechol moiety, exhibit secondary antioxidant activity by reducing the production of hydroxyl radicals via the ascorbic acid anion pathway. These findings provide further validation of the potent antioxidant properties of BPs and shed light on their mechanism of action in physiological environments.

Exploring the Antioxidant Properties of Caffeoylquinic and Feruloylquinic Acids: A Computational Study on Hydroperoxyl Radical Scavenging and Xanthine Oxidase Inhibition

Caffeoylquinic (5-CQA) and feruloylquinic (5-FQA) acids, found in coffee and other plant sources, are known to exhibit diverse biological activities, including potential antioxidant effects. However, the underlying mechanisms of these phenolic compounds remain elusive. This paper investigates the capacity and mode of action of 5-CQA and 5-FQA as natural antioxidants acting as hydroperoxyl radical scavengers and xanthine oxidase (XO) inhibitors. The hydroperoxyl radical scavenging potential was investigated using thermodynamic and kinetic calculations based on the DFT method, taking into account the influence of physiological conditions. Blind docking and molecular dynamics simulations were used to investigate the inhibition capacity toward the XO enzyme. The results showed that 5-CQA and 5-FQA exhibit potent hydroperoxyl radical scavenging capacity in both polar and lipidic physiological media, with rate constants higher than those of common antioxidants, such as Trolox and BHT. 5-CQA carrying catechol moiety was found to be more potent than 5-FQA in both physiological environments. Furthermore, both compounds show good affinity with the active site of the XO enzyme and form stable complexes. The hydrogen atom transfer (HAT) mechanism was found to be exclusive in lipid media, while both HAT and SET (single electron transfer) mechanisms are possible in water. 5-CQA and 5-FQA may, therefore, be considered potent natural antioxidants with potential health benefits.

Elucidation of reactive oxygen species scavenging pathways of norbergenin utilizing DFT approaches

Bergenin is a polyphenolic compound that contains isocoumarin skeletal derived from C-glycosylated 4-O-methylgallic acid. The biological activities of this compound and its derivatives are quite diverse. Recent studies reveal neuroprotective effects in vitro and in vivo in Alzheimer's. Norbergenin is a demethylated form of bergenin, known for better antioxidant capacity and associated with neuroprotective properties through oxidative stress inhibition. This study focused on investigating the scavenging mechanism of norbergenin with the ^•OH, ^•OOH, and O 2 ∙ - as a radical model under physiological and lipid environments. The thermodynamic and kinetic parameters of the hydrogen transfer (HT), single electron transfer (SET), sequential proton lost-electron transfer (SPLET) and radical adduct formation (RAF) mechanisms were determined theoretically by the density functional theory (DFT) at M06-2X/6-311 + + G(d,p) level of theory. Based on the computational results, this compound has proved as an excellent ^•OOH and ^•OH scavenger under physiological conditions better than Trolox and vitamin C, whereas its radical demonstrated as an efficient O 2 ∙ - scavenger.

Insights on the kinetics and mechanisms of the peroxyl radical scavenging capacity of caftaric acid: the important role of the acid–base equilibrium

Considering the acid–base equilibrium, caftaric acid has been shown to be one of the best antioxidants among phenolic acids in the aqueous physiological environment.