Radical scavenging activity of ascorbic acid analogs: kinetics and mechanisms

Radical scavenging activity of bromophenol analogs: analysis of kinetics and mechanisms

CONTEXT

This theoretical study explores the antioxidant activity of five bromophenol analogs, with a particular focus on their interaction with different solvent environments of varying polarities. Key findings include the correlation between increased solvent polarity and enhanced antioxidant activity of these analogs, comparable in some instances to ascorbic acid. Notably, compound 5, developed by our research team, demonstrates superior antioxidant activity in both lipid and aqueous solutions, surpassing that of ascorbic acid and other tested analogs. This research contributes to the understanding of bromophenol analogs, presenting the first known kinetic and chemical stability data such as rate constants, pKa values, and branching ratios for reactions with the methylperoxyl radical (CH3OO•).

METHODS

The computational analyses were conducted using the Gaussian 09 software suite at the M05-2X/6-31 + G(d) computational level. These analyses employed conventional transition state theory to account for various potential mechanisms and effects of solvent polarity on the antioxidant activities of bromophenol analogs. The study meticulously calculated enthalpy under standard conditions (298.15 K and 1 atm) with necessary thermodynamic corrections. Additionally, the Quantum Mechanics-based Test for Overall Radical Scavenging Activity (QMORSA) protocol guided the evaluation of radical scavenging activity, ensuring a comprehensive assessment of the antioxidant potential of the compounds.

Theoretical Insights into the Oxidative Stress-Relieving Properties of Pinocembrin─An Isolated Flavonoid from Honey and Propolis

Bee products are a valuable group of substances that have a wide range of applications for humans. They contain a high level of polyphenolic compounds, which have been shown to combat radicals and effectively reduce oxidative stress. In this study, density functional theory was utilized to determine the anti-OOH activity, sequestration of free Cu(II) and Fe(III) ions, the potential pro-oxidative activity of the formed complexes, and the repairing capabilities toward essential biomolecules. The kinetic constants for scavenging of hydroperoxide radical were found to be low, with an order of magnitude not exceeding 10-3 M-1 s-1. Chelating properties showed slightly more satisfactory outcomes, although most complexes exhibited pro-oxidant activity. Pinocembrin, however, proved effective in repairing oxidatively damaged biological compounds and restoring their original functionality. The study found that whilst the system displays limited type I and type II antioxidant activity, it may support the role of physiological reductants already present in the biological matrix.

Quantum-mechanical characteristics of apigenin: Antiradical, metal chelation and inhibitory properties in physiologically relevant media

Density functional theory was used to examine the antioxidant activity of apigenin. All protonated species that are present in a non-negligible population at physiological pH were considered in the study. The ability to scavenge the hydroperoxide radical was evaluated in lipid and aqueous environments. The capacity to halt the Fenton reaction by chelating Fe(III) and Cu(II) ions was also investigated, as was the ability to inhibit xanthine oxidase. The results indicate that these activities may be particularly important in describing the beneficial effects of apigenin, especially because of its lower anti-•OOH potential than Trolox or vitamin C. The findings underscore the significant role of dianion in the antiradical and chelating properties, despite its presence in much lower molar fractions than other ions.

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

The antioxidative nature of chemicals is now routinely studied using computational quantum chemistry. Scientists are constantly proposing new approaches to investigate those methods, and the subject is evolving at a rapid pace. The goal of this review is to collect, consolidate, and present current trends in a clear, methodical, and reference-rich manner. This paper is divided into several sections, each of which corresponds to a different stage of elaborations: preliminary concerns, electronic structure analysis, and general reactivity (thermochemistry and kinetics). The sections are further subdivided based on methodologies used. Concluding remarks and future perspectives are presented based on the remaining elements.

Antiradical properties of curcumin, caffeic acid phenethyl ester, and chicoric acid: a DFT study

The antiradical properties and possible mechanisms of action of the tautomers of curcumin, caffeic acid phenethyl ester (CAPE), and chicoric acid (CA) have been studied within density functional theory (DFT). We calculated global chemical reactivity descriptors from conceptual DFT, pK_a, bioavailability, and toxicity to evaluate the antiradical properties and characterize these species. Our final level of theory is the M06-2X functional with the 6-31 + G* basis set; we selected this level after performing a benchmark calibration and validation among different levels. Solvent effects were modeled via the continuum solvation model based on density (SMD). We used water and pentyl ethanoate as solvents to simulate the physiological conditions. The free radical scavenger capacity was analyzed for three possible oxidative stress mechanisms: single electron transfer (SET), hydrogen atom transfer (HAT), and xanthine oxidase (XO) inhibition. The results indicate that neutral curcumin, CA, and CAPE behave as antireductants. The most favorable mechanism turns out to be HAT, where CA and CAPE stand out. In conclusion, our DFT study strongly indicates that neutral curcumin, CAPE, and CA would very likely perform well as antiradical drugs with recommended therapeutic use, supported by their non-toxic nature.

Surface Modification of Poly(lactic acid) Film via Cold Plasma Assisted Grafting of Fumaric and Ascorbic Acid

Plant-based materials have found their application in the packaging with a yearly growing production rate. These naturally biodegradable polymers are obtained from renewable and sustainable natural resources with reduced environmental impact and affordable cost. These materials have found their utilization in fully-renewable plant-based packaging products, such as Tetra Pak^®-like containers, by replacing commonly-used polyethylene as the polymer component. Poly(lactic acid) (PLA) is one of the representative plant-based polymers because of its eco-friendliness and excellent chemical and mechanical properties. In this work, a PLA surface was modified by various food additives, namely ascorbic acid (ASA) and fumaric acid (FA), using plasma-initiated grafting reactions in order to improve the surface and adhesion properties of PLA. Various analytical and microscopic techniques were employed to prove the grafting process. Moreover, the improved adhesion of the modified PLA foil to aluminum (Al) foil in a laminate configuration was proven by peel resistance measurements. The peel resistance of modified PLA increased by 74% and 184% for samples modified by ASA and FA, respectively, compared with untreated PLA.

Impact of ascorbic acid in reducing the incidence of vancomycin associated nephrotoxicity in critically ill patients: A preliminary randomized controlled trial

Background Antioxidants show nephroprotective effect against vancomycin associated nephrotoxicity (VAN) in animals. This study aimed to assess the ascorbic acid nephro-protective role against VAN clinically.

Methods Forty-one critically ill patients were randomly assigned to one of two groups: intervention group (vancomycin IV plus ascorbic acid, n=21) or control group (vancomycin IV only, n=20). Primary outcomes were the incidence of VAN and the absolute change in creatinine parameters, while mortality rate was the secondary outcome. Nephrotoxicity was defined as an increase in serum creatinine (S.cr) by at least 0.5 mg/dL or 50% of baseline for at least two successive measurements. This study is registered at Clinicaltrials.gov (NCT03921099), April 2019.

Results Mean absolute S.cr increase was significant when compared between both groups, P-value = 0.036, where S.cr increased by 0.05(0.12) and 0.34(0.55) mg/dL in the intervention and control groups, respectively. Mean absolute Cr.cl decline was significant when compared between both groups, P-value = 0.04, where Cr.cl was decreased by 5.9(17.8) and 22.3(30.4) ml/min in the intervention and control groups, respectively. Incidence of VAN was 1/21(4.7%) versus 5/20(25%) in the intervention and control groups, respectively (RR: 0.19; CI: 0.024–1.49; P-value = 0.093). Mortality was higher in the control group; however, it was not statistically significant, P-value = 0.141.

Conclusion Co-administration of ascorbic acid with vancomycin preserved renal function and reduced the absolute risk of VAN by 20.3%, however, the reduction in VAN incidence didn’t reach statistical significance level. Further large multicenter prospective trials are recommended.

Herbal Extracts as Potential Antioxidant, Anti-Aging, Anti-Inflammatory, and Whitening Cosmeceutical Ingredients

The aim of this research was to investigate and compare the antioxidant, anti-tyrosinase, anti-aging, and anti-inflammatory activities of 16 herbal extracts for topical application in cosmetic/cosmeceutical products. Herbal plant materials were extracted by infusion in boiled water for 15 min. The total phenolic content and total flavonoid content of each extract were investigated by the Folin-Ciocalteu and aluminum chloride methods, respectively. Antioxidant activities were investigated using 2,2'-diphenyl-1-picrylhydrazyl and a ferric reducing antioxidant power assay. Anti-tyrosinase and anti-aging activities were investigated using an in vitro enzymatic-spectrophotometric method. Anti-inflammatory activities were investigated using an enzyme-linked immunosorbent assay. The findings show that the Stevia rebaudiana extract has the most significant levels of both phenols and flavonoids (p<0.05). The S. rebaudiana, Rosa damascene, and Phyllanthus emblica extracts possessed the most significant antioxidant activities (p<0.05) and a promising whitening effect with moderate anti-tyrosinase activities. Furthermore, the Echinacea purpurea extract possessed the most significant anti-collagenase (78.5±0.0 %), anti-elastase (69.0±1.4 %), and anti-hyaluronidase activity (64.2±0.3 %). The Morus alba extract possessed the most significant anti-inflammatory activity since it could inhibit the secretion of interleukin-6 and tumor necrosis factor-α (p<0.05). Therefore, these herbal extracts have promising skin benefits and have potential for use as active ingredients in cosmetic/cosmeceutical products.

Preparation of Progressive Antibacterial LDPE Surface via Active Biomolecule Deposition Approach

The use of polymers in all aspects of daily life is increasing considerably, so there is high demand for polymers with specific properties. Polymers with antibacterial properties are highly needed in the food and medical industries. Low-density polyethylene (LDPE) is widely used in various industries, especially in food packaging, because it has suitable mechanical and safety properties. Nevertheless, the hydrophobicity of its surface makes it vulnerable to microbial attack and culturing. To enhance antimicrobial activity, a progressive surface modification of LDPE using the antimicrobial agent grafting process was applied. LDPE was first exposed to nonthermal radio-frequency (RF) plasma treatment to activate its surface. This led to the creation of reactive species on the LDPE surface, resulting in the ability to graft antibacterial agents, such as ascorbic acid (ASA), commonly known as vitamin C. ASA is a well-known antioxidant that is used as a food preservative, is essential to biological systems, and is found to be reactive against a number of microorganisms and bacteria. The antimicrobial effect of grafted LDPE with ASA was tested against two strong kinds of bacteria, namely, Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), with positive results. Surface analyses were performed thoroughly using contact angle measurements and peel tests to measure the wettability or surface free energy and adhesion properties after each modification step. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to analyze the surface morphology or topography changes of LDPE caused by plasma treatment and ASA grafting. Surface chemistry was studied by measuring the functional groups and elements introduced to the surface after plasma treatment and ASA grafting, using Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). These results showed wettability, adhesion, and roughness changes in the LDPE surface after plasma treatment, as well as after ASA grafting. This is a positive indicator of the ability of ASA to be grafted onto polymeric materials using plasma pretreatment, resulting in enhanced antibacterial activity.