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An Improved System to Evaluate Superoxide-Scavenging Effects of Bioflavonoids.

ABSTRACT: The pyrogallol autoxidation method has been widely utilized to evaluate various antioxidants in antioxidative bioactivities. However, this method is generally not appropriate for estimating the ^. O₂ ^- radical scavenging capacity of bioflavonoids, as it enables bioflavonoids to generate ^. O₂ ^- radical in oxygen-alkaline (pH 8.2) surroundings. In the present study, an improved DMSO (dimethyl sulfoxide) system (pH 7.25, versus pH 8.2 of the pyrogallol autoxidation) was successfully developed to evaluate the ^. O₂ ^- radical scavenging capacity of bioflavonoids by EPR technique and using the spin trapping reagent DMPO (5,5-dimethyl-1-pyrroline-N-oxide). The non-protonic environment supplied by the system promotes the stabilization of the ^. O₂ ^- radical and therefore ensures a much more accurate measurement of ^. O₂ ^- radical scavenging capacity in bioflavonoids if compared to protonic solvents. The results demonstrated that the effects of scavenging ^. O₂ ^- radicals in natural bioflavonoids follows the order: dihydromyricetin>myricetin>quercetin>kaempferol>baicalein>chrysin, which are well associated with numbers of hydroxyl groups attached to their molecular skeletons and/or active H of their configurations. Interestingly, the higher superoxide-anion scavenging effect measured for dihydromyricetin with respect to myricetin is possibly attributed to the fact that dihydromyricetin can be transformed into myricetin in the presence of ^. O₂ ^- radical, resulting from the homolysis of active H donated from C3-H bond of DMY via ^. O₂ ^- radicals.

SUBMITTER: Yao Y

PROVIDER: S-EPMC8080285 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The advancement of neural prostheses requires implantable neural electrodes capable of electrically stimulating or recording signals from neurons chronically. Unfortunately, the implantation injury and presence of foreign bodies lead to chronic inflammation, resulting in neuronal death in the vicinity of electrodes. A key mediator of inflammation and neuronal loss are reactive oxygen and nitrogen species (RONS). To mitigate the effect of RONS, a superoxide dismutase mimic compound, manganese(III) meso-tetrakis-(N-(2-aminoethyl)pyridinium-2-yl) porphyrin (iSODm), was synthesized to covalently attach to the neural probe surfaces. This new compound showed high catalytic superoxide scavenging activity. In microglia cell line cultures, the iSODm coating effectively reduced superoxide production and altered expression of iNOS, NADPH oxidase, and arginase. After 1 week of implantation, iSODm coated electrodes showed significantly lower expression of markers for oxidative stress immediately adjacent to the electrode surface, as well as significantly less neurons undergoing apoptosis. STATEMENT OF SIGNIFICANCE: One critical challenge in the translation of neural electrode technology to clinically viable devices for brain computer interface or deep brain stimulation applications is the chronic degradation of the device performance due to neuronal degeneration around the implants. One of the key mediators of inflammation and neuronal degeneration is reactive oxygen and nitrogen species released by injured neurons and inflammatory microglia. This research takes a biomimetic approach to synthesize a compound having similar reactivity as superoxide dismutase, which can catalytically scavenge reactive oxygen and nitrogen species, thereby reducing oxidative stress and decreasing neuronal degeneration. By immobilizing the compound covalently on the surface of neural implants, we show that the neuronal degeneration and oxidative stress around the implants is significantly reduced.

Project description:Background:Oxidative stress and nonenzymatic protein glycation lead to serious diabetic complications that increase the risk of mortality. Rhinacanthus nasutus leaf crude extracts are previously reported for their antidiabetic, antiglycation, and antioxidant potential. Objective:The present study was performed to prepare a standardized rhinacanthins-rich extract (RRE) and evaluate its superoxide scavenging and antiglycation effects as compared to its marker compounds, namely, rhinacanthin-C (RC), rhinacanthin-D (RD), and rhinacanthin-N (RN). Materials and Methods:RRE was obtained by microwave-assisted green extraction along with a simple step of fractionation using Amberlite® column. RC, RD, and RN were isolated from the RRE using silica gel column chromatography. Superoxide scavenging activity was performed by cyclic voltammetry, and fructose-mediated human serum albumin glycation model was used for antiglycation activity. In silico studies were conducted to identify the structure-activity relationships of rhinacanthins. Results:On the basis of kinetic measurements, RRE exhibited the most potent antioxidant activity via ErCi mechanism, with a 50% inhibitory concentration (IC50) value of 8.0 ?g/mL, antioxidant capacity of 39439 M-1, and binding constant of 45709 M-1. Antiglycation assay showed that RRE exhibited almost equivalent glycation inhibitory effect to that of RC, with IC50 values of 39.7 and 37.3 ?g/mL, respectively, but higher than that of RD (IC50 of 50.4 ?g/mL), RN (IC50 of 89.5 ?g/mL), as well as the positive control, rutin (IC50 of 41.5 ?g/mL). Conclusions:The potent superoxide scavenging and albumin glycation inhibitory effect of RRE rationalized its therapeutic application in various chronic diseases, especially in the complications of diabetes. SUMMARY:Rhinacanthins-rich extract (RRE) exhibited potent superoxide scavenging activityRRE and rhinacanthin-C showed remarkable and comparable antiglycation effectRhinacanthins exhibited antiglycation activity by masking specific residues of albumin. Abbreviations used: RRE: Rhinacanthins-rich extract; RC: Rhinacanthin-C; RD: Rhinacanthin-D; RN: Rhinacanthin-N; IC50: 50% inhibitory concentration; Kao: Antioxidant activity coefficient; Kb: Binding constant; ErCi: Reversible electron transfer followed by an irreversible chemical reaction; DM: Diabetes mellitus; AGEPs: Advanced glycation end products; NMR: Nuclear magnetic resonance; HPLC: High-performance liquid chromatography; CV: Cyclic voltammetry; DMSO: Dimethyl sulfoxide; Ipa: Anodic peak current; Ipc: Cathodic peak current; HSA: Human serum albumin; MOE: Molecular operating environment; PASSonline: Online prediction of activity spectra for substances.

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An Improved System to Evaluate Superoxide-Scavenging Effects of Bioflavonoids.

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