Programmable flow system for automation of oxygen radical absorbance capacity assay using pyrogallol red for estimation of antioxidant reactivity

Fast ORAC-SIA method for antioxidant capacity determination in food samples

A novel fluorescent ORAC-SIA method to determine antioxidant capacity in several food samples using fluorescein as the probe was developed. The optimization of the method was through a multivariable design, decreasing the analysis time to 5 min and the AAPH concentration to 67% compared with 90 min in the standard 96-well microplate method. The aspiration order was AAPH-sample/standard-fluorescein injected into a stream of a water-based carrier. The calculation of the antioxidant capacity was done from the fluoresceine peak heigh, so neither delay time nor area measurement was necessary. The proposed method showed excellent precision (RDS < 3%) with a LOD of 3.13 µmol L^-1 and recoveries from 90% to 107%. The results from the ORAC-SIA method did not show a significant difference from the microplate method.

Methods to evaluate the scavenging activity of antioxidants toward reactive oxygen and nitrogen species (IUPAC Technical Report)

This project was aimed to identify the quenching chemistry of biologically important reactive oxygen and nitrogen species (ROS/RNS, including radicals), to show antioxidant action against reactive species through H‐atom and electron transfer reactions, and to evaluate the ROS/RNS scavenging activity of antioxidants with existing analytical methods while emphasizing the underlying chemical principles and advantages/disadvantages of these methods. In this report, we focused on the applications and impact of existing assays on potentiating future research and innovations to evolve better methods enabling a more comprehensive study of different aspects of antioxidants and to provide a vocabulary of terms related to antioxidants and scavengers for ROS/RNS. The main methods comprise the scavenging activity measurement of the hydroxyl radical (•OH), dioxide(•1–) (O2 •–: commonly known as the superoxide radical), dihydrogen dioxide (H2O2: commonly known as hydrogen peroxide), hydroxidochlorine (HOCl: commonly known as hypochlorous acid), dioxidooxidonitrate(1–) (ONOO−: commonly known as the peroxynitrite anion), and the peroxyl radical (ROO•). In spite of the diversity of methods, there is currently a great need to evaluate the scavenging activity of antioxidant compounds in vivo and in vitro. In addition, there are unsatisfactory methods frequently used, such as non-selective UV measurement of H2O2 scavenging, producing negative errors due to incomplete reaction of peroxide with flavonoids in the absence of transition metal ion catalysts. We also discussed the basic mechanisms of spectroscopic and electrochemical nanosensors for measuring ROS/RNS scavenging activity of antioxidants, together with leading trends and challenges and a wide range of applications. This project aids in the identification of reactive species and quantification of scavenging extents of antioxidants through various assays, makes the results comparable and more understandable, and brings a more rational basis to the evaluation of these assays and provides a critical evaluation of existing ROS/RNS scavenging assays to analytical, food chemical, and biomedical/clinical communities by emphasizing the need for developing more refined, rapid, simple, and low‐cost assays and thus opening the market for a wide range of analytical instruments, including reagent kits and sensors.

Investigation of the spectroelectrochemical behavior of quercetin isolated from Zanthoxylum bungeanum

Flavonoids are common bioactive components in plants. Quercetin is the most abundant flavonoid in the human diet, accounting for more than half of the total daily consumption of flavonoids. In this study, adsorption and electrocatalytic activities of quercetin isolated from Zanthoxylum bungeanum on an electrode was studied via homemade electrodes. An in situ UV-Visible thin-layer spectroelectrochemical method was used to study the electrochemical behavior of quercetin in detail and to explore its electrochemical reaction mechanism. This experiment proves that UV-Vis thin-layer spectroelectrochemistry is a feasible way for studying the electrochemical reaction mechanism of flavonoids in plants.

Determination of Punicalagins Content, Metal Chelating, and Antioxidant Properties of Edible Pomegranate (Punica granatum L) Peels and Seeds Grown in Morocco

Pomegranate (Punica granatum L) is widely cultivated in the Mediterranean countries especially in Morocco. Pomegranate peel and seed contain considerable amounts of phenolic compounds with antioxidant activity. The aim of the present study was to phytochemically characterize the pomegranate peels and seeds obtained from three Moroccan provinces, using UHPLC-DAD. In addition, total phenolic content (TPC), total flavonoid contents (TFC), and metal chelating of pomegranate peel were also evaluated. The results showed that pomegranate peel possesses the highest phenolic (TPC: 224.39 mg GAE/g dw) and flavonoid (TFC: 62.64 mg rutin/g dw) contents. Punicalagin-β and punicalagin-α, are the abundant compounds found in peel: 216.36 ± 9.94 mg/g, 154.94 ± 5.21 mg/g, respectively. Pomegranate peels showed significantly (p < 0.05) high antioxidant activity 1-diphenyl-2-picrylhydrazyl (DPPH) EC50: 42.71 ± 0.04 μg/mL, 2.2'-Azino-bis(3-Ethylbenzothiazoline-6-Sulfonic Acid) (ABTS) EC50: 62.15 ± 0.01 μg/mL), and chelating activity (FRAP 1.85 ± 0.00 mg ascorbic acid equivalents/100 g, Fe2+: 2.52 ± 0.01 μmol EDTA equivalents/g dw) compared to seeds. A positive correlation between antioxidant activity and total phenolic was found. According to achieved results, high antioxidant capacity of pomegranate extracts, especially peel, shed light to further use as natural food preservatives. Pomegranate peel could be used for the fortification of food with fiber by introducing it in dietary, as well as in health applications due to its higher antioxidant capacity.

NADPH oxidase activity: Spectrophotometric determination of superoxide using pyrogallol red

A simple and fast spectrophotometric methodology able to quantify superoxide released by NADPH oxidase from differentiated promyelocytic leukaemia (HL-60) cells using pyrogallol red is described.The latter is based on the known stoichiometry of the reaction between superoxide and pyrogallol red and the inability of pyrogallol red to react with hydrogen peroxide. In addition, we developed a 96-wells microplate-based method able to determine NADPH oxidase activity. Using this method, we determined pharmacological properties of the NADPH oxidase inhibitors VAS2870 and diphenyleneiodonium and the obtained IC50 values were in good agreement with previous reported data. NOX2 is highly expressed in differentiated promyelocytic leukaemia cells, whereas other isoforms are not detected or expressed at low amounts. Likewise, this methodology may be a useful assay for NOX2 inhibitor screening. NADPH oxidases are involved in several physiological and pathological processes, rendering its pharmacological modulation an attractive research target. In this context, this simple assay can be used for NADPH oxidase inhibitor screening as well as aiding in the study of different biological conditions that involve NADPH oxidase activity.