Use of Pyrogallol Red and Pyranine as Probes to Evaluate Antioxidant Capacities towards Hypochlorite

Abstract

Hypochlorite is a strong oxidant able to induce deleterious effects in biological systems. The goal of this work was to investigate the use of PGR and PYR as probes in assays aimed at evaluating antioxidant activities towards hypochorite and apply it to plant extracts employed in Chilean folk medicine. The consumption of PGR and PYR was evaluated from the decrease in the visible absorbance and fluorescence intensity, respectively. Total phenolic content was determined by the Folin Ciocalteau assay. PGR and PYR react with hypochlorite with different kinetics, being considerably faster the consumption of PGR. Different stoichiometric values were also determined: 0.7 molecules of PGR and 0.33 molecules of PYR were bleached per each molecule of added hypochlorite. Both probes were protected by antioxidants, but the rate of PGR bleaching was too fast to perform a kinetic analysis. For PYR, the protection took place without changes in its initial consumption rate, suggesting a competition between the dye and the antioxidant for hypochlorite. Plant extracts protected PYR giving a PYR-HOCl index that follows the order: Fuchsia magellanica ≈ Marrubium vulgare ≈ Tagetes minuta > Chenopodium ambrosoides ≈ Satureja montana > Thymus praecox. Based on both the kinetic data and the protection afforded by pure antioxidants, we selected PYR as the best probe. The proposed methodology allows evaluating an antioxidant capacity index of plant extracts related to the reactivity of the samples towards hypochlorite.

Chemical composition, antioxidant, antimicrobial and cytotoxic activities of Tagetes minuta and Ocimum basilicum essential oils

“…Despite polyphenol absence TMO exhibited significant radical scavenging activity. This antioxidant activity was confirmed by previous researches with IC50 between 35 and 344 lg/mL (Gong et al 2012;Gupta et al 2012;Perez-Cruz et al 2013). Thus, TMO analyzed in this research showed stronger antioxidant activity compared to previously analyzed TMOs.…”

International Regulations ofPropolisQuality: Required Assays do not Necessarily Reflect their Polyphenolic‐RelatedIn VitroActivities

“…Working solutions were prepared as follow: To a solution containing PGR (15 μM) with or without EEP, was added an aliquot of hypochlorite (30 μL, 1 mM) to obtain a final hypochlorite concentration of 10 μM in a 3mL of final experiment volume. The consumption of PGR was evaluated from the progressive absorbance decrease measured at 540 nm in a thermostatized cuvette of a Hewlett Packard 8453 (Palo Alto) UV‐visible spectrophotometer (Perez‐Cruz and others ). The PGR‐HOCl values are relative to Trolox activity and reported as mean ± SD of 3 independent determinations.…”

“…These rules have established as assays, to determine the total phenolic and flavonoid contents, the Folin–Ciocalteu (FC) and the Al(OH) 3 ‐based methodologies, respectively. Nevertheless, previous reports suggest that the FC index does not always adequately reflect the in vitro scavenging and antimicrobial activities of complex samples (Alarcon and others ; Cabral and others ; Perez‐Cruz and others ). For such reasons, this work addressed the actual existence (or not) of a direct relationship between the total phenolic and flavonoid contents of various propolis samples (obtained from the VI region of Chile) with such in vitro activities.…”

“…Most reported data strongly supports the existence of dependence between the chemical structure of polyphenols and their in vitro antioxidant capacity (Pandey and Rizvi ; Castro and others ). Among these activities, the ability of polyphenols to scavenge reactive species such as free radicals, as well as, hypochlorous and nitrous acid, has been highlighted (Oldreive and others ; Kumar and Pandey ; Perez‐Cruz and others ; Vione and others ). In the case of the reaction with nitrous acid, which could be present in the stomach cavity, it also produces nitric oxide (NO; Peri and others ; Gago and others ), ascribing to polyphenols new potential beneficial actions in gastric environments (Rocha and others ).…”

A Novel Spectrofluorometric Probe for the Determination of Peroxynitrite Anion Scavenging Activity of Biothiols and Amino Acids

“…PR has been used as a HOCl-sensitive probe for determining the antioxidant activity of polyphenols, [17][18][19] and also as an indicator for the oxygen radical absorbance capacity (ORAC) assay where its bleaching induced by ROO…”