A novel colorimetric sensor for measuring hydroperoxide content and peroxyl radical scavenging activity using starch-stabilized gold nanoparticles

Gardenia yellow pigment: Extraction methods, biological activities, current trends, and future prospects

Food coloring plays a vital role in influencing consumers' food choices, imparting vibrant and appealing colors to various food and beverage products. Synthetic food colorants have been the most commonly used coloring agents in the food industry. However, concerns about potential health issues related to synthetic colorants, coupled with increasing consumer demands for food safety and health, have led food manufacturers to explore natural alternatives. Natural pigments not only offer a wide range of colors to food products but also exhibit beneficial bioactive properties. Gardenia yellow pigment is a water-soluble natural pigment with various biological activities, widely present in gardenia fruits. Therefore, this paper aims to delve into Gardenia Yellow Pigment, highlighting its significance as a food colorant. Firstly, a thorough understanding and exploration of various methods for obtaining gardenia yellow pigment. Subsequently, the potential functionality of gardenia yellow pigment was elaborated, especially its excellent antioxidant and neuroprotective properties. Finally, the widespread application trend of gardenia yellow pigment in the food industry was explored, as well as the challenges faced by the future development of gardenia yellow pigment in the field of food and health. Some feasible solutions were proposed, providing valuable references and insights for researchers, food industry professionals, and policy makers.

Determination of primary and secondary oxidation products in vegetable oils with gold nanoparticle based fluorometric turn-on nanosensor: A new total oxidation value

Oxidation of fats and oils gives rise to lipid hydroperoxides as primary oxidation products (POPs) and carbonyl compounds as secondary oxidation products (SOPs). Here, we report the sensitive detection of POPs and SOPs (oxidation products) involving direct and indirect redox reactions with iodide ions, respectively, using the fluorophore probe (fluorescein-5-isothiocyanate-gold nanoparticles; FITC-AuNPs). Iodide released the fluorescent FITC from FITC-AuNPs in the turn-on mode. In case of SOPs, an indirect iodide determination was made through the use of chloramine-T as carbonyl reagent. To various vegetable oil samples, deep frying process (at 160 °C, simulating frying conditions) and soft oil oxidation (at 100 °C, simulating cooking conditions) were carried out for a period of time (1, 5 and 10 days). Total content of POPs varied between 4.00 and 5.70 g TBHP (t-butylhydroperoxide)/kg oil, and the amount of SOPs was found as 1.12-4.11 g t-2-nonenal/kg oil in non-oxidized oil samples. The proposed method was validated against FOX and p-anisidine value (p-AV) assays. Sensory analyses (taste, color, smell and appearance) results of non-oxidized and deep-fried oil samples were consistent with those of the proposed FITC-AuNP nanosensor. Finally, a new total oxidation (TOD) value (expressed as iodide equivalent meq/kg oil) was proposed to determine the overall oxidation state and quality of the oils. Our proposed TOD value is not only mathematically precise with respect to its units (i.e. POPs and SOPs are added up in the same equivalent units to obtain TOD) but also is in better accordance with the results of sensory analysis.

Peroxyl radical scavenging activity measurement of antioxidants using histidine-stabilized and glutathione-capped fluorescent gold nanoclusters

A fluorescent gold nanocluster was used for determining peroxyl radical scavenging activity of antioxidants. Histidine was used as a green reducing and protective agent, and glutathione (GSH) enhanced the fluorescence intensity of histidine-stabilized gold nanoclusters (AuNCs) by ligand exchange process. When AAPH-induced oxidation of GSH occurred, the initial fluorescence intensity of GSH-capped AuNCs (λ_ex = 450 nm λ_em = 502 nm) was decreased with static quenching. The decline of fluorescence intensity of the GSH-capped AuNCs upon peroxyl radical attack is diminished with the addition of antioxidants to the reaction medium, the difference in fluorescence intensity being related to peroxyl radical scavenging activity of antioxidants. The 50 % inhibitive concentration of related antioxidant compounds were determined and compared to those of crocin bleaching assay. Inhibition % of sage (Salvia officinalis L.) and green tea (Camellia sinensis) infusions against peroxyl radicals were investigated. The proposed assay can be used for simple and selective estimation of the peroxyl radical scavenging activity in complex matrices, as histidine-stabilized GSH-capped AuNCs were selective toward peroxyl radicals, not affected by other ROS at the studied concentrations.

Comparative Colorimetric Sensor Based on Bi-Phase γ-/α-Fe2O3 and γ-/α-Fe2O3/ZnO Nanoparticles for Lactate Detection

This work reports on Fe₂O₃ and ZnO materials for lactate quantification. In the synthesis, the bi-phase γ-/α-Fe₂O₃ and γ-/α-Fe₂O₃/ZnO nanoparticles (NPs) were obtained for their application in a lactate colorimetric sensor. The crystalline phases of the NPs were analyzed by XRD and XPS techniques. S/TEM images showed spheres with an 18 nm average and a needle length from 125 to 330 nm and 18 nm in diameter. The γ-/α-Fe₂O₃ and γ-/α-Fe₂O₃/ZnO were used to evaluate the catalytic activity of peroxidase with the substrate 3,3,5,5-tetramethylbenzidine (TMB), obtaining a linear range of 50 to 1000 μM for both NPs, and a 4.3 μM and 9.4 μM limit of detection (LOD), respectively. Moreover, γ-/α-Fe₂O₃ and γ-/α-Fe₂O₃/ZnO/lactate oxidase with TMB assays in the presence of lactate showed a linear range of 50 to 1000 µM, and both NPs proved to be highly selective in the presence of interferents. Finally, a sample of human serum was also tested, and the results were compared with a commercial lactometer. The use of ZnO with Fe₂O₃ achieved a greater response toward lactate oxidation reaction, and has implementation in a lactate colorimetric sensor using materials that are economically accessible and easy to synthesize.

Rapid screening of antioxidant from natural products by AAPH-Incubating HPLC-DAD-HR MS/MS method: A case study of Gardenia jasminoides fruit

A new AAPH-Incubating HPLC-DAD-HR MS/MS method was developed for the rapid and high-throughput screening of antioxidants directly in natural products and applied to Gardenia jasminoides fruit. This method was assumed that the peak areas of compounds with potential antioxidant activity in HPLC chromatograms would be significantly reduced or disappeared after incubating with the AAPH which can release ROO at physiological conditions (37 °C, pH 7.4). Additionally, the activity of antioxidants can be evaluated by comparing the peak reduction rates and the screened components can be further identified by HRMS/MS. Then, 17 potential natural antioxidants from the crude extract of GJF was screened. Among them, three major components including crocin I, crocin II and crocetin showed excellent ROO scavenging activity, which were further validated by the ORAC assay. In conclusion, our study provided a simple and effective strategy to rapidly screen antioxidants in natural products.

Selective colorimetric detection of Cr(VI) using starch-stabilized silver nanoparticles and application for chromium speciation

The selective quantitation of Cr(VI) was developed through colorimetric detection using starch-stabilized silver nanoparticles (starch-AgNPs). The detection of Cr(VI) was based on oxidative degradation of starch-AgNPs as the reduction of UV-Vis signal and the distinctive color change from yellow to colorless of starch-AgNPs were observed. To achieve the highest sensitivity by this method, pH 3, and only 1 min were required for the determination of Cr(VI). For analytical performances, two linear ranges of 0-6 µM and 10-80 µM with limit of detection of 0.93 µM (48 µg/L) and 11.57 µM (0.60 mg/L) were obtained, respectively. The developed colorimetric method was combined with inductively coupled plasma optical emission spectroscopy (ICP-OES) for the speciation analysis of chromium. The concentration of Cr(III) was calculated by subtraction of Cr(VI) from the total chromium concentration determined by ICP-OES. A satisfactory accuracy and precision based on the AOAC guidelines also proved that this simple and rapid sensor was successfully applied for speciation of chromium in real water samples.

Biomarkers of Oxidative Stress and Antioxidant Defense

A number of reactive oxygen and nitrogen species are produced during normal metabolism in human body. These species can be both radical and non-radical and have varying degrees of reactivity. Although they have some important functions in the human body, such as contributing to signal transmission and the immune system, their presence must be balanced by the antioxidant defense system. The human body has an excellent intrinsic enzymatic antioxidant system in addition to different non-enzymatic antioxidants having small molecular masses. An extrinsic source of antioxidants are foodstuffs such as fruits, vegetables, herbs and spices, mostly rich in polyphenols. When the delicate biochemical balance between oxidants and antioxidants is disturbed in favor of oxidants, "oxidative stress" conditions emerge, under which reactive species can cause oxidative damage to biomacromolecules such as proteins, carbohydrates, lipids and DNA. This oxidative damage is often associated with cancer, aging, and neurodegenerative disorders. Because reactive species are extremely short-lived, it is almost impossible to measure their concentrations directly. Although there are certain methods such as ESR / EPR that serve this purpose, they have some disadvantages and are quite costly systems. Therefore, products generated from oxidative damage of proteins, lipids and DNA are often used to quantify the extent of oxidative damage rather than direct measurement of reactive species. These oxidative damage products are usually known as biomarkers. Determination of the concentrations of these biomarkers and changes in the concentration of protective antioxidants can provide useful information for avoiding certain diseases and keep healthy conditions.