Determination of antioxidant activity of spices and their active principles by differential pulse voltammetry

Evaluation of novel green walnut liqueur as a source of antioxidants: Multi-method approach

In this study, a novel green walnut liqueur (GWL) based on green walnuts, as the main ingredient, with the addition of fruits, aromatic plants, chocolate and honey, was produced at the pilot-scale. Antioxidant activity (AO) of the obtained GWL was determined using multiple AO assays in parallel, standard spectrophotometric (FC, DPPH and FRAP) and recently developed electrochemical ones, HydroxoPerhydroxoMercury(II) Complex and Mercury Reduction Antioxidant Power, and compared to similar commercial alcoholic beverages. Characterization of the GWL in terms of volatile and polyphenolic components was performed using SPE-GC-MS and HPLC-DAD-MS/MS, respectively. Sensory quality assessment was performed by experts in the field of sensory analysis of alcoholic beverages, using a scoring method. According to all AO assays applied, AO activity and total phenolics content of GWL were superior in comparison to commercial spirits considered. The volatile fraction of GWL was mainly composed of eugenol, α-terpineol and vanillin, while the most prevalent phenolic compounds were gallic (5.054 mg/L) and chlorogenic acid (1.307 mg/L) and flavonoids such as catechine (0.882 mg/L), quercetin (0.499 mg/L) and its sugar-conjugated derivatives, quercetin 3-O-glucoside (0.774 mg/L) and quercetin-3-O-rhamnoside (0.614 mg/L). Gallic acid is the major contributor to total AO activity, especially determined by DPPH and FRAP, followed by catechine, quercetin and chlorogenic acid. Among the terpenoids, contribution of eugenol to total AO activity is estimated as the highest. Excellent sensory quality (18.52 of maximum 20 scores) was ascribed to GWL. Consequently, the presence of bioactive compounds and high AO activity of GWL, in addition to high sensory quality score, indicates a high market potential for this high-value product.

Natural phenolic antioxidants electrochemistry: Towards a new food science methodology

Natural phenolic compounds are abundant in the vegetable kingdom, occurring mainly as secondary metabolites in a wide variety of chemical structures. Around 10,000 different plant phenolic derivatives have been isolated and identified. This review provides an exhaustive overview concerning the electron transfer reactions in natural polyphenols, from the point of view of their in vitro antioxidant and/or pro-oxidant mode of action, as well as their identification in highly complex matrixes, for example, fruits, vegetables, wine, food supplements, relevant for food quality control, nutrition, and health research. The accurate assessment of polyphenols' redox behavior is essential, and the application of the electrochemical methods in routine quality control of natural products and foods, where the polyphenols antioxidant activity needs to be quantified in vitro, is of the utmost importance. The phenol moiety oxidation pathways and the effect of substituents and experimental conditions on their electrochemical behavior will be reviewed. The fundamental principles concerning the redox behavior of natural polyphenols, specifically flavonoids and other benzopyran derivatives, phenolic acids and ester derivatives, quinones, lignins, tannins, lignans, essential oils, stilbenes, curcuminoids, and chalcones, will be described. The final sections will focus on the electroanalysis of phenolic antioxidants in natural products and the electroanalytical evaluation of in vitro total antioxidant capacity.

Inhibitory profiles of spices against free and protein-bound heterocyclic amines of roast beef patties as revealed by ultra-performance liquid chromatography-tandem mass spectrometry and principal component analysis

The effects of various levels of chili pepper, Sichuan pepper, and black pepper on the amounts of 17 heterocyclic amines (HAs) from seven categories of both free and protein-bound states in roast beef patties were assessed by ultra-performance liquid chromatography-tandem mass spectrometry combined with principal component analysis. Three groups of HA, including imidazopyridines (DMIP), imidazoquinoxalines (MeIQx and 4,8-MeIQx), and β-carbolines (norharman and harman), were detected and quantified in both their free and protein-bound states, whereas PhIP was detected only in its free state, and imidazoquinolines (IQ, IQ[4,5-b], and MeIQ), α-carbolines (AαC and MeAαC), and phenylpyridines (Phe-P-1) were detected only in their protein-bound states. The results demonstrate that the peppers at all three levels had significant inhibitory effects on free PhIP, DMIP, MeIQx, and 4,8-DiMeIQx and could promote free norharman. Harman was significantly suppressed by chili pepper and black pepper, but enhanced by Sichuan pepper. All 11 protein-bound HAs, with the exception of IQ, IQ[4,5-b], and MeIQx with added chili pepper, were significantly reduced by the three peppers. The total amounts of the free and protein-bound states of all 11 HAs (1692.4 ± 78.9 ng g^-1), imidazopyridines (5.5 ± 0.2 ng g^-1), imidazoquinolines (7.2 ± 0.2 ng g^-1), imidazoquinoxalines (6.9 ± 0.2 ng g^-1), α-carbolines (20.1 ± 0.4 ng g^-1), and β-carbolines (1651.7 ± 79.5 ng g^-1) were suppressed by each level of all of the three peppers except for 0.5% and 1.0% chili pepper. Our findings may facilitate the inhibition of HA formation in the processing of meat products.

Synthesis of Stilbene Derivatives: A Comparative Study of their Antioxidant Activities

A series of structurally simple compounds belonging to thestilbene family were synthesized by means of a Ti(III)-mediated methodology that allows access, in an efficient manner, to derivatives of dihydrostilbene, E-stilbene, and stilbene oxide, with high yields. The antioxidant activity of these compounds has been evaluated by means of two electrochemical assays, which provide complementary information, showing that the majority of these stilbene analogs exhibit significant antioxidant activity dependent on the electronic structure and functionalization of the molecule in each case.

Effect of six Chinese spices on heterocyclic amine profiles in roast beef patties by ultra performance liquid chromatography-tandem mass spectrometry and principal component analysis

The effects of Chinese spices on the profiles of 17 heterocyclic amines (HAs) from seven HA categories were investigated in roast beef patties using Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry (UPLC-MS/MS) and principal component analysis. Three groups of HAs, imidazopyridines (PhIP, DMIP, and 1,5,6-TMIP), imidazoquinoxalines (MeIQx and 4,8-DiMeIQx), and β-carbolines (harman and norharman), were detected and quantified in all of the samples. The results demonstrated that the total HA and imidazopyridine profiles could clearly be affected by 1% pricklyash peel (14.1 ± 0.76 and 6.06 ± 0.32 ng/g), chilli (41.0 ± 0.01 and 23.0 ± 0.52 ng/g), and cumin (59.9 ± 2.44 and 31.1 ± 3.06 ng/g), in comparison with control values of 21.8 ± 2.40 and 14.3 ± 2.04 ng/g, respectively. The difference was only significant (p < 0.05) for cumin. The imidazoquinoxaline profile was significantly (p < 0.05) affected by 1% pricklyash peel (0.57 ± 0.05 ng/g) and cumin (2.36 ± 0.20 ng/g) compared to the control (1.16 ± 0.11 ng/g). The β-carboline profile was only markedly (p < 0.05) affected by 1% cumin (26.4 ± 0.82 ng/g) compared to the control (6.26 ± 0.26 ng/g). In general, pricklyash peel inhibited HA formation, whereas star anise, fennel, cumin, chilli, and black pepper promoted HA formation. The findings could facilitate the selection of spices in meat processing to minimize HA formation.