QUENCHER Procedure Research Articles

Analysis of the Leaves and Cones of Lithuanian Hops (Humulus lupulus L.) Varieties by Chromatographic and Spectrophotometric Methods.

This work involves a comprehensive chemical composition analysis of leaf and cone samples of Lithuanian hop varieties. This study aimed to determine the chemometric properties of the leaves and cones of five Lithuanian hop varieties. Determined properties were the following: (a) xanthohumol content, (b) phenolic compounds, (c) flavonoids, (d) radical scavenging activity, and (e) the qualitative composition of volatile compounds. The total content of phenolic compounds in aqueous 75% methanolic extracts varied between 31.4–78.2 mg of rutin equivalents (RE)/g, and the concentration of flavonoids was between 11.0–23.3 mg RE/g. Radical scavenging activity varied between 34.4–87.2 mg RE/g. A QUENCHER analysis procedure showed 91.7–168.5 mg RE/g of the total phenolic compound content, 12.7–21.4 mg RE/g of flavonoids, and 48.4–121.0 mg RE/g of radical scavenging activity. ‘Fredos taurieji’ and ‘Fredos derlingieji’ varieties have shown maximum values of phenolic compounds and radical scavenging activity both in leaf and cone suspensions. These varieties accumulated a higher amount of xanthohumol in leaves. The concentration of xanthohumol in the samples varied between 0.0014–0.2136% of dry mass, with the highest concentration in the cones of ‘Kauno gražieji’. We identified 19 volatile compounds in leaves, and in cones, we identified 32. In both of them, α-humulene and β caryophyllene dominated. ‘Raudoniai’ leaves were exceptional in their aroma due to dominating compound nagina ketone (Kovats index 1306). The QUENCHER procedure has shown a great potential for the unextractable residue of hop raw material. Further investigation and valorization of different hop biomass components, not only cones, are essential.

Antioxidant activity of extracts obtained by high-pressure extraction procedures from Asparagus stipularis Forssk

Roots and rhizomes of Asparagus stipularis Forssk were separately extracted using supercritical CO2 extraction (SCCO2) and pressurized liquid extraction (PLE) and their Total Phenols Content and antioxidant potential was investigated. The results indicated that the roots and rhizomes are a potential source of natural antioxidants. The PLE method gave better extraction yields than SFE and its fractions present the highest antioxidant activity. Direct evaluation of antioxidant capacity using the QUENCHER procedure showed that also the solid residue of the plant material remaining after the SCCO2 and PLE may be of interest as a source of valuable phytochemicals.

Physical, Total Phenolic and Total Flavonoid Properties of Chia (<i>Salvia hispanica</i> L.) Seeds Grown in Kenya

In the recent past, there has been an increased uptake of chia seeds (Salvia hispanica L.) by consumers resulting in the increased adoption of chia farming, particularly in Kenya whereby most farmers are practising subsistence farming and a few farming it commercially. The widespread farming of chia seeds in Kenya translates to increased uptake at household level while offering a niche for industrial processing of chia seeds necessitating the need for studies on physical, total phenolic and flavonoid properties of chia seeds grown in Kenya. The physical, total phenolic and flavonoid properties of chia seeds from two chia planning seasons April to August 2019 and September to December 2019 were evaluated. The physical attributes (length, width and thickness) were determined using a digital vernier calliper while proximate components were determined using AOAC standard methods. The Quencher procedure was used to determine the total phenolic and flavonoid contents. Chia seeds revealed a length of 1.82 to 2.32 (mm), a width of 1.15 to 1.31 (mm) and a thickness of 0.77 to 0.88 (mm). The percentage moisture content of chia seeds was 7.23 to 10.67, percentage of crude fat was 31.48 to 42.45, percentage of crude ash was 3.63 to 6.82, and percentage of crude fibre was 30.95 to 38.65 and percentage of crude protein was17.82 to 28.97. The total phenolic content observed for chia seeds was 0.73 to 0.87 mg GAE g-1 while total flavonoid content was 0.39 to 0.57 mg GAE g-1. The proximate components of chia seeds varied significantly (p .

Behaviour of Trolox with macromolecule-bound antioxidants in aqueous medium: Inhibition of auto-regeneration mechanism

This work aimed at investigating the behaviour of Trolox, vitamin E analogue, in presence of macromolecule-bound antioxidants in aqueous radical medium. Three main groups of macromolecule-bound antioxidants were assayed: dietary fiber (DF), protein and lipid-bound antioxidants, represented by whole wheat, soybean and olive oil products, respectively. Experimental studies were carried out in aqueous ABTS (2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)) radical medium. Trolox and macromolecule-bound antioxidants were added to radical separately and together in different concentrations. Antioxidant capacities were determined using QUENCHER procedure. pH of radical media was altered for DF and protein-bound antioxidant studies to examine its effect. Chemometric tools were used for experimental design and multivariate data analysis. Results revealed antagonistic interactions for Trolox with all macromolecule-bound antioxidants. The reason behind this antagonism was investigated through oxidation reactions of Trolox via mass spectrometry analysis. Consequently, a proof was obtained for inhibitory effect of bound-antioxidants on auto-regeneration reactions of Trolox.

Effect of roasting and brewing on the antioxidant capacity of espresso brews determined by the QUENCHER procedure

This study aimed to evaluate the changes in the antioxidant capacity of coffee after roasting to several degrees, and also the corresponding espresso brews using the direct QUENCHER procedure. In addition, volumetric fractions were collected in partitions during brewing of espresso to observe the extractability of antioxidant capacity in green and roasted beans. Roasting provided a 35% increase in the Trolox equivalent antioxidant capacity after roasting at 220°C for 20min. Approximately half of the antioxidant capacity can be brewed to espresso beverage from ground coffee independent of the roasting degree. During brewing espresso, 30mL was shown enough to get the 76% of the antioxidant activity with respect to longer extraction volumes. Extraction of 5-caffeoylquinic acid showed a similar pattern to antioxidant capacity. On dry matter basis, antioxidant capacity of the volume fractions increased both in green and roasted coffee. This indicated that the fraction having higher antioxidant capacity extracts more difficultly during espresso brewing.

Optimization of a New Methodology for Determination of Total Phenolic Content in Rice Employing Fast Blue BB and QUENCHER Procedure

Response surface methodology was used to optimize the total phenolic content (TPC) result in white rice, using a new methodology that employed Fast Blue BB (FBBB) reagent, which reacts more specifically with phenolic compounds, along with direct QUENCHER procedure. This is the first time in which such conciliation between FBBB reagent and QUENCHER was done. The obtained model allowed to evaluate how the factors influenced the method linearity (R2), improving the choice of the optimal system condition. Furthermore, the similarity between experimental results and values generated by the model indicated the method validity within the studied region. Thus, the optimal condition determined in the present work was 30 min reaction time, 0.17 mL FBBB reagent and use of 5% NaOH as the catalyst for the reaction. This optimized condition suggested that the combination of the method, which used FBBB reagent and the direct QUENCHER procedure, was rapid and effective, yielding high TPC values (1488.73 mg of gallic acid equivalent per 100 g).

Antioxidant Capacity in Tilapia Fillets Enriched with Extract of Acerola Fruit Residue

This work evaluated the effect of supplementation with ethanolic extract of acerola fruit residue (EEAR) on the antioxidant capacity of tilapia fillets over a period of 60 days. Different methodologies were used following the QUENCHER procedure, and the hydrophilic and lipophilic fractions of the oxygen radical absorbance capacity (ORACFL) assay were analysed. The fatty acid composition was also evaluated, as high concentrations of linoleic and oleic acids were observed in the fillets, as well as satisfactory polyunsaturated fatty acids/saturated fatty acids (PUFA/SFA) ratios. The highest antioxidant capacities in 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assays (1778.87 and 4892.77 µmol Trolox equivalent antioxidant capacity (TEAC) g-1, respectively) were found at 15 days, and these trials showed the highest correlation coefficient (R = 0.9388). The ORACFL assay indicated that the hydrophilic fraction is the largest contributor to the total antioxidant capacity (TAC). Thus, the significant increase observed in antioxidant capacity makes supplementation with EEAR a potent tool in the elevation of the antioxidant capacity of tilapia fillets.

Evaluation of antioxidant potential of Brazilian rice cultivars

This study quantified the fatty acids and evaluated the proximate composition, antioxidant activity (using the Quencher procedure), and total phenolic compound concentrations in Brazilian rice cultivars. The cultivars studied showed high amounts of unsaturated fatty acids, such as linoleic and oleic acid. The ratios of polyunsaturated and saturated fatty acids obtained were high. Regarding the antioxidant activity, the best results were found using the ABTS method and the worst in the DPPH assay. The results of the DPPH and FRAP assays showed the highest correlation. The antioxidant capacity results obtained were also much higher than those reported for other varieties worldwide. Therefore, the Quencher procedure is highly suitable for application in cereals such as rice, especially when combined with the ABTS radical capture method.

Soluble Antioxidant Compounds Regenerate the Antioxidants Bound to Insoluble Parts of Foods

This study aimed to investigate the regeneration potential of antioxidant capacity of an insoluble food matrix. Investigations were performed in vitro with several food matrices rich in dietary fiber (DF) and bound antioxidants. After removal of the soluble fraction, the antioxidant capacity (AC) of the insoluble fraction was measured by the QUENCHER procedure using ABTS(•+) or DPPH(•) radicals. After measurement, the insoluble residue was washed out to remove the excess of radicals and treated with pure antioxidant solution or antioxidant-rich beverage to regenerate depleted antioxidants on the fiber. Results revealed that the antioxidant capacity of compounds chemically bound to the insoluble moiety could be reconstituted in the presence of other hydrogen-donating substances in the liquid phase. Regeneration efficiency was found to range between 21.5 and 154.3% depending on the type of insoluble food matrix and regeneration agent. Among the food matrices studied, cereal products were found to have slightly higher regeneration efficiency, whereas antioxidant-rich beverages were more effective than pure antioxidants as regeneration agents. Taking wheat bran as reference insoluble material, the regeneration abilities of beverages were in the following order: green tea > espresso coffee > black tea > instant coffee > orange juice > red wine. These results highlighted the possible physiological relevance of antioxidants bound to the insoluble food material in the gastrointestinal tract. During the digestion process they could react with the free radicals and at the same time they can be regenerated by other soluble antioxidant compounds present in the meal.

Relationship between total antioxidant capacities of cereals measured before and after in vitro digestion

Total antioxidant capacity (TAC), which is the cumulative capacity of different antioxidants to reduce oxidative stress, proved to be very useful to correlate the antioxidant capacity of the diet with the incidence of some disease or with modification of disease biomarkers. Therefore, it is important to estimate the real antioxidant potential of cereals. Most methods are based mainly on extractive methods which may largely underestimate the TAC of cereals. Several recent articles have reported a direct approach, the Quencher procedure, which produces a higher TAC compared to extractive methods. However, both the extractive methods and the Quencher procedure are performed prior to digestion. In this article, an in vitro approach using enzymatic digestion, designed to mimic digestion in the gastrointestinal tract (physiological conditions), had been used to release antioxidants from cereals. Seven whole cereals were employed for the determination of DPPH as well as ABTS radical scavenging activity before and after simulated digestion. The objective was to compare the in vitro procedure of antioxidant extraction with the Quencher procedure and water extraction. The values of the TAC’s from the cereal grains obtained from the in vitro procedure were 1.8–10.3 times higher than the Quencher procedure and 3.5–10.5 times higher than water extraction. Correlation between the results of the TAC obtained using the three different procedures was also investigated. The in vitro gastrointestinal digestion procedure is more useful in the screening of grains, assessing their beneficial health effects compared to the Quencher procedure or water extraction.

Direct measurement of total antioxidant capacity of cereals: QUENCHER-CUPRAC method

Polyphenols in cereal samples are distributed as free, soluble-esterified, and insoluble-bound forms either esterified or etherified to cell wall constituents. In the evaluation of total antioxidant capacity (TAC) of cereals, rather difficult and time-consuming acid, alkaline and enzymatic treatments of residue have been applied to complete the extraction of bound phenolic compounds. Thus, this work is aimed to measure the TAC of cereals (i.e. barley, wheat, rye, oat) by the ‘QUENCHER procedure’ (involving forced solubilization of bound phenolics by oxidizing TAC reagents) with the direct use of copper(II)–neocuproine (Cu(II)–Nc) reagent of the CUPric Reducing Antioxidant Capacity (CUPRAC) assay. In this novel ‘QUENCHER-CUPRAC’ method, reaction time and solvent composition parameters were optimized, and the method was applied to cereal samples with CUPRAC reagent dissolved in 1:1 (v/v) ethanol–water mixture. The antioxidant capacities of soluble and insoluble fractions were simultaneously measured to give a hierarchic TAC order of cereals as: barley>rye>oat>wheat. The TAC values of cereals measured by QUENCHER-CUPRAC were higher than those of original QUENCHER method using ABTS•+ and DPPH reagents. Polyphenolic mixtures in a cellulose matrix gave additive TAC values with QUENCHER-CUPRAC. The proposed method correlated linearly with QUENCHER-ABTS•+ (r=0.956) and QUENCHER-DPPH (r=0.976).

Antioxidant Activity of Brazilian Bean Cultivars

This study quantified fatty acids and evaluated the proximate composition, antioxidant activity paired with Quencher procedure and total phenolic compounds in Brazilian bean cultivars. The samples showed high amounts of polyunsaturated fatty acids, such as linoleic acid (191.54 to 329.50 mg g-1 of total lipids) and α-linolenic acid (228.03 to 367.27 mg g-1 of total lipids). The obtained ratios between Omega 6 and 3 fatty acids were low, between 0.71 and 1.12. In relation to antioxidant activity assays, the cultivars showed the best results upon employing the 2,2-azinobis (3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS) method (2401.34 to 4394.80 µmol Trolox equivalent g-1). The lowest results were observed in the ferric reducing antioxidant power (FRAP) assays, 530.93 to 1440.13 µmol Trolox equivalent g-1. The results from 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ABTS methods showed the greatest correlation between themselves (r = 0.619). High concentrations of total phenolic compounds were also detected in the studied cultivars, which varied from 81.85 to 173.65 mg gallic acid equivalent 100g-1.

Solvent effects on total antioxidant capacity of foods measured by direct QUENCHER procedure

This study aimed to investigate the effects of solvent composition of different radicals (ABTS, DPPH) on measured total antioxidant capacity (TAC) of foods determined by the QUENCHER procedure. The working solutions of ABTS radical were prepared in the mixture of water–ethanol with different volume ratios (0:100, 25:75, 50:50, 75:25, 100:0). The solvent composition had a significant effect on the measured antioxidant capacity of various food matrices including cereals, fruits and vegetables, pulses and nuts (p<0.05). The use of ethanol alone gave the lowest values during measurement while introducing water to ethanol significantly improved the levels of antioxidant capacity. These results suggested that the mixture of water–ethanol (50:50, v/v) may be the most appropriate solution for standardizing the TAC database of foods tested by the QUENCHER procedure. The need of water is due to its ability to open the structure enabling better access of radicals to functional ends of the food matrices.

Total antioxidant capacities of raw and cooked meats

This study investigated the total antioxidant capacity (TAC) of meats (beef, chicken, pork and fish) and its changes on thermal treatment. The QUENCHER procedure, which is performed directly on the solid material without extraction, was selected and proved to be particularly suitable for meat samples. The ABTS+ scavenging capacity of raw meats ranged between 25.9±1.0 and 51.7±1.2mmol Trolox Eq./kg. Raw chicken had the highest TAC followed by pork, beef and fish. Upon heating at 180°C, TAC of meats increased to an apparent maximum at 5min followed by sudden decreases until 15min, while the final stage of heating was characterized by slight increases. The modifications of TAC during cooking can be explained considering factors such as denaturation and exposure of reactive protein sites, degradation of endogenous antioxidants and the formation of Maillard reaction products having antioxidant properties.

A combined procedure to evaluate the global antioxidant response of bread

Baking is the most representative manufacturing process applied to bread, involving thermal and moisture conditions that facilitate the Maillard reaction (MR) and, at the same time, the destruction-formation of natural-labile and thermally-induced antioxidant compounds respectively. In the present paper, the use of a new approach to measure the Global Antioxidant Response (GAR) of cereal derivatives is proposed: a combination of in vitro digestion – which enables measurement of the bioaccessible fraction – and the QUENCHER, which makes it possible to determine the antioxidant activity of the insoluble fraction, since it is a simple and direct procedure for determining the total antioxidant capacity of solid products. After digestion, the results obtained by the antioxidant assays are up to 20-fold higher than those reported using the standard extraction methods. The non-extractable residue displayed significant antioxidant activity that accounted for up to 17% of the total antioxidant activity. Moreover, the GAR obtained in some of the assays developed was 10–40% higher than the antioxidant activity registered by the QUENCHER procedure in wheat bread, and the difference was even higher in wheat bran bread. Therefore, the use of the GAR approach could avoid underestimation of the antioxidant activity of cereal derivatives.