Antioxidant Phenolic Compounds Research Articles

Preparation of Silicon Oxycarbide (SiCO) Ceramics from Different Polymer Architectures and Assessment on the Performance as Electrodic Materials for Voltammetric Sensing of Antioxidant Phenolic Compounds

Silicon oxycarbide (SiCO) ceramics obtained from polymer pyrolysis and with varied carbon contents were prepared and evaluated as new electrodic materials for sensing of tert‑butylhydroquinone (TBHQ) and butylated hydroxyanisole (BHA) antioxidants. Three polymers were synthesized varying molecular architecture and aromatic carbon groups, followed by pyrolysis at 1000 and 1500 °C to obtain SiCO ceramics. Graphitization and crystallization processes were evidenced, in different extent, according to precursor chemistry. SiCO at 1500 °C with intermediary carbon content provided slight improvement in the peak anodic separation of TBHQ and BHA and higher peak current compared with glassy carbon electrode (GCE). Higher acidic sites concentration together with more ordered residual carbon phase produced in situ contributed to great electrochemical performance of SiCO towards phenolic compounds detection. Therefore, the ceramic herein prepared exhibits highly efficient features as a new SiCO composited electrode for simultaneous determination of antioxidant phenolic compounds bearing in mind further analytical applications.

Rubus idaeus L. fruit nutrients are affected by different growing technologies

The biochemical compounds of red raspberry (Rubus idaeus L.) fruits cultivated with conventional growing technology and on a nutrient substrate were studied during 2019–2020 at the Federal Horticultural Research Center for Breeding, Agrotechnology and Nursery, Moscow, Russia. The antioxidant activity, phenolic compounds, and ash constituents of the fruits and the metabolites of the alcoholic extract of the raspberries were determined. The effect of growing technologies, i.e., conventional vs. nutrient substrate, on the accumulation of macro- and microelements in raspberry fruits was established. In red raspberries grown on nutrient substrate, the antioxidant activity decreased by 25 times (aqueous extract) and 1.5 times (alcoholic extract). The K and Na contents and Se contents of red raspberries grown on nutrient substrate were 1.5 and 3 times higher than those of raspberries of grown with conventional technology. Raspberries grown with conventional technology contained 2 times more Ca, Ni, and Mn and 7.4 times more Fe than raspberries grown on nutrient substrate. The total amount of elements in raspberries grown through soilless cultivation was 5.5% higher than that in berries grown conventionally. A total of 48 compounds were identified in the alcoholic extracts, and only 29 substances were found in berries grown on a nutrient substrate. Sugar and citric acid constituted the largest share of red raspberry components. Fructose and turanose disaccharide synthesis in raspberries grown on nutrient substrate was 20% higher than that in conventionally grown raspberries. A total of 48 organic compounds with different biological activities were identified. They included five substances with antimicrobial activity, three phenolic substances, eight organic acids, four sugar acids, nine amino acids, and 19 sugars and their derivatives. At the same time, 42 compounds were found in raspberries grown with traditional technology, and 21 compounds were identified in raspberry fruits grown on nutrient substrate. Three fatty acids, namely, ɑ-linoleic acid (polyunsaturated omega-6 fatty acid), palmitic acid, and stearic acid (saturated fatty acid), along with cinnamic acid, shikimic acid, and chrysin were found in berries grown conventionally.

Assessment of the Phytochemical and Nutrimental Composition of Dark Chia Seed (Salvia hispánica L.).

Chia seeds are rich sources of different macro and micronutrients associated with health benefits; thus, they may be considered as a functional food. However, the composition depends on the variety, origin, climate and soil. Here, we show a comprehensive characterization of extractable and non-extractable phenolic compounds of dark chia seed Salvia hispanica L. using high-performance liquid chromatography–electrospray ionization–quadrupole time-of-flight (HPLC-ESI-QTOF) and discuss potential health benefits associated with the presence of a number of nutritional and bioactive compounds. We report that dark chia from Jalisco is a high-fiber food, containing omega-3 polyunsaturated fatty acids, essential amino acids (phenylalanine and tryptophan), and nucleosides (adenosine, guanidine and uridine), and rich in antioxidant phenolic compounds, mainly caffeic acid metabolites. Our data suggest that chia seeds may be used as ingredients for the development of functional foods and dietary supplements.

Antioxidant potential, anti-nutritional factors, volatile compounds and phenolic composition of microwave heat-treated plum (Prunus domestica. L.) kernels: an analytical approach

PurposeThe study was aimed to explore the potential impact of microwave heating (450 W for 2, 4, 6 and 8 min) on antioxidant activity, anti-nutritional factors, volatile and phenolic compounds of the plum kernels.Design/methodology/approachPlum kernels are rich in proteins, lipids and bioactive compounds that are mostly underused and undervalued.FindingsThe results showed that microwave heating at 450 W for 6 min significantly (p < 0.05) increased the antioxidant activity, total phenolic and flavonoid content, while the longer treatment time (450 W for 8 min) adversely affected the phenolic compounds. Most importantly, the anti-nutritional factors like amygdalin, hydrocyanic acid, phytic acid and tannin content were reduced up to 87.1, 84.7, 20.9 and 46.2%, respectively at 450 W for 6 min treatment conditions, which was confirmed from the larger shifts observed in FT-IR spectra near 1,157 cm−1. Microwave heating at 450 W for 6 min also proved beneficial in improving the bioavailability of volatile and phenolic compounds including chlorogenic acid, gallic acid, syringic acid, (+)-catechin, caffeic acid, ß-carotene, trans-ferulic acid, rutin trihydrate, 3,4-dihydroxybenzoic acid, tannic acid and quercetin by liberating them from the plant matrix.Originality/valueThe results thus indicate that controlled microwave heating could be an effective approach for the reduction of anti-nutritional factors besides leading to an overall improvement in antioxidant potential and volatile and phenolic compounds. This novel technological approach can proliferate the use of plum kernels in different diversified food formulations.

Entrapment of rosemary extract by liposomes formulated by Mozafari method: physicochemical characterization and optimization

A major obstacle in the utilization of phenolic antioxidant compounds is their sensitivity and as a result stability issue. The current study aimed to encapsulate polyphenolic compounds, extracted from Rosemary, in liposomes prepared by the Mozafari method without the utilization of toxic solvents or detergents. The extract was prepared and converted into a powder by freeze-drying. The process conditions were optimized using response surface analysis, and the optimal parameters were as follows: phosphatidylcholine (PC), 2.5% (25 mg/mL); extract, 0.7% (7 mg/mL); process temperature, 70 °C and process time, 60 min. The entrapment efficiency in optimal sample was 54.59%. Also, optimal glycerosomes formulation were finally physicochemical characterized (permeability, zeta potential, and size distribution). The mean size of empty and containing rosemary extract glycerosome were 265.4 nm and 583.5 nm, respectively, and the Z-potential of optimal glycerosome was -65.1 mV. Total phenolic content was obtained 151.38 mg gallic acid/g extract, in optimal liposomal formulation, which was measured by Folin-Ciocalteu's phenol reagent. Also, the antioxidant activity of rosemary extract by DPPH for the free and optimal liposomal formulation was determined to be 84.57% and 92.5% respectively. It can be concluded that the liposomal rosemary extract formulation prepared in this study, employing a safe, scalable, and green technology, has great promise in food and pharmaceutical applications.

Valorization of Carrot Pomace: UVC Induced Accumulation of Antioxidant Phenolic Compounds

Carrot pomace is the main waste residue obtained during carrot juice extraction. Plant tissues respond to abiotic stresses (i.e., wounding stress and ultraviolet C (UVC) radiation) by accumulating bioactive compounds. Due to the mechanical damage occurring during juice extraction, carrot pomace undergoes extreme wounding stress. In this study, the effects of UVC light (11.8 W m−2, 0–120 min) and storage time (48 h, 25 °C) on the accumulation of phenolics compounds and the antioxidant activity (AOX) of carrot pomace were evaluated. Carrot pomace that was non-treated with UVC (control) showed a 709.5% increase in total phenolics at 48 h. A high correlation of AOX values against total phenolics (R2 = 0.87) was observed, indicating that phenolics were the main contributors to the AOX of the tissue. After UVC treatment, the pomace that was radiated for 120 min with UVC showed an increase (40.4%) in chlorogenic acid (CHA) content. At 24 h, protocatechuic acid and 3,5-dicaffeoylquinic acid, which were not detected before storage, showed accumulation by 166.5 mg/kg and 169.4 mg/kg, respectively, in UVC treated pomace. Chlorogenic acid showed the highest increase (143.6%) at 48 h in the control. Valorization of carrot pomace was achieved by increasing its concentration of antioxidant phenolics through UVC radiation.

Comparative Study of Phenolic Compound Antioxidant and Antimicrobial Activities of Fruits Peel and Cladodes from Tunisian Opuntia Stricta

Similarly, the bacterial strains tested were most sensitive to fruit peels than especially against Staphylococcus aureus with inhibition zones (DIZ), minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 15.22±2.14 mm, 4.68 mg/mL and 37.5 mg/mL respectively. However, aqueous extract of cladodes have high antifongical activity particularly against Fusarium oxysporum with DIZ (20±0.2 mm), MIC (4.68mg/mL) and MFC (75 mg/mL) value

Flavone, flavanone and flavonol metabolism from soybean and flaxseed extracts by the intestinal microbiota of adults and infants.

Flaxseed and soybean are an important source of lignans and flavonoids. Previously, the metabolism of isoflavones and lignans from soybean and flaxseed extracts by the microbiota of adult individuals (n=14) and infants (n=23) was analyzed. Thus, the present study aimed to examine the metabolism of flavones, flavanones and flavonols, as well as the production of phenolic acids, by the intestinal microbiota of these individuals. Concentrations of aglycones of flavonoids, such as herbacetin, quercetin, quercetagetin, myricetin, kaempferol, apigenin and luteolin, increased for most of individuals as a consequence of deglycosylation reactions. On the other hand, a diminution in the antioxidant activity and phenolic compound concentration and an increase in the concentration of 3,4-dihydroxyphenylacetic acid, 2-(4-hydroxyphenyl)-propionic acid, protocatechuic acid and catechol was also observed. The present study found that deglycosylation reactions were the main reactions and accelerated the formation of more bioavailable flavonoids, with greater biological activity, in most of the individuals. However, other reactions also occurred, including the total or partial catabolism of flavonoids. © 2021 Society of Chemical Industry.

Antioxidant Activities and Phenolic Compounds of Extract from Hallasan Wormwood

Background: Many Artemisia species are used in traditional medicine to treat gastrointestinal disorders and various other ailments. However, the antioxidant and phenolic compounds present in Hallasan wormwood (Artemisia japonica var. hallaisanensis) have not been investigated yet.<BR>Methods and Results: Extracts of Hallasan wormwood (aerial parts and roots) were extracted using methanol and sequentially treated with solvent-solvent fractionation using n-hexane, ethyl acetate, and water-saturated butanol, to yield fractions with variations in polarity. The phenolic compounds present in the extracts and fractions were determined using high performance liquid chromatography (HPLC) and colorimetry. The antioxidant activities were determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, trolox equivalent antioxidant capacity (TEAC), ferric reducing antioxidant power (FRAP), and oxygen radical antioxidant capacity (ORAC) methods. The results revealed that the ethyl acetate fraction had high total phenolic and total flavonoid contents. Furthermore, the ethyl acetate fraction of roots showed the highest antioxidant activity.<BR>Conclusions: Metanolic extracts from the roots and aerial parts of Hallasan wormwood showed different antioxidant activities; nine phenolic acids and one flavonoid were detected in Hallasan wormwood. Thus, the finding of this study provide valuable data for research on functional substances from plants.

Dehydrated at Different Conditions and Powdered Leek as a Concentrate of Biologically Active Substances: Antioxidant Activity and Phenolic Compound Profile.

This study aimed to analyze the antioxidant activity, phenolic acid profile, color changes, and chemical composition of dried and powdered leek (Allium porrum). Leek was divided into white shaft (WH) and green shaft (GR) and subjected to drying by different methods—convection drying, vacuum drying, and freeze-drying (FD)—at a temperature of 60 °C. A sample freeze-dried at a temperature of 20 °C was used as control. Analyses of the dried leek samples revealed that GR contained a higher amount of ash, protein, fat, fiber, phenolic acids, and flavonoids, and exhibited higher antioxidant capacity compared to WH. The dominant phenolic acid in WH was p-cumaric acid followed by synapic and protocatechuic acids. GR had a several-fold higher content of phenolic acids than WH, with ferulic acid being dominant (about 85% of the total phenolic content). It was also observed that a higher drying temperature resulted in the degradation of phenolic compounds and reduced the antioxidant properties of leek shafts. Most importantly, FD under a temperature of 60 °C caused a similar degree of degradation of biologically active compounds as air drying. An increase in drying temperature was associated with a slight decrease in the lightness of GR, whereas in the case of WH no significant change in this parameter was observed.

Optimal drying conditions for valorization of industrial apple pomace: Potential source of food bioactive compounds

AbstractApple pomace contains a large amount of useful bioactive compounds that have wide application in the food industry. In this study the effect of drying temperature and pressure (high temperature 80 °C and low temperature 60 °C using a conventional oven and a combination of conventional plus vacuum drying oven) on the antioxidant capacity and phenolic compounds of apple pomace extract was investigated. For a combination of conventional and vacuum drying ovens, samples were first dried by a conventional oven to a moisture content of approximately 10% then vacuum dried to reach a final moisture content of 3–4%. After the drying processes, ethanolic extraction was performed and the amount of total polyphenol and the antioxidant capacity (FRAP) were evaluated to determine a best drying method. The drying curves were also determined. The drying temperature affects the duration of the drying, the rate of water loss, and the remaining amount of antioxidant compounds.

Antioxidative activities, phenolic compounds and marine food allergens in the macroalgae Saccharina latissima produced in integrated multi-trophic aquaculture systems

The concept of “Integrated Multi-Trophic Aquaculture” (IMTA) is considered one of several strategies to increase biomass production from the sea by combined culture of different organisms, such as low-level trophic macroalgae, profiting from and reducing the environmental impact of fish farming. However, due to lack of data and scientific evidence, appropriate food regulations are lacking for IMTA to guide the production of macroalgae and their application as food products. Macroalgae are reported to be nutritious and to have valuable bioactivities including antioxidative activity. Besides valuable compounds, macroalgae can also contain elements with unwanted effects such as allergens. Thus, there is a growing concern from the food industry and food safety authorities regarding the potential occurrence of contaminating marine allergens in seaweed food products. As seaweed is produced in the ocean, allergens of marine species, such as crustaceans, molluscs or even fish might find their way into the production line and these hazards must be monitored to evaluate the risk for allergenic incidents and the need for appropriate labelling for future food products. To date, there is little data in this aspect on seaweed production in IMTA systems, where especially the occurrence of contaminating allergens could be increased due to close contact with cohabitant species. Hence, the occurrence of marine food allergens (fish parvalbumin, mollusc and crustacean tropomyosins), as well as total phenolic compounds and antioxidant activity have here been assessed in S. latissima produced in three different locations in 2020 in the vicinity of salmonids farms in Norway. We confirm the presence of phenolic compounds and antioxidative activity in S. latissima, produced in IMTA systems, in a similar range for all assessed locations and comparable to previous studies. Of the tested allergens, only crustacean tropomyosin could be detected in all locations of this study up to 1 mg/kg dry weight, however not representing a critical level for consumption.

Physicochemical Parameters, Phytochemical Profile and Antioxidant Properties of a New Beverage Formulated with Xique-Xique (Pilosocereus gounellei) Cladode Juice.

This study elaborated different formulations with xique-xique (Pilosocereus gounellei) cladode, passion fruit and lime juice and sugar cane syrup. The formulated beverages were subjected to physical and physicochemical analysis, determination of total carotenoid, total flavonoid and total phenolic compound contents, as well as of their antioxidant activity (ABTS and FRAP method), organic acid, sugar and phenolic compound profile during 21 days of refrigeration storage (4 °C). Significant variations were found among formulated beverages for most of the measured parameters during storage. Beverages with xique-xique juice were less acidic (7.90–10.27 g/100 mL) than beverages without this juice (11.66–12.76 g/100 mL). Beverages with xique-xique juice had overall higher contents of bioactive compounds and higher antioxidant activity when compared to the control formulation. Beverages with the highest xique-xique juice concentrations had the highest contents of carotenoids (51.51–59.27 µg/100 mL), flavonoids (1.39–2.15 mg CE/100 mL), phenolic compounds (68.49–115.66 mg EGA/100 mL) and antioxidant activity, as measured by ABTS (0.71–0.84 µmol Trolox/mL) and FRAP (0.33–0.39 µmol Trolox/mL). These results indicate that the incorporation of xique-xique cladode juice in these mixed beverages enhanced their bioactive properties, especially of antioxidant compounds, enabling the development of a new product with potential functional properties to the beverage industry.

Physiological, photochemical, and antioxidant responses of wild and cultivated Carthamus species exposed to nickel toxicity and evaluation of their usage potential in phytoremediation.

The impacts of Ni toxicity on growth behaviors, photochemical, and antioxidant enzymes activities of wild (Carthamus oxyacantha M. Bieb.) and cultivated (Carthamus tinctorius L.) safflower species were investigated in this study. Fourteen-day-old seedlings were treated with excessive Ni levels [control, 0.5, 0.75, and 1.0 mM NiCl2·6H2O] for 7 days. The results of chlorophyll a fluorescence indicated that toxic nickel exposure led to changes in specific, phenomenological energy fluxes and quantum yields in thylakoid membranes, and activities of donor and acceptor sides of photosystems. These changes resulted in a significant decrease in the photosynthetic activities by about 50% in both species, but these negative effects of Ni were not in a level to destroy the functionality of the photosystems. At the same time, toxic Ni affected membrane integrity and the amount of photosynthetic pigments in the antenna and active reaction centers. Additionally, the accumulation of Ni was higher in roots than in stem and leaves for both species. Depending on Ni accumulation, a significant reduction in dry biomass of root by approx. 64.8 and 45.7% and shoot by 41 and 24.7% were observed in wild and cultivated species, respectively. Two species could probably withstand deleterious Ni toxicity with better upregulating own protective defense systems such as antioxidant enzymes and phenolic compounds. Among of them, SOD and POD activities were increased with increasing Ni concentrations. The POD activities of both species were most prominent and consistently increased (approx. 2 folds in roots and 6 folds in leaves) in highly toxic Ni levels and may be protected them from damaging effect of H2O2. When all results are evaluated as a whole, Carthamus species produced similar responses to toxicity and also both species have bioconcentration (BCF) and bioaccumulation factor (BF) > 1 and translocation factor < 1 under Ni toxicity may be regarded a good indication of Ni tolerance. Furthermore, it is possible to use the Carthamus species as phytostabilizers of soils contaminated with nickel, because of their roots accumulating more nickel.

Identification of key phenolic compounds responsible for antioxidant activities of free and bound fractions of blackberry varieties' extracts by boosted regression trees.

Free fractions of different blackberry varieties' extracts are high in phenolic compounds with antioxidant activities. However, the phenolic profiles and antioxidant activities against peroxyl radicals of bound fractions of different blackberry varieties' extracts have not been previously reported. In addition, what the key antioxidant phenolic compounds are in free and bound fractions of blackberry extracts remain unknown. This study aimed to investigate the phenolic profiles and antioxidant activities of free and bound fractions of eight blackberry varieties' extracts and reveal the key antioxidant phenolic compounds by boosted regression trees. Fifteen phenolics (three anthocyanins, four flavonols, three phenolic acids, two proanthocyanidins, and three ellagitannins) were identified in blackberry by ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry. Ferulic acid, ellagic acid, procyanidin C1, kaempferol-O-hexoside, ellagitannins hex, and gallic acid were major bound phenolics. Bound fractions of eight blackberry varieties' extracts were high in phenolics and showed great antioxidant activity. Boosted regression trees analysis showed that cyanidin-3-O-glucoside and chlorogenic acid were the most significant compounds, contributing 48.4% and 15.9% respectively to the antioxidant activity of free fraction. Ferulic acid was the most significant antioxidant compound in bound fraction, with a contribution of 61.5%. Principal component analysis showed that Kiowa was the best among the eight varieties due to its phenolic profile and antioxidant activity. It was concluded that blackberry varieties contained high amounts of bound phenolics, which confer health benefits through reducing oxidative stress. Ferulic acid was the key compound to explain the antioxidant activities of bound fractions. © 2021 Society of Chemical Industry.

Ultrasound-assisted extraction of antioxidant phenolic compounds from Lavandula angustifolia flowers using natural deep eutectic solvents: An experimental design approach

In this study, the green extraction of antioxidant phenolic compounds from Lavandula angustifolia was investigated using ultrasound-assisted extraction coupled with natural deep eutectic solvents (NADESs). One variable at a time, fractional factorial design, steepest ascent/descent method, and central composite design were used to optimize the extraction conditions. Eighteen NADESs based on choline chloride, organic acids, and sugars were tested by one variable at a time approach. The NADES composed of choline chloride and glycerol with a molar ratio of 1:2 showed higher extraction performance than other NADESs and benchmark solvents (70 % ethanol and 80 % methanol). After solvent selection, other extraction parameters including ultrasound amplitude (20–100 %), temperature (40–70 °C), time (5–30 min), liquid to solid ratio (10–50 mL/g), and water content in NADES (10–50 %) were screened using fractional factorial design. Subsequently, the steepest ascent/descent method was applied to approach the suitable level of the selected parameters. Finally, response surface methodology was used to determine the optimal extraction conditions. The optimum conditions were ultrasound amplitude of 60 %, temperature of 60 °C, time of 17.5 min, liquid to solid ratio of 31.7 mL/g, and water content in NADES of 33.5 % with the predicted phenolic content of 50.50 mg gallic acid equivalent/g, flavonoid content of 35.79 mg catechin equivalent/g, antioxidant capacity (AC)DPPH of 41.60 mg Trolox equivalent (TE)/g, ACABTS of 77.13 mg TE/g, and ACCUPRAC of 163.33 mg TE/g. Phenolics and volatiles were analyzed by HPLC and GC-MS, respectively. The results showed a sustainable, green, and effective extraction of antioxidant phenolic compounds from L. angustifolia.

Photochemoprotective Effects of Ethyl Acetate Fraction from Senegalia polyphylla Leaves in Ultraviolet-Irradiated L929 Fibroblasts

Objectives: Unprotected exposure to ultraviolet radiation causes oxidative damages to skin cells. Topical administration of antioxidants is a feasible strategy to prevent oxidative alterations. Therefore, the present study evaluated the photodamage attenuating potential of plant materials from Senegalia polyphylla leaves, due to previous studies relating Senegalia species as a source of antioxidant phenolic compounds. Materials and Methods: The ethanolic extract (EE) and its ethyl acetate (EAF), hydromethanolic and hexane fractions were evaluated for their total phenolic content and antioxidant capacity. The photochemoprotective effects of plant materials with higher antioxidant potential were assessed in L929 fibroblasts against ultraviolet-B (UVB) and Ultraviolet-A (UVA) radiations. Phytochemical investigation of bioactive plant material was performed and compounds identified by nuclear magnetic resonance analysis. Results: The EE and EAF presented the highest total phenolic content and antioxidant capacity, showing ferric reducing power and ability to scavenge free radicals DPPH•, ABTS•+, O2•− and ROO•. The EE and EAF treatments prior to UVB and UVA irradiation prevented the decrease in cell viability, and attenuated reactive oxygen species generation, reduced glutathione depletion, lipid peroxidation and plasma membrane disruption, especially with EAF treatment. Vitexin and isoquercetin, known antioxidant compounds, were isolated from EAF, which may be correlated with its photochemoprotective ability. Conclusion: Findings indicate the potential of polyphenol-enriched botanical materials, such as EAF from S. polyphylla, in preventing UVB and UVA-induced oxidative damages, due to its effective antioxidant activity and ability to attenuate redox imbalance and reduce cell damages.

The effect of application of arbuscular mycorrhizal fungi with some microorganisms and chemical compounds on the antioxidant enzymes activity and phenolic compounds of corn under drought stress

The effect of application of arbuscular mycorrhizal fungi with some microorganisms and chemical compounds on the antioxidant enzymes activity and phenolic compounds of corn under drought stress

Optimization of phenolic compound recovery and antioxidant activity from Fumaria officinalis L. using response surface methodology

The purpose of this study was to optimize the extraction of antioxidant phenolic compounds from Fumaria officinalis by two approaches, single-factor experiment and response surface methodology (RSM). After extraction optimization, the content of polyphenols, flavonoids, and tannins was performed. Antioxidant activities of optimal extract were evaluated by DPPH, ABTS, and iron chelating activities. Single-factor experiments showed that all extraction parameters had significant effects (p &lt; 0.05) on total phenolic content and free radical scavenging activity. From the optimization process using response surface methodology through Box-Behnken design regarding the three selected significant parameters (solvent concentration, extraction time, and temperature), it was established that the best extraction conditions were 47% methanol, 54.40°C, and 168.02 min, respectively. Under these optimal conditions, the recorded values for TPC and DPPH scavenging activity were successively 1510.10 mg GAE/100g DW and 69.85%. These results were in accordance with model predictions indicating that the model was suitable for the extraction process. Furthermore, higher flavonoids and tannins contents and strong iron-chelating and ABTS scavenging activities were obtained.

High-Throughput Quantification of 32 Bioactive Antioxidant Phenolic Compounds in Grapes, Wines and Vinification Byproducts by LC-MS/MS.

The well-established, health-benefitting effects of grapevines and derivatives (wines and vinification byproducts) are attributed to their antioxidant phenolic content. The dearth of an efficient method for the simultaneous quantitation of antioxidant phenolics prompted us to develop a novel method utilizing triple quadrupole LC–MS/MS for the accurate, fast, simultaneous quantitation of the 32 most abundant grapevine phenolics. The fully validated, novel method is capable to simultaneously record the quantitative presence of 12 phenolic acids, 19 polyphenols and coniferyl aldehyde (a phenolic compound extracted from cork stoppers into wines) and is applicable for the determination of antioxidant phenolics content of grape berries, pomace, stems and wines. Its utility was demonstrated for three native Greek grapevine varieties, two red (Mandilaria and Aidani mavro) and one white (Monemvassia). Results herein highlighted the stems of the Monemvassia white variety as particularly rich in antioxidant phenolics such as the flavonol monomer (+)-catechin (387 mg/kg) and the dimer procyanidin B1 (400 mg/kg) along with stilbene phytoalexin trans-resveratrol (24 mg/kg). These results are in line with the TPC, TFC and TTC content of stems and the determined antioxidant capacities, highlighting the stems of this Vitis vinifera variety as potentially exploitable source of antioxidant phenolics.