Bound phenolics in foods, a review

Optimized hydrolytic methods by response surface methodology to accurately estimate the phenols in cereal by HPLC-DAD: The case of millet

Extraction of free and bound phenols from millet in acidic and basic hydrolytic conditions were compared for the first time. Acidic hydrolysis was able to extract the highest amount of total phenolic compounds (up to 178 mg/100 g) while the basic hydrolysis underestimates the phenolic concentration. Our findings pointed out for the first time that methyl ferulate is naturally present as bound phenol in millet. Response Surface Methodology was then applied to both acidic and basic hydrolytic extractive conditions: the acidic procedure, optimized in terms of extractive time and temperature and concentration of the acidic mean, gave the best results, allowing definition of Method Operable Design Region and quantitation of the total amount of phenols in millet samples in a single extractive step. This optimized method is suitable for further accurate investigations of the typical phenols of the numerous varieties of this recently re-discovered minor cereal.

Lactic Fermentation as a Strategy to Improve the Nutritional and Functional Values of Pseudocereals

One of the greatest challenges is to reduce malnutrition worldwide while promoting sustainable agricultural and food systems. This is a daunting task due to the constant growth of the population and the increasing demands by consumers for functional foods with higher nutritional values. Cereal grains are the most important dietary energy source globally; wheat, rice, and maize currently provide about half of the dietary energy source of humankind. In addition, the increase of celiac patients worldwide has motivated the development of gluten-free foods using alternative flour types to wheat such as rice, corn, cassava, soybean, and pseudocereals (amaranth, quinoa, and buckwheat). Amaranth and quinoa have been cultivated since ancient times and were two of the major crops of the Pre-Colombian cultures in Latin- America. In recent years and due to their well-known high nutritional value and potential health benefits, these pseudocereals have received much attention as ideal candidates for gluten-free products. The importance of exploiting these grains for the elaboration of healthy and nutritious foods has forced food producers to develop novel adequate strategies for their processing. Fermentation is one of the most antique and economical methods of producing and preserving foods and can be easily employed for cereal processing. The nutritional and functional quality of pseudocereals can be improved by fermentation using Lactic Acid Bacteria (LAB). This review provides an overview on pseudocereal fermentation by LAB emphasizing the capacity of these bacteria to decrease antinutritional factors such as phytic acid, increase the functional value of phytochemicals such as phenolic compounds, and produce nutritional ingredients such as B-group vitamins. The numerous beneficial effects of lactic fermentation of pseudocereals can be exploited to design novel and healthier foods or grain ingredients destined to general population and especially to patients with coeliac disease.

Analysis by UPLC-DAD-ESI-MS of Phenolic Compounds and HPLC-DAD-Based Determination of Carotenoids in Noni ( Morinda citrifolia L.) Bagasse

Noni bagasse is usually wasted after the noni juice extraction process. The purpose of this study was to investigate the phytochemical composition of noni bagasse (with and without seeds) obtained after a 1 week period of a short-term juice drip-extraction process from over-ripe noni fruit. Totals of free phenolics, flavonoids, condensed tannins, carotenoids, and most of the minerals were higher in bagasse without seeds (NSB) than in bagasse with seeds (WSB), whereas bound phenolics and total and insoluble dietary fiber were higher in WSB than in NSB. β-Carotene and lutein, quantified by HPLC-DAD, were higher in both bagasse than in juice. A total of 16 phenolic compounds and 2 iridoids were determined by UPLC-DAD-ESI-MS. Among them, procyanidin B-type dimer, caffeoylquinic-acid-hexoside, and quercetin-hexose-deoxyhexose have not been previously reported in noni bagasse, noni juice, or noni fruit. Isorhamnetin-3- O-rutinoside was the most abundant compound in both bagasses. In conclusion, both bagasses are potential sources of phytochemical compounds for the food and pharmaceutical industries.

Characterization, quantification of free, esterified and bound phenolics in Kainth (Pyrus pashia Buch.-Ham. Ex D.Don) fruit pulp by UPLC-ESI-HRMS/MS and evaluation of their antioxidant activity

UPLC-ESI-HRMS/MS was used to identify the free, esterified and bound phenolic compounds in Kainth fruit extracts. In total, around 17, 15 and 18 free, esterified and bound phenolic compounds respectively were identified. Among these, Procyanidin B₂, Epicatechin, Phloridzin, Hesperetin, etc. are being reported for the first time. The total phenolic content of free, esterified and bound fractions were 178.33 ± 6.90, 151.33 ± 7.73 and 707.16 ± 19.77 mg GAE/100 g of fruit. The major phenolic compounds quantified were chlorogenic acid (7.97 mg/100 g), arbutin (7.05 mg/100 g) and catechin (44.56 mg/100 g) in free, esterified and bound form respectively. Various antioxidant assays (DPPH, ABTS, TAC and FRAP) were performed for all the extracts. Among different extracts, the bound phenolics exhibited the highest antioxidant activity. Systematic identification and quantitative profiling of phenolics in Kainth fruit being presented for the first time would help in utilising this fruit for designing functional food formulations.

Ultrasound assisted purification of polyphenols of apple skins by adsorption/desorption procedure

The ultrasound (US) assisted purification of polyphenols of apple skins by adsorption/desorption on the poly-aromatic Amberlite adsorbent XAD-16 was studied. The adsorption steps were done at different temperatures (T = 25-40 °C) with application of US at different intensities (P = 0-400 W). The desorption steps were tested in aqueous ethanol solution at different concentrations of ethanol (C_et = 0-96%). The isotherm of polyphenol adsorption was well described using the Freundlich model. The data on adsorption kinetics and static isotherm evidenced the presence of adsorption on heterogeneous surface with broad distribution of adsorption times that can depend on content of polyphenols in the solutions and applied power of sonication. The studies of desorption revealed the optimum desorption efficiency of polyphenols at 50% concentration of ethanol. The desorption ratio was positively affected by the sonication during the adsorption step. The highest adsorption/desorption efficiency (recovery) was observed for polyphenols as compared with proteins and soluble matter content and it reached of ≈30.6% (0 W) and 68.9% (50 W) in absence and presence of sonication, respectively. The effects of high US power on the damage of XAD-16 were discussed. The obtained data evidenced on good perspective of application of adsorption/desorption procedure assisted by sonication for purification of polyphenols from apple skin extracts.

Purple pigment from Peltogyne mexicana heartwood as a potential colorant for food

ABSTRACT

Peltogyne mexicana heartwood might be a novel purple pigment source. The results of the present study demonstrate that the purple pigment is an important source of phenolic compounds (698.22 ± 2.99 mg GAE/g) and flavonoids (48.01 ± 0.51 mg EPE/g). UV-Vis spectrum and color parameters (L* a* b*) showed that purple pigment has different shades of purple-red (H° value 19.32 ± 0.02 in methanol and 22.85 ± 0.01 in ethanol) depending on the solvent and the pH. Also, the purple pigment did not exhibit acute oral toxicity at a single dose (2000 mg/kg body weight). No mutagenicity was observed in the Ames test with three Salmonella typhimurium strains. The purple pigment exhibited considerable coloring properties with a wider range of citric acid-dependent color hues in gelatin (H° from 280.3 to 319.9 and from 68.0 to 88.1), and higher color intensity than commercial anthocyanin. Minor variations in the hue were found in yogurt, for purple pigment with H° values from 317.5 to 315.0, and commercial anthocyanin from 82.6 to 88.7 and 276.9 to 295.5. However, purple pigment required lower concentrations to achieve superior effects. For gelatin and yogurt samples, similar variations in the color parameters L*, a*, b*, and pigment degradation were observed for purple pigment and commercial anthocyanin in the stability assay.

GRAPHICAL ABSTRACT

Effect of In Vitro Digestion on Phytochemical Profiles and Cellular Antioxidant Activity of Whole Grains

Most of the previous in vitro digestion treatments were conducted directly to whole grains without extraction of free phenolics, thus the bioaccessible phenolics contained both free phenolics that survived the digestion and digested phenolics released by digestion. However, the profiles of digested phenolics released by digestion remain unknown. This study was designed to investigate the phytochemical contents, peroxyl radical scavenging capacities (PSCs), and cellular antioxidant activities (CAAs) of free, digested, and bound fractions of whole grains. Total phenolic contents of whole grains were highest in digested fraction, followed by free and bound fractions. The predominant phenolics were 12 phenolic acids and one flavonoid, which mostly existed in bound forms, then in digested and free forms. The digested phenolics bound to proteins were in conjugated form. The bound fractions had the highest PSCs, followed by free and digested fractions. CAAs were highest in bound fractions, followed by digested and free fractions.

Review on nutritional composition of orange-fleshed sweet potato and its role in management of vitamin A deficiency

A wide variety of the roots and tubers plays a major role in human diet, animal feed, and industrial raw materials. Sweet potatoes (SPs) play an immense role in human diet and considered as second staple food in developed and underdeveloped countries. Moreover, SP production and management need low inputs compared to the other staple crops. The color of SP flesh varied from white, yellow, purple, and orange. Scientific studies reported the diversity in SP flesh color and connection with nutritional and sensory acceptability. Among all, orange-fleshed sweet potato (OFSP) has been attracting food technologists and nutritionists due to its high content of carotenoids and pleasant sensory characteristics with color. Researchers reported the encouraging health effects of OFSP intervention into the staple food currently practicing in countries such as Uganda, Mozambique, Kenya, and Nigeria. Scientific reviews on the OFSP nutritional composition and role in vitamin A management (VAM) are hardly available in the published literature. So, this review is conducted to address the detailed nutritional composition (proximate, mineral, carotenoids, vitamins, phenolic acids, and antioxidant properties), role in vitamin A deficiency (VAD) management, and different food products that can be made from OFSP.

Mung Bean (Vigna radiata L.): Bioactive Polyphenols, Polysaccharides, Peptides, and Health Benefits

Mung bean (Vigna radiata L.) is an important pulse consumed all over the world, especially in Asian countries, and has a long history of usage as traditional medicine. It has been known to be an excellent source of protein, dietary fiber, minerals, vitamins, and significant amounts of bioactive compounds, including polyphenols, polysaccharides, and peptides, therefore, becoming a popular functional food in promoting good health. The mung bean has been documented to ameliorate hyperglycemia, hyperlipemia, and hypertension, and prevent cancer and melanogenesis, as well as possess hepatoprotective and immunomodulatory activities. These health benefits derive primarily from the concentration and properties of those active compounds present in the mung bean. Vitexin and isovitexin are identified as the major polyphenols, and peptides containing hydrophobic amino acid residues with small molecular weight show higher bioactivity in the mung bean. Considering the recent surge in interest in the use of grain legumes, we hope this review will provide a blueprint to better utilize the mung bean in food products to improve human nutrition and further encourage advancement in this field.

Flaxseed Lignans as Important Dietary Polyphenols for Cancer Prevention and Treatment: Chemistry, Pharmacokinetics, and Molecular Targets

Cancer causes considerable morbidity and mortality across the world. Socioeconomic, environmental, and lifestyle factors contribute to the increasing cancer prevalence, bespeaking a need for effective prevention and treatment strategies. Phytochemicals like plant polyphenols are generally considered to have anticancer, anti-inflammatory, antiviral, antimicrobial, and immunomodulatory effects, which explain their promotion for human health. The past several decades have contributed to a growing evidence base in the literature that demonstrate ability of polyphenols to modulate multiple targets of carcinogenesis linking models of cancer characteristics (i.e., hallmarks and nutraceutical-based targeting of cancer) via direct or indirect interaction or modulation of cellular and molecular targets. This evidence is particularly relevant for the lignans, an ubiquitous, important class of dietary polyphenols present in high levels in food sources such as flaxseed. Literature evidence on lignans suggests potential benefit in cancer prevention and treatment. This review summarizes the relevant chemical and pharmacokinetic properties of dietary polyphenols and specifically focuses on the biological targets of flaxseed lignans. The consolidation of the considerable body of data on the diverse targets of the lignans will aid continued research into their potential for use in combination with other cancer chemotherapies, utilizing flaxseed lignan-enriched natural products.

Comparative Study of Phenolic Profiles, Antioxidant and Antiproliferative Activities in Different Vegetative Parts of Ramie (Boehmeria nivea L.)

Ramie (Boehmeria nivea L.) is usually cultivated as a fiber crop, but it is also well known for its potential use in animal feeding with viable commercial applications. In this study, the phenolics profile as well as cellular antioxidant and antiproliferative activities were investigated in free and bound fractions of six different vegetative parts from Boehmeria nivea L. The highest total phenolic content was observed in bud (4585 ± 320 mg GAE/100 g DW), whereas root and petiole had the lowest total phenolic contents, 442.8 ± 9.8 and 630.9 ± 27.0 mg GAE/100 g DW, respectively. Likewise, phloem had the most abundant total flavonoids (2755 ± 184 mg CE/100 g DW), whereas the lowest flavonoid contents was found in root and petiole, 636.9 ± 44.2 and 797.4 ± 87.6 mg CE/100 g DW, respectively. Xylem and bud depicted remarkable antioxidant and antiproliferative activities, which could be explained by their diverse phenolic composition, especially chlorogenic acid and epicatechin. The Boehmeria nivea L. plant might be a valuable resource for high value-added phenolic compounds used in food and non-food industries.

Natural antioxidants of plant origin

Interest in the content of natural antioxidants in plant-based foods can be from the human health perspective, in terms of how these compounds might help promote one's health and wellness, or from the storage point-of-view, as the endogenous antioxidant constituents aid to extend a foodstuff's shelf-life. This chapter reports essential information about the mechanism of antioxidant action and methods employed for determination of their activity, classes of phenolic compounds (phenolic acids, flavonoids, lignans, stilbenes, tannins), sources of plant antioxidants (oil seeds, cereals, legumes, plants of the Lamiaceae family, tea and coffee, tree nuts, fruits, and berries), extraction strategies of phenolic compounds from plant material, and the influence of processing and storage on the content of natural antioxidants in foods and their antioxidant activity. Thermal processing, if not releasing bound phenolics from the structural matrices of the food, tends to decrease the antioxidant potential or, in the best case scenario, has no significant negative impact. Gentler sterilization processes such as high-pressure processing tend to better retain the antioxidant potential of a foodstuff than thermal treatments such as steaming, boiling, or frying. The impact of processing can be assessed by determining the antioxidant potential of foodstuffs either at the point of formulation or after different periods of storage under specified conditions.

Effect of enzyme pretreatment in the ultrasound assisted extraction of finger millet polyphenols

Polyphenols from plant sources are increasingly recognized as functional ingredients with multiple health benefits. Finger millet (Eleusine coracana), a major millet grown in Asia and Africa is a significant source of polyphenols. The extraction of polyphenols from millets which are under-utilized has received less research attention compared to other plant matrices. Therefore, the present study was carried out to identify an effective method of extracting the polyphenols from finger millet (v. GPU 28) seed coat (FMSC). Two eco friendly methods namely ultrasonication (UA) and enzyme treatment followed by ultrasonication (EUA) were compared with the conventional heat reflux method (HR). The polyphenolic profile and content along with the antioxidant potential of the extract were evaluated. Phenolic yield increased 2.3 fold using EUA with xylanase (XUA) compared to heat reflux extraction (HR). However, yield with UA was equivalent to the conventional method. Total flavonoids increased 1.4 fold in UA and 1.3 fold in XUA, similarly, tannins also showed a significant increase (1.1 fold in UA and 1.2 fold in XUA). FTIR spectra revealed the presence of all phenolic functional groups and ESI-MS showed 80% similarity in the individual polyphenols in the extracts. Catechins, luteolin and cyanidin were identified in the UA and XUA treated samples, whereas, shikimic acid derivatives- caffeoyl and di caffeoyl were present only in XUA extracts. This is the first report on enhanced extraction of polyphenols from FMSC using a combination of enzyme treatment and ultrasonication, providing a green technology for utilization of polyphenols in nutraceuticals and functional foods.

Particle size of milled chokeberry pomace did not influence in vitro cellular absorption and transport efficiencies of anthocyanins, phenolic acids and flavonols

Industrial chokeberry pomace is very rich in polyphenols. The main focus here lies on the possible relationship between the particle size of chokeberry milled pomace and an enhanced absorption and transport of polyphenols by Caco-2 cells. Wet milling was used to produce materials with particle size distributions in the micrometre and in the sub-micrometre to nanometre ranges starting from chokeberry pomace. Milled materials with about 50% of the particles with a mean size (x_50,3) of 223 ± 13 µm (coarse milling) and about 90% of the particles with x_50,3 of 160 ± 40 nm (fine milling, sonication) were obtained. None of the milled materials exhibited cytotoxic effects within the tested concentration-ranges. The polyphenol absorption and the transport efficiencies from the fine and the coarse milled materials were similar. Thus, no effect of the particle size upon cellular uptake and transport could be established, but agglomeration of particle during incubation cannot be excluded as the cause. Furthermore, based on polyphenol stability we postulate that direct milling may be applied to valorise the processing by-product from commercial fruit juice production.

Correlations between disintegration degree of fruit skin cells induced by ultrasound and efficiency of bio-compounds extraction

The ultrasound (US) assisted extraction of bio-compounds from different fruit skins (apples, bananas and persimmons) was studied. The aqueous suspensions of skins were treated by US with different energy inputs (0.033-0.299 kW·h/kg) and total time of aqueous extraction was up to 2700 s. The ionic, Z_i, and total polyphenol, Z_p, extraction indexes of the liquid extracts were analyzed. From microscopic images the cell wall disintegration index, Z_m, was determined. Increase in US energy input caused the increase of values of Z_i, Z_p and Z_m. The correlations between extraction parameters and the disintegration index, Z_m, were discussed.

Effect of processing on quality attributes and phenolic profile of quince dried bar snack

BACKGROUND

Fruit and vegetable processing can often alter and damage antioxidants. Phenolic compounds, which are major antioxidants in these products, can suffer dissociation and changes in their concentration. Quince is an excellent source of antioxidants, with health-improving potential for consumers. The phenolic profile (by ultra-high-performance liquid chromatography-mass spectrometry) and quality attributes (pH, soluble solids, acidity, water activity) were determined for processed quince products (fresh fruit puree, cooked puree and dried bars), in addition to the effect of puree cooking time (5, 10, 15 and 20 min).

RESULTS

Soluble solids in purees averaged 14.4 °Brix and increased to 75 °Brix in bars, as did titratable acidity, reaching 1.5 g malic acid kg^-1 fresh weight after 20 min of cooking at 120 °C. Quercetin, p-coumaric acid and trans-cinnamic acid were predominant in fresh fruit puree. Thermal processing significantly increased the concentration of p-coumaric acid, trans-cinnamic acid, apigenin and quercetin, and decreased gallic acid. This increase was 242%, on average, for all of them when comparing fresh fruit puree with bars on a fresh weight basis, demonstrating their concentration throughout the dehydration process during bar production.

CONCLUSION

Although a minimum puree cooking time of 5 min was sufficient to obtain the highest concentration of most phenolics, p-coumaric acid showed a higher concentration after 20 min of cooking. © 2018 Society of Chemical Industry.

Comparison of Free, Esterified, and Insoluble-Bound Phenolics and Their Bioactivities in Three Organs of Lonicera japonica and L. macranthoides

Dried flower buds of Lonicera japonica and L. macranthoides have long been used as herbs in numerous Chinese traditional medicines. Comparisons of three phenolic fractions (i.e., free, esterified, and insoluble-bound phenolics) in three different organs (i.e., flower, leaf, and stem) of the two species revealed that the free phenolics were the highest in terms of total phenol and total flavonoid content, composed of the most numerous phenolics and flavonoids; thus, they exhibited the most excellent antioxidant activities (2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonate) (ABTS), and oxygen radical absorbance capacity (ORAC)), as well as protective effects on DNA damage induced by free radicals. In identical free and esterified phenolics of a same organ, higher contents and bioactivities were observed in L. macranthoides than in L. japonica. Phenolics identified by ultra-performance liquid chromatography with a diode array detector, alongside tandem mass spectrometry coupled with a quadrupole time-of-flight mass spectrometer (UPLC-DAD⁻QTOF-MS/MS) mainly included chlorogenic acid and its five derivatives, three flavonoids that were only found in the free phenolic fraction and closely correlated with its bioactivity, and caffeic acid that was the major contributor to antioxidant activity of the esterified and insoluble-bound phenolic fractions. It was, thus, concluded that, like L. japonica, L. macranthoides, which was underestimated since being separately listed by the 2010 edition of the Chinese Pharmacopoeia, is also a good (and better) herbal medicine.

Cultivar-specific responses in red sweet peppers grown under shade nets and controlled-temperature plastic tunnel environment on antioxidant constituents at harvest

Antioxidant constituents such as carotenoids (capsanthin, phytoene, lutein, β-cryptoxanthin), polyphenols content (p-coumaric, ferulic, p-hydroxybenzoic, caffeic acid, sinapic acid, and quercetin-3-glucoside) and marketable yield were investigated in 11 sweet pepper cultivars grown under controlled temperature plastic tunnel and white shade net. Marketable yield was not affected by either of the environments, while the interaction between cultivar and growing environment significantly affected the accumulation of antioxidant constituents. The principal component analysis illustrated that controlled temperature plastic tunnel improved the accumulation of carotenoid components and ascorbic acid and vitamin C content in most cultivars. On the contrary, white shade nets favoured the accumulation of phenolic compounds and ORAC activity in most cultivars. A strong correlation was noted between phytoene and carotenoid components in this study (capsanthin r = 0.60; P < 0.001; lutein r = 0.75; P < 0.001; β-carotene r = 0.78; P < 0.001) while ORAC correlated with phenolic compounds. Based on this study, it is possible to refine the choice of environment and cultivar to enhance individual antioxidant constituent groups to improve health benefits for consumers.

Effects of anthocyanin-rich purple corn (Zea mays L.) stover silage on nutrient utilization, rumen fermentation, plasma antioxidant capacity, and mammary gland gene expression in dairy goats1

Eight healthy multiparous Saanen dairy goats (41.50 ± 1.84 kg) were assigned to a double 4 × 4 Latin square design. The four treatment diets were: (i) negative control, rice straw (NC); (ii) first positive control, sticky corn stover silage (PC1); (iii) second positive control, PC1 with 1 g/d commercial purple corn pigment (PC2); and (iv) anthocyanin-rich purple corn stover silage (PSS; AR). DMI did not differ (P > 0.05) among the treatments. Goats receiving the NC tended (P < 0.05) to reduce nutrient apparent digestibility, nitrogen (N) absorption, N retention, and volatile fatty acid production relative to the other groups. The levels of 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity and superoxide dismutase (SOD) in plasma were greater (P < 0.05) in goats fed PC2 and AR compared with NC and PC1. The inclusion of PC2 and AR increased (P < 0.05) the abundance of nuclear factor (erythroid-derived 2)-like 2 (NFE2L2), but decreased (P < 0.05) the level of tumor necrosis factor in the mammary gland. Moreover, goats receiving AR tended to increase (P < 0.05) the levels of SOD2, GPX1, and GPX2 mRNA expression in the mammary gland. There were significant (P < 0.05) positive correlations between DPPH scavenging activity, total antioxidant capacity, SOD, catalase enzymes in plasma, and the abundance of NFE2L2 in the mammary gland. In addition, stronger (P < 0.05) positive correlations were noted between the expression of several inflammation related and antioxidant genes. Collectively, the results from the current study indicated that the consumption of anthocyanin-rich PSS by dairy goats had the potential to enhance antioxidant potential by improving antioxidant capacity in plasma and by modulating the abundance of several inflammation related and antioxidant genes in the mammary gland.

Leaf Disc Assays for Rapid Measurement of Antioxidant Activity

Antioxidant levels are key parameters for studies of food quality, stress responses, and plant health. Herein, we have demonstrated that excised leaf disc has both radical scavenging activity and reducing power, and used this concept to develop 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and potassium permanganate reduction (PPR) leaf disc assays. Reaction time and reagent concentration for these assays were optimized using leaves from spinach, kale, collards, mustard, and watermelon. Further, these assays were validated for linearity and intra-assay precision. Ultra-high performance liquid chromatography coupled to an electrospray quadrupole time-of-flight mass spectrometer (UPLC/ESI-HR-QTOFMS) was used for phytochemical profiling and studying relative abundances of certain phenolic compounds in various leaf discs suspended and cell-free extracts. The mass spectral analysis showed that leaf disc suspended methanolic extracts had almost same phytochemical profiles to those of cell-free extracts. The DPPH leaf disc assay demonstrated better radical scavenging potential than the conventional cell-free extract method. By contrast, the observed antioxidant activity values in ABTS and PPR leaf disc assays were lower than those of conventional cell-free extract-based methods. In conclusion, the developed leaf disc assays are simple and rapid for the qualitative and comparative assessment of the antioxidant potential of leaf samples, as well as can be a good alternative to conventional cell-free extract based methods.

Monitoring of acrylamide and phenolic compounds in table olive after high hydrostatic pressure and cooking treatments

Acrylamide and phenolic compounds on both fresh and cooked olives were monitored by HPLC/MS-MS and reversed-phase-HPLC methods along different procedures: elaboration process, high hydrostatic pressure (HHP), cooking treatment and bioavailability evaluation. Acrylamide was not detected during the elaboration process and after HHP treatment. Hydroxytyrosol, tyrosol, oleuropein and verbascoside were the most important phenols after HHP treatment. The frying and baking processes on olives enhanced the formation of acrylamide and a significant reduction in the phenolic compounds. The frying process produced lower acrylamide concentration and less reduction of phenolic compounds than the baking process, while in the gastrointestinal digestion these compounds were slightly reduced if compared to the initial stage. As a conclusion, the best way to ingest high quantities of phenols and reduce acrylamide consumption is by ingesting the olives when they are fresh. In case the olives need to be cooked, specific time and temperature conditions shall be applied.

In vitro digestion of meat- and cereal-based food matrix enriched with grape extracts: How are polyphenol composition, bioaccessibility and antioxidant activity affected?

The aim of this study was to evaluate the effect of enriching a complex food matrix (FM) with grape extracts on polyphenol content, composition, bioaccessibility and antioxidant activity during digestion. The grape extracts and FM were separately tested under the same conditions as controls. The FM by itself contains a significant amount of phenolic acids and flavonols, influencing the final recovery of polyphenols from grape extracts. The FM significantly increased the total recovery of polyphenols after digestion of grape seed extracts compared to those digested without the FM; however, a low recovery of proantocyanidins and total flavonoids was observed. Digestive fluids and FM compounds significantly increased the total polyphenol content of grape digests and significantly contributed to their ABTS⁺ scavenging activity and ferrous-ion-chelating capacity. The present study suggested that enrichment of meat- and cereal-based products with grape polyphenol extracts could be a good strategy to formulate a healthier diet.

Blackberry (Rubus ulmifolius Schott): Chemical composition, phenolic compounds and antioxidant capacity in two edible stages

The berries of the genus Rubus has been highlighted as important source of bioactive and health promoting constituents, however, information about chemical composition and antioxidant potential of the specie Rubus ulmifolius are still scarce. In this regard, this study aimed to assess the physicochemical characteristics, total monomeric anthocyanins (TMA), individual phenolics, minerals, sugars, and antioxidant properties of mature and fully mature R. ulmifolius. With the advance of maturation, changes in the physicochemical composition suggest pleasant characteristics for consumption especially in the fully mature stage. High levels of TMA and sugars (fructose and glucose) were also verified in the fully mature stage, as well as, expressive antioxidant potential, with values of 241.06 μM Fe⁺² g^-1 for ferric reducing antioxidant power and 28.22 mg gallic acid equivalent g^-1 for Folin-Ciocalteu reducing capacity (all expressed in dry matter, DM). In contrast, minerals (potassium, calcium, sodium) and most of the studied phenolic compounds showed the highest concentrations in mature fruits. Among the phenolics investigated, 26 compounds were identified and quercetin and isoquercitrin were the predominant phenolic compounds in the fruit. The results reinforce the nutritive and antioxidant potential of Rubus ulmifolius in both maturation stages studied.

Extrusion of apple pomace increases antioxidant activity upon in vitro digestion

Apple pomace, a by-product of juice production, is a high-fibre, high-polyphenol functional food ingredient.