Bound phenolics in foods, a review

Nutritional properties of the largest bamboo fruit Melocanna baccifera and its ecological significance

Melocanna baccifera is a unique bamboo which produces the largest fruits in the grass family. Its gregarious flowering once in 45-50 years in north east India and adjacent regions is a botanical enigma, resulting in a glut of fruits. Proper utilization of M. baccifera fruits is not extant, and huge quantities of fruits are left underexploited due to lack of scientific information on their chemical composition and nutritional potential. Here we report the nutritional properties of M. baccifera fruits, and the ecological significance of its fruiting. This pear-shaped, fleshy bamboo fruit is rich in amino acids (lysine, glutamic acid), sugars (sucrose, glucose, fructose) and phenolics (ferulic acid). Protein content (free, bound) in M. baccifera fruits is very low. Fruits are rich in saturated fatty acids (palmitic acid), minerals (potassium), and only B series vitamins (B3) are detected in them. Rat feeding experiments showed that M. baccifera fruit alone is not a complete food, but with other protein supplements, it is a valuable food additive. This study could lead to better utilization of M. baccifera fruits during future flowering/fruiting events. These results could also help in the successful management of rodent outbreaks and other ecological problems associated with M. baccifera fruiting.

Multi-response optimisation of the extraction solvent system for phenolics and antioxidant activities from fermented soy flour using a simplex-centroid design

A simplex-centroid design comprising three solvents (water, ethanol and methanol) was used to optimise the extraction mixture for phenolics and antioxidant activities from defatted soy flour fermented with Monascus purpureus or Aspergillus oryzae. Total phenolics were more efficiently extracted using only water for both samples. The highest antioxidant activities by the DPPH and ABTS methods were obtained using extraction mixtures containing at least 75 wt% water. Specific water:ethanol:methanol ratios promoted the joint optimisation of the total phenolic and isoflavone contents as well as antioxidant activities: 0.5:0.375:0.125 (wt/wt/wt) and 0.5:0.3:0.2 (wt/wt/wt) from defatted soy flour fermented with M. purpureus or A. oryzae, respectively. However, a water:ethanol ratio of 0.5:0.5 (wt/wt) was deemed optimal because it is comprised of green solvents and yielded results that were greater than 90% of the multi-response maximum values. Both the solvents and the sample matrix strongly influenced the extractability of total phenolics and isoflavones.

Effect of enzymatic (thermostable α-amylase) treatment on the physicochemical and antioxidant properties of extruded rice incorporated with soybean flour

In order to determine the effect of enzymatic extrusion on the physicochemical and antioxidant properties of rice/soybean mixture, different mass ratios (100/0, 95/5, 85/15, 70/30, 50/50 and 25/75%, w/w) were treated with thermostable α-amylase. The reduced special mechanical energy and the enhanced product temperature were closely and regularly linked with the increase of soybean content. The bulk density and water solubility index increased, and the water absorption index and viscosities decreased remarkably after enzymatic extrusion, however, the modification caused by α-amylase were dramatically eliminated with the increase of soybean content to ∼50%. Moreover, the addition of enzyme exhibited an improvement of the total phenolic/flavonoid content (TPC/TFC) and antioxidant capacities compared to traditional extrusion. The TPC/TFC retention of extrudate (ratios of 85/15 and 70/30%) attained over 90%, but dramatically decreased (72.91 and 67.81%, respectively) with soybean added to 75%, probably due to the great reduction of starch substrate for enzymatic hydrolysis.

The revisited levels of free and bound phenolics in rice: Effects of the extraction procedure

The effects of the type of solvolytic solution and number of extraction steps on the recovery of free phenolics, anthocyanins and proanthocyanidins from different rice samples were evaluated. Moreover, bound phenolic acids were determined as a function of enzymatic and/or alkaline hydrolysis treatment of the rice residue obtained after the extraction of free phenolics. The Acetone/Water (70:30 v/v) was the most effective solvolytic solution for extracting free phenolics from pigmented rice, as well as anthocyanins from black and wild rice, and proanthocyanidins from red rice. The application of three extraction steps increased the recovery of free phenolics up to 10%. The adoption of an enzymatic treatment, with α-amylase in order to reduce the paste viscosity of the residue, increased the extractability of bound phenolics. α-Amylase at 37°C during 15min followed by an alkaline hydrolysis at 37°C was the best treatment for the recovery of bound phenolics.

High-Pressure-Assisted Enzymatic Release of Peptides and Phenolics Increases Angiotensin Converting Enzyme I Inhibitory and Antioxidant Activities of Pinto Bean Hydrolysates

Pinto bean protein concentrate was hydrolyzed by subtilisins at 0.1, 100, and 200 MPa and 50 °C for 15 min. Alcalase hydrolysis at 100 MPa led to higher ACE inhibition, reducing power, and free radical scavenging activity of hydrolysates. However, hydrolysate obtained by Savinase at 200 MPa showed the best ACE-inhibitory and radical scavenging activities. Proteolysis by Savinase at 200 MPa was considered the most effective treatment to increase small peptides (<3 kDa), flavonoids, total phenolic compounds, and oxygen radical absorbance capacity in hydrolysates. In this hydrolysate, small phaseolin fragments with reported ACE-inhibitory and antioxidant sequences were identified. Catechin, pelargonidin 3-glucoside, and ferulic acid were the main phenolic compounds. Hihg-pressure-assisted hydrolysis of common bean protein concentrates would provide benefits in the production of functional hydrolysates providing higher functionality and added value to the resulting hydrolysate due to synergistic effects of bioactive peptides and soluble phenolics.

Bound Phenolics of Quinoa Seeds Released by Acid, Alkaline, and Enzymatic Treatments and Their Antioxidant and α-Glucosidase and Pancreatic Lipase Inhibitory Effects

Unextractable phenolics from plant foods and their role in health benefits have become increasingly important. Meal residues of three quinoa seeds free of fat and extractable phenolics were subjected to acid, alkaline, and enzymatic hydrolyses. The total and individual phenolic compounds released were analyzed, and 19 phenolics, predominantly phenolic acids and several flavonoids, were identified. The concentration of bound phenolics was highest in black quinoa followed by red and white, regardless of the hydrolysis method. Higher phenolic contents also showed stronger antioxidant activities and inhibition of α-glucosidase and pancreatic lipase activities. Carbohydrases, that is, pectinase, xylanase and feruloyl esterase, which effectively liberated bound phenolics are known to be secreted by colonic bacteria, suggesting potential antioxidant and anti-inflammatory effects by these compounds in the large intestine during colonic fermentation. These results can also be applied to treat foods high in bound phenolics to enhance bioaccessibility.

Changes in the Bioactive Compounds Content of Soybean as a Function of Grain Moisture Content and Temperature during Long-Term Storage

Soybean is a rich source of bioactive compounds, such as phenolic acids, flavonoids, isoflavones, carotenoids, and tocopherols. The amount of bioactive compounds in freshly harvested soybeans and their derived products has been determined; however, when they are used in the food industry, soybeans are generally stored prior to being processed. This study aimed to evaluate the effects of soybean moisture content (12%, 15%, and 18%) and storage temperature (11, 18, 25, and 32 °C) on the free phenolic, total flavonoid, vanillic acid, total carotenoid, and δ- and γ-tocopherol content of soybeans stored for 12 mo. Moreover, the ABTS and DPPH radical scavenging activities of phenolic extracts were determined. There was an increase in free phenolics and total flavonoids in the stored grains compared with the grains on the 1st d of storage. Vanillic acid showed a decrease in soybeans stored at 15% and 18% moisture content and 25 or 32 °C, which indicated some degradation into other metabolites. Total carotenoid content decreased as a function of storage temperature and showed some temperature-dependent degradation. The δ- and γ-tocopherol content also tended to decrease in grains stored at 15% or 18% moisture content or 25 or 32 °C, regardless of the moisture content studied.

Identification of Quantitative Trait Loci for the Phenolic Acid Contents and Their Association with Agronomic Traits in Tibetan Wild Barley

Phenolic acids have been of considerable interest in human nutrition because of their strong antioxidative properties. However, even in a widely grown crop, such as barley, their genetic architecture is still unclear. In this study, genetic control of two main phenolic acids, ferulic acid (FA) and p-coumaric acid (p-CA), and their associations with agronomic traits were investigated among 134 Tibetan wild barley accessions. A genome-wide association study (GWAS) identified three DArT markers (bpb-2723, bpb-7199, and bpb-7273) associated with p-CA content and one marker (bpb-3653) associated with FA content in 2 consecutive years. The contents of the two phenolic acids were positively correlated with some agronomic traits, such as the first internode length, plant height, and some grain color parameters, and negatively correlated with the thousand-grain weight (TGW). This study provides DNA markers for barley breeding programs to improve the contents of phenolic acids.

Accumulation of Phenolic Compounds and Expression Profiles of Phenolic Acid Biosynthesis-Related Genes in Developing Grains of White, Purple, and Red Wheat

Polyphenols in whole grain wheat have potential health benefits, but little is known about the expression patterns of phenolic acid biosynthesis genes and the accumulation of phenolic acid compounds in different-colored wheat grains. We found that purple wheat varieties had the highest total phenolic content (TPC) and antioxidant activity. Among phenolic acid compounds, bound ferulic acid, vanillic, and caffeic acid levels were significantly higher in purple wheat than in white and red wheat, while total soluble phenolic acid, soluble ferulic acid, and vanillic acid levels were significantly higher in purple and red wheat than in white wheat. Ferulic acid and syringic acid levels peaked at 14 days after anthesis (DAA), whereas p-coumaric acid and caffeic acid levels peaked at 7 DAA, and vanillic acid levels gradually increased during grain filling and peaked near ripeness (35 DAA). Nine phenolic acid biosynthesis pathway genes (TaPAL1, TaPAL2, TaC3H1, TaC3H2, TaC4H, Ta4CL1, Ta4CL2, TaCOMT1, and TaCOMT2) exhibited three distinct expression patterns during grain filling, which may be related to the different phenolic acids levels. White wheat had higher phenolic acid contents and relatively high gene expression at the early stage, while purple wheat had the highest phenolic acid contents and gene expression levels at later stages. These results suggest that the expression of phenolic acid biosynthesis genes may be closely related to phenolic acids accumulation.

Use of Modified Phenolic Thyme Extracts (Thymus vulgaris) with Reduced Polyphenol Oxidase Substrates as Anthocyanin Color and Stability Enhancing Agents

Residual enzymatic activity in certain foods, particularly of polyphenoloxidase (PPO), is responsible for the majority of anthocyanin degradation in food systems, causing also parallel losses of other relevant nutrients. The present work explored the feasibility of modifying phenolic profiles of thyme extracts, by use of chromatographic resins, to obtain phenolic extracts capable of enhancing anthocyanin colour and stability in the presence of PPO activity. Results indicated that pretreatment of thyme extracts with strong-anion exchange resins (SAE) enhanced their copigmentation abilities with strawberry juice anthocyanins. Phenolic chromatographic profiles, by HPLC-PDA, also demonstrated that thyme extracts subjected to SAE treatments had significantly lower concentrations of certain phenolic compounds, but extracts retained their colour enhancing and anthocyanin stabilization capacities though copigmentation. Additional testing also indicated that SAE modified extract had a lower ability (73% decrease) to serve as PPO substrate, when compared to the unmodified extract. Phenolic profile modification process, reported herein, could be potentially used to manufacture modified anthocyanin-copigmentation food and cosmetic additives for colour-stabilizing applications with lower secondary degradation reactions in matrixes that contain PPO activity.

Physicochemical Properties and in Vitro Digestibility of Cooked Regular and Nondarkening Cranberry Beans (Phaseolus vulgaris L.) and Their Effects on Bioaccessibility, Phenolic Composition, and Antioxidant Activity

Cranberry beans from regular (RR) and nondarkening (CND) genotypes were pressure cooked, and free, conjugated, and bound phenolics were analyzed. Simulated in vitro gastrointestinal digestion was used to assess the bioaccessibility of these phenolic fractions. Total phenolic content decreased after cooking and digestion, whereas individual phenolic compounds were affected differently. Cooking significantly increased the release of bound ferulic and sinapic acids and flavanols, whereas digestion released p-coumaric, ferulic, and sinapic acids in both genotypes, and p-hydroxybenzoic acid, epicatechin, and catechin in only RR. Bioaccessibility of phenolics in RR and CND was 8.75 and 14.69%, respectively. Difference in total phenolics was smaller after digestion, and enzymes potentially secreted by colonic bacteria released similar amounts of phenolic acids in both varieties. Resistant and slowly digestible starch contents showed no differences between RR and CND. These results suggest that the lower phenolic content in raw CND may not completely negate its impact on gut health.

Evaluation of Minerals, Phytochemical Compounds and Antioxidant Activity of Mexican, Central American, and African Green Leafy Vegetables

The green leafy vegetables Cnidoscolus aconitifolius and Crotalaria longirostrata are native to Mexico and Central America, while Solanum scabrum and Gynandropsis gynandra are native to Africa. They are consumed in both rural and urban areas in those places as a main food, food ingredient or traditional medicine. Currently, there is limited information about their nutritional and phytochemical composition. Therefore, mineral, vitamin C, phenolic and flavonoid concentration, and antioxidant activity were evaluated in multiple accessions of these leafy vegetables, and their mineral and vitamin C contribution per serving was calculated. The concentrations of Ca, K, Mg and P in these leafy vegetables were 0.82-2.32, 1.61-7.29, 0.61-1.48 and 0.27-1.44 mg/g fresh weight (FW), respectively. The flavonoid concentration in S. scabrum accessions was up to 1413 μg catechin equivalents/g FW, while the highest antioxidant activities were obtained in C. longirostrata accessions (52-60 μmol Trolox equivalents/g FW). According to guidelines established by the US Food and Drug Administration, a serving size (30 g FW) of C. longirostrata would be considered an excellent source of Mo (20 % or more of the daily value), and a serving of any of these green leafy vegetables would be an excellent source of vitamin C. Considering the importance of the minerals, phytochemicals and antioxidants in human health and their presence in these indigenous green leafy vegetables, efforts to promote their consumption should be implemented.

Grapevine-shoot stilbene extract as a preservative in red wine

This paper reports the use of a grapevine-shoot stilbene extract (Vineatrol®) as a preservative in red wine. Its effectiveness to preserve red wine quality under two different winemaking systems (traditional and Ganimede) was studied at bottling and after twelve months of storage in bottle. Enological parameters, color related parameters, volatile composition, sensory analysis and olfactometric profile were evaluated. At bottling wines treated with Vineatrol showed higher color related parameters and higher score in sensory analysis than those treated with SO2. The use of SO2 increased ester and alcohol volatile compounds in relation to the use of Vineatrol. Wine olfactometric profile was modified by Vineatrol addition. Two new odorant zones with high modified frequency appeared in wines treated with Vineatrol. After 12months of storage in bottle, wines treated with Vineatrol showed parameters related to oxidation. The weak point of the process seemed to be the evolution during the storage in bottle.

Accumulation pattern of endogenous cytokinins and phenolics in different organs of 1-year-old cytokinin pre-incubated plants: implications for conservation

A better understanding of phytohormone physiology can provide an essential basis to coherently achieve a conservation drive/strategy for valuable plant species. We evaluated the distribution pattern of cytokinins (CKs) and phenolic compounds in different organs of 1-year-old greenhouse-grown Tulbaghia simmleri pre-treated (during micropropagation) with three aromatic CKs (benzyladenine = BA, meta-topolin = mT, meta-topolin riboside = mTR). The test species is highly valuable due to its medicinal and ornamental uses. Based on UHPLC-MS/MS quantification, mT and mTR pre-treated plants had the highest total CK, mostly resulting from the isoprenoid CK-type, which occurred at highest concentrations in the roots. Although occurring in much lower concentrations when compared to isoprenoid CKs, aromatic CKs were several-fold more abundant in the root of mT pre-treated plants than with other treatments. Possibly related to the enhanced aromatic CKs, free bases and ribonucleotides, plants pre-treated with mT generally displayed better morphology than the other treatments. A total of 12 bioactive phenolic compounds, including four hydroxybenzoic acids, five hydroxycinnamic acids and three flavonoids at varying concentrations, were quantified in T. simmleri. The occurrence, distribution and levels of these phenolic compounds were strongly influenced by the CK pre-treatments, thereby confirming the importance of CKs in phenolic biosynthesis pathways.

Metabolic and Microbial Modulation of the Large Intestine Ecosystem by Non-Absorbed Diet Phenolic Compounds: A Review

Phenolic compounds represent a diverse group of phytochemicals whose intake is associated with a wide spectrum of health benefits. As consequence of their low bioavailability, most of them reach the large intestine where, mediated by the action of local microbiota, a series of related microbial metabolites are accumulated. In the present review, gut microbial transformations of non-absorbed phenolic compounds are summarized. Several studies have reached a general consensus that unbalanced diets are associated with undesirable changes in gut metabolism that could be detrimental to intestinal health. In terms of explaining the possible effects of non-absorbed phenolic compounds, we have also gathered information regarded their influence on the local metabolism. For this purpose, a number of issues are discussed. Firstly, we consider the possible implications of phenolic compounds in the metabolism of colonic products, such as short chain fatty acids (SCFA), sterols (cholesterol and bile acids), and microbial products of non-absorbed proteins. Due to their being recognized as affective antioxidant and anti-inflammatory agents, the ability of phenolic compounds to counteract or suppress pro-oxidant and/or pro-inflammatory responses, triggered by bowel diseases, is also presented. The modulation of gut microbiota through dietetic maneuvers including phenolic compounds is also commented on. Although the available data seems to assume positive effects in terms of gut health protection, it is still insufficient for solid conclusions to be extracted, basically due to the lack of human trials to confirm the results obtained by the in vitro and animal studies. We consider that more emphasis should be focused on the study of phenolic compounds, particularly in their microbial metabolites, and their power to influence different aspects of gut health.

Genetic Diversity of Individual Phenolic Acids in Barley and Their Correlation with Barley Malt Quality

Phenolic acids have been quite extensively studied in food science research because of their antioxidative effect. In this study, the genotypic difference and genetic control of phenolic acids, and their correlation with malt quality, were investigated in barley. Ferulic acid (FA) and p-coumaric acid (p-CA) were identified as two main phenolic acids, showing wide variations among 68 barley genotypes. The mean content of FA and p-CA were 2.15 μg g(-1) and 1.10 μg g(-1) in grains and 4.07 μg g(-1) and 1.44 μg g(-1) in malt, respectively. After malting, FA and p-CA were increased significantly in 55 and 37 genotypes and were reduced in 2 and 14 genotypes, respectively. Both malt FA and p-CA were positively correlated with soluble N content and Kolbach index and negatively correlated with malt extract and viscosity. The results indicated that the effect of malting on the change of an individual phenolic acid is genotype independent. Association mapping identified that 8 markers on Chromosomes 1H, 2H, 4H, and 7H are associated with grain p-CA and 4 markers on Chromosomes 3H and 7H are linked with grain FA. However, only a single marker on Chromosome 3H was found to be associated with malt FA. Moreover, a lack of overlapping markers between grain and malt indicated the genetic diversity of phenolic acids in barley grain and malt. Our results strengthen the understanding of phenolic acids in barley and their responses to the malting process.

Polishing and parboiling effect on the nutritional and technological properties of pigmented rice

This study aims to evaluate the effects of polishing and parboiling on proximate composition, structure, phenolic compounds, antioxidant activity, cooking time and hardness of IAC-600 black rice cultivar and MPB-10 red rice lineage. Proximate analysis and light micrographs revealed higher migration of red rice proteins than black rice proteins to the endosperm as a result of parboiling. Parboiling reduced the ash content of red rice while no difference was determined in black rice. Gelatinized starch granules from both genotypes showed similar appearance. There was a decrease in relative crystallinity on both black and red rice subjected to parboiling, which was an indicative of crystallites disruption. Polishing removed more than 90% of free phenolics for both genotypes, while parboiling allowed the partial preservation of free phenolics content in polished rice. Parboiling induced an increase in the cooking time of red rice, but a decrease in the cooking time of black rice.

Effects of food processing on polyphenol contents: a systematic analysis using Phenol-Explorer data

SCOPE

The Phenol-Explorer web database (http://www.phenol-explorer.eu) was recently updated with new data on polyphenol retention due to food processing. Here, we analyze these data to investigate the effect of different variables on polyphenol content and make recommendations aimed at refining estimation of intake in epidemiological studies.

METHODS AND RESULTS

Data on the effects of processing upon 161 polyphenols compiled for the Phenol-Explorer database were analyzed to investigate the effects of polyphenol structure, food, and process upon polyphenol loss. These were expressed as retention factors (RFs), fold changes in polyphenol content due to processing. Domestic cooking of common plant foods caused considerable losses (median RF = 0.45-0.70), although variability was high. Food storage caused fewer losses, regardless of food or polyphenol (median RF = 0.88, 0.95, 0.92 for ambient, refrigerated, and frozen storage, respectively). The food under study was often a more important determinant of retention than the process applied.

CONCLUSION

Phenol-Explorer data enable polyphenol losses due to processing from many different foods to be rapidly compared. Where experimentally determined polyphenol contents of a processed food are not available, only published RFs matching at least the food and polyphenol of interest should be used when building food composition tables for epidemiological studies.

Improved release and metabolism of flavonoids by steered fermentation processes: a review

This paper provides an overview on steered fermentation processes to release phenolic compounds from plant-based matrices, as well as on their potential application to convert phenolic compounds into unique metabolites. The ability of fermentation to improve the yield and to change the profile of phenolic compounds is mainly due to the release of bound phenolic compounds, as a consequence of the degradation of the cell wall structure by microbial enzymes produced during fermentation. Moreover, the microbial metabolism of phenolic compounds results in a large array of new metabolites through different bioconversion pathways such as glycosylation, deglycosylation, ring cleavage, methylation, glucuronidation and sulfate conjugation, depending on the microbial strains and substrates used. A whole range of metabolites is produced, however metabolic pathways related to the formation and bioactivities, and often quantification of the metabolites are highly underinvestigated. This strategy could have potential to produce extracts with a high-added value from plant-based matrices.

Determination of bioactive components in Chinese herbal formulae and pharmacokinetics of rhein in rats by UPLC-MS/MS

Rhein (4,5-dihydroxy-9,10-dioxoanthracene-2-carboxylic acid, cassic acid) is a pharmacological active component found in Rheum palmatum L. the major herb of San-Huang-Xie-Xin-Tang (SHXXT), a medicinal herbal product used as a remedy for constipation. Here we have determined multiple bioactive components in SHXXT and investigated the comparative pharmacokinetics of rhein in rats. A sensitive and specific method combining liquid chromatography with electrospray ionization tandem mass spectrometry has been developed and validated to simultaneously quantify six active compounds in the pharmaceutical herbal product SHXXT to further study their pharmacokinetics in rats. Multiple reaction monitoring (MRM) was employed for quantification with switching electrospray ion source polarity between positive and negative modes in a single run. There were no significant matrix effects in the quantitative analysis and the mean recovery for rhein in rat plasma was 91.6%±3.4%. The pharmacokinetic data of rhein demonstrate that the herbal formulae or the single herbal extract provide significantly higher absorption rate than the pure compound. This phenomenon suggests that the other herbal ingredients of SHXXT and rhubarb extract significantly enhance the absorption of rhein in rats. In conclusion, the herbal formulae (SHXXT) are more efficient than the single herb (rhubarb) or the pure compound (rhein) in rhein absorption.

Microwave-assisted extraction of herbacetin diglucoside from flax (Linum usitatissimum L.) seed cakes and its quantification using an RP-HPLC-UV system

Flax (Linum usitatissimum L.) seeds are widely used for oil extraction and the cold-pressed flaxseed (or linseed) cakes obtained during this process constitute a valuable by-product. The flavonol herbacetin diglucoside (HDG) has been previously reported as a constituent of the flaxseed lignan macromolecule linked through ester bonds to the linker molecule hydroxymethylglutaric acid. In this context, the development and validation of a new approach using microwave-assisted extraction (MAE) of HDG from flaxseed cakes followed by quantification with a reverse-phase HPLC system with UV detection was purposed. The experimental parameters affecting the HDG extraction yield, such as microwave power, extraction time and sodium hydroxide concentration, from the lignan macromolecule were optimized. A maximum HDG concentration of 5.76 mg/g DW in flaxseed cakes was measured following an irradiation time of 6 min, for a microwave power of 150 W using a direct extraction in 0.1 M NaOH in 70% (v/v) aqueous methanol. The optimized method was proven to be rapid and reliable in terms of precision, repeatability, stability and accuracy for the extraction of HDG. Comparison with a conventional extraction method demonstrated that MAE is more effective and less time-consuming.