Impact of thermal processing on the activity of gallotannins and condensed tannins from Hamamelis virginiana used as functional ingredients in seafood

Effectiveness of plant-based hand sanitizer incorporating Quercus infectoria gall extract

AIMS

Quercus infectoria (Qi), a traditional herbal plant with a broad spectrum of activities on multidrug-resistant bacteria, has been developed for hand sanitizer applications.

METHODS AND RESULTS

Antimicrobial activity was evaluated using agar-well diffusion and broth microdilution method. Bactericidal activity was determined following the European Standard 1276 antibacterial suspension test. Neutralization assay was performed to assess antirespiratory syncytial virus. Safety, stability, and skin permeation of Qi hand gel was investigated. Qi hand sanitizer gel inhibited microorganisms ranging from 99.9% to 99.999% against Enterococcus faecalis, Staphylococcus aureus, methicillin-resistant Staph. aureus, Staph. epidermidis, Staph. pseudintermedius, Staph. saprophyticus, Streptococcus pyogenes, Acinetobacter baumannii, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Candida albicans. A significant reduction in main human dermatophytes including Microsporum canis, M. gypseum, and Talaromyces marneffei of ∼50% was observed (P < .05). Qi hand sanitizer gel inactivated >99% viral particles entering human laryngeal epidermoid carcinoma cells in a dose-dependent manner. Scanning electron micrographs further illustrated that Qi hand sanitizer gel disrupted microbial cell membrane after 1-min contact time resulting in cell death. Qi hand sanitizer gel delivered emollient compounds through simulated human skin layers and showed no cytotoxicity on fibroblast cells. Moreover, Qi hand sanitizer gel demonstrated stability under extreme conditions.

CONCLUSIONS

Qi hand sanitizer gel was able to inhibit various microorganisms including bacteria, dermatophytes, and virus.

Bioactive Compounds, Antioxidant Activity and Sensory Properties of Northern Red Oak (Quercus rubra L., syn. Q. borealis F. Michx) Seeds Affected by Roasting Conditions

The nutritional value and health-promoting properties cause the fruits (acorns) of Quercus spp. to have great potential for use in the food industry as functional ingredients and antioxidants source. The aim of this study was to examine the bioactive compound's composition, antioxidant potential, physicochemical properties and taste characteristics of northern red oak (Quercus rubra L.) seeds subjected to roasting at different temperatures and times. The results indicate that the roasting markedly affects the composition of bioactive components of acorns. In general, the use of roasting temperatures greater than 135 °C causes a decrease in the total phenolic compound content of Q. rubra seeds. Furthermore, along with an increase in temperature and thermal processing time, a remarkable increase in melanoidins, which are the final products of the Maillard reaction, was also observed in processed Q. rubra seeds. Both unroasted and roasted acorn seeds had high DPPH radical scavenging capacity, ferric reducing antioxidant power (FRAP) and ferrous ion chelating activity. Roasting at 135 °C caused negligible changes in total phenolics content and antioxidant activity of Q. rubra seeds. Almost all samples had lower antioxidant capacity along with an increase in the roasting temperatures. Additionally, thermal processing of acorn seeds contributes to the development of the brown color and the reduction of bitterness, and the creation of a more pleasant taste of the final products. Overall, the results of this study show that both unroasted and roasted Q. rubra seeds may be an interesting source of bioactive compounds with high antioxidant activity. Therefore, they can be used as a functional ingredient of beverages or food.

Necrosis of Microcystis aeruginosa causing tannin derivatives in Rhus chinensis stem

BACKGROUND

Algal infestation in Korean lakes, rivers, and in agroecosystems is a catastrophic problem resulting in contaminated drinking and agricultural irrigation water. Developing allelochemical-based algicides has previously faced difficulties, including dosage requirements and chemical instability. Despite these challenges, these algicides have enormous potential for eco-friendly use. This study presents the efficient use of tannin derivatives as antialgal chemicals modeled on a tannin-rich stem extract of Rhus chinensis in a thermal processing application.

RESULTS

Tannic acids are the key component of algal necrosis in R. chinensis stem extract, and although heat extraction from the stem increased the crude extraction yield 1.8-fold, the procedure induced the conversion of tannic acids to gallic acid, resulting in lower antialgal activity. Gallotannin showed stronger antialgal activity (The 50% lethal dosage (LD₅₀ )= 44.6 mg L^-1 ) than gallic acid (LD₅₀  = 99.2 mg L^-1 ), and the nonheated extract exhibited 3.7-fold lower LD₅₀ (0.66 g L^-1 ) than the heated extract (LD₅₀  = 2.45 g L^-1 ), resulting in 2.6-fold higher content of gallotannin.

CONCLUSION

These results demonstrate that heat treatment of R. chinensis stems during the extraction process is not beneficial to algal control because of the acceleration of thermal tannin degradation, despite it showing higher crude extract yields. Therefore, it is suggested extraction processes minimizing the loss of tannic acids should be the preferred methods used to develop tannin-based natural algicides for controlling algal infestation. Tannic acids showed higher toxicity into necrosis of M. aeruginosa than gallic acid where heat-processed extraction of R. chinensis stems produces more gallic acid content resulting in thermal degradation of tannic complexes than the extraction of nonthermal treatment. © 2022 Society of Chemical Industry.

Recognition of Gallotannins and the Physiological Activities: From Chemical View

Gallotannins, characterized with the glycosidic core and galloyl unit, are seemed as vital components of hydrolyzable tannins. Benefit from the more and more discoveries of their bioactivities and edibility, application of gallotannins in food industry, pharmacy industry, and other fields is increasing. Inheriting previous study achievements, chemical structure of gallotannins was illustrated and degradation as well as synthetic routes to gallotannins were summarized. On this basis, distribution in the nature also including the distinction of gallotannins was discussed. More than that, activities involving in antioxidant, anti-inflammatory, enzyme inhibitions, protein binding, and so on, as well as applications in the field of food industry, biopharmaceutical science, agricultural production, etc., were combed. Finally, improvement of bioavailability, chemical modification of the structure, and accurate determination of new gallotannins were pointed out to be the orientation in the future.

The Different Contributors to Antioxidant Activity in Thermally Dried Flesh and Peel of Astringent Persimmon Fruit

In the thermal-drying processing of astringent persimmon fruit, the tissue-specific changes in the key antioxidants have hardly been investigated, while they have been well investigated in the flesh. We report here the different patterns of the antioxidant activities in the thermally processed flesh and peel of astringent persimmon, with analyses of the carotenoids, the condensed and hydrolysable tannins, and the total phenolics and flavonoids. The persimmon powders presented different colors on the basis of the drying temperatures: brown in 30 °C; light yellow in 60 °C; and dark brown in 90 °C, respectively. Non-maillard reaction and reduction of carotenoids caused the light-yellow color of 60 °C dried persimmon. Thermal drying reduced the antioxidant activities of the flesh in a temperature-dependent manner, with decreases in the carotenoids, the condensed and hydrolysable tannins, and the total phenolics and flavonoids, whereas it enhanced the antioxidant activities of the peel. The increase in the antioxidant activities in the peel were mainly the result of the increase in the total phenolics by the thermal effect, and especially in the content of the hydrolysable tannins, although the thermal processing decreased the other components. The heat-induced increase of antioxidant activity in the peel showed a strong significant correlation only with the contents of total phenolics (r² = 0.9493) and total hydrolysable tannins (r² = 0.9288), suggesting that the main antioxidant contributors differ from the flesh.

Human Metabolites of Hamaforton™ (Hamamelis virginiana L. Extract) Modulates Fibroblast Extracellular Matrix Components in Response to UV-A Irradiation

Hamamelis virginiana L. a rich source of both condensed and hydrolyzable tannins, utilized to treat dermatological disorders. Since no experimental and clinical data is available for its use as oral formulation in skin related disorders, the purpose of this study was to investigate the effects of Hamaforton™ (Hamamelis virginiana extract) metabolites on gene dysregulation induced by ultraviolet A radiation in cultured human dermal fibroblasts. A combination of in vivo and ex vivo experimental designs has been exploited in order to take into account the polyphenol metabolic transformation that occurs in humans. 12 healthy volunteers received either a capsule of Hamaforton™ or a placebo in a randomized, blinded crossover trial. After Hamaforton™ ingestion, the kinetic of appearance of galloyl derivatives was measured in plasma. Then, in the ex vivo experiment, the serum isolated after supplementation was used as a source of Hamaforton™ metabolites to enrich the culture medium of dermal fibroblasts exposed to ultraviolet A radiation. Three different gallic acid metabolites (4-O-methyl gallic acid, 4-O-methyl gallic acid sulphate and trimethyl gallic acid glucuronide) were identified in volunteer plasma. While, ultraviolet A irradiation of dermal fibroblasts affected the expression of extracellular matrix genes, the presence of Hamaforton™ metabolites in the culture media did not affect the expression of most of those genes. However, the activation of the expression of 10 different genes involved in repair processes for the maintenance of skin integrity, suggest that the metabolites can play a role in damage recovery. To our knowledge, this is the first study that demonstrates the bioavailability of Hamaforton™ phenolic compounds, and the effects of its metabolites on cultured dermal fibroblast response to ultraviolet A irradiation.

The Protective Effect of Hamamelis virginiana Stem and Leaf Extract on Fine Dust-Induced Damage on Human Keratinocytes

Witch hazel extracts have been used for decades as cosmetic ingredients in skin care products. Our present study aims to evaluate its potential in anti-pollution products using a previously reported in vitro model. Calcium is a universal second messenger, and we used human respiratory and skin cells to detect changes in intracellular Ca2+ concentrations upon particulate matter contact. Both an increase in pro-inflammatory markers and a decrease in tight junction proteins were confirmed, as previously reported. Witch hazel stem and leaf extract showed significant attenuation of Ca2+ response upon the challenge; it displayed systematic regulations of the signal generator, PAR-2; a pro-inflammatory marker, NF-κB; and a tight junction protein, Occludin. We identified hexagalloylglucose from the extract and concluded that it is a major component regulating protection from particulate matter. Based on these results, witch hazel extract containing hexagalloylglucose is an active ingredient in anti-pollution skin care products.

Preventive Applications of Polyphenols in Dentistry-A Review

Polyphenols are natural substances that have been shown to provide various health benefits. Antioxidant, anti-inflammatory, and anti-carcinogenic effects have been described. At the same time, they inhibit the actions of bacteria, viruses, and fungi. Thus, studies have also examined their effects within the oral cavity. This review provides an overview on the different polyphenols, and their structure and interactions with the tooth surface and the pellicle. In particular, the effects of various tea polyphenols on bioadhesion and erosion have been reviewed. The current research confirms that polyphenols can reduce the growth of cariogenic bacteria. Furthermore, they can decrease the adherence of bacteria to the tooth surface and improve the erosion-protective properties of the acquired enamel pellicle. Tea polyphenols, especially, have the potential to contribute to an oral health-related diet. However, in vitro studies have mainly been conducted. In situ studies and clinical studies need to be extended and supplemented in order to significantly contribute to additive prevention measures in caries prophylaxis.

Chemical, Microbiological and Sensory Stability of Steam Extracted Jaboticaba (Myrciaria jaboticaba) Juice

Jaboticaba (Myrciaria jaboticaba) is a Brazilian berry rich in phenolic compounds, much appreciated for its sweet and slightly acid taste, and highly perishable. Thus, we aimed at producing jaboticaba juice by steam extraction and at investigating its microbiological, sensorial and chemical qualities during storage for up to 168 days. Juice was microbiologically safe and even though unsweetened juice was well accepted, sucrose addition further improved flavor (21%), overall impression (11%) and purchase intent (21%) scores. Cyanidin-3-O-glucoside (C3G) was the major phenolic (40%), followed by gallic (28%) and ellagic acids (21%). Total phenolics contents decreased from 27% (50 °C) to 50% (25 °C), mainly driven by C3G degradation. At 60 °C, total phenolics contents did not change after 42 days since C3G degradation was counterbalanced by gallic acid formation (129%), which followed zero-order reaction kinetics. Anthocyanins degradation followed first-order reaction kinetics (C3G half-life at 25 °C = 21.7 days) and was associated with color changes during storage. In conclusion, steam extraction followed by hot-filling technique ensured a juice with at least six months of shelf life.

The application of polyphenols in food preservation

Polyphenols are a kind of complex secondary metabolites in nature, widely exist in the flowers, bark, roots, stems, leaves, and fruits of plants. Numerous studies have shown that plant-derived polyphenols have a variety of bioactivities due to their unique chemical structure, such as antioxidant, antimicrobial, and prevention of chronic diseases, cardiovascular disease, cancer, osteoporosis, and neurodegeneration. With the gradual rise of natural product development, plant polyphenols have gradually become one of the research hotspots in the field of food science due to their wide distribution in the plants, and the diversity of physiological functions. Owing to the extraordinary antioxidant and antibacterial activity of polyphenols, plant-derived polyphenols offer an alternative to chemical additives used in the food industry, such as oil, seafood, meat, beverages, and food package materials. Based on this, this chapter provides an overview of the potential antioxidant and antibacterial mechanisms of plant polyphenols and their application in food preservation, it would be providing a reference for the future development of polyphenols in the food industry.

Antimicrobial Capacity of Plant Polyphenols against Gram-positive Bacteria: A Comprehensive Review

BACKGROUND

Multi-drug-resistant bacteria such as Methicillin-Resistant Staphylococcus aureus (MRSA) disseminate rapidly amongst patients in healthcare facilities and suppose an increasingly important cause of community-associated infections and associated mortality. The development of effective therapeutic options against resistant bacteria is a public health priority. Plant polyphenols are structurally diverse compounds that have been used for centuries for medicinal purposes, including infections treatment and possess, not only antimicrobial activity, but also antioxidant, anti-inflammatory and anticancer activities among others. Based on the existing evidence on the polyphenols' antibacterial capacity, polyphenols may be postulated as an alternative or complementary therapy for infectious diseases.

OBJECTIVE

To review the antimicrobial activity of plant polyphenols against Gram-positive bacteria, especially against S. aureus and its resistant strains. Determine the main bacterial molecular targets of polyphenols and their potential mechanism of action.

METHODOLOGY

The most relevant reports on plant polyphenols' antibacterial activity and their putative molecular targets were studied. We also performed virtual screening of thousand different polyphenols against proteins involved in the peptidoglycan biosynthesis to find potential valuable bioactive compounds. The bibliographic information used in this review was obtained from MEDLINE via PubMed.

RESULTS

Several polyphenols: phenolic acids, flavonoids (especially flavonols), tannins, lignans, stilbenes and combinations of these in botanical mixtures, have exhibited significant antibacterial activity against resistant and non-resistant Gram-positive bacteria at low μg/mL range MIC values. Their mechanism of action is quite diverse, targeting cell wall, lipid membrane, membrane receptors and ion channels, bacteria metabolites and biofilm formation. Synergic effects were also demonstrated for some combinations of polyphenols and antibiotics.

CONCLUSION

Plant polyphenols mean a promising source of antibacterial agents, either alone or in combination with existing antibiotics, for the development of new antibiotic therapies.

Effect of fragaria vesca, hamamelis and tormentil on the initial bacterial colonization in situ

OBJECTIVE

The presentin situ study aims to examine the influence of the polyphenolic tea drugs fragaria vesca, hamamelis and tormentil on the initial oral bioadhesion.

DESIGN

Initial biofilm formation was performed on bovine enamel slabs which were carried intraorally by 12 subjects. After 1 min of intraoral pellicle formation, the subjects rinsed with fragaria vesca, tormentil (0.8 mg/8 mL) and hamamelis (0.2 mg/8 mL) for 10 min. Tap water served as negative control, 0.2 % CHX as positive control. The investigations took place on different days (wash-out: 2 days). Afterwards, fluorescence microscopy has been performed per test solution (n = 5) and per subject (n = 12) to visualize bacterial adhesion and glucan formation (8 h oral exposition) with DAPI, ConA and BacLight. Additionally, TEM was used to visualize the pellicle ultrastructure and expectorate samples. Statistical evaluation was carried out using the Kruskal-Wallis- (p < 0.5), Mann-Whitney U test (p < 0.5) and Bonferroni-Holm-correction (p < 0.1).

RESULTS

Rinsing with the polyphenolic tea extracts reduced significantly initial bacterial colonization (DAPI) compared to the negative control. There was no significant difference betweenfragaria vesca, hamamelis and tormentil. All solutions showed a reducing effect on the glucan formation. No significant difference was observed between fragaria vesca and CHX. Considerable alterations of the pellicle's ultrastructure manifested by an increase in thickness and electron density resulted from rinsing with the three polyphenolic aqueous extracts.

CONCLUSIONS

Fragaria vesca, hamamelis and tormentil significantly reduce initial bioadhesion and glucan formation in situ and are therefore recommended as adjuvant antibacterial oral therapeutics.

Methodology optimization for the analysis of phenolic compounds in chestnut (Castanea sativa Mill.)

Phenols are bioactive substances of great interest because of their involvement in plant physiology, their use in many industrial processes, and their impact on human health. This work aims to summarize the varied approaches to the phenolic analysis of chestnut (bark and wood of trunk and branches, leaves, catkins, burs, and fruit) and to collate the optimal conditions into an easy to follow and execute protocol. Phenolic compounds were extracted by solid-liquid extraction and separated by liquid-liquid extraction. Total phenols content was determined by Folin-Ciocalteu assay, condensed tannins by vanillin assay, and hydrolyzable tannins (gallotannins and ellagitannins) by high-performance liquid chromatography quantification of methyl gallate and ellagic acid following acid methanolysis. The lowest temperature for conservation (-80 ℃), lyophilization, and milling (liquid N₂) were the most effective pretreatments for samples. For quantification of tannins, the use of water clearly reduced the sensitivity of the analysis of condensed tannins, whilst the more efficient degradation capacity of sulfuric acid improved the methanolysis of hydrolyzable tannins. These findings were validated using a range of chestnut tissues, and thus confirm the utility and effectiveness of this easy to implement, cost-effective, and efficient protocol.

Roasting carob flour decreases the capacity to bind glycoconjugates of bile acids

Carob is the fruit obtained from Ceratonia siliqua L. and it is a source of bioactive compounds that have been linked to several health promoting effects, including lowering blood cholesterol concentration.

Evaluation of microfiltration and heat treatment on the microbiological characteristics, phenolic composition and volatile compound profile of pomegranate (Punica granatum L.) juice

BACKGROUND

Since processing technology and storage may influence the sensory and nutritional value as well as the shelf life of pomegranate juice (PJ), mild technologies based on microfiltration may be a promising alternative to heat treatments for fruit juice preservation. In this study, physicochemical and microbiological properties of raw (RPJ), microfiltered (MPJ) and cloudy pasteurized (PPJ) PJ were compared over a period of 4 weeks.

RESULTS

Data demonstrated that microfiltration was comparable to pasteurization in guaranteeing microbiological stability of the juice, avoiding spoilage of the final product. After treatment, PPJ showed the highest amounts of gallic acid (GA) and ellagic acid derivatives (EAs). During storage, the amount of ellagitannins, EAs and GA similarly decreased in all types of juice. Trends towards variations of monomeric anthocyanins in MPJ and variations of polymeric and copigmented anthocyanins in both MPJ and PPJ were found over storage.

CONCLUSION

The optimization of pretreatments and filtration parameters can lead to the industrial scale-up of microfiltration technology for the development of high-quality non-heat-treated PJ. © 2017 Society of Chemical Industry.

Impact of different post-harvest processing methods on the chemical compositions of peony root

The impact of key processing steps such as boiling, peeling, drying and storing on chemical compositions and morphologic features of the produced peony root was investigated in detail by applying 15 processing methods to fresh roots of Paeonia lactiflora and then monitoring contents of eight main components, as well as internal root color. The results showed that low temperature (4 °C) storage of fresh roots for approximately 1 month after harvest resulted in slightly increased and stable content of paeoniflorin, which might be due to suppression of enzymatic degradation. This storage also prevented roots from discoloring, facilitating production of favorable bright color roots. Boiling process triggered decomposition of polygalloylglucoses, thereby leading to a significant increase in contents of pentagalloylglucose and gallic acid. Peeling process resulted in a decrease of albiflorin and catechin contents. As a result, an optimized and practicable processing method ensuring high contents of the main active components in the produced root was developed.

The Influence of Different Air-Drying Conditions on Bioactive Compounds and Antioxidant Activity of Berries

The aim of the present research was to study the effect of convective drying on color, bioactive compounds, and antioxidant activity of berry fruits and to chemically characterize the polyphenolic composition of raspberry, boysenberry, redcurrants, and blackcurrants fruit. Drying berries at 65 °C provoked the best conservations of color, particularly for boysenberry and blackcurrant. Drying at 65 °C was also the condition that showed higher level of polyphenols, while drying at 50 or 130 °C showed above % degradation of them due to the long time or high temperature drying. Radical scavenging activity was the predominant antioxidant mechanism in all samples, with 65 °C dried berries being the most active ones possibly because of polyphenol depolymerization. The anthocyanin profile showed that delphinidin and cyanidin derivatives were the most abundant anthocyanidins with different predominance between berry genera. Degradation of anthocyanins was increased with drying temperature been Cy 3-glucoside and Cy 3-rutinoside the most abundant.

Subcritical water extraction of phenolic and antioxidant constituents from pistachio (Pistacia vera L.) hulls

Pistachio hulls, important by-products of pistachio processing, were extracted using an environmentally friendly process with subcritical water (SCW) at a pressure of 6.9 MPa in the range of 110 and 190 °C, and a flow rate of 4 ml/min. Detailed HPLC-DAD-ESI/MSⁿ analyses allowed the identification of 49 phenolic compounds in the SCW extracts. Total gallotannin yields up to 33 g/kg were reached at 150-170 °C, where gallic acid (22.2 g/kg) and penta-O-galloyl-β-d-glucose (9.77 g/kg) levels were 13.2- and 10.6-fold higher than those in the aqueous methanol extracts. Flavonols were also effectively extracted at 110-150 °C (4.37-5.65 g/kg), while anacardic acid recovery was poor (1.13-2.77 g/kg). Accordingly, high amounts of anacardic acids (up to 50.7 g/kg) were retained in the extraction residue, revealing that SCW extraction allowed selective extraction of gallotannins and flavonols. Antioxidant capacities ranged from 0.68 to 1.20 mmol Trolox equivalents (TE)/g for SCW extracts increasing with temperature up 190 °C.

Tannins from Hamamelis virginiana bark extract: characterization and improvement of the antiviral efficacy against influenza A virus and human papillomavirus

Antiviral activity has been demonstrated for different tannin-rich plant extracts. Since tannins of different classes and molecular weights are often found together in plant extracts and may differ in their antiviral activity, we have compared the effect against influenza A virus (IAV) of Hamamelis virginiana L. bark extract, fractions enriched in tannins of different molecular weights and individual tannins of defined structures, including pseudotannins. We demonstrate antiviral activity of the bark extract against different IAV strains, including the recently emerged H7N9, and show for the first time that a tannin-rich extract inhibits human papillomavirus (HPV) type 16 infection. As the best performing antiviral candidate, we identified a highly potent fraction against both IAV and HPV, enriched in high molecular weight condensed tannins by ultrafiltration, a simple, reproducible and easily upscalable method. This ultrafiltration concentrate and the bark extract inhibited early and, to a minor extent, later steps in the IAV life cycle and tannin-dependently inhibited HPV attachment. We observed interesting mechanistic differences between tannin structures: High molecular weight tannin containing extracts and tannic acid (1702 g/mol) inhibited both IAV receptor binding and neuraminidase activity. In contrast, low molecular weight compounds (<500 g/mol) such as gallic acid, epigallocatechin gallate or hamamelitannin inhibited neuraminidase but not hemagglutination. Average molecular weight of the compounds seemed to positively correlate with receptor binding (but not neuraminidase) inhibition. In general, neuraminidase inhibition seemed to contribute little to the antiviral activity. Importantly, antiviral use of the ultrafiltration fraction enriched in high molecular weight condensed tannins and, to a lesser extent, the unfractionated bark extract was preferable over individual isolated compounds. These results are of interest for developing and improving plant-based antivirals.

Alterations in the intestinal assimilation of oxidized PUFAs are ameliorated by a polyphenol-rich grape seed extract in an in vitro model and Caco-2 cells

The (n-3) PUFAs 20:5 (n-3) (EPA) and 22:6 (n-3) (DHA) are thought to benefit human health. The presence of prooxidant compounds in foods, however, renders them susceptible to oxidation during both storage and digestion. The development of oxidation products during digestion and the potential effects on intestinal PUFA uptake are incompletely understood. In the present studies, we examined: (1) the development and bioaccessibility of lipid oxidation products in the gastrointestinal lumen during active digestion of fatty fish using the in vitro digestive tract TNO Intestinal Model-1 (TIM-1); (2) the mucosal cell uptake and metabolism of oxidized compared with unoxidized PUFAs using Caco-2 intestinal cells; and 3) the potential to limit the development of oxidation products in the intestine by incorporating antioxidant polyphenols in food. We found that during digestion, the development of oxidation products occurs in the stomach compartment, and increased amounts of oxidation products became bioaccessible in the jejunal and ileal compartments. Inclusion of a polyphenol-rich grape seed extract (GSE) during the digestion decreased the amounts of oxidation products in the stomach compartment and intestinal dialysates (P < 0.05). In Caco-2 intestinal cells, the uptake of oxidized (n-3) PUFAs was ~10% of the uptake of unoxidized PUFAs (P < 0.05) and addition of GSE or epigallocatechin gallate protected against the development of oxidation products, resulting in increased uptake of PUFAs (P < 0.05). These results suggest that addition of polyphenols during active digestion can limit the development of (n-3) PUFA oxidation products in the small intestine lumen and thereby promote intestinal uptake of the beneficial, unoxidized, (n-3) PUFAs.

Significance of antioxidants for seafood safety and human health

The demand for high-quality seafood products is constantly growing worldwide. Nevertheless, seafood is susceptible to rapid rancidity mainly due to lipid oxidation and microbiological spoilage. Thus, treatment with antioxidants offers a preservation technique that can prolong the shelf life of seafood. However, because of food safety and health concerns about the use of synthetic antioxidants, there is growing interest in the application of natural antioxidants, mainly plant extracts and compounds, as an alternate means of confronting the problem of lipid oxidation. In this review, up-to-date information and recent discoveries about different naturally occurring antioxidants on the oxidation progress, synthetic antioxidants and their health concerns, health benefits of antioxidants, antioxidants used for seafood, and food safety concerns are addressed. The antibacterial effects of natural antioxidants are also reviewed. Finally, the most effective methods for analyzing a wide range of antioxidants in plants are described.

Conversion of phenolic constituents in aqueous Hamamelis virginiana leaf extracts during fermentation

INTRODUCTION

Hamamelis virginiana, known for its high level of tannins and other phenolics is widely used for treatment of dermatological disorders. Although reports on hydroalcoholic and aqueous extracts from Hamamelis leaf and bark exist, knowledge on fermented leaf preparations and the underlying conversion processes are still scant.

OBJECTIVE

Aqueous Hamamelis leaf extracts were monitored during fermentation and maturation in order to obtain an insight into the bioconversion of tannins and other phenolics.

METHODOLOGY

Aliquots taken during the production period were investigated by HPLC-DAD-MS/MS as well as GC-MS after derivatisation into the corresponding trimethylsilyl compounds.

RESULTS

In Hamamelis leaf extracts, the main constituents exhibited changes during the observational period of 6 months. By successive depside bond cleavage, the gallotannins were completely transformed into gallic acid after 1 month. Although not completely, kaempferol and quercetin glycosides were also converted during 6 months to yield their corresponding aglycones. Following C-ring fission, phloroglucinol was formed from the A-ring of both flavonols. The B-ring afforded 3-hydroxybenzoic acid from quercetin and 3,4-dihydroxybenzoic acid as well as 2-(4-hydroxyphenyl)-ethanol from kaempferol. Interestingly, hydroxycinnamic acids remained almost stable in the same time range.

CONCLUSION

The present study broadens the knowledge on conversion processes in aqueous fermented extracts containing tannins, flavonol glycosides and hydroxycinnamic acids. In particular, the analogy between the microbial metabolism of phenolics from fermented Hamamelis extracts, fermented sourdough by heterofermentative lactic acid bacteria or conversion of phenolics by the human microbial flora is indicated.

Galloylated polyphenols as inhibitors of hemoglobin-catalyzed lipid oxidation in fish muscle

The influence of galloyl residues on the antioxidant mechanism of polyphenols to prevent hemoglobin-promoted lipid oxidation was investigated by using polyphenolic fractions with different degrees of galloylation: nongalloylated structures from pine bark (IVP), medium-galloylated from grape pomace (IVG), and high-galloylated from witch hazel bark (IVH). Hemoglobin (Hb) from the pelagic fish horse mackerel (Trachurus trachurus) was employed as a Hb standard. In vitro experiments showed an important increase in the deoxygenation and autoxidation of horse mackerel Hb at acidic pH values. All polyphenolic fractions significantly reduced the redox stability of Hb in buffer solutions, showing a greater deoxygenation and methemoglobin (metHb) formation in the presence of IVH, followed in decreasing order by IVG and IVP. However, galloylated polyphenols (IVH and IVG) were efficient to inhibit the oxidation of the oxygenated Hb (OxyHb) and the formation of lipid oxidation products in chilled washed fish muscle. This antioxidant activity of galloylated proanthocyanidins showed a positive relationship with the phenolic concentration. Polyphenols devoid of galloyl groups (IVP) were less active to prevent either Hb oxidation or lipid oxidation in fish muscle. The results draw attention to the potential role of galloyl residues to lessen Hb-catalyzed lipid oxidation in muscle and to maintain Hb in reduced and oxygenated states, which exhibit lower pro-oxidant activity as compared to the metHb and deoxyHb species.

Structure-activity relationships of polyphenols to prevent lipid oxidation in pelagic fish muscle

The influence of polymerization (number of monomers) and galloylation (content of esterified gallates) of oligomeric catechins (proanthocyanidins) on their effectiveness to prevent lipid oxidation in pelagic fish muscle was evaluated. Non-galloylated oligomers of catechin with diverse mean polymerization (1.9-3.4 monomeric units) were extracted from pine (Pinus pinaster) bark. Homologous fractions with galloylation ranging from 0.25 to <1 gallate group per molecule were obtained from grape (Vitis vinifera) and witch hazel (Hamamelis virginiana). The results showed the convenience of proanthocyanidins with medium size (2-3 monomeric units) and low galloylation degree (0.15-0.25 gallate group/molecule) to inhibit lipid oxidation in pelagic fish muscle. These optimal structural characteristics of proanthocyanidins were similar to those lately reported in fish oil-in-water emulsions using phosphatidylcholine as emulsifier. This finding suggests that the antioxidant behavior of polyphenols in muscle-based foods can be mimicked in emulsions prepared with phospholipids as emulsifier agents. The present data give relevant information to achieve an optimum use of polyphenols in pelagic fish muscle.

Contribution of galloylation and polymerization to the antioxidant activity of polyphenols in fish lipid systems

Polyphenolic fractions extracted from pine (Pinus pinaster) bark, grape (Vitis vinifera) pomace, and witch hazel (Hamamelis virginiana) bark were selected for investigating the influence of the number of phenolic units, polymerization, and the content of esterified galloyl residues (galloylation) on their efficacy for inhibiting lipid oxidation in fish lipid enriched foodstuffs. Experiments carried out with nongalloylated pine bark fractions with different polymerization degrees demonstrated that the number of catechin residues per molecule modulates their reducing and chelating properties in solution. In real food systems such as bulk fish oil and fish oil-in-water emulsions, the efficacy against lipid oxidation was highly dependent on the physical location of the antioxidant at the oxidative sensitive sites. The lowest polymerized fractions were the most efficient in bulk fish oil samples, whereas proanthocyanidins with an intermediate polymerization degree showed the highest activity in fish oil-in-water emulsions. Galloylation did not influence the antioxidant effectiveness of proanthocyanidins in bulk fish oils. The presence of galloyl groups favored the antioxidant activity of the polyphenols in emulsions, although results indicated that a high degree of galloylation did not improve significantly the activity found with medium galloylated proanthocyanidins. The results obtained in this research provide useful information about the relationship between structure and antioxidant activity in order to design antioxidant additives with application in fish oil-enriched functional foods.