Polyphenols constitute one of the most numerous and ubiquitous groups of plant metabolites and are an integral part of both human and animal diets. Ranging from simple phenolic molecules to highly polymerized compounds with molecular weights of greater than 30,000 Da, the occurrence of this complex group of substances in plant foods is extremely variable. Polyphenols traditionally have been considered antinutrients by animal nutritionists, because of the adverse effect of tannins, one type of polyphenol, on protein digestibility. However, recent interest in food phenolics has increased greatly, owing to their antioxidant capacity (free radical scavenging and metal chelating activities) and their possible beneficial implications in human health, such as in the treatment and prevention of cancer, cardiovascular disease, and other pathologies. Much of the literature refers to a single group of plant phenolics, the flavonoids. This review offers an overview of the nutritional effects of the main groups of polyphenolic compounds, including their metabolism, effects on nutrient bioavailability, and antioxidant activity, as well as a brief description of the chemistry of polyphenols and their occurrence in plant foods.

Polyphenols: Chemistry, Dietary Sources, Metabolism, and Nutritional Significance

Phenolic compounds in plants and agri-industrial by-products: Antioxidant activity, occurrence, and potential uses

The American Cancer Society (ACS) publishes Nutrition and Physical Activity Guidelines to serve as a foundation for its communication, policy, and community strategies and ultimately, to affect dietary and physical activity patterns among Americans. These Guidelines, published every 5 years, are developed by a national panel of experts in cancer research, prevention, epidemiology, public health, and policy, and as such, they represent the most current scientific evidence related to dietary and activity patterns and cancer risk. The ACS Guidelines include recommendations for individual choices regarding diet and physical activity patterns, but those choices occur within a community context that either facilitates or interferes with healthy behaviors. Community efforts are essential to create a social environment that promotes healthy food choices and physical activity. Therefore, this committee presents one key recommendation for community action to accompany the four recommendations for individual choices to reduce cancer risk. This recommendation for community action recognizes that a supportive social environment is indispensable if individuals at all levels of society are to have genuine opportunities to choose healthy behaviors. The ACS Guidelines are consistent with guidelines from the American Heart Association and the American Diabetes Association for the prevention of coronary heart disease and diabetes, as well as for general health promotion, as defined by the Department of Health and Human Services' 2005 Dietary Guidelines for Americans.

http://www.iacld.ir/DL/elm/ajcguidelinesonnutritionandphysicalactivityforcancerprevention.pdf

American Cancer Society Guidelines on Nutrition and Physical Activity for Cancer Prevention: Reducing the Risk of Cancer with Healthy Food Choices and Physical Activity

Cellulases and related enzymes in biotechnology

The structure, function, and biosynthesis of plant cell wall pectic polysaccharides.

Nine commercial varieties of tomato (Rambo, Senior, Ramillete, Liso, Pera, Canario, Durina, Daniella and Remate) produced in Spain were analysed for their lycopene content, content of phenolic compounds and antioxidant capacity. The phenolic compounds were characterised as flavonoids (quercetin, kaempferol and naringenin) and hydroxycinnamic acids (caffeic, chlorogenic, ferulic and p-coumaric acids). Antioxidant activity was measured using the DPPH and ABTS assays. The concentrations of lycopene and the various phenolic compounds as well as the antioxidant activity were significantly influenced by the tomato variety. Quercetin, the most abundant flavonoid, was found in concentrations ranging between 7.19 and 43.59 mg kg -1 fresh weight, while naringenin levels were lower than 12.55 mg kg -1 . The most abundant hydroxycinnamic acid was chlorogenic acid, with values ranging from 14 to 32 mg kg -1 fresh weight, followed by caffeic acid, while p-coumaric and ferulic acids showed similar concentrations lower than 5 mg kg -1 . The highest content of lycopene was found in Ramillete, Pera and Durina (>50 mg kg -1 fresh weight), while the concentration in the other varieties was between 50 and 30 mg kg -1 , with the exception of Liso (less than 20 mg kg 1 ). The antioxidant activity of tomato extracts varied with the tomato variety and the assay method used. Individual compounds found to be significantly related to antioxidant capacity were lycopene and ferulic and caffeic acids, but not quercetin and chlorogenic acid. Les tomates (Lycopersicum esculentum) sont consommees crues ou apres transformation et peuvent fournir une part significative des antioxydants totaux du regime alimentaire. Ceux-ci se trouvent principalement sous la forme de carotenes et de composes phenoliques. Parmi les carotenoides, les lycopenes predominent et sont responsables de la couleur rouge des tomates. L'objectif de cette etude est de determiner la teneur des flavonoides principaux, des acides hydroxycinnamiques et des lycopenes dans des varietes commerciales de tomates cultivees en Espagne et d'explorer la relation entre les concentrations de ces composes et l'activite antioxydante totale du fruit.

Phenolic compounds, lycopene and antioxidant activity in commercial varieties of tomato (Lycopersicum esculentum)

Isolated rumen bacteria were examined for growth and, where appropriate, for their ability to degrade cellulose in the presence of the hydroxycinnamic acids trans-p-coumaric acid and trans-ferulic acid and the hydroxybenzoic acids vanillic acid and 4-hydroxybenzoic acid. Ferulic and p-coumaric acids proved to be the most toxic of the acids examined and suppressed the growth of the cellulolytic strains Ruminococcus albus, Ruminococcus flavefaciens, and Bacteroides succinogenes when included in a simple sugars medium at concentrations of >5 mM. The extent of cellulose digestion by R. flavefaciens and B. succinogenes but not R. albus was also substantially reduced. Examination of rumen fluid from sheep maintained on dried grass containing 0.51% phenolic acids showed the presence of phloretic acid (0.1 mM) and 3-methoxyphloretic acid (trace) produced by hydrogenation of the 2-propenoic side chain of p-coumaric and ferulic acids, respectively. The parent acids were found in trace amounts only, although they represented the major phenolic acids ingested. Phloretic and 3-methoxyphloretic acids proved to be considerably less toxic than their parent acids. All of the cellulolytic strains (and Streptococcus bovis) showed at least a limited ability to hydrogenate hydroxycinnamic acids, with Ruminococcus spp. proving the most effective. No further modification of hydroxycinnamic acids was produced by the single strains of bacteria examined. However, a considerable shortfall in the recovery of added phenolic acids was noted in media inoculated with rumen fluid. It is suggested that hydrogenation may serve to protect cellulolytic strains from hydroxycinnamic acids.

Influence of plant phenolic acids on growth and cellulolytic activity of rumen bacteria.

Partial table of contents: Biotechnology in Animal Feeds and Animal Feeding: An Overview Silage Additives Transgenic Plants with Improved Protein Quality Protected Proteins and Amino Acids for Ruminants Antibacterials in Poultry and Pig Nutrition Microbial Probiotics for Pigs and Poultry Microbial Feed Additives for Pre-Ruminants Transgenic Plants with Improved Energy Characteristics Biotechnology in the Treatment of Animal Manure Feed Additives and Other Interventions for Decreasing Methane Emissions.

Biotechnology in animal feeds and animal feeding.

The action of sodium hydroxide on the rate and extent of loss of wall polysaccharides from wheat and barley straws incubated in the rumen of the sheep was studied using a nylon bag technique. Cellulose loss reached a maximum in straws treated with 10 g NaOH 100 g−1 straw. Further increase in amounts of alkali applied resulted in additional solubilisation of straw constituents, particularly xylan, but did not further enhance cellulose degradation. Rates of degradation of isolated straw, cotton and wood celluloses correlated with three of four measures of cellulose crystallinity obtained by X-ray diffraction and infrared analysis. Treatment of cellulose samples with 20 g NaOH 100 g−1 cellulose did not affect rates of loss or produce detectable changes to cellulose morphology. Loss of acetic acid esters, which accompanied alkali treatment, did not relate to improvements to digestibility. The rate of loss of cellulose from delignified neutral detergent fibre (NDF) was that shown by the isolated straw cellulose, despite the presence of acetylated hemicellulose. Deacetylation of delignified NDF with NaOH or sodium methoxide did not enhance rates of xylose or cellulose loss. In lignified wall material (NDF) the molar ratio acetyl:xylose (approximately 1:3.5) and proportion of the major phenolic acids (p-coumaric and ferulic acids) remained essentially constant throughout the course of degradation in the rumen. It is suggested that loss of phenolic acids, while not directly contributing to digestibility enhancement, may model the susceptibility of ester linkages formed between polysaccharide and polyphenolic material to alkali. The extent of solubilisation of p-coumaric acid produced by NaOH showed a linear relationship with cellulose digestibility. An upper limit of 40% acid detergent lignin and 55% of total phenolics were released by NaOH, the extent of release closely paralleling cellulose digestibility. Phenolic material resistant to alkali remained associated with wall polysaccharides and was not released from nylon bags until over 50% of cellulose (and hemicellulose) had been degraded.

Effects of sodium hydroxide on cereal straws in relation to the enhanced degradation of structural polysaccharides by rumen microorganisms

The distribution of alkali labile substituents of the neutral sugar components of hemicellulose in unfractionated cell walls of early- and late-cut perennial ryegrass, wheat and barley straw, and white clover, before and after extended incubation in the rumen, was determined by a modified methylation technique. Xylose residues were found to be extensively substituted, with 50% of residues in the Gramineae and 75% in white clover carrying substituent groups on O-2 and/or O-3. Acetyl groups could account for 50–70% of substitutions, the remainder being to unknown cell wall components. The distribution of alkali-labile substituents of xylose was the same in the original plant material as in residues recovered from the rumen, and was not affected by delignification under conditions which preserved the acetyl content of cell walls. Arabinose residues were heavily substituted at O-5, with 40–60 % of residues from the Gramineae, but only 10% of residues from the white clover, carrying substituent groups at this site. Linkages to O-5 of arabinose were preserved during digestion and accumulated in residues recovered from the rumen. In all plants examined, the extent of O-5 substitution strongly correlated with the proportion of total phenolics (r=0.844) and total phenolics minus phenolic acids (r=0.779) present. The correlation was improved when restricted to the Gramineae (r=0.879 and 0.881 respectively). Within the Gramineae, the increase in the extent of substitution to O-5 of arabinose correlated well with the increase in the proportion of total material in digested residues (r=0.899). As correlations were retained or improved when values for phenolic acids were subtracted from total phenolics, and as the proportion of phenolic acids decreased during digestion, it is suggested that linkages to O-5 of arabinose represent one form of lignin-carbohydrate bonding. The importance of such linkages to the control of polysaccharide degradation and the effect of their cleavage by alkali-treatment is discussed.

Substituent groups linked by alkali-labile bonds to arabinose and xylose residues of legume, grass and cereal straw cell walls and their fate during digestion by rumen microorganisms

Andrew Chesson

Papers

Phenolic compounds, lycopene and antioxidant activity in commercial varieties of tomato (Lycopersicum esculentum)

Influence of plant phenolic acids on growth and cellulolytic activity of rumen bacteria.

Biotechnology in animal feeds and animal feeding.

Effects of sodium hydroxide on cereal straws in relation to the enhanced degradation of structural polysaccharides by rumen microorganisms

Substituent groups linked by alkali-labile bonds to arabinose and xylose residues of legume, grass and cereal straw cell walls and their fate during digestion by rumen microorganisms