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1. The present work was undertaken to study the effects of cooking, pH and polyphenol level on carbohydrate composition and nutritional quality of sorghum (Sorghum bicolor (L.) Moench). Three different sorghum varieties; Dabar, Feterita and Argentine containing zero, intermediate to low and high levels of polyphenols respectively were used in the study. From these varieties uncooked, uncooked acidified, cooked, and cooked acidified diets were prepared. Diets were characterized with regard to resistant starch (RS), dietary fibre (DF), acid-detergent fibre (ADF) and amino acid content. Raw materials were further analysed for content and composition of non-starch polysaccharides and Klason lignin. The nutritional properties were studied in balance trials with rats. True protein digestibility (TD), biological value (BV), net protein utilization, digestible amino acids, digestible energy (DE) and digestible DF were used as criteria in the nutritional study. 2. Cooking at neutral and acid pH resulted in significantly higher assayed values for DF. Increase in DF could be accounted for by formation of RS. Approximately 50% of RS was recovered in the faeces. 3. In vitro values for protein associated with ADF and in vivo balance values using rats suggest that an endosperm protein fraction, kafirins, was made unavailable during cooking. This resulted in reduced TD and increased BV. It is assumed that unavailable kafirins serve as a nitrogen source for microflora in the hind-gut. 4. Dietary polyphenols changed the excretory route for N from urine to faeces. This resulted in lower TD and higher BV in Argentine (high in polyphenols) than in Dabar and Feterita (low in polyphenols), although dietary lysine (first limiting amino acid) was the same in the three varieties. 5. Variation in DE of the diets was attributed to DF, RS and the amount of faecal protein, which in turn were influenced by undigested kafirins and polyphenols.
The polyphenolic compounds present in raw and cooked, and dried, with and without the cooking broth of common white, black and red beans (Phaseolus vulgaris) were measured by the Folin-Denis method for total polyphenols, and by the protein precipitation method of Hagerman-Butler, which measures their biological activity. The polyphenol content was measured during 20 consecutive days on the same sample, using three different extracts of volume from each sample. Statistical analysis of the results by the Folin-Denis method indicated that variability among the three aliquots was different for each bean color. A non-parametric analysis, however, indicated that the average in the three levels of concentration for beans of all colors, was the same. A similar analysis of the results by the Hagerman-Butler method demonstrated that variability and average values for the three aliquots were equal for black and red beans but not for white beans. The coefficient of variation was lower for the higher aliquot of the extract. A significant correlation (r = 0.72, P less than 0.05, n = 60) was found between the two methods for all beans using the larger aliquot of the extract. The correlation was highly significant (r = 0.84, P less than 0.05) when white bean values were eliminated. The polyphenolic content varied with seed color and the thermic process reduced their content, as measured by the two methods. The losses in polyphenolics as measured by the Folin-Denis in the cooked beans dried with broth, varied from 31.4 to 36.3%, and from 39.8 to 51.1% for the cooked bean flour dried without broth. The losses by the Hagerman-Butler method were from 25.0 to 93.5% in the cooked bean flours dried with cooking broth, and from 33.3 to 95.7% when dried without the broth. The higher losses were recorded for red beans. In vivo digestibility for cooked bean flours, dried and without broth, were 73.2, 69.6 and 64.5%, and 71.9, 71.9 and 68.8% for white, red and black beans, respectively. A negative correlation (r = -0.39) and significant (p less than 0.05) was found between polyphenolic content in the diet and in vivo protein digestibility.
OBJECTIVES: Despite its protective role, the dentine pellicle has rarely been studied, therefore we aimed to map out the proteomic profile of in vitro dentine pellicles before and after modification. MATERIALS AND METHODS: A total of 135 human dentine specimens were prepared. After initial pellicle formation with 150 µl pooled human saliva (37 °C, 30 min), the dentine specimens were immersed in one of 9 pellicle modification solutions (2 ml/specimen): deionized water (non-modified pellicle), SnCl2/NaF/AmF (commercial solution containing 800 ppm Sn2+ and 500 ppm F-), NaF solution (500 ppm F- ), and six polyphenol solutions (2 mg / ml) with or without 500 ppm F-: blueberry extract (BBE and BBE + F-), green tea extract (GTE and GTE + F-) and grape seed extract (GSE and GSE + F-). After another aliquot of saliva (150 µl, 37 °C, 60 min), the pellicles were harvested with sodium dodecyl sulphate by rubbing with cotton balls, and taken to proteomic analyses by Liquid Chromatography-Tandem Mass Spectrometry after tryptic digestion. RESULTS: A total of 382 proteins were identified in all the proteomic analyses for all groups. Pellicle modification with fluoride, either NaF or SnCl2/NaF/AmF, led to the presence of 12 or 14 exclusive proteins, respectively, whereas modification with the solutions containing polyphenols presented less exclusive proteins (4-6 proteins). The number of exclusive proteins was even lower for when polyphenols and fluoride (GTE + F- and GSE + F-) were used, with lower abundance of proteases. CONCLUSIONS: We conclude that NaF and SnCl2/NaF/AmF significantly modify the proteome of the dentine pellicle. The combination of fluoride with polyphenols further lowers the abundance of proteins and proteases, which explains the positive effect of these solutions on the dentine pellicles. CLINICAL RELEVANCE: Plant extract solutions with fluoride can significantly modify the proteomic structure of the dentine pellicle, which clarifies the mechanism of action of polyphenols on the protection of dentine demineralization.
The in vitro interaction of pure polyphenols and polyphenol extracts of coffee pulp with pure proteins was studied. The polyphenols used for the assays were tannic acid, chlorogenic acid and catechin, and the proteins were gelatin, casein and bovine serum albumin (BSA). Different pHs and different polyphenol/protein ratios were used in the experiments. Extracts of coffee pulp in methanol, methanol-water (50:50), ammonium hydroxide 3%, and calcium hydroxide 1%, were used. In general, the maximum binding of polyphenol with protein was obtained at a polyphenol/protein ratio of 1/2, at a pH of 5.0. The higher binding percentages were found with the ammonium hydroxide extract and with tannic acid. The lowest binding percentage was obtained with the methanol-water extract. The other extracts presented intermediate binding degrees. The results herein reported demonstrate that the polyphenols of coffee pulp have capacity to bind proteins in vitro at the pHs assayed. This phenomenon may be the cause of the deficient protein utilization when coffee pulp is included in the animals' diet.
The polyphenol content of coffee pulp extracts was determined using the Folin-Ciocalteau method. The use of polyvynilpirrolidone (PVP) was introduced in order to eliminate interferences. Condensed polyphenols in the extracts were determined by the method of acidified vanillin. Chlorogenic acid and catechin were used as standards for Folin-Ciocalteau and Vanillin methods, respectively, and a calibration curve was constructed for each solvent. The solvents used were methanol, methanol-water (50:50), ammonium hydroxide (3%) and calcium hydroxide (1%), using times of extraction of 10 minutes and 1 hour. No differences were found in the amount of polyphenols extracted by the different solvents at the two extraction times. After 10 minutes, the alkaline solvents NH4OH (3%) and Ca(OH)2 (1%), extracted more polyphenols than the other two solvents. Nevertheless, ammonium hydroxide (3%) was more efficient in extracting condensed polyphenols. The results herein presented suggest that treating coffee pulp with mild alkaline solvents may improve its nutritive value.
The hydrolytic products of lignins, humic acids and industrial waste including hydroquinone, catechol, resorcinol, pyrogallol and 1,2,4-benzenetriol are widely distributed in water sources. These polyphenols can interact with chlorine or nitrite to yield new derivatives. Generally, these new products possess more mutagenic potential than their original compounds. Furthermore, the mutagenicity of these polyphenols and their derivatives can be dramatically reduced by rodent liver microsomal enzymes (S9). The mutagenicity of polyphenols is in this order: hydroquinone greater than 1,2,4-benzenetriol greater than pyrogallol, while catechol, resorcinol and phloroglucinol are non-mutagenic. The ultimate product of chlorination or nitrosation of hydroquinone has been identified to be p-benzoquinone. The formation of active oxygen species including superoxide anion and hydrogen peroxide by polyphenols has been demonstrated and this may contribute partly to the molecular mechanisms of polyphenol mutagenicity.
The effect of the polyphenols of coffee pulp on iron absorption was studied using the method of ligated segments in rats. Optimal conditions to measure iron absorption, were determined using as criteria the concentration of Fe59 and the time that produced the highest value of blood radioactivity. A concentration of 0.4 uCi/dose of Fe59 and a 3-hr period were chosen to measure iron absorption. Experimental groups were formed assigning six rats randomly to each group. Each group was injected with a solution of 59Fe and either with the standard polyphenol solution or with the coffee pulp extract, except the control group which was injected with the Fe59 solution only. The effect of two polyphenol concentrations was also studied. Iron uptake from the duodenum was found to be the best indicator of iron absorption when compared to the sum of iron uptake by the tissues (blood, liver, spleen, kidneys, heart and carcass). Therefore, this indicator was used to interpret the results obtained. Catechin, tannic acid and the coffee pulp extract decreased significantly iron absorption when compared with the control group. The level of polyphenols used in these experiments is similar to the amounts consumed by animals fed coffee pulp at a 10% level. Therefore, we can conclude that the antinutritional effect of coffee pulp polyphenols may be partially due to their capacity to bind iron.
Human milk offers the best nutrition to the infant, which is crucial for the child's proper development and health status across the lifespan. Besides providing the substances optimally supplying the baby with energy and building materials, breast milk contains several immunometabolically active components. Those include molecules fully de novo synthesized by the mother, such as human milk oligosaccharides (HMO), and substances of nonhuman origin, transferred to the infant through mother's milk, such as dietary plant polyphenols. In this review, we outline the basic biology of HMO and polyphenols and deeply characterize their effects on the development of allergic disorders on the basis of available literature reporting data from in vitro, animal, and human studies. Further, we review the abundance of HMO and polyphenols, commonly present in mother's milk, and their mutual interactions in the context of the mechanisms underlying predisposition to, or protection against, the development of allergies. Finally, we discuss the potential of HMO and polyphenols in allergy prevention and therapy.
Tea is grown in about 30 countries but is consumed worldwide, although at greatly varying levels. It is the most widely consumed beverage aside from water with a per capita worldwide consumption of approximately 0.12 liter per year. Tea is manufactured in three basic forms. Green tea is prepared in such a way as to preclude the oxidation of green leaf polyphenols. During black tea production oxidation is promoted so that most of these substances are oxidized. Oolong tea is a partially oxidized product. Of the approximately 2.5 million metric tons of dried tea manufactured, only 20% is green tea and less than 2% is oolong tea. Green tea is consumed primarily in China, Japan, and a few countries in North Africa and the Middle East. Fresh tea leaf is unusually rich in the flavanol group of polyphenols known as catechins which may constitute up to 30% of the dry leaf weight. Other polyphenols include flavanols and their glycosides, and depsides such as chlorogenic acid, coumarylquinic acid, and one unique to tea, theogallin (3-galloylquinic acid). Caffeine is present at an average level of 3% along with very small amounts of the other common methylxanthines, theobromine and theophylline. The amino acid theanine (5-N-ethylglutamine) is also unique to tea. Tea accumulates aluminum and manganese. In addition to the normal complement of plant cell enzymes, tea leaf contains an active polyphenol oxidase which catalyzes the aerobic oxidation of the catechins when the leaf cell structure is disrupted during black tea manufacture. The various quinones produced by the enzymatic oxidations undergo condensation reactions which result in a series of compounds, including bisflavanols, theaflavins, epitheaflavic acids, and thearubigens, which impart the characteristic taste and color properties of black tea. Most of these compounds readily form complexes with caffeine. There is no tannic acid in tea. Thearubigens constitute the largest mass of the extractable matter in black tea but their composition is not well known. Proanthocyanidins make up part of the complex. Tea peroxidase may be involved in their generation. The catechin quinones also initiate the formation of many of the hundreds of volatile compounds found in the black tea aroma fraction. Green tea composition is very similar to that of the fresh leaf except for a few enzymatically catalyzed changes which occur extremely rapidly following plucking. New volatile substances are produced during the drying stage. Oolong tea is intermediate in composition between green and black teas.
Tobacco (Nicotiana tabacum L.) is an important economic crop, from which polyphenols are crucial for regulating its growth and development as well as shaping its quality. However, few genes associated with polyphenol accumulation have been cloned from tobacco, and the molecular mechanisms underlying this process remain poorly understood. Here, we found that the tobacco transcription factor EARLY FLOWERING 3 (NtELF3), which is highly expressed in tobacco leaves, positively regulates the accumulation of chlorogenic acid, neochlorogenic acid, cryptochlorogenic acid, rutin, scopoletin, and total polyphenols in tobacco middle leaves. The metabolomic and transcriptomic analyses of middle leaves showed that a total of 177 differentially accumulated metabolites and 7409 differentially expressed genes (DEGs) were identified in ntelf3-1 mutant versus wild type, respectively. Further investigation identified that 17 DEGs were involved in phenylpropanoid metabolic and flavonoid metabolic processes. Combined analysis indicated that the phenylpropanoid and flavonoid biosynthesis pathways were also co-enriched in kyoto encyclopedia of genes and genomes enrichment analysis. Molecular biology experiment demonstrated that NtELF3 directly binds to the promoters of NtFLS-1 and NtCHIL-2 that are both associated with phenylpropanoid and flavonoid biosynthesis, and promotes their expression. Taken together, our results not only provide new theoretical support for in-depth understanding of the regulatory mechanisms underlying polyphenol accumulation in tobacco, but also offer excellent genes and germplasm resources for tobacco quality breeding.
The ability of polyphenolic compounds to form insoluble complexes with other macro-molecules such as proteins has long been associated with the observed reduction in nutritive value resulting from their inclusion in animal diets. Naturally occurring polyphenols, and in particular condensed tannins isolated from various plant sources, have been shown to inhibit in vitro a number of digestive enzymes including trypsin, alpha-amylase and lipase. In addition, the results of various feeding trials suggest that similar reductions in intestinal digestive enzyme activity may result from the feeding of high polyphenolic diets. The evidence for this is summarised and discussed in relation to the possible effect of enzyme inhibition on reduced nutritive value and it is concluded that the observed reduction in protein availability found in vivo on consuming high tannin diets cannot simply be explained by the formation of dietary protein tannin complexes and that the ability of polyphenolic compounds to inhibit digestive enzymes may be of greater significance than realised previously.
A green tea polyphenol fraction was evaluated for its ability to inhibit tumor initiation by polycyclic aromatic hydrocarbons and tumor promotion by a phorbol ester in the skin of CD-1 mice. Topical application of the green tea polyphenol fraction inhibited benzo[a]pyrene- and 7,12-dimethylbenz[a]-anthracene-induced tumor initiation as well as 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced tumor promotion. Topical application of the green tea polyphenol fraction also inhibited TPA-induced inflammation, ornithine decarboxylase activity, hyperplasia and hydrogen peroxide formation. Studies with individual polyphenolic compounds in green tea indicated that topical application of (-)-epigallocatechin gallate, (-)-epigallocatechin and (-)-epicatechin gallate inhibited TPA-induced inflammation in mouse epidermis.
A variety of synthetic and natural polyphenols protect mammalian cells from hydrogen peroxide (H2O2). Cytotoxicity of H2O2 on Chinese hamster V79 cells was assessed with a colony formation assay, and several polyphenols prevented the decrease in the number of colonies caused by H2O2. A study of the structure-activity relationship revealed that affinity of the polyphenols for the cell membrane and the presence of an ortho-dihydroxy moiety in their structure proved essential to this protection.
In view of the pharmacological interest in phenolic substances, we have determined the total amount of anthocyanins and polyphenols present in the berries of several cultivars of Ribes, Rubus, and Vaccinium genera. The in vitro antiradical activity of the crude extracts on chemically-generated superoxide radicals as well as the inhibitory activity towards the enzyme xanthine oxidase were studied. All the crude extracts examined showed a remarkably high activity towards chemically-generated superoxide radicals. The activities were greater than those expected on the basis of the quantities of anthocyanins and polyphenols present in the samples. Furthermore, the extracts showed a certain inhibitory activity towards xanthine oxidase. Ribes nigrum extracts exhibit the highest activity, being the richest in both anthocyanins and polyphenols. On the other hand, Ribes rubrum extracts seem to contain more active substances than the other crude extracts.