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

Polyphenols are the most abundant antioxidants in the diet and are widespread constituents of fruits, vegetables, cereals, dry legumes, chocolate, and beverages, such as tea, coffee, or wine. Experimental studies on animals or cultured human cell lines support a role of polyphenols in the prevention of cardiovascular diseases, cancers, neurodegenerative diseases, diabetes, or osteoporosis. However, it is very difficult to predict from these results the effects of polyphenol intake on disease prevention in humans. One of the reasons is that these studies have often been conducted at doses or concentrations far beyond those documented in humans. The few clinical studies on biomarkers of oxidative stress, cardiovascular disease risk factors, and tumor or bone resorption biomarkers have often led to contradictory results. Epidemiological studies have repeatedly shown an inverse association between the risk of myocardial infarction and the consumption of tea and wine or the intake level of some particular flavonoids, but no clear associations have been found between cancer risk and polyphenol consumption. More human studies are needed to provide clear evidence of their health protective effects and to better evaluate the risks possibly resulting from too high a polyphenol consumption.

Dietary polyphenols and the prevention of diseases

The concentrations of bases, nucleosides, and nucleosides mono-, di- and tri-phosphate are compared for about 600 published values. The data are predominantly from mammalian cells and fluids. For the most important ribonucleotides average concentrations ±SD (μM) are: ATP, 3,152±1,698; GTP, 468±224; UTP, 567±460 and CTP, 278±242. For deoxynucleosidestriphosphate (dNTP), the concentrations in dividing cells are: dATP, 24±22; dGTP, 5.2±4.5; dCTP, 29±19 and dTTP 37±30. By comparison, dUTP is usually about 0.2 μM. For, the 4 dNTPs, tumor cells have concentrations of 6–11 fold over normal cells, and for the 4 NTPs, tumor cells also have concentrations 1.2–5 fold over the normal cells. By comparison, the concentrations of NTPs are significantly lower in various types of blood cells. The average concentration of bases and nucleosides in plasma and other extracellular fluids is generally in the range of 0.4–6 μM; these values are usually lower than corresponding intracellular concentrations. For phosphate compounds, average cellular concentrations are: Pi, 4400; ribose-1-P, 55; ribose-5-P, 70 and P-ribose-PP, 9.0. The metal ion magnesium, important for coordinating phosphates in nucleotides, has values (mM) of: free Mg2+, 1.1; complexed-Mg, 8.0. Consideration of experiments on the intracellular compartmentation of nucleotides shows support for this process between the cytoplasm and mitochondria, but not between the cytoplasm and the nucleus.

Physiological concentrations of purines and pyrimidines.

Phenolics in Food and Nutraceuticals is the first single-source compendium of essential information concerning food phenolics. This unique book reports the classification and nomenclature of phenolics, their occurrence in food and nutraceuticals, chemistry and applications, and nutritional and health effects. In addition, it describes antioxidant activity of phenolics in food and nutraceuticals as well as methods for analysis and quantification. Each chapter concludes with an extensive bibliography for further reading. Food scientists, nutritionists, chemists, biochemists, and health professionals will find this book valuable.

Phenolics in food and nutraceuticals

It is well-known that deficiency or over exposure to various elements has noticeable effects on human health. The effect of an element is determined by several characteristics, including absorption, metabolism, and degree of interaction with physiological processes. Iron is an essential element for almost all living organisms as it participates in a wide variety of metabolic processes, including oxygen transport, deoxyribonucleic acid (DNA) synthesis, and electron transport. However, as iron can form free radicals, its concentration in body tissues must be tightly regulated because in excessive amounts, it can lead to tissue damage. Disorders of iron metabolism are among the most common diseases of humans and encompass a broad spectrum of diseases with diverse clinical manifestations, ranging from anemia to iron overload, and possibly to neurodegenerative diseases. In this review, we discuss the latest progress in studies of iron metabolism and bioavailability, and our current understanding of human iron requirement and consequences and causes of iron deficiency. Finally, we discuss strategies for prevention of iron deficiency.

http://jrms.mui.ac.ir/index.php/jrms/article/download/9860/4105

Review on iron and its importance for human health.

1. Non-haem iron absorption from a variety of vegetable meals was studied in parous Indian Women, using the erythrocyte utilization of radioactive Fe method.2. The studies were undertaken to establish whether Fe absorption could be correlatedwith the chemical composition of the foodstuff.3. Addition of the following organic acids commonly found in vegetables, improved the geometric mean Fe absorption from a basic rice meal as follows: from 0·028 to 0·085 with 1 g citric acid, from 0·031 to 0·081 with 15 mg ascorbic acid, from 0·048 to 0·095 with 1 g L-malic acid, from 0·041 to 0·096 with 1 g tartaric acid. The only exception was oxalic acid; the addition of 1 g calciumoxalate to cabbage (Brassica oleraceae) was associated with some depression in Fe absorption from 0·320 to 0·195.4. There was a marked inhibition of the geometric mean absorption when 500 mg tannic acid was added to a broccoli (Brassica oleraceae) meal (0·015 v. 0·297). Sodium phytate (2 g) caused a similar, though less profound inhibition (0·035 to 0·152).5. When 3 mg ferrous sulphate was added to different vegetables the geometric mean absorption varied widely. Vegetables of low Fe bioavailability were wheat germ (Triticum aestivum) 0·007, aubergine (Solanum melongena) 0·007, butter beans (Phaseolus lunatus) 0·012, spinach (Spinacea oleraceae) 0·014, brown lentils (Lens culinaris) 0·024, beetroot greens (Beta vulgaris) 0·024 and green lentils (Lens culinaris) 0·032. In contrast, bioavailability was moderate or good with carrot (Daucus carota) 0·098, potato (Solanum tuberosum) 0·115, beetroot (Beta vulgaris) 0·185, pumpkin (Cucurbita mixta) 0·206, broccoli 0·260, tomato (Lycopersicon esculentum) 0·224, cauliflower (Brassica oleraceae) 0·263, cabbage 0·320, turnip (Brassica rapa) 0·327 and sauerkraut 0·327.6. All the vegetables associated with moderate or good Fe bioavailability contained appreciable amounts of one or more of the organic acids, malic, citric and ascorbic acids.7. Poor Fe bioavailability was noted in vegetables with high phytate contents (e.g. wheat germ 0·007, butter beans 0·012, brown lentils 0·024 and green lentils 0·032).8. The fact that a number of vegetables associated with low Fe-absorption turned bluish-black when Fe was added to them, suggested that the total polyphenol content in them was high. The vegetables included aubergine spinach, brown lentils, green lentils and beetroot greens. When the total polyphenol content in all the vegetables tested was formally measured, there was a significant inverse correlation (r 0·859, P < 0·001) between it and Fe absorption. The inverse correlation between the non-hydrolysable polyphenol content and Fe absorption was r 0·901 (P < 0·001).9. The major relevance of these findings is the fact that the total absorption of non-haem-Fe from a mixed diet may be profoundly influenced by the presence of single vegetables with either marked enhancing or inhibiting effects on Fe bioavailability.

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The effects of organic acids, phytates and polyphenols on the absorption of iron from vegetables.

In normal adult males, about 25%o of the body iron content is in storage depots (1). This iron exists in two forms: as a diffuse soluble fraction called ferritin, in which the molecules are dispersed , and as insoluble aggregates of hemosiderin, which can be visualized by conventional micros-copy (2). Although the liver is regarded as the chief storage organ, chemical analyses suggest that it normally contains up to 300 mg (3-5), which is only between one-quarter and one-third of what can be mobilized from total stores when healthy young males are repeatedly phlebotomized (6). Although little is known of the quantities present in other organs, hemosiderin can be seen in the reticuloendothelial cells of the bone marrow (7) and spleen (8), and there is some chemical evidence to indicate that significant amounts of storage iron may be present in skeletal muscles (9, 10). The present study was undertaken to find out how much iron is normally stored in the reticulo-endothelial cells of the bone marrow and to define the extent to which these stores can expand when iron overload is present. In addition, a comparison was made between the concentrations of iron present in the bone marrows and livers of subjects with varying quantities of storage iron. MATERIALS AND METHODS Clinical material. The total iron stores present in bone marrow were estimated in 61 adult subjects undergoing thoracotomy. Forty-one were white and the remainder were Bantu. The individual diagnoses are shown in Table I. The chemical concentrations of storage iron were estimated in the livers and bone marrows of adult Bantu and white subjects dying in the hospital. The Bantu specimens (58 males and 44 females) were obtained from Baragwanath Hospital, Johannesburg, and the white specimens (25 males and 28 females) from the General Hospital, Johannesburg. The use of radioiron as a marrow label. When a tracer quantity of radioiron is injected intravenously, most of it is taken up by the red-cell precursors of the bone marrow (11). This iron is subsequently released over the next few days as part of the hemo-globin of new red cells, and the percentage present in circulation at 10 to 14 days has been used as a measure of the fraction initially taken up by the bone marrow (12). If a specimen of bone marrow is therefore removed between 18 and 24 hours after the injection of the radioiron (i.e., at a time …

/pdf/the-quantitative-estimation-of-total-iron-stores-in-human-3d08iwnu88.pdf

The quantitative estimation of total iron stores in human bone marrow

Non-haem-iron absorption from a variety of cereal and fibre meals was measured in parous Indian women, using the erythrocyte utilization of radioactive Fe method. The present study was undertaken to establish whether alteration of the phytate and polyphenol contents of sorghum (Sorghum vulgare) affected Fe absorption from sorghum meals, and to assess the influence of fibre on Fe absorption. Removing the outer layers of sorghum grain by pearling reduced the polyphenol and phytate contents by 96 and 92% respectively. This treatment significantly increased the geometric mean Fe absorption from 0.017 to 0.035 (t 3.9, P less than 0.005). The geometric mean Fe absorption from a sorghum cultivar that lacked polyphenols (albino sorghum) was 0.043, which was significantly greater than the 0.019 absorbed from bird-proof sorghum, a cultivar with a high polyphenol content (t 2.83, P less than 0.05). Fe was less well absorbed from the phytate-rich pearlings of the albino sorghum than from the pearled albino sorghum (0.015 v. 0.035 (t 8.4, P less than 0.0005]. Addition of sodium phytate to a highly Fe-bioavailable broccoli (Brassica oleracea) meal reduced Fe absorption from 0.185 to 0.037. The geometric mean Fe absorption from malted sorghum porridge was 0.024 when 9.5 mg ascorbic acid were added and 0.094 when the ascorbic acid was increased to 50 mg (t 3.33, P less than 0.005). This enhancing effect of 50 mg ascorbic acid was significantly depressed to 0.04 by tea (t 38.1, P less than 0.0005).(ABSTRACT TRUNCATED AT 250 WORDS)

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/57515BE1639CF5622D6570C223DD4DE6/S0007114584000088a.pdf/div-class-title-factors-affecting-the-absorption-of-iron-from-cereals-div.pdf

Factors affecting the absorption of iron from cereals

The effects of the chemical composition of fruit juices and fruit on the absorption of iron from a rice (Oryza sativa) meal were measured in 234 parous Indian women, using the erythrocyte utilization of radioactive Fe method. The corrected geometric mean Fe absorptions with different juices varied between 0.040 and 0.129, with the variation correlating closely with the ascorbic acid contents of the juices (rs 0.838, P less than 0.01). Ascorbic acid was not the only organic acid responsible for the promoting effects of citrus fruit juices on Fe absorption. Fe absorption from laboratory 'orange juice' (100 ml water, 33 mg ascorbic acid and 750 mg citric acid) was significantly better than that from 100 ml water and 33 mg ascorbic acid alone (0.097 and 0.059 respectively), while Fe absorption from 100 ml orange juice (28 mg ascorbic acid) was better than that from 100 ml water containing the same amount of ascorbic acid (0.139 and 0.098 respectively). Finally, Fe absorption from laboratory 'lemon juice' (100 ml orange juice and 4 g citric acid) was significantly better than that from 100 ml orange juice (0.226 and 0.166 respectively). The corrected geometric mean Fe absorption from the rice meal was 0.025. Several fruits had little or no effect on Fe absorption from the meal (0.013-0.024). These included grape (Vitis vinifera), peach (Prunus persica), apple (Malus sylvestris) and avocado pear (Persea americana). Fruit with a mild to moderate enhancing effect on Fe absorption (0.031-0.088) included strawberry (Fragaria sp.) (uncorrected values), plum (Prunus domestica), rhubarb (Rheum rhaponticum), banana (Musa cavendishii), mango (Mangifera indica), pear (Pyrus communis), cantaloup (Cucumis melo) and pineapple (Ananas comosus) (uncorrected values). Guava (Psidium guajava) and pawpaw (Carica papaya) markedly increased Fe absorption (0.126-0.293). There was a close correlation between Fe absorption and the ascorbic acid content of the fruits tested (rs 0.738, P less than 0.0001). There was also a weaker but significant correlation with the citric acid content (rs 0.55, P less than 0.03). Although this may have reflected a direct effect of citric acid on Fe absorption, it should be noted that fruits containing citric acid also contained ascorbic acid (rs 0.70, P less than 0.002).(ABSTRACT TRUNCATED AT 400 WORDS)

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J. D. Torrance

Papers

The effects of organic acids, phytates and polyphenols on the absorption of iron from vegetables.

The quantitative estimation of total iron stores in human bone marrow

Factors affecting the absorption of iron from cereals

The effects of fruit juices and fruits on the absorption of iron from a rice meal.

Iron overload in bantu subjects; studies on the availability of iron in bantu beer.