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© 2003 The American Society for Nutritional Sciences J. Nutr. 133:3248S-3254S, October 2003

Supplement: Proceedings of the Third International Scientific Symposium on Tea and Human Health

Overview of Dietary Flavonoids: Nomenclature, Occurrence and Intake1

Gary R. Beecher2

Foods and Nutrition Consultant, Lothian, MD 20711

2To whom correspondence should be addressed. E-mail: gbeecher{at}earthlink.net.


   ABSTRACT
TOP
 ABSTRACT
Nomenclature
 Flavonoid content of foods
 Flavonoid consumption
 DISCUSSION
 LITERATURE CITED
 
Flavonoids and their polymers constitute a large class of food constituents, many of which alter metabolic processes and have a positive impact on health. Flavonoids are a subclass of polyphenols. They generally consist of two aromatic rings, each containing at least one hydroxyl, which are connected through a three-carbon "bridge" and become part of a six-member heterocyclic ring. The flavonoids are further divided into subclasses based on the connection of an aromatic ring to the heterocyclic ring, as well as the oxidation state and functional groups of the heterocyclic ring. Within each subclass, individual compounds are characterized by specific hydroxylation and conjugation patterns. Many flavonoids in foods also occur as large molecules (tannins). These include condensed tannins (proanthocyanidins), derived tannins and hydrolysable tannins. For proanthocyanidins, three subclasses (15 characterized) have been identified in foods. Monomers are connected through specific carbon-carbon and ether linkages to form polymers. Derived tannins are formed during food handling and processing, and found primarily in black and oolong teas. Flavonoids are widely distributed in nature, albeit not uniformly. As a result, specific groups of foods are often rich sources of one or more subclasses of these polyphenols. The polyphenolic structure of flavonoids and tannins renders them quite sensitive to oxidative enzymes and cooking conditions. Scientists in several countries have estimated intakes of a few subclasses of flavonoids from limited food composition databases. These observations suggest large differences in consumption, due in part to cultural and food preferences among populations of each country.

KEY WORDS: • flavonoids • tannins • thearubigins • polyphenols • detary intake

Foods, because they are derived from biological systems, contain many compounds in addition to traditional nutrients (1–3). Many of these compounds have the capacity to alter enzymatic and chemical reactions, and therefore may impact human health both positively and negatively (4). These compounds have become known by names such as phytochemicals, phytonutrients, and nontraditional nutrients. One of the largest groups of these phytonutrients that may provide beneficial health effects is the flavonoids and their polymers. Over 60 years ago, extracts of foods presumably containing flavonoids were shown by Szent-György and his colleagues to have beneficial biological properties (5). Although these early results were not corroborated, modulation of many biological systems by flavonoids, tannins and other phytonutrients has been demonstrated by a plethora of investigators (6). Papers from this symposium update the current state of knowledge of tea flavonoids on those biological actions related to chronic disease. This paper however, will review the nomenclature, occurrence in foods and intake of flavonoids with emphasis on those prevalent in tea.


   Nomenclature
TOP
 ABSTRACT
 Nomenclature
Flavonoid content of foods
 Flavonoid consumption
 DISCUSSION
 LITERATURE CITED
 
Flavonoids are a subclass of the polyphenols, which are characterized as containing two or more aromatic rings, each bearing at least one aromatic hydroxyl and connected with a carbon bridge (7). For flavonoids, this bridge consists of three carbons that combines with an oxygen and two carbons of one of the aromatic rings (A ring) to form a third 6-member ring [C ring (Fig. 1)]. In contrast, the lignans, another subclass of biologically active polyphenols, have a four-carbon bridge that leads to many different chemical structures in nature. The flavonoids are further divided into subclasses based on the connection of the B ring to the C ring, as well as the oxidation state and functional groups of the C ring. Table 1 lists the subclasses of flavonoids in ascending order of oxidation state along with the other significant attributes that identify each subclass. Within each subclass, individual flavonoids and isoflavones are identified and characterized by hydroxylation and conjugation patterns of the B ring, as well as the conjugation patterns of hydroxyls on the A and C rings. Structures of flavonoids common to foods have been widely published (10). The names of the prominent food flavonoids within each flavonoid subclass are also listed in Table 1. Most flavonoids are present in nature as glycosides and other conjugates (flavanols are an exception), which contribute to their complexity and the large number of individual molecules that have been identified (>5000) (11).



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  		FIGURE 1 General structure and numbering pattern for common food flavonoids. See Table 1 for unique linkages, unsaturation positions and functional groups of each flavonoid subclass. For most food flavonoids, R4'-H, R5-OH and R6-H. Exceptions include, biochanin A, R4'-CH3; formononetin, R4'-CH3, R5-R6-H; glycitein, R5-H, R6-OH; and hesperitin, R4'-CH3. Additional individual flavonoids within each subclass are characterized by unique functional groups at R3, R3', and R5'.

 

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  		TABLE 1 Flavonoid subclasses, their chemical characteristics, names of prominent food flavonoids and typical food sources1

 
Many flavonoids in foods are polymerized into large molecules, either by the plants themselves or as a result of food processing. These polymers are called tannins and were so named based on their function, i.e., precipitate proteins and some alkaloids convert animal hide to leather (12). There are several subclasses of tannins, three of which are important to foods and perhaps health [Table 2 (7)].


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  		TABLE 2 Tannin subclasses common to foods1

 
Condensed tannins or proanthocyanidins consist of monomeric units of flavans linked through carbon—carbon and ether linkages. Fifteen subclasses of proanthocyanidins have been identified (13), however, only three appear to be prominent in human foods of plant origin, procyanidins ([epi]catechin polymers), prodelephinidins ([epi]gallocatechin polymers) and propelargonidins ([epi]afselechin) polymers or their mixtures (14). In these tannins, the monomeric units are primarily linked through single 4->6 or 4->8 carbon-carbon bonds (B linkages), or through 4->8 carbon-carbon linkages and 2->7 ether bonds (A linkages). Other linkages also have been identified, but were isolated from nonfood plants or constitute minor compounds of foods such as cocoa (13). Tannins can range from dimers through large polymers and are found in a wide variety of foods, e.g., apples, berries, chocolate, red wines and nuts (15–17).

A second class of food tannins is the derived tannins (7). These complex compounds are formed primarily under oxidative enzymatic and atmospheric conditions during the manipulation of plants and subsequent processing into foods, e.g., oolong and black teas, red wines and coffee. Because of the complexity of the compounds of this class of tannins, strict chemical nomenclature has been difficult and often trivial names have been assigned as a consequence. Clifford (7) has proposed a series of naming rules for many dimers of derived tannins. Of importance to oolong and black teas are the flavanol-derived theaflavins. The unique feature of the theaflavins is the benztropolone ring, a seven-member ring, which is formed by the oxidation of the B ring of either (-)-epigallocatechin or (-)-epigallocatechin-3-gallate, loss of CO2 and simultaneous merger with the B ring of a second molecule of (-)-epicatechin or (-)-epicatechin-3-gallate (Fig. 2). As a result, four possible compounds are formed, all of which have been separated by HPLC methods (18) and tabulated in at least one database (8).



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  		FIGURE 2 General structure for theaflavins. Specific compounds are as follows: theaflavin, R1-R2-H; theaflavin-3-gallate, R1-gallate, R2-H; theaflavin-3'-gallate, R1-H, R2-gallate; and theaflavin-3,3'-digallate, R1-R2-gallate.

 
Subjecting foods containing flavanols to conditions that favor formation of theaflavins also results in a heterogenous group of high-molecular-weight (1–10 kDa) compounds loosely termed thearubigins. Thearubigins are also members of derived tannins (Table 2). The complexity and molecular size of these compounds has made definitive elucidation of their structures difficult (19). Nontheless, thearubigins are in relatively high concentrations in most black and oolong teas (Table 3) and may be important in the health related properties of these foods (20–22).


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  		TABLE 3 Transformation and losses of flavonoids during tea processing1

 
Another class of common food tannins is the hydrolysable tannins, which consist of gallic acid or ellagic acid to which a nonaromatic polyol, such as a sugar or quinic acid, is esterified (7). Although this class of tannins was named for the ease of cleavage of the ester linkage, several other linkages may occur (C—C, C—O—C) to form dimers and higher complexes, which have varying degrees of resistance to chemical breakdown (23). Although hydrolysable tannins are widespread in some plant foods, e.g., grapes and wines, and contribute important organoleptic qualities, they have received little attention in terms of their impact on human health.


   Flavonoid content of foods
TOP
 ABSTRACT
 Nomenclature
 Flavonoid content of foods
Flavonoid consumption
 DISCUSSION
 LITERATURE CITED
 
Although flavonoids are widely distributed in nature and in foods, they lack uniform distribution throughout the plant kingdom. Table 4 lists the flavonoid and tannin content of selected foods on an mg/serving basis. In general these data show that a serving of teas, fruits (apples, blueberries), dark chocolate and red wine are moderate to high in flavonoid and/or tannin content. However, a serving of broccoli or selected fruit juices (cranberry and orange) provides relatively low levels of these phytonutrients. More important than the total flavonoid/tannin content of foods per se, may be the content of flavonoid and tannin subclasses. As an example, soy and soy-based foods, e.g., tofu, are unique sources of isoflavones (Table 4), which appear to have unique health-related biological properties. Similarly, although cranberries contain only moderate levels of proanthocyanidins, these tannins have a substantial proportion of unique molecular structures (A linkages) (25), which may contribute to their bacterial antiadhesion activity (26,27). However, cocoa contains primarily B linkages and appears to be effective against several biomarkers of cardiovascular disease (28,29). Black and oolong teas have high contents of derived tannins (theaflavins, thearubigins, etc.), which may contribute to the health-promoting benefits of these beverages (Table 3).


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  		TABLE 4 Flavonoid and tannin content of selected foods1

 
Food processing.

Two aspects of food processing are pertinent for discussion relative to flavonoids: 1) transformation during processing and 2) losses during processing and cooking. Relative to transformation, black and oolong teas are the foods that undergo the largest change of flavan-3-ols during their production. The most dramatic changes are the reduction of flavan-3-ols levels with a concomitant increase in the concentration of thearubigins (Table 3; compare brewed green tea with brewed black tea and brewed oolong tea). In contrast, total flavonols remain relatively low and constant during conversion of green tea leaves into black or oolong tea (Table 3), and theaflavins concentrations increases only slightly (data not shown). As outlined above, these changes are due to the oxidative processes that occur during production of black and oolong tea, in which flavan-3-ols are converted primarily into thearubigins and, to a much lesser extent, into theaflavins. The data in Table 3 do not permit the assessment of the stoichiometry of these conversions, however, due to the complexity of these reactions it is reasonable to assume that some of the flavan-3-ols are converted to products other than compounds measured as theaflavins and thearubigins.

Several other processes common to the production of commercial teas also alter their flavonoid content. Decaffeination and manipulations employed in the preparation of instant and ready-to-drink teas all appear to decrease either flavanol levels (Table 3; decaffeinated green tea) or both concentrations of flavanols and thearubigins (Table 3; black teas). It is important to point out that some of the fluctuations in flavonoid content among different teas may be due to blends of different teas relative to type, area of production and cost. The flavonoid content of leaf tissue is very sensitive to environmental conditions such as amount of light energy and pollutants (30). Thus, as teas are blended based on organoleptic and visual factors, flavonoid levels also may be altered.

Flavonoids also are susceptible to other food processing and food handling procedures. For example, storage of onions results in the loss of 25 to 33% of the quercetin during the 1st 12 d, but only small losses thereafter (31). When cooked in water, those foods having a high surface area or ruptured cell walls results in a substantial reduction in the levels of flavonoids (32,33). These losses may be explained by the solubility of the flavonoids in water (a polar solvent) and the ease with which they can escape the cellular compartment of vegetables. In contrast, quercetin conjugates of onion are quite stable to high temperatures (100°C) with only a small amount degraded at temperatures of hot vegetable oil (31). These observations suggest that during food processing, enzymatic transformations are more important relative to changes in flavonoid content than the cooking process per se.

Flavonoid databases.

The association between ingestion of a class or classes of micronutrients and health promotion is often demonstrated through epidemiological studies. Such studies require databases of the food content of each member of the class(es) of phytonutrients of interest. For flavonoids, several countries have assembled databases of values for those compounds assumed to be rich in their respective food supply (Table 5). Information in several of the databases is available on the Internet (see Literature Cited for web address). The lack of data for a subclass of flavonoids within a country suggests several possibilities including 1) low consumption of foods containing that subclass(es), 2) analytical technology is not available, and 3) cost-benefit analysis has failed to raise the flavonoid subclass consumption-health promotion association to a sufficiently high priority. However, because of the apparent flavonoid-health benefit relationship, several countries are developing or expanding flavonoid and tannin food composition databases.


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  		TABLE 5 Estimates of flavonoid consumption in several countries1

 

   Flavonoid consumption
TOP
 ABSTRACT
 Nomenclature
 Flavonoid content of foods
 Flavonoid consumption
DISCUSSION
 LITERATURE CITED
 
Scientists have calculated flavonoid intakes of individuals for several countries (Table 5). Consumption of total flavonoids ranges from about 20 mg/d (United States, Denmark, Finland) to >70 mg/d (Holland). These values are considerably lower than earlier estimates (several hundred mg/d), which were based on limited analyses of only a few foods (43,44). Also contributing to the disagreement of consumption data may be the lack of comprehensive food composition data for one or more flavonoid subclasses (and all of the tannin subclasses) in the countries listed in Table 5.

From a health perspective, the consumption of selected subclasses of flavonoids may be more important than total flavonoid intake. Intakes of both flavones and flavonols were determined for the five countries listed in Table 5. In that regard, consumption of flavonoids in these two subclasses is lowest in Finland (~4 mg/d) and generally similar for the populations studied in Denmark, Japan, Holland and United States (16–32 mg/d). The similarity of intakes for occupants of these four developed countries is remarkable considering the wide divergence of populations and cultural habits. Only two countries calculated intakes of flavanones, those flavonoids common to citrus foods (Denmark and Finland). Both countries have similar intakes of 7–14 mg/d (Denmark) and 20 mg/d (Finland) (Table 5). Similarly, scientists have calculated intakes of flavan-3-ols only for the Dutch, and isoflavones for populations of three countries (Table 5). Although limited, these values provide estimates of flavonoid intakes primarily from tea (50 mg/d flavan-3-ols) and soy foods (<1–47 mg/d isoflavones).

Cultural dietary habits often dictate which foods are consumed and, in turn, the subclass(es) and amount of flavonoids that are ingested. For example, soy and soy foods are highly consumed in Japan and as a result, isoflavone consumption has been assessed and found to be higher than intakes of other flavonoid subclasses (Table 5). Cultural habits remain strong in terms of consumption of soy foods; Asians who have migrated to the U.S. still retain a relatively modest intake of isoflavones compared with residents of Japan and nonAsian residents of the U.S. (Table 5). Similarly, flavan-3-ol consumption has been determined in large populations in Holland because of the popularity of tea as a beverage in this country (37,45). The intake data (Table 5) reflect that these flavonoids are the most highly consumed subclass of those investigated in Holland. As food composition databases for food flavonoids and tannins are more fully developed, the completeness, accuracy and precision of the consumption data for these polyphenols also will improve.


   DISCUSSION
TOP
 ABSTRACT
 Nomenclature
 Flavonoid content of foods
 Flavonoid consumption
 DISCUSSION
LITERATURE CITED
 
Foods have many components other than traditional nutrients, e.g., protein, amino acids, vitamins, minerals, etc., many of which have been associated with biological activities consistent with reduced risk of several chronic diseases and other maladies (1–3). Two groups of these food components include flavonoids and tannins, which are large classes of polyphenols. Unlike traditional nutrients whose absence in the diet causes deficiency diseases, removal of flavonoids and tannins from diets fails to induce such abnormalities and is the primary reason these food components have not been classified as a vitamin(s) in the United States (46). In the case of traditional nutrients, dietary adequacy is established through manipulation of diets and menus using biomarkers and symptoms of the disease as endpoints. However, for chronic diseases, because of the long period (often decades) required for manifestation of symptoms and the lack of adequate animal models, epidemiologic studies have been a primary tool for making associations between consumption of food components and incidence of the disease (47). Such studies require extensive databases of values for the flavonoid and tannin content of foods consumed by the population of interest. Unlike traditional nutrients, for which such databases were developed after the nutrient was classified as essential, accurate and extensive food composition databases are needed to improve the accuracy and precision of the prediction of relationships between consumption of these nonessential nutrients and incidence of chronic disease(s).

In many countries, teas provide rich dietary sources of flavan-3-ols, flavonols and derived tannins, yet databases of values for some of these components (derived trannins) are weak at best and in most cases nonexistent. Analysis of flavonoids and tannins of foods is difficult and time consuming (10,18). Relative to the derived tannins of teas, only recently has an analytical approach been agreed upon (48), and limited data generated employing this procedure (8). Improvement and completion of data in food composition databases for those teas commonly consumed in each country will provide the tools necessary to accurately assess the role of tea in the reduction of chronic disease risk and maintenance of health.


   FOOTNOTES
 
1 Presented as part of "The Third International Scientific Symposium on Tea and Human Health: Role of Flavonoids in the Diet," given at the United States Department of Agriculture, September 23, 2002. This conference was sponsored by the American Cancer Society, American College of Nutrition, American Health Foundation, American Society for Nutritional Sciences, Food and Agriculture Organization, and the Linus Pauling Institute at Oregon State University and was supported by a grant from the Tea Council of the U.S.A. Guest editor for this symposium was Jeffrey Blumberg, PhD, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA 02111. Back


   LITERATURE CITED
TOP
 ABSTRACT
 Nomenclature
 Flavonoid content of foods
 Flavonoid consumption
 DISCUSSION
 LITERATURE CITED
 

1. Beecher, G. R. (1999) Phytonutrients’ role in metabolism: effects on resistance to degenerative processes. Nutr. Rev. 9(Part II):S3-S6.

2. Hines, E. (1999) New nutritive substances: beyond the ABCs. Food Quality 6:39-43.

3. Rhodes, M. & Price, K. R. (1999) Phytochemicals: classification and occurrence. Sadler, M. J. Strain, J. J. Caballero, B. eds. Encyclopedia of Human Nutrition 1999:1539-1549 Academic Press/Harcourt Brace & Company Publishers New York, NY. .

4. Thompson, L. U. (1993) Potential health benefits and problems associated with antinutrients in foods. Food Res. Intnl. 26:131-149.

5. Berg, P. A. & Daniel, P. T. (1988) Effects of flavonoid compounds on the immune response. Cody, V. Middleton, E., Jr Harborne, J. B. Beretz, A. eds. Plant Flavonoids in Biology and Medicine II: Biochemical, Cellular, and Medicinal Properties 1988:157-171 Alan R. Liss, Inc. New York, NY. .

6. Middleton, E., Jr & Kandaswami, C. (1993) The impact of plant flavonoids on mammalian biology: implications for immunity, inflammation and cancer. Harborne, J. B. eds. The Flavonoids. Advances in Research since 1986 1993:619-652 Chapman & Hall London, UK. .

7. Clifford, M. (2001) A nomenclature for phenols with special reference to tea. Crit. Rev. Food Sci. Nutr. 41(Suppl.):393-397.

8. Anonynmous (2003) USDA database for the flavonoid content of selected foods—2003 http://www.nal.usda.gov/fnic/foodcomp/Data/Flav/flav.html. Accessed March 26, 2003.

9. Anonynmous (2002) USDA-Iowa State University database on the isoflavone content of foods, release 1.3–2002 http://www.nal.usda.gov/fnic/foodcomp/Data/isoflav.isoflav.html. Accessed July 14, 2003.

10. Merken, H. M. & Beecher, G. R. (2000) Measurement of food flavonoids by high-performance liquid chromatography: a review. J. Agric. Food. Chem. 48:577-599.[Medline]

11. Harborne, J. B. & Williams, C. A. (2000) Advances in flavonoid research since 1992. Phytochem. 55:481-504.

12. Haslam, E. (1998) Practical Polyphenolics: From Structure to Molecular Recognition and Physiological Action 1998:438 Cambridge University Press Cambridge, UK.

13. Porter, L. J. (1993) Flavans and proanthocyanidins. Harborne, J. B. eds. The Flavonoids. Advances in Research since 1986 1993:23-55 Chapman & Hall London, UK. .

14. Gu, L., Kelm, M. A., Hammerstone, J. F., Beecher, G., Holden, J., Haytowitz, D. & Prior, R. L. (2003) Screening foods containing proanthocyanidins and their structural characterization using LC-MS/MS and thiolytic degradation. J. Agric. Food Chem. (In press).

15. Hammerstone, J. F., Lazarus, S. A. & Schmitz, H. H. (2000) Procyanidin content and variation in some commonly consumed foods. J. Nutr. 130(Suppl):2086S-2092S.[Abstract/Free Full Text]

16. Prior, R. L., Lazarus, S. A., Cao, G., Muccitelli, H. & Hammerstone, J. F. (2001) Identification of procyanidins and anthocyanidins in blueberries and cranberries (Vaccinium Spp.) using high-performance liquid chromaotography/mass spectrometry. J. Agric. Food Chem. 49:1270-1276.[Medline]

17. Gu, L., Kelm, M. A., Hammerstone, J. F., Beecher, G. R., Holden, J. M., Haytowitz, D. & Prior, R. L. () Analysis of ologomeric and polymeric procyanidins in nuts by normal phase HPLC-MS with fluorescent detection. J. Agric. Food Chem. (In press).

18. Finger, A., Kuhr, S. & Engelhardt, U. H. (1992) Chromatography of tea constituents. J. Chromatogr. 624:293-315.[Medline]

19. Bailey, R. G., Nursten, H. E. & McDowell, I. (1992) The isolation and analysis of a polymeric thearubigin fraction from black tea. J. Sci. Food Agric. 59:365-375.

20. Riemersma, R. A., Rice-Evans, C. A., Tyrell, R. M., Clifford, M. N. & Lean, M. E. (2001) Tea flavonoids and cardiovascular health. Q. J. M. 94:277-282.

21. Kris-Etherton, P. M. & Keen, C. L. (2002) Evidence that the antioxidant flavonoids in tea and cocoa are beneficial for cardiovascular health. Curr. Opinion Lipidology 13:41-49.[Medline]

22. Hakim, I. A., Alsaif, M. A., Alduwaihy, M., Al-Rubeaan, K., Al-Nuaim, A. R. & Al-Attas, O. S. (2003) Tea consumption and the prevalence of coronary heart disease in Saudi adults: results from a Saudi national study. Prev. Med. 36:64-70.[Medline]

23. Okuda, T., Yoshida, T. & Hatano, T. (1993) Review article number 73. Classification of ologomeric hydrolysable tannin and specificity of their occurrence in plants. Phytochemistry 32:507-521.

24. Waterhouse, A. L. (2002) Wine phenolics. Ann. N. Y. Acad. Sci. 957:21-36.[Medline]

25. Gu, L., Kelm, M. A., Hammerstone, J. F., Beecher, G. R., Cunningham, D., Vannozzi, S. & Prior, R. L. (2002) Fractionation of polymeric procyanidins from lowbush blueberry and quantification of procyanidins in selected foods with an optimized normal-phase HPLC-MS fluorescent detection method. J. Agric. Food Chem. 50:4852-4860.[Medline]

26. Foo, L. Y., Lu, Y., Howell, A. B. & Vorsa, N. (2000) The structure of cranberry proanthocyanidins which inhibit adherence of uropathogenic P-fimbriated Escherichia coli in vitro. Phytochemistry 54:173-181.[Medline]

27. Foo, L. Y., Lu, Y., Howell, A. B. & Vorsa, N. (2000) A-type proanthocyanidin trimers from cranberry that inhibit adherence of uropathogenic P-fimbriated Escherichia coli. J. Nat. Prod. 63:1225-1228.[Medline]

28. Karim, M., McCormick, K. C. & Kappagoda, T. (2000) Effects of cocoa extracts on endothelium dependent relaxation. J. Nutr. 130(Suppl):2105S-2108S.[Abstract/Free Full Text]

29. Schrewe, T., Sadik, C., Klotz, L-O., Yoshimoto, T., Kühn, H. & Sies, H. (2001) Polyphenols of cocoa: inhibition of mammalian 15-lipoxygenase. Biol. Chem. 382:1687-1696.[Medline]

30. Herrmann, K. (1976) Flavonols and flavones in food plants: a review. J. Food Technol. 11:433-448.

31. Price, K. R., Bacon, J. R. & Rhodes, M.J.C. (1997) Effect of storage and domestic processing on the content and composition of flavonol glucosides in onion (Allium cepa). J. Agric. Food Chem. 45:938-942.

32. Price, K. R., Casuscelli, R., Calquhoun, I. J. & Rhodes, M.J.C. (1998) Composition and content of flavonol glycosides in broccoli florets (Brassica olearacea) and their fate during cooking. J. Sci. Food Agric. 77:468-472.

33. Price, K. R., Colquhoun, I. J., Barnes, K. A. & Rhodes, M.J.C. (1998) Composition and content of flavonol glycosides in green beans and their fate during processing. J. Agric. Food Chem. 46:4898-4903.

34. Dragsted, L. O., Strube, M. & Leth, T. (1997) Dietary levels of plant phenols and other non-nutritive components: could they prevent cancer?. Eur. J. Can. Prevention 6:522-528.

35. Kneht, P., Kumpulainen, J., Järvinen, R., Rissanen, H., Heliövaara, M., Reunanen, A., Hakulinen, T. & Aromaa, A. (2002) Flavonoid intake and risk of chronic diseases. Am. J. Clin, Nutr. 76:560-568.[Abstract/Free Full Text]

36. Hertog, M. G., Hollman, P.C.H., Katan, M. B. & Kromhout, D. (1993) Intake of potentially anticarcinogenic flavonoids and their determinants in adults in The Netherlands. Nutr. Cancer 20:21-29.[Medline]

37. Arts, I. C., Hollman, P.C.H., Feskens, E. J., Bueno de Mesquita, H. B. & Kromhout, D. (2001) Catechin intake and associated dietary and lifestyle factors in a representative sample of Dutch men and women. Eur. J. Clin. Nutr. 55:76-81.[Medline]

38. Boker, L. K., Van der Schouw, Y. T., De Kleijn, M. J., Jacques, P. F., Grobbee, D. E. & Peeters, P. H. (2002) Intake of dietary phytoestrogens by Dutch women. J. Nutr. 132:1319-1328.[Abstract/Free Full Text]

39. Arai, Y., Watanabe, S., Kimira, M., Shimoi, K., Mochizuki, R. & Kinae, N. (2000) Dietary intakes of flavonols, flavones, and isoflavones by Japanese women and the inverse correlation between quercetin intake and plasma LDL cholesterol concentration. J. Nutr. 130:2243-2250.[Abstract/Free Full Text]

40. Sampson, L., Rimm, E., Hollman, P.C.H., de Vries, J.H.M. & Katan, M. B. (2002) Flavonol and flavone intakes in US health professionals. J. Am. Dietet. Assoc. 102:1414-1420.[Medline]

41. de Kleijn, M. J., van der Schouw, M. J., Wilson, P. W., Adlercreutz, H., Mazur, W., Grobbee, D. E. & Jacques, P. F. (2001) Intake of dietary phytoestrogens is low in postmenopausal women in the United States: the Framingham study(1–4). J. Nutr. 131:1826-1832.[Abstract/Free Full Text]

42. Wu, A. H., Wan, P., Ahankin, J., Tseng, C. C., Yu, M. C. & Pike, M. C. (2002) Adolescent and adult soy intake and risk of breast cancer in Asian-Americans. Carcinogenesis 23:1491-1496.[Abstract/Free Full Text]

43. Kühnau, J. (1976) The flavonoids: a class of semi-essential food components: their role in human nutrition. World Rev. Nutr. Diet. 24:117-191.[Medline]

44. Scalbert, A. & Williamson, G. (2000) Dietary intake and bioavailability of polyphenols. J. Nutr. 130:2073S-2085S.[Abstract/Free Full Text]

45. Arts, I. C., Hollman, P.C.H., Feskens, E. J., Bueno de Mesquita, H. B. & Kromhout, D. (2001) Catechin intake might explain the inverse relation between tea consumption and ischemic heart disease: the Zutphen Elderly Study. Am J. Clin. Nutr. 74:227-232.[Abstract/Free Full Text]

46. Vickery, H. B., Nelson, E. M., Almquist, H. J. & Elvehjem, C. A. (1950) Term "Vitamin P" recommended to be discontinued. Science 112:628.[Free Full Text]

47. ILSI North America Technical Committee on Food Components for Health Promotion Scientific criteria for evaluating health effects of food components. Crit. Rev. Food Sci. Nutr. 42(Suppl):651-676.

48. Wiseman, S., Waterhouse, A. & Korver, O. (2001) The health effects of tea and tea components: opportunities for standardizing research methods. Crit. Rev. Food Sci. Nutr. 41:387S-412S.




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