Studies of polymer polyphenols in tea

Kuhr, Susanne; Herzig, Birgit; Engelhardt, Ulrich H.

doi:10.1007/bf01192944

Cited by 10 publications

(3 citation statements)

References 20 publications

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“…Bailey et al (1994a) found that an anthocyanidin is present in group I pigments. Kuhr et al (1994) detected anthocyanidins in a hydrolysate of TR obtained by ultrafiltration. Liberated anthocyanidins from proanthocyanidin-like polymers could account for the purple color in strong acidic solutions.…”

Section: Resultsmentioning

confidence: 99%

Isolation of Black Tea Pigments Using High-Speed Countercurrent Chromatography and Studies on Properties of Black Tea Polymers

Degenhardt

Engelhardt

Wendt

et al. 2000

J. Agric. Food Chem.

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Isolation of theaflavins and epitheaflavic acids from black tea using high-speed countercurrent chromatography (HSCCC) on a preparative scale is demonstrated. HSCCC also enabled the isolation of a polymeric fraction from black tea. According to Roberts' classification, the polymeric fraction mainly consisted of SII thearubigins (TR). HPLC analysis showed that the isolated material is free of any known chromatographically resolved tea constituents and eluted from reversed-phase packings as a convex "hump" (a broad signal). The antioxidant activity of the TR fraction was 3.6 mmol of Trolox equivalents per gram. The total phenolic content of this fraction was determined to be 34.7 g/100 g (as gallic acid equivalents).

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Section: Resultsmentioning

confidence: 99%

Isolation of Black Tea Pigments Using High-Speed Countercurrent Chromatography and Studies on Properties of Black Tea Polymers

Degenhardt

Engelhardt

Wendt

et al. 2000

J. Agric. Food Chem.

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“…Flavones occur mainly as 7‐ O ‐glycososides, but C ‐glycosides (the sugar is directly attached to an aromatic carbon atom) are also known. Comparatively few data are available for the flavone‐ C ‐glycosides, although they occur in teas18, 19 and cereals 20–22 . D ‐Glucose is the most frequent sugar; other sugar residues found are D ‐galactose, L ‐rhamnose, L ‐arabinose, D ‐xylose and D ‐apiose, but also D ‐glucuronic acid.…”

Section: Occurrencementioning

confidence: 99%

Flavonols, flavones and flavanols - nature, occurrence and dietary burden

Hollman

Arts

2000

J. Sci. Food Agric.

468

250

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Total flavonol and flavone contents of foods have been determined with validated state‐of‐the‐art methods. Quercetin dominates, and flavonol levels found in vegetables and fruits are below 10 mg kg−1. However, high concentrations are found in onions (300 mg kg−1), kale (450 mg kg−1), broccoli (100 mg kg−1), beans (50 mg kg−1), apples (50 mg kg−1), blackcurrants (40 mg kg−1), and tea (30 mg l−1). The dietary intake of flavonols varies 10‐fold between countries (6–60 mg day−1). Flavones are of minor importance in the diet. Tea, wine and fruits are the most important sources of flavanols, but there are gaps in our knowledge on flavanol levels of many foods. The absorption of dietary quercetin glycosides in humans ranges from 20 to 50%. The sugar moiety is an important determinant of the bioavailability of flavonols. The presence of a glucose moiety significantly enhances absorption. The extent of absorption of flavanols in humans seems similar to that of flavonols but has been little studied. Flavonols and flavanols are extensively metabolised, as only 1–2% of them are excreted with an intact flavonoid backbone. Hepatic biotransformations include glucuronidation and sulphatation of the phenolic hydroxyls and O‐methylation of catechol groups. Bacteria of the colon cleave the C‐ring of the flavonoid nucleus to phenolic acids which are subsequently absorbed. Apart from conjugates, virtually no metabolites have been characterised in humans. Absorption of flavanols is rather fast, with times to reach peak values between 0.5 and 4 h. Flavanols are rapidly excreted, with elimination half‐lives of 1–6 h. Quercetin glycosides show rapid to slow absorption; peak values are reached between < 0.5 and 9 h. The type of glycoside determines the rate of absorption. Excretion of quercetin glycosides is slow: elimination half‐lives are 24 h, independent of the type of glycoside. Analytical data for flavanols in foods are needed. Tea, as an important dietary source, has to be studied. Research on the bioavailability of flavonols and flavanols has to be expanded. Attention is needed for the identification and quantification of their metabolites in body fluids. © 2000 Society of Chemical Industry

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“…Thearubigins have been claimed to be the most abundant polyphenolic fraction of black tea (2). They contribute to taste, depth of color, and body of a tea brew, and thus influence the quality as evaluated by tea tasters (3). Theaflavins are benzotropolone compounds of known structure; they have been synthesized by chemical oxidation, but a detailed examination of the oxidation products of green tea polyphenolics has not been carried out as yet.…”

Section: Introductionmentioning

confidence: 99%