The most abundant polyphenols are the condensed tannins, found in virtually all families of plants, and comprising up to 50\% of the dry weight of leaves. Tannins of tropical woods tend to be of a cathetic nature rather than of the gallic type present in temperate woods.  Tannin in Tropical Woods  . Doat J, Bois. For Tmp., 1978, volume 182, pages 34–37 Tannins are classified as ergastic substances, i.e., non-protoplasm materials found in cells. Tannins, by definition, precipitate proteins. In this condition, they must be stored in organelles able to withstand the protein precipitation process. Idioblasts are isolated plant cells which differ from neighboring tissues and contain non-living substances. They have various functions such as storage of reserves, excretory materials, pigments, and minerals. They could contain oil, latex, gum, resin or pigments etc. They also can contain tannins. In Japanese persimmon (Diospyros kaki) fruits, tannin is accumulated in the vacuole of tannin cells, which are idioblasts of parenchyma cells in the flesh.  Identification of Molecular Markers Linked to the Trait of Natural Astringency Loss of Japanese Persimmon (Diospyros kaki) Fruit  . Shinya Kanzaki, Keizo Yonemori and Akira Sugiura, J. Am. Soc. Hort. Sci., 2001, 126(1), pages 51–55 (article ) Ferric chloride test Use of ferric chloride (FeCl3) tests for phenolics in general. Powdered plant leaves of the test plant (1.0 g) are weighed into a beaker and 10 ml of distilled water are added. The mixture is boiled for five minutes. Two drops of 5\% FeCl3 are then added. Production of a greenish precipitate is an indication of the presence of tannins."Antibacterial activity of leave extracts of Nymphaea lotus (Nymphaeaceae) on Methicillin resistant Staphylococcus aureus (MRSA) and Vancomycin resistant Staphylococcus aureus (VRSA) isolated from clinical samples". Akinjogunla O. J., Yah C. S., Eghafona N. O. and Ogbemudia F. O., Annals of Biological Research, 2010, 1 (2), pages 174–184 Alternatively, a portion of the water extract is diluted with distilled water in a ratio of 1:4 and few drops of 10\% ferric chloride solution is added. A blue or green color indicates the presence of tannins (Evans, 1989)."Phytochemical Analysis and Antimicrobial Activity Of Scoparia dulcis and Nymphaea lotus". Jonathan Yisa, Australian Journal of Basic and Applied Sciences, 2009, 3(4): pages 3975–3979 Other methods The hide-powder method is used in tannin analysis for leather tannin and the Stiasny method for wood adhesives.  Tannin analysis of Acacia mearnsii bark - a comparison of the hide-powder and Stiasny methods  . Zheng G.C., Lin Y.L. and Yazaki Y., ACIAR Proceedings Series, 1991, No. 35, pages 128–131 (abstract )Study on Fast Determination Content of Condensed Tannin Using Stiasny Method. Chen Xiangming, Chen Heru and Li Weibin, Guangdong Chemical Industry, 2006-07 (abstract ) Statistical analysis reveals that there is no significant relationship between the results from the hide-powder and the Stiasny methods.Leather Chemists' Pocket-Book: A Short Compendium of Analytical Methods. Henry Richardson Procter, Edmund Stiasny and Harold Brumwel, E. & F.N. Spon, Limited, 1912–223 pages (book at Internet Archive ) Nuts Nuts vary in the amount of tannins they contain. Some species of acorns of oak contain large amounts. For example, acorns of Quercus robur and Quercus petraea in Poland were found to contain 2.43-5.17\% and 2.57-4.75 \% tannins as a proportion of dry matter, but the tannins can be removed by leaching in water so that the acorns become edible. Other nuts - such as hazelnuts, walnuts, pecans, and almonds - contain lower amounts. Tannin concentration in the crude extract of these nuts did not directly translate to the same relationships for the condensed fraction. Principal human dietary sources of tannins are tea and coffee. Most wines aged in charred oak barrels possess tannins absorbed from the wood. Soils high in clay also contribute to tannins in wine grapes.Oz Clarke Encyclopedia of Grapes pg 155–162 Harcourt Books 2001 This concentration gives wine its signature astringency.
The most abundant polyphenols are the condensed tannins, found in virtually all families of plants, and comprising up to 50\% of the dry weight of leaves. Tannins of tropical woods tend to be of a cathetic nature rather than of the gallic type present in temperate woods. " Tannin in Tropical Woods " . Doat J, Bois. For Tmp., 1978, volume 182, pp. 34–37 Tannins are classified as ergastic substances, i.e., non-protoplasm materials found in cells. Tannins, by definition, precipitate proteins. In this condition, they must be stored in organelles able to withstand the protein precipitation process. Idioblasts are isolated plant cells which differ from neighboring tissues and contain non-living substances. They have various functions such as storage of reserves, excretory materials, pigments, and minerals. They could contain oil, latex, gum, resin or pigments etc. They also can contain tannins. In Japanese persimmon (Diospyros kaki) fruits, tannin is accumulated in the vacuole of tannin cells, which are idioblasts of parenchyma cells in the flesh. " Identification of Molecular Markers Linked to the Trait of Natural Astringency Loss of Japanese Persimmon (Diospyros kaki) Fruit " . Shinya Kanzaki, Keizo Yonemori and Akira Sugiura, J. Am. Soc. Hort. Sci., 2001, 126(1), pp. 51–55 (article ) Ferric chloride test Use of ferric chloride (FeCl3) tests for phenolics in general. Powdered plant leaves of the test plant (1.0 g) are weighed into a beaker and 10 ml of distilled water are added. The mixture is boiled for five minutes. Two drops of 5\% FeCl3 are then added. Production of a greenish precipitate is an indication of the presence of tannins."Antibacterial activity of leave extracts of Nymphaea lotus (Nymphaeaceae) on Methicillin resistant Staphylococcus aureus (MRSA) and Vancomycin resistant Staphylococcus aureus (VRSA) isolated from clinical samples". Akinjogunla O. J., Yah C. S., Eghafona N. O. and Ogbemudia F. O., Annals of Biological Research, 2010, 1 (2), pages 174–184 Alternatively, a portion of the water extract is diluted with distilled water in a ratio of 1:4 and few drops of 10\% ferric chloride solution is added. A blue or green color indicates the presence of tannins (Evans, 1989)."Phytochemical Analysis and Antimicrobial Activity Of Scoparia dulcis and Nymphaea lotus". Jonathan Yisa, Australian Journal of Basic and Applied Sciences, 2009, 3(4): pp. 3975–3979 Other methods The hide-powder method is used in tannin analysis for leather tannin and the Stiasny method for wood adhesives. " Tannin analysis of Acacia mearnsii bark – a comparison of the hide-powder and Stiasny methods " . Zheng G.C., Lin Y.L. and Yazaki Y., ACIAR Proceedings Series, 1991, No. 35, pp. 128–131 (abstract )Study on Fast Determination Content of Condensed Tannin Using Stiasny Method. Chen Xiangming, Chen Heru and Li Weibin, Guangdong Chemical Industry, 2006-07 (abstract ) Statistical analysis reveals that there is no significant relationship between the results from the hide-powder and the Stiasny methods.Leather Chemists' Pocket-Book: A Short Compendium of Analytical Methods. Henry Richardson Procter, Edmund Stiasny and Harold Brumwel, E. & F.N. Spon, Limited, 1912–223 pages (book at Internet Archive ) Nuts Nuts vary in the amount of tannins they contain. Some species of acorns of oak contain large amounts. For example, acorns of Quercus robur and Quercus petraea in Poland were found to contain 2.4–5.2\% and 2.6–4.8 \% tannins as a proportion of dry matter, but the tannins can be removed by leaching in water so that the acorns become edible. Other nuts – such as hazelnuts, walnuts, pecans, and almonds – contain lower amounts. Tannin concentration in the crude extract of these nuts did not directly translate to the same relationships for the condensed fraction. Principal human dietary sources of tannins are tea and coffee. Most wines aged in charred oak barrels possess tannins absorbed from the wood. Soils high in clay also contribute to tannins in wine grapes.Oz Clarke Encyclopedia of Grapes pp. 155–162 Harcourt Books 2001 This concentration gives wine its signature astringency.
A
"
A
"
R
pages
pp.
A
"
A
"
R
pages
pp.
R
pages
pp.
A
"
R
-
–
A
"
R
pages
pp.
R
2.43-5.17\% and 2.57-4.75
2.4–5.2\% and 2.6–4.8
R
-
–
R
-
–
R
pg
pp.