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Quercitannic acid is one of the two forms of tannic acid〔(L'Energie Homo-Hydrogne By Patricia Le Roux (French) )〕 found in oak bark and leaves.〔(''Quercus'' on www.henriettesherbal.com )〕 The other form is called gallotannic acid and is found in oak galls. The quercitannic acid molecule is also present in quercitron, a yellow dye obtained from the bark of the Eastern black oak (''Quercus velutina''), a forest tree indigenous in North America. It is described as a yellowish brown amorphous substance.〔(Quercitannic on everything2.com )〕 In 1838, Jöns Jacob Berzelius wrote that quercitannate is used to dissolve morphine.〔Traité de chimie, Volume 2. Jöns Jakob Berzelius (friherre) and Olof Gustaf Öngren, A. Wahlen et Cie., 1838〕 In 1865 in the fifth volume of "A dictionary of chemistry", Henry Watts wrote : It exhibits with ferric salts the same reactions as gallotannic acid. It differs however from the latter in not being convertible into gallic acid, and not yielding pyrogallic acid by dry distillation. It is precipitated by sulfuric acid in red flocks. (Stenhouse, Ann. Ch. Pharm. xlv. 16.) In 1880, Etti gave for it the molecular formula C17H16O9. He described it as an unstable substance, having a tendency to give off water to form anhydrides (called phlobaphenes), one of which is called ''oak-red'' (C34H30O17). For him, it was not a glycoside.〔Über die Gerbsäure der Eichenrinde. C. Etti, Monatshefte für Chemie, Volume 1, Number 1, 262-278, 1880 (German)〕〔Zur Geschichte der Eichenrindegerbsäuren. C. Etti, Monatshefte für Chemie, Volume 4, Number 1, 512-530, 1883 (German)〕 In Allen’s "Commercial Organic Analysis", published in 1912, the formula given was C19H16O10.〔The nature of tea infusions. Henry L. Smith, The Lancet, Volume 181, Issue 4673, 22 March 1913, Page 846, 〕 Other authors gave other molecular formulas like C28H26O15, while another formula found is C28H24O11.〔(What are the historic and contemporary ethnobotanical uses of native Rhode Island wetlands plants? by Courtney Reckford, 1997 )〕 According to Lowe, two forms of the principle exist – one soluble in water, of the formula C28H28O14, and the other scarcely soluble, C28H24O12. Both are changed by the loss of water into oak red, C28H22O11.〔(A manual of organic materia medica and pharmacognosy - An introduction to the study of the vegetable Kingdom and the vegetable and animal drugs (Sayre's Materia Medica) fourth edition , by Lucius E Sayre )〕 Quercitannic acid was for a time a standard used to assess the phenolic content in spices, given as ''quercitannic acid equivalent''.〔Government standards for spices. Journal of the American Pharmaceutical Association, Volume 12, Issue 12, pages 1091–1094, December 1923, 〕 ==References== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Quercitannic acid」の詳細全文を読む スポンサード リンク
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