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Quercetin is a crystalline powder of a brilliant citron yellow color, entirely insoluble in cold water and dissolving only sparingly in hot water, but quite soluble in alcohol. Either by itself or in some form of its glucoside quercitrin, quercetin is found in several vegetable substances, among others in cutch, in Persian berries (Rhamnus catharticus), buckwheat leaves (Fagopyrum esculentum), Zante fustic wood (Rhus cotinus), and in rose petals. Quercitron was first introduced as yellow dye in 1775, but it is principally used in the form of flavin, which is the precipitate from a boiling decoction of quercitron and sulfuric acid. Chemically, quercetin is a member of a fairly extensive class of natural coloring matters derived from phenyl benzoyl-pyrone or flavone, the constitution of which followed on the researches of St von Kostanecki, A. G. Perkin, Herzig, Goldschmidt and others. Among the related, coloring matters are: chrysin from poplar buds, apigenin from parsley, luteolin from weld and dyers broom, fisetin from young fustic and yellow cypress, galangin from galanga root, and myricetin from Nageia nagi.