102. Quercus, N.F.—White oak.
DESCRIPTION OF DRUG.—Flat pieces about 6 mm. (1/4 in.) thick, deprived of the thick, corky layer; pale brown; coarsely fibrous; inner surface traversed by prominent longitudinal ridges; fracture coarse, fibrous (the tissue contains groups of stone cells and crystals of calcium oxalate); odor faintly tan-like; taste very astringent. It is usually found in the shops as a coarse, fibrous powder.
Powder.—Pale brown. Characteristic elements: Parenchyma of cortex, rather thin-walled, pale brownish rosy hue, some with brown resin or irregular brownish-yellow tannin masses; calcium oxalate, aggregate or prisms (10 to 20 µ in diam.); sclerenchyma with stone cells (25 to 40 µ in diam.), thick-walled; bast fibers 15 to 30 A thick, long, rather large, thick-walled; crystal fibers with aggregate and prismatic crystals of calcium oxalate (10 to 20 µ in diam.); cork cells, pentagonal or hexagonal (20 to 30 µ in diam.).
CONSTITUENTS.—Quercitannic acid 6 to 11 per cent., a coloring matter, a bitter principle (quercin), sugar (quercite), resin, etc. The active principles are soluble in water and alcohol. The amount of tannin varies with the species, the part of the tree, and the season of the year when gathered; the young bark contains a greater proportion than the old.
Quercitannic Acid.—Two forms of this principle exist, according to Lowe - 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.
Quercitron.—Under this name large quantities of black oak (Quercus tinctoria) bark deprived of its epidermis and reduced to a coarse powder are sent from the United States to Europe as a dye. The coloring principle is called quercitron, C36H38O30. This glucoside splits up by hydrolysis into quercetin and isodulcite, or rhammose, C6H12O5.C5H9O5.H3). Quercetron (Xantho rhamnin) forms yellowish crystals, odorless and tasteless, but in hot aqueous or alcoholic solution has a bitter taste.
Preparation of Quercin.—Boil bark in acidulated (H2SO4) water; add milk of lime to neutralize; filter; add K2CO3. Yellow needles slowly form on evaporation of alcoholic solution of above precipitate.
ACTION AND USES—Astringent and tonic, generally used externally in infusion or decoction as an astringent and tonic bath, injection, etc. Dose: 15 to 60 gr. (1 to 4 Gm.). Fluidextractum Quercus, average dose 2 mils.