Related entry: Galla.—Nutgall
The bark of Quercus alba, Linné.
COMMON NAME: Oak bark.
ILLUSTRATIONS: White oak and others in Bentley and Trimen's Medical Plants, 248, 250, 251.
Botanical Source.—Quercus alba is a forest tree, varying in size according to the climate and the soil, attaining the height of from 60 to 90 feet, with a diameter of 3 to 6 feet. It is covered with a whitish bark, often interspersed with dark spots. The leaves are oblong, pinnatifid, sinuate, smooth, bright-green above, pale or glaucous beneath, dilated above, and obliquely divided into from 3 to 5 lobes, which are oblong, or linear, obtuse, mostly entire, and sometimes tapering at their base. The flowers are monoecious and amentaceous. Cup hemispherical, naked, much shorter than the acorn, deep, and tuberculate. Acorns are large, ovate, coriaceous, 1-celled, 1-seeded, surrounded at base by the cup, and are solitary, or borne in pairs upon long peduncles (W.—G.).
History and Description.—Quercus is a very extensive and valuable genus, consisting of many species, a large proportion of which grow in the United States. Their usual character is that of astringents, and the one above described, also Quercus rubra and Quercus tinctoria, are those which have been more particularly employed in medicine. The bark of the tree is the official portion. White oak grows throughout the Union, but is more abundant in the middle states. Its wood is strong and durable, and is extensively employed in ship-building, cooperage, carriage-making, etc. (W.). Tanners occasionally make use of its bark, but that of the Q. rubra, Linné (Red oak), Q. tinctoria, Bartram (Black oak), Q. coccinea, Wangenheim (Scarlet oak), and Q. elongata, Willdenow, are commonly used. White-oak bark is the one chiefly used in medicine. Its epidermis contains no astringency and should, therefore, be removed. The bark thus prepared is of a pale-brownish color, faintly odorous, very astringent, with a slight bitterness, tough, breaking with a stringy or fibrous fracture, and not readily powdered. Its astringency is imparted to water or alcohol. The best time for gathering the bark is in the spring, when it contains the most tannic acid.
The bark of Quercus alba is described by the U. S. P. as "in nearly flat pieces, deprived of the corky layer, about 5 Mm. (1/5 inch) thick; pale-brown; inner surface with short, sharp, longitudinal ridges; tough; of a coarse, fibrous fracture, a faint, tan-like odor, and a strongly astringent taste. As met with in the shops, it is usually an irregularly coarse, fibrous powder, which does not tinge the saliva yellow"—(U. S. P.). The latter provision aims to exclude black oak (Quercus tinctoria). The bark of Quercus Robur, Linné, is official in the German Pharmacopoeia, and was official in the British Pharmacopoeia, 1885, but is excluded in the present edition (1898).
Chemical Composition.—In addition to the chief constituent, quercitannic acid, and its decomposition product, oak-red, oak bark contains terpene-resin, fat, wax, chlorophyll, bitter matter, ellagic and gallic acids; all of the latter substances are soluble in ether. Pectin, the carbohydrate laevulin (C6H10O5), and the sugar, quercit (C6H12O5), are also present. Quercitannic acid (C17H16O9, Etti, Amer. Jour. Pharm., 1884, p. 135; C28H28O14, water-soluble; and C28H26O11, much less soluble, Löwe, 1881) is not identical with gallotannic acid, and is an unstable substance, having a tendency to give off water, forming anhydrides, which are coloring matters (phlobaphenes), one of which is oak-red (C28H22O11). According to Prof. Trimble (The Tannins, Vol. II, p. 49), each species of oak has its characteristic phlobaphene, e.g., quercitrin is that which characterizes Quercus tinctoria. Prof. Trimble (loc. cit.) found the dried inner bark of white oak, collected in March, to contain 6.96 per cent of tannin, while a specimen of galls from leaves of the same species yielded 17.89 per cent. The highest percentage of oak-bark tannin recorded is 14.21, found in the bark of Quercus bicolor. (Also see investigation on the tannin of Quercus alba, by Prof. Henry Kraemer, Amer. Jour. Pharm., 1890, p. 236.)
Action, Medical Uses, and Dosage.—Oak bark is slightly tonic, powerfully astringent, and antiseptic. It is useful, internally in chronic diarrhoea, chronic mucous discharges, passive hemorrhages, and wherever an internal astringent is required. In colliquative sweats, the decoction is usually combined with lime-water. It is, however, more generally used in decoction, as an external agent, which forms an excellent gargle for relaxed uvula and sore throat, a good stimulating astringent lotion for ulcers with spongy granulations, and an astringent injection for leucorrhoea, prolapsus ani, hemorrhoids, etc. The ground bark, made into a poultice, has proved useful in gangrenous or mortified conditions. In sickly, debilitated children, and in severe diarrhoeas, especially when the result of fevers, the decoction, given internally, and used as a bath to the body and limbs, 2 or 3 times a day, will be found very efficient. When given for diarrhoea or dysentery, it should be combined with aromatics, and sometimes with castor oil. A bath is often advantageous in some cutaneous diseases. The green bark of elder and white oak bruised together, or in strong decoction, forms a very useful and valuable application to abrasions. Dose of the decoction, 1 to 2 fluid ounces; of the extract, from 5 to 20 grains. A coffee made from roasted acorns, has been highly recommended in the treatment of scrofula.
Specific Indications and Uses.—Relaxation of mucous membranes, with unhealthy discharge; ulcerations, with spongy granulations.
Related Species.—Quercus rubra, Linné, or Red oak, is a lofty, wide-spreading tree, attaining the height of about 70 feet, with a diameter of 3 or 4 feet. Leaves 6 to 10 inches in length, on long petioles, oblong, smooth on both sides, pale beneath, obtusely sinuate, with short and entire, or sparingly dentate, mucronate lobes, 4 to 6 on each side. Fructification biennial. Acorns oblong-ovoid, about an inch long, surrounded at base by a saucer-shaped, shallow, even cup, very much shorter than the acorn, of very small and close scales, and subsessile (G.—W.). Red oak is more common in the northern states and Canada; its wood is reddish and coarse-grained, and used principally for fuel. Its bark is extensively used in tanning. It contains considerable tannin, and is generally employed as an external agent. An extract of the bark, as well as the potash obtained from its ashes, were both formerly much employed as local applications in the treatment of cancer, indolent ulcers, etc. Prof. Scudder valued a combination of rumex, red-oak bark, and alnus, both locally and internally, in eczema, and obstinate scrofula, with "old ulcers, feeble tissues, and cicatrices."
Quercus tinctoria, Bartram (Q. velutina, Lamarck), Quercitron, or Black oak, is one of the loftiest trees in the forest, frequently attaining the height of 80 to 100 feet, with a diameter of 4 or 5 feet. Bark deeply furrowed, black or deep-brown. Leaves 6 to 8 inches long, obovate, oblong, more or less rusty-pubescent beneath, finally glabrous, slightly or sometimes deeply sinuate-lobed, with oblong, obtuse, mucronate, somewhat toothed lobes. Acorns brown, nearly spherical or depressed-globose, about one-half immersed in a deep, thick, flat, conspicuously scaly cup, which is subsessile. The leaves turn dark-red after frost (G.—W.). This species was regarded by Prof. Asa Gray as a variety of the Scarlet oak (Q. coccinea, Wangenheim.. Black oak is common to the United States; the bark of this forest tree is much used in tanning and for dyeing. It has a strong odor, a very bitter, styptic taste, and when masticated imparts a yellow tinge to the saliva (compare Quercus alba). It is seldom employed internally on account of its disposition to derange the bowels, but is valuable as an external astringent. It contains tannin, quercitrin, and quercetin. The dye-stuff, called quercitron, is the inner bark of this tree, and is much used in Europe as a yellow dye-stuff. Chevreul obtained therefrom the coloring principle, which he named quercitron; it has since been named quercitric acid (quercitrin), on account of its forming salts with bases. It is obtained by allowing a concentrated aqueous infusion or decoction to crystallize; the substance is purified by recrystallization from diluted alcohol. By another, method, the bark is exhausted with alcohol, and the tannin removed by means of a moistened animal membrane; after filtering, the alcohol is distilled, and the residue recrystallized. Quercitrin (C36H38O20, Liebermann and Hamburger, 1879; C21H22O12, J. Herzig, 1893) forms sulphur-yellow, microscopic plates, in aqueous or alcoholic solution of neutral reaction and faintly bitter taste. It is little soluble in ether and cold water (2485 parts), more soluble in hot water (143 parts; 425 parts by another statement). Soluble in 23 parts of cold, 3.9 parts of boiling alcohol, readily soluble in alkalies and aqua ammoniae. Neutral lead acetate precipitates it from solution. Its solution is colored dark-green by ferric chloride. It is a glucosid, being hydrolyzed, by boiling with diluted acids, into crystallizable quercetin (C24H16O11, Liebermann and Hamburger; C15H10O7, J. Herzig, 1891) and isodulcite (C6H14O6). Quercitrin, or similar principles, occurs also in the leaves and cotyledons of the horse-chestnut, in the leaves of the ash tree, in Rhus Coriaria, or sumach, in Sophora japonica (sophorin), Viola tricolor, Thuja occidentalis (thujin), etc. These all stand in close chemical relationship to one another (see Rud. Wachs, Amer. Jour. Pharm., 1894, p. 35; also see graphic formula of quercitrin given by J. Herzig, in Chem. Centralblatt, 1893, p 433). Quercetin is likewise frequently found in nature, e.g., in the horse-chestnut, in Podophyllum (which see), in the outer skin of the onion (Perkin and Hummel, 1893), in fustic wood (from Rhus cotinus), in the bark of the apple tree, in Gambier catechu (A. G. Perkin, Chem. Centralblatt, Vol. II, 1897, p. 1047), etc.
Quercus Robur, Linné, is the species official in the British Pharmacopoeia, 1885, the bark being collected in the spring time. Quercin, a neutral bitter principle, obtained from the European oak bark (Quercus Robur), by Gerber (1831), was probably impure quercite (see Quercus alba).
Quercus suber, Linné.—The Live oak, growing in the Mediterranean region, especially Algeria and Spain. Its suberous layer furnishes commercial cork. According to K. Kügler (Dissert.; see Amer. Jour. Pharm., 1884, p. 240; also Archiv der Pharm., 1884, pp. 217-230), air-dry cork leaves about 0.58 per cent of ash, one-fourth of which is manganese, and another fourth is lime. Chloroform extracts about 12.5 per cent of soluble matter, of which one-third consists of cerin (C20H32O) (not the cerotic acid or cerin of beeswax). It is imbedded in the cork-cells in the form of small prisms (Höhnel, 1877 ). Boiling alcohol now takes up from 5 to 6 per cent of tannin and phlobaphene (coloring matters due to altered tannin). Alcoholic caustic potash now dissolves the peculiar fat, suberin, which is saponifiable, upon heating the solvent, into glycerin (2.65 per cent) and fatty acids (30 per cent), the latter consisting of stearic and phellonic acids (C22H42O3); a little coniferin was also extracted and converted into vanillin. Water now extracted from the cork 8 per cent of humin compounds and left 22 per cent of cellulose. Gilson (1890; see Flückiger, Amer. Jour. Pharm., 1890, p. 367) finds that solution of sodium carbonate abstracts the coloring matter of cork, while it leaves suberin unaffected. The latter may then be extracted by a hot, 3 per cent alcoholic potash solution. By oxidation of cork with nitric acid, a mixture of acids, possessing a waxy appearance, is obtained (cerinic acid), from which suberic acid (C6H12[COOH]2) was isolated by Brugnatelli. The fat, suberin, should not be confounded with the cork, reduced to a fine powder, sold under the name suberin. This tree has been introduced into our southern states. Suberin has been used as a dusting powder for intertrigo, chapped surfaces, etc.
Quercus virens, Aiton, Live oak, and Quercus falcata, Michaux, Spanish oak, yield bark very rich in tannin.
Quercus agrifolia, Née; Quercus chrysolepsis, Liebman;and Quercus oblongifolius, Torrey, all of the Pacific slope, are known as Live oaks.
SEMEN QUERCUS, Acorns.—Contain fixed oil, volatile oil, bitter substance, starch (about 38 per cent), citric acid, uncrystallizable sugar, and a crystallizable sugar, called by Dessaignes (1851) quercit (C6H7[OH]5). Roasted acorns (Semen Quercus Tostum) were formerly used to check hemorrhage, and to cure scrofula and indigestion.