Coto Bark.—In the years 1873 and 1874 a bark bearing this name appeared in the London drug market, coming from Bolivia. Its botanical origin still remains unknown. Under the name of coto-coto, the bark of a rubiaceous plant (Palicourea densiflora. is employed in Brazil in rheumatism. Whether this be the Bolivian plant or not is uncertain. (See also Paracoto).
Coto bark occurs in pieces 3 dm. or more long, from 3 to 6 cm. wide, and from 5 to 15 mm. thick. The outer surface is irregular, often looking as though it had been shaved or split off, and in other parts covered with a fine adherent corky layer free from lichens; the inner surface also ia irregular, with numerous rather closely placed, longitudinal projecting bark bundles.
The general color approaches cinnamon-brown; upon fresh cross-section the bark is seen to be filled with yellowish spots, except in the outer portions. The odor is aromatic, and much more apparent if bruised; the taste hot, and somewhat aromatic; the powder is very pungent to the nostrils. The microscope shows the outer bark to be composed of thin-walled, colorless, parenchymatous cells, containing starch granules, with numerous yellowish sclerenchymatous cells joined into groups. The inner bark contains numerous yellow bark cells, mostly joined into bundles of from twenty to fifty. For microscopic structure, see P. J., vi, 301, also Ph. Era, May, 1888. The coto bark which we have seen in the American market conforms with the original description, but other barks are said to pass under the name. The most important of these is the so-called Paracoto bark, which is stated to differ from the true coto bark chiefly in its having a less pungent but more agreeably spicy taste, and being marked with deep whitish furrows upon its surface. Wittstein found in coto bark a volatile alkaloid, a pungent aromatic volatile oil, yellowish-brown soft resin, brown hard resin, starch, gum, sugar, calcium oxalate, tannin, and formic, butyric, and acetic acids. (A. Pharm., iii, 4, 219.) Jobst and Hesse obtained a crystallizable body, cotoin, from true coto bark, by making an ethereal extract from the powdered bark, treating this with warm petroleum benzin, and allowing the mixture to stand until clear. The clear liquid yields cotoin in crystals on spontaneous evaporation. The oily resinous residue contains considerable cotoin, which may be obtained by boiling with milk of lime and adding to the solution hydrochloric acid. After twenty-four hours the clear liquid will be found studded with large, glistening, laminated crystals of cotoin, of a pale yellow color. Cotoin (methyl-trioxy-benzophenone), C14H12O4, is sparingly soluble in cold water, more soluble in hot water, insoluble in petroleum benzin, very soluble in alcohol, chloroform, benzol, acetone, and carbon disulphide. Nitric acid becomes blood-red in contact with cotoin, sulphuric acid is colored brownish-yellow, and ferric chloride blackens a dilute solution of cotoin. O. Hesse described a coto bark which did not contain cotoin but cotellin, C20H20O6. (Ph. Ztg., 1905, 845.)
Paracotoin, C12H8O4, is extracted from paracoto bark, in which it exists associated with hydrocotoin, C15H14O4, protocotoin, C16H14O6, methyl-hydrocotoin, C16H16O4, and methylprotocotoin, C34H32O10. Paracotoin may be distinguished from cotoin by giving no reaction with ferric chloride. Piperonylic acid (methyleneprotocatechuic acid), C8H6O4, is present in both barks.
Coto bark is decidedly irritating: its powder, rubbed upon the skin, is said to produce heat and redness, and, according to Burkart, fifteen grains (1.0 Gm.) taken into the stomach produce persistent burning pain, followed by repeated vomiting. The remedy was first introduced as serviceable in diarrhea, and seems to have established its reputation. Although observers are not explicit upon this point, it is evident that when there is a tendency to acute inflammation it must be used. with great caution. Inpens (D. M. W., 1913, 1827) from his physiological studies concludes that it acts by lessening intestinal peristalsis. The paracoto bark is said to resemble it in its action, but to be much less powerful. The fluidextract and tincture are very eligible preparations, the former made with alcohol in the usual way, and the tincture 1 part in 10 of alcohol, which may be given in from five-to fifteen-minim (0.3-0.9 mil) doses every two or three hours.
The active principle, cotoin, is given by Dr. Burkart in doses of three-quarters of a grain (0.048 Gm.) every two or three hours. He states that he could detect it in the urine from four to six hours after the ingestion of the dose. Balz (Tokio, Japan) is said to have treated cholera successfully by hypodermic injections of three grains (0.2 Gm.) of paracotoin. The value of cotoin in the treatment of diarrhea has been confirmed by various clinicians. It has been used in catarrhal diarrheas and the diarrheas of tubercular ulceration, of typhoid fever, and of other conditions. (See B. G. T., vol. xi, 167.) It does appear to have some special effect upon the alimentary canal, as, according to Pribram (Prager Med. Wochens., 1880) and Albertoni (A. E. P. P., xvii, 293), it markedly lessens the excretion of indican. Albertoni also believes that it actively dilates the abdominal vessels and thereby hastens absorption, and Bibrana, that it is an antiseptic. It is not probable that cotoin has any general action upon the system, and Jobst found that even fifteen grains (1.0 Gm.) injected hypodermically into the rabbit produced no other than local symptoms. Dose, of cotoin, from one to three grains (0.065-0.2 Gm.); of fluidextract of coto, from five to twenty minims (0.3-1.3 mils), four to six times a day.