Papain is an impure enzyme of considerable power, prepared from the juice of the unripe fruit of Carica Papaya, Linn. (N.O. Cucurbitaceae), a native of South America, the West Indies, and other tropical parts. The juice is always more or less acrid or even vesicant, but processes for destroying its acridity weaken its digestive properties. The impure enzyme is usually obtained by adding to the freshly drawn milky juice twice its bulk of alcohol, the precipitate formed being drained and dried. By dissolving this crude papain in water, and reprecipitating with alcohol, it is obtained as a light-coloured product. The colour is to some extent indicative of its quality, as generally the lighter the colour the more active the preparation. Papain occurs as an amorphous or slightly granular powder, varying in colour from white to light brown, very liable to change, odourless when prepared as above, and having a faint pepsin-like taste. It possesses a solvent action on animal protein, and acts in acid, alkaline, or neutral media. The activity of the enzyme, though checked in presence of alcohol, is less susceptible to destruction by such anti-zymotics as glycerin, phenol, salicylic acid, etc., than is pepsin; indeed they have been used as preservatives. Its proteolytic action is similar to that of pepsin in producing peptones from albumin or fibrin. It is most active when working in a relatively small quantity of liquid, dilution of the digestive solution having a very marked retarding influence on the progress of the hydrolysis. For the determination of its digestive power blood fibrin in slightly alkaline solution is mostly used, and the digestion carried on at a temperature of about 45° to 50°. A good sample should dissolve 200 to 250 times its weight of blood fibrin in four to five hours. The activity of papain in solution is destroyed at about 82°; in the dry state, however, it is much more stable, and may be heated to 100° without being destroyed. It is stated that a solution of 2 decigrams in 4 mils of water with 1 mil of nitric acid (specific gravity, 1.153), filtered, after standing for one hour, should not be rendered turbid by a solution of tannin (5 per cent.).
Soluble in water or glycerin; insoluble in alcohol.
Action and Uses.—Papain is employed to assist protein digestion in chronic dyspepsia, gastric fermentation, and gastritis. Its activity is exerted both in the stomach and intestines. Some commercial varieties of papain act best in alkaline solutions, while others are most active in acid solution. It may be administered in powders, or enclosed in a cachet, or in solution as Elixir Papaini or Glycerinum Papaini. Lozenges are also prepared, containing 1 grain in each, and pills may be made with syrup of glucose as an excipient. Solutions of papain (10 per cent.) are applied to diphtheritic membrane, and to digest dead tissue and promote healing of abscesses, ulcers, and fissures of the tongue. Solutions of a similar strength have been recommended, in doses of from 3 to 12 decimils (0.3 to 1.2 milliliters) (5 to 20 minims), for injection into tumours, malignant and benign, to promote their absorption.
Dose.—1 to 6 decigrams (2 to 10 grains).
- Elixir Papaini, B.P.C.—ELIXIR OF PAPAIN. 1. in 20.
- This elixir assists protein digestion, and acts in acid or alkaline media. It is given for atonic dyspepsia. Dose.—2 to 4 mils (½ to 1 fluid drachm), with meals.
- Elixir Papaini, C.F. —ELIXIR OF PAPAIN.
- Papain, 3.65; diluted hydrochloric acid, 0.8; distilled water, 15; glycerin, 15; sherry, 15; gluside, 0.115; aromatic elixir, to 100. Macerate the papain in the acid and water for four days, with occasional agitation. Dissolve the gluside in the sherry and 50 of the elixir, add the glycerin, mix with the papain mixture and filter; then add sufficient aromatic elixir to make 100.
- Glycerinum Papaini, B.P.C.—GLYCERIN OF PAPAIN.
- Papain, 9.15; diluted hydrochloric acid, 8.34; simple elixir, 5; glycerin, to 100. A digestive, for use instead of pancreatin, in painful dyspepsia and gastric fermentation. It acts in neutral, alkaline, or slightly acid solutions. Dose.—2 to 4 mils (½ to 1 fluid drachm).
- Liquor Papaini et Iridini, B.P.C.—SOLUTION OF PAPAIN AND IRIDIN.
- Papain, 1.83; extract of iris, 1.83; glycerin, 10; sherry 25; chloroform water to 100. Used as a digestive tonic and liver stimulant. The papain acts in neutral, or moderately acid or alkaline, solutions; its activity is, therefore, not destroyed in the stomach. Dose.—2 to 4 mils (½ to 1 fluid drachm).