Occasionally the drug is found with the brown, dried rind intact. A Persian colocynth occurs in the London markets, having a shrivelled appearance, with the seeds tightly imbedded in the pulp, owing to the fact that it has been peeled while still fresh, but the drug of commerce is usually divested of its rind after having been dried. He obtained the bitter principle in an impure form, and called it colocynthin . According to Walz, colocynthin is a glucosid, the action of diluted acids resolving it into colocynthein , a resinous body, and sugar. Walz also describes a crystalline substance, colocynthitin , insoluble in water and cold absolute alcohol, but soluble in ether and boiling alcohol.
Tannic acid precipitates it completely from aqueous solution.
From 5 kilograms of colocynth deprived of seeds, Henke obtained only 30 grams of colocynthin, and recommends the use of the drug in fresh condition. E. Johannson, in 1885, found colocynthein to be less soluble than colocynthin in water, and in acid solution soluble in benzene, which affords a means of separating it from colocynthin. Colocynthin he also found soluble in acetic ether. Action, Medical Uses, and Dosage. It acts very powerfully, producing copious watery evacuations.