GB658766A - Improvements in and relating to the purification of antibiotics - Google Patents

Abstract

Partially purified polymyxin is purified further by treating in solution the polymyxin as the free base or as a salt thereof with BETA-naphthalene sulphonic acid, separating the salt thus obtained, purifying the salt by recrystallization and recovering the polymyxin therefrom. The free polymyxin as its salt is reacted in aqueous medium, and as the free base is reacted in solution in an alcohol containing 2 to 5 carbon atoms. The recrystallized salt may be reacted with an acid to give the salt of polymyxin, or may be reacted with ammonia to liberate the polymyxin which may then be reacted with an acid to form the salt. The partially purified polymyxin is preferably obtained by the process of Specification 647,925. In examples: (1) polymyxin b -hydrochloride and b -naphthalene sulphonic acid are reacted in aqueous solution. The product, an oil, is dissolved in aqueous ethanol, and more ethanol then added till the solution is cloudy, when crystallization begins. After a charcoal treatment the crystallization is repeated. The crystals suspended in methanol or ethanol are then treated with concentrated sulphuric acid and polymyxin sulphate precipitates on dilution with water; (2) polymyxin B, liberated from its hydrochloride, b -naphthalene sulphonic acid and dry ethanol are mixed, water is then added until a clear solution is obtained, and more ethanol is then added to cause precipitation. The product is re-crystallized by dissolving in aqueous ethanol and then adding dry ethanol. Polymyxin is then obtained by adding aqueous ammonia, and is converted into its sulphate or hydrochloride.