Water-soluble rifamycin derivs. - prepd. by reacting rifamycin-sv hydrazone, aryl hydrazone or oxime derivs. with alkali salts of aliphatic, aromatic or steroid acids

New water-soluble rifamycins are cpds. of formula R.An (where R is the molecule of the hydrazone, arylhydrazone or oxime of rifamycin SV A is the molecule of the alkaline salt of 1-16C straight-chain or brached aliphatic organic acid, an opt. nuclear-substd. aromatic acid, or an acid with steroid structure; and n = 0.5-5). (I) are amorphous or macrocrystalline, orange to dark red/brown substances which are very soluble inhalogenated hydrocarbons, soluble in water and lower aliphatic alcohols, and poorly soluble in aliphatic hydrocarbons. Rifamycin derivs. have antibacterial (esp. antitubercular), antiviral, immunosuppressant and antileukaemic activity. The solubility properties of (I) means that in testing, solvents such as dimethyl sulphoxide or detergents are not needed, so that falsification of results due to solvent or detergents are avoided. In therapeutic nitrations, the good solubility properties reduces the risk of liver damage arising from hepato-biliary circulation of the zifamycin deriv.