216 THE ANTIBIOTICS 



Netropsin 



Produced by: Streptomyces netropsis. 



Method of extraction: Broth acidified to pH 2.0 with H3PO4, filtered on 

 Super-Cel. Filtrate adjusted to pH 6.5 with NaOH and ammonium 

 oxalate added; precipitate filtered off. Broth then adjusted to pH 5.5 

 with HC1, and Orange II added. The dye precipitate is filtered off on 

 Super-Cel and washed with distilled water. The air-dry cake is sus- 

 pended in a mixture of 20 per cent methanol and 80 per cent acetone, 

 and 50 per cent of a methanolic solution of trimethylamine sulfate 

 added. Filtered, washed with acetone-methanol, and extracted with 

 distilled water. The netropsin sulfate solution contains 485 streptomy- 

 cin units/mg. 



Chemical and physical properties: Netropsin sulfate melts at 224-225° and 

 has a solubility of about 30 mg/ml in water at 80°C, but less than 0.5 

 mg/ml at 25°C. It is quite insoluble in the common organic solvents. 

 The strong basicity of the antibiotic appears to be due to a substi- 

 tuted guanidine group, but this does not account for all of the nitrogen 

 present. Maximum light absorption of sulfate, at pH 5.5, at 236 and 

 296 mju; C-^NifA. 



Biological activity: Inhibits the growth of various gram-positive and gram- 

 negative organisms, in concentration of 3-40 jug/ml. It is effective 

 against clothes moth larvae and the black carpet beetle. Active in 

 experimental mice vaccinal infections. No activity, in mice, against 

 the viruses of feline pneumonitis, influenza, Western equine encephalo- 

 myelitis, and poliomyelitis. 



Toxicity: LD 6 o (mice), intravenous, 17 mg/kg; subcutaneous, 70 mg/kg. 



Utilization: None so far. 



Reference: Finlay, A. C, and Sobin, B. A., U. S. Patent 2,586,762, 1952; 

 J. Am. Chem. Soc, 73, 1951, 341; Schabel, F. M., Laster, W. R., 

 Brockman, R. W., and Skipper, H. E., Proc. Soc. Exptl. Biol. Med., 

 83, 1953, 1-3. 



Nigericin 



Produced by: Streptomyces sp. 



Method of extraction: Precipitation at pH 2 to 3. Precipitate dissolved in 

 base. Precipitation of salt at pH 8.5. Can also be extracted from broth 

 with n-butanol, butyl acetate, ethyl acetate, or ethyl ether. Can be 

 adsorbed on charcoal and eluted with alcohol. 



Chemical and physical properties: Organic acid. Mol. wt. = 715-735, sodium 

 salt = colorless needles, m.p. 246-254°C. Soluble in ethyl, methyl, 

 and n-butyl alcohols; slightly soluble in water. At pH 7.0, stable 2 

 hours at 100°C. C 39 H 69 O u . 



