234 THE ANTIBIOTICS 



Elution with 0.1 iV HC1 saturated with butanol. Eluate neutralized 

 and extracted with chloroform. Solvent back extracted with acid 

 water (pH 2.0). Antibiotic precipitated from the water solution with 

 picric acid or ammonium reineckate. Twenty-four transfer counter- 

 current distribution between chloroform and phosphate buffer, at 

 pH 4.4, separates xanthomycin B (tubes 1-4) and xanthomycin A 

 (tubes 12-20). A third component, xanthomycin C, is relatively inactive 

 and is present in tubes 23-24. Xanthomycin A makes up 65 to 90 per 

 cent of the total antibiotic. 



Chemical and physical properties: Basic compounds, solvent-soluble, yellow 

 at acid pH, pink at alkaline reaction. Xanthomycin A hydrochloride 

 is a yellow amorphous material very soluble in water and methanol. 

 Maximum ultraviolet light absorption at 265, 326 m/x in water. Maxi- 

 mum stability at acid reaction. 



Biological activity: Active against gram-positive and gram-negative bac- 

 teria. Very limited activity against mycobacteria. 



Toxicity: LD 60 (mice), intravenous, about 0.16 mg/kg. 



Utilization: None. 



References: Thorne, C. B., and Peterson, W. H., J. Biol. Chem., 176, 

 1948, 413-428; Rao, K. V., and Peterson, W. H., Abstr. papers 12th 

 Intern. Congr. Pure Appl. Chem., New York, 1951, p. 282. 



