ANTIBIOTIC GROUPS 175 



II. Yellow pigments, insoluble in water. 



1. Soluble in organic solvents. 



Thiolutin 

 (Aureothricin) 



2. Slightly soluble in organic solvents. Unstable at alkaline pH. 



Griseolutein 

 III. Pigmented compounds. 



1. Red color due to a metallic element; weak acid, containing iron 

 and amino acids, soluble in water and phenol. 



Grisein 

 (Antibiotic 3510) 



2. Orange-yellow, contains sulfur. 



Thioaurin 

 TV. Basic polypeptides, which contain guanidino or creatinine groups 

 or both. 



1. Both guanidino and creatinine groups present. 



Vinactin A, B 



2. Compound containing creatinine group but no guanidino group. 



Vinactin C 



3. Compound containing a guanidino but no creatinine group, 

 fairly low toxicity. 



Viomycin 



4. Chemical nature not well established. 



Neonocardin 



C. Substances active against bacteria, rickettsiae, and larger viruses. 



I. Basic substances, slowly dissolving in water. 



1. Low toxicity. . .Erythromycin 



2. Said to possess somewhat higher toxicity than erythromycin. 



Carbomycin 



3. Compounds related to erythromycin and carbomycin. 



Leucomycin 

 II. Neutral, amphoteric, or weakly basic substances, soluble in or- 

 ganic solvents other than ether, slightly soluble in water; yellow- 

 colored; active against various bacteria, rickettsiae, and larger 

 viruses. 



1. Weak base, contains nonionic chlorine. 



Chlortetracycline 



2. Does not contain nonionic chlorine. 



Oxytetracycline 



