60 



NATURE, FORMATION, AND ACTIVITIES 



amino sugars and amino acids. Typical 

 products of the hydrolysis of a strepto- 

 thricin-type compound include (1) a di- 

 aminocaproic acid (L-|8-lysine), (2) an 

 imidazole derivative, streptolidine, and (3) 

 the amino sugar a-D-gulosamine. 



The streptothricins are active not only 

 against bacteria but also against fungi. The 

 most important streptothricin-type anti- 

 biotics are lavendulin, actinorubin, antibiotic 

 136, roseothricin, geomycin, pleocidin, and 

 miicothricin. The antimycobacterial anti- 

 biotic viomijcin also yields |3-lysine upon 

 hydrolysis. 



Miscellaneous Pigmented Antibiotics 

 which Act as pH Indicators 



A number of antibiotics are colored sub- 

 stances which act as pH indicators, the 

 color changing with the pH of their solution. 



The structure of one of these substances, 

 actinorhodin, is partially known. It has a 

 dinaphthazarin nucleus. The structure of 

 naphthazarin is: 



OH O 



OH O 



Two such units are thus hooked together 

 and are variously substituted. 



Another pH indicator, granaticin, is a 

 tricyclic tetrahydroxyciuinonedicarboxylic 

 acid (C22H20O10). 



Litmocidin, also a pH indicator, is be- 

 lieved to be related to the anthocyanin pig- 

 ments. As such, it is believed to have a 

 molecular nucleus of the following type: 



Nothing is known about the chemical struc- 

 ture of other pH indicators, such as coeli- 

 colorin, mitomycin C, nocardorvbin, rhodo- 

 mycetin, and ruhidin. 



The rhodomycins are a group of pH in- 

 dicator antibiotics active against gram-posi- 

 tive bacteria. They are formed of a ciuinoid 

 chromophore called rhodomycinon, to which 

 is attached a moiety which contains rhodos- 

 amine, an isomer of desosamine. 



Compounds Containing Phenazine or 

 Quinoxaline Nuclei 



One antifungal antibiotic, 1 ,6-dih]jdr<)X]j- 

 phenazine, and two antibacterial antibiotics, 

 griseolutein A and B, have a phenazine 

 nucleus which is substituted as follows: 



The hydrolysates of another such indica- 

 tor, mycorhodin, include reducing sugars. 



1 ,G-Dihydroxyj)hen:iziiie: Ri = Rn = H; 



R = II, = OH 



Griseolutein A: R = OCH3 ; 



R, = CH2— O— CO— CH4)H; 



R, = H; R3 = COOH 

 Griseolutein B: R = OCH3 ; 



R, = CH.— O— CHOH— CH.OH; 



R: = H; R, = COOH 



1 ,6-Dihydroxyphenazine is closely re- 

 lated to the bacterial antibiotic pigment 

 iodinin, from which it can be obtained by 

 reduction. Iodinin is the .") , 10-dioxide of 

 1 , 6-dihydroxyphenazine and is active 

 against bacteria. In contrast, 1 , 6-dihydroxy- 

 phenazine has no antibacterial activity. 

 Both griseolutein A and B are acti\'e against 

 gram-positive and gram-negative bacteria. 

 The only difference between the two mole- 

 cules is two hydrogen atoms in the Ki chain. 

 Despite this small difference, only slight 

 cross-resistance was observed between these 

 two antibiotics. 



