ANTIMICROBIAL AND ANTITUMOR ACTIVITIES 



89 



of the drug without apparently interfering 

 with its activity. 



2. Alodification of the aromatic aryl, the 

 (lichloroacetyl, and the C'HoOH groups in 

 the chloramphenicol molecule results in the 

 complete destruction of its activity. 



3. The degradation of chlortetracycline to 

 tetracycline, whereby the chlorine atom in 

 the first ring is replaced by a hydrogen atom, 

 results in a decrease in the antimicrobial 

 activities of the molecule, and is believed to 

 give a less toxic and more stable compound. 

 Dechlorination of chlortetracycline in- 

 creases its stability markedly. 



4. The activitv of actithiazic acid agauist 



the tuberculosis organism has been related 

 to its thiazolidone structure. 



These facts are too limited to justify any 

 broad generalization concerning specific 

 structure and activity of antibiotics. One 

 point is clear, however. The antibiotics of 

 actinomycetes represent such a wide variety 

 of chemical structures and biological ac- 

 tivities that we must conclude that we are 

 dealing here with a new field of natural 

 products, \-arying greatly in chemical com- 

 position, in antimicrobial activities, and in 

 othei- biological properties that render them 

 potentially of great importance to human 

 health and human economy. 



