695 Addendum 



The structure of the antifungal antibiotic, variotin, 

 CifiHo.O.N, is :'•"«" 



O 



II 

 CHaCHj— CH.— CH C— CH =C— CH=CH— CH=CH— C— NH— CH,— CH,— CH> 



OH CHs 



O 



— C— OCH3 

 Thus, while it is a tetraene, it is not of the macrolide 

 class. 



Siderochromes. 



A number of microorganisms have been found to 

 produce iron-containing pigments which absorb in the 

 ultraviolet at 420-440 m^u, and have other properties in 

 common. It has been suggested that these be called 

 siderochromes.^^* 



Some of these substances are antibiotic and are called 

 sideromycins. Others are growth factors and may be 

 designated sideramines. The antibiotic sideromycins 

 seem to function by inhibiting the growth factor sidera- 

 mines. 



It remains to be seen how broadly the significance of 

 these substances will extend. Some 50 strains of strepto- 

 mycetes produce sideromycin-like antibiotics.^-* Of 32 

 common microbial species examined 10 produced 

 coprogen-like substances. ^^^ The sideramines seem to 

 perform a coenzyme-like function in many microorgan- 

 isms. 



Grisein A and albomycin have broad antibiotic activ- 

 ity. In gram-positive microorganisms, but not in gram- 

 negative ones, their effects are inhibited by sideramines. 

 Ferrimycin is 10 to 50 times as effective as penicillin 

 against gram-positive microorganisms in animal studies. 

 The following table shows some of the siderochromes 

 which have been best characterized: 

 ^^^" Setsuo Takeuchi, Hiroshi Yonehara, Hamao Umezawa and 

 Yusuke Sumiki, ibid. 13A 289 (1960). 



^■* H. Bickel, E. Gaumann, W. Keller-Schierlein, V. Prelog, E. 

 Vischer, A. Wettstein and H. Zahner, Experientia 16 129-133 

 (1960). 



1"'= C. W. Hesseltine, A. R. WhitehlU, C. Pidacks, M. Ten Hagen, N. 

 Bohonos, B. L. Hutchings and J. H. Williams, Mycologia 45 7 (1953). 



