162 BACTERIOLOGICAL CHEMISTRY 



dysenteriw and Vibrio cotunba l>eing inhibited by 0-8 

 mg./ml. Flavicin is bactericidal as well as bacteriostatic. 

 When injected in small doess, 50 mg./kg. of body weight, 

 it protects mice against infection by Type I pneumococci. 



Flavicin resembles penicillin in being a soluble acid 

 which is unstable in acid solution. It differs from 

 penicillin in being more active against C. diphtherice, 

 B. anthracis and Brucella abortus. 



Fumigacin. — Aspergillus fumigatus produces, in syn- 

 thetic media, in the first few days of growth the antibiotic 

 fumigacin, which is readily soluble in chloroform or 

 ethanol and to a limited extent in ether or water. It is 

 precipitated from alcoholic solution on cooling as colour- 

 less long, slender, needle-shaped crystals. Fumigacin 

 has m.p.220°C. and [a]D= -132° (c=0-4 in chloroform), 

 contains neither nitrogen nor sulphur, is weakly acidic, 

 and gives a methyl ester corresponding to the formula 

 C29 H38_4o07 for the original substance. The silver salt, 

 liowever, corresponds to C32H4403Ag. Fumigacin contains 

 a lactone group in addition to the carboxyl group and on 

 treatment with alkali gives a crystalline, inactive sodium 

 salt. Its general properties agree with those of helvolic 

 acid (see p. 167) which has a formula C32H44O8, corres- 

 ponding to that of the silver salt mentioned above. 

 The specific rotation of helvolic acid is given as 

 [ajo = —49-4° in chloroform, a difference which may, 

 possibly, be due to complete or partial conversion of the 

 lactone to the free acid. It is active against Gram -positive 

 organisms at dilutions of 1 in 200,000 to 1 in 600,000 and 

 only slightly active against Gram -negative bacteria 

 (dilution of 1 in 1000). In concentrations of 200 /Mg. 

 per ml. it is bactericidal. It is thermostable, and not 

 very toxic to animals but doses near the toxic limit are 

 necessary to protect mice against infection with 

 Streptococcus pyogenes. 



