ANTIBIOTICS 167 



l'2ixg./ml., V. comma at 25 ju,g./ml. and P. vulgaris at 

 100 /Ltg./mL, as well as to Gram -positive organisms. 



Helvolic Acid. — A mutant of A. fumigatus mut. 

 Helvola when grown on a glucose-salts medium gives a 

 substance which can be adsorbed on charcoal at ^^H 4 

 and eluted with 80 per cent, acetone. It can be purified 

 by chromatography of a chloroform solution and re- 

 crystallised from acetone. The yield is 0-4 g. from 100 

 litres of medium. It is a monobasic acid, C32H44O8, 

 containing three active hydrogen atoms per molecule, 

 m.p.205°C, [a]??-49-4° in chloroform. It is almost 

 insoluble in water, but gives a soluble sodium 

 salt ; salts with other metals are very sparingly soluble. 

 Its activity is not affected by heating to 100°C. with 

 2 N acid for fifteen minutes, or in neutral solution or 

 with alkali at pH 10. It is bacteriostatic to Gram- 

 positive but not to Gram -negative organisms, but has 

 no effect on the respiration of suspensions of staphylococci. 

 Human tubercle bacilli are inhibited by a 1 in 10,000 

 dilution of helvolic acid. ]\Iice will tolerate 5 mg. of 

 sodium helvolate intravenously and 20 mg. orally, 

 leucocytes are not injured by a dilution of 1 in 1600 

 nor are tissue cultures by 1 in 2500 sodium helvolate. 

 It is absorbed from subcutaneous tissue and from the 

 gut and is excreted in the urine and bile. Although 

 antibacterial concentratioixs can be maintained in the 

 blood stream, repeated injection leads to liver damage. 

 This probably accounts for the fact that the lives of 

 mice infected with staphylococci or streptococci can be 

 prolonged but not saved by sodium helvolate. 



Helvolic acid is probably the acid corresponding to 

 the lactone, fumigacin (see p. 162). 



lodinin. — Chroinohacteriiim iodinum gives the pigment 

 iodinin wliich is the di-N-oxide of a dihydroxy j^henazine, 



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