SUBSTANCES PRODUCED BY FUNGI 179 



HoO. This penicillin was strongly dextrorotatory and had an adsorp- 

 tion maximum of 2,750 A°. The preparation had an activity of 32,000,- 

 000 dilution units against hemolytic streptococci, which corresponds to 

 about 240 Oxford units per milligram. 



The most suitable form for general use is the barium salt. In this 

 form, it retains its antibacterial activity for an indefinite period. The Ba 

 salt of penicillin is soluble in absolute methyl alcohol, but is insoluble in 

 absolute ethyl alcohol. Penicillin forms water-soluble salts with most 

 heavy metals, except Fe^"^"^. It is inactivated by a number of heavy metal 

 ions, especially Cu, Pb, Zn, and Cd. Penicillin is stable toward atmos- 

 pheric oxygen, but is oxidized by H0O2 and KMn04, the antibacterial 

 activity being lost (2, 5, 1 1 1 ). 



In assaying penicillin, tests are made for potency by one of several 

 procedures: sterility, moisture content, presence of pyrogenic sub- 

 stances, and toxicity (249). 



Several derivatives of penicillin have been obtained: 



1 . Penicillamine, a degradation product ( 6) , is produced by hydroly- 

 sis of the barium penicillin for one hour at 100° C. with N/io sulfuric 

 acid J the formula C«HiiN04.HCl has been suggested for itj the pres- 

 ence of a glyoxal nucleus has been indicated. 



2. Penillic acid (210), a dextrorotatory substance having a pale blu- 

 ish fluorescence, is insoluble in ether and soluble in butyl alcohol; it is 

 produced by keeping penicillin in aqueous solution at ^H 2.0 ; it has 

 some of the properties of an amino acid. 



3. Methyl, ethyl, «-butyl, and benzohydryl esters of penicillin have 

 been prepared (599, 600) ; these are insoluble in neutral or slightly al- 

 kaline buffers, but soluble in benzene j these esters are much less active 

 than true penicillin m vitro but are active in vivo. 



The chemical nature and mode of action of the second antibacterial 

 substance produced by P. notatum- are given in Table 34. This sub- 

 stance is a protein and acts as a glucose oxidase, oxygen being required. 

 It is characterized by its action not only upon gram-positive but also 

 upon many gram-negative bacteria, and by the fact that the presence of 

 glucose is required for its activity. Its action is inhibited by the presence 

 of catalase (151, 416, 751). 



Flavicin, a substance found (100, 461, s^s^ 5^7, 929) to be similar 



