SUBSTANCES PRODUCED BY FUNGI 209 



/-rotatory (in alcohol) and nearly insoluble in water. It changes in 

 color from lemon-yellow at /)H 4.6 to orange-pink at ^H 5.6 to 5.8 and 

 to cherry-red at fH 9.9. The addition of FeCls to the culture solution 

 gives a heavy buff-colored precipitate, which dissolves in an excess of 

 reagent to give an intense iodine-brown solution. Citrinin has little if 

 any activity against gram-negative bacteria and about 50,000 dilution 

 units against B. sub tills and S. aureus (33, 907). 



Penicillic Acid 



Penicillic acid was first isolated in 19 13 by Alsberg and Black 

 (16) as a metabolic product of P. fuberulum. It is also produced by P. 

 cyclofium. A limited air supply and an acid reaction of the medium 

 favor the production of this acid. It is isolated (698, 703) by evapora- 

 tion of the culture solution, the crude acid crystallizing on cooling. It 

 is purified by recrystallization from hot water. Yields greater than 2 

 gm. per liter of culture were obtained. It is a monobasic acid, stable, 

 colorless, appreciably soluble in cold water, giving a series of colorless 

 and readily soluble salts (61, 487). It is optically inactive, and its m.p. 

 is 87° C. (anhydrons), 64° to 65° C. (+ HoO). It has limited activity 

 against gram-positive and gram-negative bacteria. It is also active 

 against yeasts, and is toxic to animals when injected subcutaneously in 

 concentrations of 0.2 to 0.3 gm. per kilogram weight. 



Fumigatin 



Fumigatin is a 3-hydroxy-4-methoxy-2,5-toluquinone or C8H8O4 

 (Figure 18). It forms maroon-colored crystals, has an m.p. of 116° C, 

 and is water-soluble (23, 743). It is extracted with chloroform from 

 acidified medium. It has limited activity against gram-positive bacteria. 



All quinones have been divided into three groups on the basis of their 

 action on Staphylococcus: (a) those that have a markedly weaker anti- 

 bacterial action than fumigatin, including toluquinone and some of its 

 derivatives; (b) those that are somewhat more effective than fumi- 

 gatin, including 3:4 dimethoxytoluquinone ; (c) those with activity 

 perceptibly greater than that of fumigatin (methoxytoluquinones). 

 The introduction of -OCH3 into the quinone nucleus results in an in- 



