212 CHEMICAL NATURE OF ANTIBIOTIC SUBSTANCES 



equal parts of petroleum ether to the concentrated extract results in 

 the separation of a crude preparation of gliotoxin. Purification is ac- 

 complished by repeated crystallizations (66$). 



Gliotoxin is sparingly soluble in water and readily soluble in alcohol. 

 It is unstable, particularly in alkaline solutions, and is sensitive to 

 oxidation and to heating (988) j it is inactivated by heating for 10 min- 

 utes at 100° C. ( 14). Its potency was found to be destroyed by bubbling 

 oxygen for 5 minutes. 



Gliotoxin is active against various bacteria and fungi. It is toxic to 

 Rh'fzoctoma hyphae in a dilution of i : 300,000, which is about two- 

 thirds of the toxicity of HgCls- The crystals, as well as the crude ma- 

 terial, were found to be toxic also to Trkhoderma, but the minimum 

 lethal dose was about 40 times greater than that required for Rhizoc- 

 tonia. 



Viridin 



Viridin is produced by Trkhoderma viride. It crystallizes in the 

 form of colorless rod-like prisms, which decompose without melting at 

 217° to 223° C. It is extracted from the medium with chloroform, 

 evaporated under reduced pressures, and crystallized from ethyl alco- 

 hol. It is optically active 5 a i per cent solution in chloroform gives 

 [a] ^^ = — 222°. The addition of phloroglucinol and HCl to a dilute 

 alcoholic solution gives a deep reddish-violet color. It is unstable in 

 aqueous solutions, but stable at ^H 3.5. It is highly fungistatic but not 

 very bacteriostatic (84). 



Other Substances 



A number of other antibacterial substances have been isolated from 

 fungi, but have not been adequately studied either chemically or bio- 

 logically. It is sufficient to mention the following: 



Puberulic acid, a colorless, optically inactive, water-soluble dibasic 

 acid, with an m.p. of 316° to 318° C, and puberulonic acid, a bright- 

 yellow acid with an m.p. of 298° C, are produced (62, 704) by various 

 species of PenkilUum (P. fuberulum) . The first is a quinol and the 

 second is quinonoid. They have moderate activity against gram-positive 

 bacteria. P. fuberulum also produces a photosensitive compound. 



