QUINONES 



Three major classes of naturally occurring quinones 

 are recognized: benzoquinones, naphthoquinones, 

 and anthraquinones (see below). In addition a few 

 complex substances of quinone structure occur (for 

 example, tripterine, in Tripterygium wilfordii, family 

 Celastraceae), but these last are too little known to 

 allow much consideration of their systematic im- 

 portance at this time. 



The most recent treatment of the chemistry 

 and distribution of quinones is that of Thomson 

 (1957). He emphasized mainly quinone chemistry, 

 but sources of all naturally occurring quinones were 

 given. 



Quinones occur in plants, animals, and 

 micro-organisms. However, in the animal kingdom, 



223 



