584 5. QUINONES 



of the fate of menadiol-diP. The low tissue levels might be taken as evidence 

 for the poor penetration of the substance, but Solvonuk et al. (1952) re- 

 ported that menadione-2-Ci*H3 does not readily enter the tissues. Although 

 this may be due in part to serum binding, it makes it impossible to interpret 

 the data of Marrian and Maxwell in terms of the metabolism or distribution 

 of the phosphate. 



NATURALLY OCCURRING QUINONES 



Several groups of naturally occurring quinones, such as the ubiquinones, 

 the members of the vitamin K series, and certain antibiotics, have been dis- 

 cussed, but a treatment of the biochemistry and pharmacology of the qui- 

 nones would not be satisfactory without at least brief mention of the sources 

 of some of the quinones used commonly in metabolic studies, and some 

 speculation as to their role, if any, in plants and animals. We can restrict our 

 comments to certain aspects of the subject inasmuch as excellent reviews 

 of the naturally occurring quinones are available ( Hoffmann- Ostenhof, 

 1950; Venkataraman, 1957; Thomson, 1957, 1962). Nearly 200 different 

 quinones have been isolated, the bulk of these coming from angiosperms 

 and fungi. The only animals containing quinones other than the ubiquitous 

 coenzymes are certain insects and marine invertebrates, especially the echi- 

 noderms (although occasionally a quinone is detected in other phyla, e. g., 

 xyloquinone in a South American spider). Some beetles when stimulated 

 emit a mixture of methyl- and ethyl-^j-benzoquinones as a defense mech- 

 anism, and possibly other quinones may serve as sex attractants in insects, 

 but the function of the echinochromes and spinachromes in the sea urchins 

 is still debatable. Poisoning from the ingestion of certain plants has been 

 attributed to their content of quinones. p-Benzohydroquinone is responsible 

 for the poisoning of farm animals eating various species oi Xanthium (cockle- 

 bur) (Kuzel and Miller, 1950). Other plants known in history as having 

 medicinal properties often contain quinones but seldom has relation between 

 the pharmacological actions and the quinones been established. We have 

 noted that Arctostaphylos uva-ursi (bearberry) has been used for many 

 years as a urinary antiseptic and for other purposes, the active principle 

 presumably being arbutin, a glucoside of p-benzohydroquinone (page 543). 

 Another plant which has a long medical history in the Orient is Plumbago 

 (leadworts), which contains plumbagin (5-hydroxymenadione), although 

 it is doubtful if the actions for which it has been mainly used are dependent 

 on this quinone. However, there is no question about the clinical efficacy 

 of the various anthraquinone cathartics of the emodin type obtained from 

 rhubarb, cascara, senna, and other plants. One cannot help but wonder if 

 the use of the African Diospyros tricolor (related to the ebony tree and the 

 persimmon) in leprosy is related to its content of diosquinone (8-hydroxy- 

 1,2-naphthoquinone). 



