SOME MISCELLANEOUS UNSAPONIFIABLE UPIDS 



99 



There is an obvious resemblance of these structures to the 2-acylphloroglucinols discussed 

 in the previous section of this chapter (e. g. , compare eugenone and eugenin). Naturally 

 occurring chromones have been reviewed by Schmid (21) and the furanochromones by 

 Huttrer and Dale (22). Both groups together contain only about a dozen compounds. 



The chromones are of interest as the active ingredients of several plants used for 

 centuries in folk medicine. Khellin is valuable as an antispasmodic and for relieving the 

 pain of renal colic, dental caries, angina pectoris, etc. Its primary action may be as a 

 vasodilator. 



Chromones are extracted from dried plant material using such solvents as ether, 

 chloroform, or acetone. They may be crystallized directly from these solvents or puri- 

 fied by chromatography on magnesium oxide or neutral, deactivated alumina. Chromones 

 with phenolic hydroxyl groups can be extracted from ether solution with dilute, aqueous 

 sodium hydroxide. Chromone glycosides are extracted by methanol. 



Chromones are usually colorless but form yellow-orange oxonium salts in the pres- 

 ence of strong mineral acids. This color reaction is useful for indicating the presence of 

 chromones, but proof of structure rests on degradation and identification of split products. 

 The ultraviolet absorption spectrum of chromones usually shows a main band at about 

 295 mil with weaker absorption at about 250 m|U. Substitution at C-8 or presence of the 

 furan ring may increase the absorption maximum to as much as 340 mji (23). Paper 

 chromatographic separation of chromones can be made using water/2-propanol mixtures 

 as the solvents. 



NAPHTHOQUINONES 



A large number of naphthoquinones are found in nature as yellow-red plant pigments. 

 Theoretically some of these might be synthesized by polyacetate condensations as follows: 









II 



•C C XOOH 



0^ \ / \ / 

 Cn2 CHo 



CHo CH2 CHg 



HOOC 



•C^Hj yCH3 



HOOC C 



il 

 



NAPHTHOQUINONES 



