190 



FLAVONOIDS AND RELATED COlvIPOUNDS 



AURONES 



The aurone or benzalcoumaranone ring system is numbered in the following way: 



2' 3' 



These are golden yellow pigments occurring in certain flowers. Only a few are known, 

 but they generally possess the hydroxylation pattern of the other flavonoids as well as 

 being found in the form of glycosides and methyl ethers. In alkaline solution they become 

 rose -red. Some examples of aurones and their glycosides are shown in Table 6. 



MISCELLANEOUS COMPOUNDS 



Several unusual plant constituents appear by their structures to be biogenetically 

 related to the flavonoids but with additional complexities. They will be mentioned briefly 

 but fit into no widespread group. 



Several compounds may be classed either with the furanocoumarins (see Chap. 4) 

 or with the flavonoids. The most important of these is the insecticide rotenone of derris 

 root. Its structure is written below so as to show its relationship to the isoflavones: 



rotenone 



OCH3 



OCH3 



A somewhat simpler but similar compound is found in the yam bean, Pachyrrhizus erosus: 



OCH3 



pachyrrhizin 



