146 Miss Wheldale, On the nature of anthocyanin. 



according to variations in the constitution of the colouring matter. 

 With aniline or toluidine nitrate and potassium nitrite they give 

 a cinnabar-red precipitate. In the plant the flavones mostly occur 

 as glucosides, the sugar being rhamnose or glucose. 



Quercetin C15HJ0O7 is very widely distributed. It may be 

 regarded as a pentahydroxy flavone : — 



OH 



JOH 



OH 



OH 



OH CO 



Quercetin occurs free, that is not as a glucoside, in many plants. 

 The following are interesting examples: — its occurrence in flowers 

 of Prunus spinosa, Crataegus oxyacantha, Delphinium Zalil, and 

 Cheiranthus Cheiri; in leaves of Rhus I'hodanthema, R. metopium, 

 Ailanthus glandulosa, Goriaria myrtifolia, Calluna vulgaris; it 

 exists also in the outer bulb scales of Allium cepa and in many 

 other plants. 



On fusion with caustic alkali, quercetin gives protocatechuic 

 acid and phloroglucin derived from the catechol and phloroglucinol 

 nuclei respectively. 



In many plants on the other hand it is combined with glucose 

 or rhamnose as glucosides. It occurs as 'osyritrin'; a glucose 

 glucoside, in leaves of Osy7'is compressa; 'osyritrin' is also identical 

 with the 'viola quercitrin' of flowers of Viola tricolor variensis and 

 with 'myrticolorin' in leaves of Eucalyptus macrorhyncha. Again 

 with one molecule of rhamnose it occurs as the glucoside 'quer- 

 citnji' in the bark of QuerciLs tinctoria and with two molecules of 

 rhamnose as 'rutin' in Ruta graveolens. The flowers of Viola 

 odorata and TrifoUum repens also contain quercetin in the form 

 of a glucoside. 



Morin, C15H10O7, occurring in the wood of Morus tinctoria and 

 Artocarpus integrifolia, may be regarded as an isomer of quercetin 

 containini/ the resorcinol instead of the catechol nucleus : — 



OH 



OH 



OH 



OH 



OH GO 



On fusion with alkali it gives /3-resorcylic acid and phloroglucin. 



