96 AROMATIC COMPOUNDS AND [CH. 



Luteolin does not appear to be widely distributed, though possibly 

 it occurs in many plants in which it has not yet been demonstrated. Its 

 formula is represented as : 



OH 



It occurs in the Dyer's Weld or Wild Mignonette (Reseda luteola) 

 (Perkin, 17), Dyer's Greenweed or Broom (Genista tinctoria) (Perkin, 23) 

 and in the yellow variety of flowers of the Snapdragon (A ntirrhinum 

 majus) (Wheldale and Bassett, 32). It has been much used as a yellow 

 dye: hence the names of the first two plants (Perkin and Horsfall, 20). 



The most important flavonol pigments are quercetin, kaempferol, 

 myricetin and fisetin. 



Quercetin is apparently one of the most widely distributed of the 

 whole group of yellow pigments, and has the formula : 



It occurs, either free, or combined with various sugars (glucose, 

 rhamnose) as glucosides, in many plants, as for instance the following : 

 in the bark of species of Oak (Quercus), in berries of species of Buck- 

 thorn (Rhamnus), in flowers of Wallflower (Cheiranthus Cheiri), Hawthorn 

 (Crataegus Oxyacantha) (Perkin and Hummel, 22), Pansy ( Viola tricolor) 

 (Perkin, 19) and species of Narcissus : in leaves of Ling (Calluna erica) 

 (Perkin, 23), and the outer scale leaves of Onion bulbs (Perkin and 

 Hummel, 21). 



Expt. 98. Preparation of a glucoside of quercetin from Narcissus flowers. The 

 species of Narcissus which can be used are N. Tazetta, N. incomparabilis, and any of 

 the common yellow trumpet varieties. Pound about 50 flowers in a mortar and then 

 extract in a flask with boiling alcohol. Filter off the alcoholic extract and evaporate 

 to dryness ; then add a little water and ether and transfer the whole to a separating 

 funnel. The ether takes up the plastid pigments, but at the plane of separation of the 

 liquids, the glucoside separates out as a crystalline deposit. This can be filtered off ; 

 with a dilute solution in alcohol make the following tests : 



() Add a little alkali. The yellow colour is intensified, but the intensification 

 disappears on adding acid. 



