Wakeman- . Pigments of Flowering Plants. 
849 
P entity dr oxides of flavone. 
Quercetin f — P entity dr oxy — 1, 2 y 3', 4 a-j flavone y or 
Tetrahydroxy-—!, 2 , 3', 4’ -flavonol. 
Quercetin which occurs very widely distributed throughout 
the plant kingdom, both in the free state and as a glucoside, has 
probably been more widely studied than any other vegetable 
coloring matter except chlorophyll and, perhaps indigo and 
alizarin. Quercetin was first extracted as a glucoside querei- 
trin by Chevreul 1 from the inner bark of Quercus tinctoria and 
later from the same source, also from the horse chestnut, by 
Rochleder. 2 The free quercetin was first obtained from the 
glucoside by Rigaud, 3 in 1854. The names of the various 
chemists who have since contributed to the literature of querce¬ 
tin, with references to their published works are given in the ap¬ 
pended list, which, although it contains the more important ar¬ 
ticles upon quercetin, is probably not at all complete. 
Our conception of the structure of quercetin comes from the 
work of Hirzig, 4 also that of Kostanecki 5 and his associates. 
Fused with alkalies it yields phloroglucin, Protocatehuic acid, 
and glycolic acid. 
C 15 H 10 O 7 + 3H 2 0 =C 6 H 3 (OH), + C 6 H 3 (OH) 2 COOH+ CH 2 
OH COOH. 
Quercetin has been synthesized by Kostanecki and his colla¬ 
borators in a manner quite similar to their synthesis of fisetin. 6 
Quercetin occurs very widely distributed in the free state, as 
alkyl ethers, and as glucosides. As a glucoside it is most 
1 Logons de Chemie appliquee £ la Teinture. 
a Wien. Acad. Ber., 33, p. 565. 
* Ann., 90, p. 283. 
* Monatsh., 12, p'. 177; 14, p. 38. 
‘Ber., 37, p. 784, 793. 
•Ber., 37, p. 784, 793. 
54—S. A. L. 
