THE FLAVONES OF RHUS 
117 
The Leaf Pigment, Myricetin 
Several variations in method were used for the isolation of myri- 
cetin from the leaves. The best yield was obtained by the method 
of Perkin. This method consists in fractionally precipitating the 
dissolved substances from an aqueous extract of the leaves, with lead 
acetate. On the addition of this reagent impurities (tannins, gums, 
resins, etc.) are first precipitated as lead compounds and may be 
removed by filtration. The flavones and their glucosides are only 
precipitated upon the addition of an excess of lead acetate. 
The dried leaf powder was treated several days with successive 
portions of boiling distilled water and the combined extracts evap- 
orated to small bulk. Lead acetate was then cautiously added to the 
boiling mixture until a further quantity produced a yellowish precipi- 
tate. In this manner the impurities were got rid of, by filtering off 
the lead compounds first precipitated. Excess of lead acetate added 
to the filtrate produced an insoluble yellow lead salt of the flavone 
glucoside. This was filtered with suction, washed thoroughly with 
water and decomposed with boiling dilute sulphuric acid. Lead sul- 
phate was filtered off, and the filtrate, when cold, shaken with ether. 
The residue after evaporation of the ether contained the flavone and 
gallic acid. The latter was removed by treatment with hot water. 
The flavone was filtered off, dried, and acetylated in the usual manner. 
The other method that we found useful in the isolation of myricetin 
was as follows. The aqueous extract of the leaves was treated with a 
large amount of hide powder to remove tannin. The filtrate was then 
evaporated to small bulk and hydrolyzed with hydrochloric acid (33 
percent by volume) for nearly an hour. An ether extract of the cold 
solution yielded the crude pigment, which was purified by the usual 
process of acetylization and recovery by hydrolysis. 
Our yields of myricetin were very small, and insaflicient for com- 
bustions to be made of the com|)ound from all of the sources from 
which it was obtained. It was likewise impossible to make a potash 
fusion. Myricetin, however, has more characteristic qualitative 
reactions^ than the other pigments of the flavone group. Ammonia 
and dilute alkalies give a green coloration, changing to blue, violet, 
and finally reddish-brown. No other known flavone gives this play 
' Perkin, A. G., and Hummel, J. J. The colouring principle contained in the 
bark of Myrica nagi. Part I. Journ. Chem. Soc. (London), Trans. 69: 1287-1294. 
1896. 
