Wakeman—Pigments of Flowering Plants. 
819 
Catechin. 
CH CH 
Catechu, also called catechinic acid and catechu tannic acid, 
was known by Runge 1 to exist in the heart wood of Acacia catechu 
as early as 1821. It has long been known as a dyestuff impart¬ 
ing yellow and brown tints to textile fabrics. The coloring 
principle, catechin, was probably first described by Nees van 
Esenbeck 2 in 1832. It has since been the subject of many 
chemical investigations, the results of which were for a long time 
so various that the chemistry of catechin remained in a very 
unsatisfactory condition. The majority of investigators of this 
pigment have considered but one catechin to exist, some, how¬ 
ever, claim that three different catechins with different melting 
points, but with other properties similar, have been isolated. 
Perkin, 3 in 1902, described two catechins, with melting points 
of 175°-176°, and 235°-237° respectively, isolated from 
Gambir catechu, and another with a melting point of 204°- 
205°, from Acacia catechu. 
Many different chemical formulae have been assigned to 
catechin by different chemists. The latest work by Perkin 4 
upon this pigment, as well as the even more recent work of Kost- 
anecki 5 and his collaborators, indicates C 15 H 14 0 6 with five hy¬ 
dro xy groups as the correct formula for the anhydrous com¬ 
pound. Perkin 6 calls attention to the great similarity of the 
catechins to quercetin, which accompanies them in the plant, 
probably as a glucoside. He points out the possibility of their 
being reduction products of quercetin. The later work of 
Kostanecki and Lampe, however, indicates the presence of a 
cumaran group, in which the six carbon ring contains only one 
1 Berz. Jahresber., 12, p. 250. 
2 Ann., 1, p. 243. 
3 Jr. Chem. Soc., 81, p. 1160. 
4 P'roc. Chem. Soc., 20, p. 177. 
5 Ber., 89, p. 4007, 4014. 
0 Jr. Chem. Soc., 81, p. 1160. 
