12 I. NAGAI: 



;ind quereitrin yielded a less bn'gLt red colour tliau cL'd mjiicetin aud qnercetiu 

 respectively. 



These oLseiTations indicate that the oxidation colours of flavones and 

 flavonoLs are lai-gely influenced by the chemical constitution of the substance 

 especially the number aud the position of OH group substituted in beta 

 phenyl gi-oup as in the case of the reduction coloiu^. 



It is now bej-oud boubt that the action of osid;ises and peroxidases on 

 flavones bears no direct relation to the chemical changes of flavones to 

 authocyanius ; nevertheless the oxidizing enzymes may play an important part 

 in other metabolic changes in the living tissue. 



3. Flavone Derivative as Chromogenic Subst.\nce3 of Reddish 

 Brown Pl.vnt Pigments (Phlobaphenes).* 



The reddish brown aud brown pigments are -»videly distributed in the 

 plant kingdom, namely in the bark, rliizome, seed coat, dead leaves and iu 

 others, some of them are known as plilobaphenes which were originally the 

 name given by Stähelin and Hofstetteh (1814)- to certain bro\\Taish red 

 substances of unknown chemica,! Constitution isolated from the bark of Pinus 

 sylvestris, Plakinus acerifdia, Bdiila cdba, Ginchomi Ccdisaya etc. According to 

 these authors aud others,' phlobaphenes ai'e considered to be the oxidatiou 

 product of tannins. Hlasiwetz considered that there are two gi'oups of sub- 

 stances wliich may respectively give rise to two gi'oups of phlobaphenes. One 

 of the gi'oups of phlobaphenes to which ' china red ', ' chinava red ', and ' oak 

 red ' etc. belong, yiekls by fusion with alkali, protocatechiiic acid alone, aud 

 the other gi'oup to which ' filix i-ed ', ' ratanhia red ' aud ' chestnut red ' be- 

 long, yields together with protooatechuic acid, phloroglucin. .ilong with them, 



1. Nagai, I., On some Keddish Brown Pknt-Pigments. Bot. Mag. Tokyo. 31:1, i;)l7. In 

 Japanese. 



2. StXhemx, C. and Hofstetter, J., Chemische Untersuchungen einiger Einden. Liebig. 

 Ann 51 : 63, 1844. 



3. Hesse, O , Ucber die humusartingen l?cstandthiUe der Cliina-rinden. luebig. Ann. 109 : 

 341. 1859. Hlasiwetz, H., Ueber die Beziehungen der Gerbsliuri', Gluooside, I'hlobaphcne iinl 

 Harze. Liebig. Ann. 143 : 209, 1867. Nierbsstexx, M., Beitrag zur Kenntnis der Gerbstoffe II. 

 Berich. d.d. ehem. Gesel. 42 : 353, 1009. See also rEnBiN, A. G. anl Evekest, .V. E., Loc. cit. juigo 

 436 et seq. 



