AUCUBIN 249 



Bergmann and Michaelis * have re-investigated the con- 

 stitution of the glucoside aucubin which is known to be 

 identical with Rhinanthin, "j* the glucoside of Rhinanthiis 

 Crista galli, and ascribe to it the formula C15H22O9 . HgO or 

 some multiple ; from this it would appear to be identical with 

 the glucoside menyanthin contained in Menyanthes trifoliata 

 and with loganin contained in Strychnos nux vomica. The 

 glucoside aucubin, required for the investigation was prepared 

 from the seeds of Plantago lanceolata, occurs in several species 

 of Plantago. The melting-point of aucubin is 181° C, and its 

 rotation aj,=— 1 64*9°. 



OROBANCHIN. 



This is a glucoside typical of the orobanchs, having been 



found in five species of this genus $ ; it is not hydrolysed by 



emulsin nor by an enzyme prepared from Rhamnus utilis 



seeds, but on hydrolysis with acid gives rise to glucose and 



rhamnose in addition to caffeic acid or 3 : 4 dihydroxycinnamic 



acid — 



/OH 



^ ' CH : CH . COOH 



whose close relationship to coumaric acid contained in meli- 

 lotosin is interesting (see below). The orobanchs contain no 

 aucubin and the darkening on drying is due to direct oxidation 

 of the glucoside orobanchin without previous hydrolysis ; the 

 oxidation can be brought about by an extract of Russula 

 delica, as well as by the oxidase contained in the plant itself. 



ASPERULIN. 



This glucoside which occurs in Asperula odorata, in Galium 

 spp. and in many other Rubiaceae resembles aucubin in giv- 

 ing on hydrolysis in addition to glucose an insoluble greenish- 

 black substance. Asperula odorata also contains a second 



* Bergmann and Michaelis : " Bar. deut. chem. Gesells.," 1927, 60, 935. 

 t Bridel and Braecke : " Bull. Soc. chim. biol.," 1925, 6, 665. Bour- 

 dier : " J. pharm. Chim.," 1907, [6], 26, 454. 



I Bridel and Charaux : " Compt. rend.," 1924. 178, 1839 ; 1925, 180, 



387. 



