126 CAROTENOID HYDROCARBONS OF KNOWN CONSTITUTION X 



3. ^-CAROTENE C^pHge 

 History 



1831 Wackenroder discovers carotene* in the roots of the carrot {Daucus 



Carota) . 

 1847 Zeise^^ describes the new pigment in more detail and determines the 



empirical formula CgHg. 

 1866 Arnaud^^ establishes that carotene is a hydrocarbon. 

 1907 Willstatter and Mieg®" prove the identity of carotene from leaves and 



carrots. They establish the correct molecular formula C4oH5g. 

 1928 Zechmeister, von Cholnoky and Vrabely establish the presence of 



II double bonds and 2 ring systems in carotene^^. 

 1929-31 Karrer and collaborators®^ elucidate the constitution of ^-carotene. 

 1932-35 KuHN and Brockmann®^ carry out extensive investigations on 



j3-carotene and obtain long-chain degradation products which confirm 



the formula assigned to /3-carotene. 



Occurrence 



|5-Carotene is very widely distributed in nature. All green parts of plants 

 (leaves®*, stalks, etc.) contain this pigment which invariably accompanies 

 chlorophyll together with xanthophyll, xanthophyll epoxide and frequently 

 a-carotene®^. 



Autumnal leaves also contain ^-carotene®®. In fact, numerous investigations 

 have shown that ^-carotene is to be found almost throughout the whole of the 

 vegetable and animal kingdoms. The following summary will give some in- 

 dication of the variety of j8-carotene sources. 



TABLE 32 



VEGETABLE SOURCES FROM WHICH /3-CAROTENE HAS BEEN ISOLATED 



Source References 



a) Fruit: 



Arbutus K. Schon, Bwcheni. J. 2g (1935) 1779. 



Capsicum frutescens jap. [skin)!^. Zechmeister and L. v. Cholnoky, Ann. 489 



(1931) 1. 

 Capsicum japonicum (skin) L. Zechmeister and L. v. Cholnoky, Ann. 454 (1927) 



54; 455 (1927) 70; 509 (1934) 269. 



Wackenroder, Geigers Magazin Pharm. 33 (1831) 141. For nearly 100 years, caro- 

 tene as isolated from the carrot was regarded as a homogenous compound. It was only by 

 means of modern chemical and physical methods of separation (particularly chromato- 

 graphy) that the complex nature of carotene was established. It was recognised by several 

 investigators simultaneously that the carrot pigment is a mixture of several isomers in 

 which ^-carotene predominates. Investigations in which several times recrystallised caro- 

 tene were employed therefore relate to materials consisting mainly of ^-carotene. 



References p. id^-i^o. 



