540 VI. CAROTENOIDS AND RELATED COMPOUNDS 



one-half of that of /S-carotene,™'^^"'^*^''^^ the potency of that prepared from 

 Miynulus longiflorus^^^ (monkey flower), and Pyracantha angustifolia 

 Schneid. (narrow-leaf firethorn) '^^ has been shown to be only approxi- 

 mately 26% of that of j3-carotene. More recently, an all-^raws-7-carotene, 

 prepared by isomerization of a natural poly-cis compound, namely pro-7- 

 carotene, has been found to have a definitely higher biological value, 

 42^190 -y-Carotene is sometimes referred to as /3-lyco-/3'-carotene, since 

 the open ring has the same configuration as lycopene. 



7-Carotene is quite widely distributed in nature, but it is usually present 

 in exceedingly small amounts. It has been found in commercial carotene, 

 especially that obtained from palm oil,^^^ to the extent of 0.1%.^® It also 

 constitutes about the same proportion in the carotene prepared from 

 carrots,*® and makes up a considerable percentage of the pigment in the 

 apricot {Prunus anneniaca) .^^^ It has also been shown to be a component 

 of the Dutch East Indian fruit Gonocaryum pyriforme,^'^'^^^ where it may 

 account for over 50% of the total carotenoids. Willstaedt"® reported the 

 preparation of 7-carotene from the fruit of the Rosa rugosa Thumb, (red 

 rugosa single rose) . According to Kuhn and Grundmann, ^^^ this carotenoid 

 is present in the rose hips of Rosa eglanteria L. (sweetbriar) . Other interest- 

 ing sources of 7-carotene are from the berries of the lily-of-the-valley 

 (Convallaria majalis)^^ and from the fruit of two varieties of pyracantha 

 (firethorn). It has been isolated in large amounts from the berries of 

 Pyracantha angiistijolia Schneid., ^^'^ while it is present in only small amounts 

 in the case of the berries of Pyracantha coccinia.^^^ MacKinney'^* found 

 that two parasitic plants commonly known as dodder, i.e., Cuscuta subin- 

 clusa and C. salina (salt-marsh dodder), are excellent sources of this pig- 

 ment. As much as 25 mg. of 7-carotene could be isolated per kilogram of 

 fresh material. Zechmeister and Schroeder^^ have also demonstrated the 

 presence of 7-carotene in the chaparral dodder, Cuscuta calif ornica. 



In some cases, flowers may also be an excellent source of 7-carotene. 

 This is ti-ue of the petals of the monkey flower (Mimulus longiflorus Grant, 

 Scrophulariaceae) from which it has been prepared in amounts of 45 to 75 



'*6 A. Winterstein, Z. physiol. Chem., 215, 51-58 (1933). 



'" R. Kuhn and H. Brockmann, Klin. Wock^chr., 12, 972-973 (1933). 



'** H. J. Deuel, Jr., C. Johnston, E. Sumner, A. Polgdr, W. A. Schroeder, and L. Zech- 

 meister, Arch. Biochem., 5, 365-371 (1944). 



i»5 H. J. Deuel, Jr., C. Hendrick, E. Strauh, A. Sandoval, J. H. Pinckard, and L. Zech- 

 meister, Arch. Biochem., I4, 97-103 (1947). 



>«° I.. Zechmeister, J. H. Pinckard, S. M. Greenberg, E. Straul), T. Fukui, and H. J. 

 Deuel, Jr., Arch. Biochem., 23, 242-245 (1949). 



"' R. F. Hunter and A. D. Scott, Biochem. J., 35, 31-38 (1941). 



i''^ H. Brockmann, Z. physiol. Chem., 216, 45-48 (1933). 



"3 R. Kuhn and C. Grundmami, Ber., 67, 339-344 (1934). 



"^ L. Zechmeister and W. A. Schroeder, Science, 94, 609-610 (1941). 



1^* G. MacKinney, J. Biol. Chem., 112, 421-424 (1935). 



