520 VI. CAROTENOIDS AND RRLATED COMPOUNDS 



is present without chlorophyll, under which condition it may confer upon 

 the fruit its yellow or orange color, as, in fact, occurs in the case of peaches 

 {Primus persica), apricots (P. armeniaca), squash {Cucurhitaceae) , mango 

 {Mangifera indica L.),^" and like products. The wide distribution of /3- 

 carotene in the leaves of various plants has been shown by the studies of 

 MacKinney,^^ which are summarized in Table 1. 



Thus, it was found that carotene is present as the major pigment in 59 

 different plant species distributed among 40 botanical families. In 40 

 cases, a-carotene was also present in amounts ranging from a trace to as 

 high as 35%. 



Strain^^ carried out a study comparable to that of MacKinney with a 

 series of leaves from trees and from many common plants. By the use of 

 magnesium oxide columns, he determined whether the carotenoid was /3- 

 or a-carotene or a mixture of both. The following leaves were found to 

 contain jS-carotene but no a-carotene: Ailanthus altissima Swingle (tree of 

 heaven) ; Cynara scolymus L. (artichoke) ; Erodivm cicutarium L'Heritier 

 de Brutelle (afileria pin-clover or heronsbill) ; Grevillea robusta Cunningham 

 (silkoak) ; Hordeum vulgare L. (barley) ; Lathyrus odoratus L. (sweet pea) ; 

 Medicago hispida Gaertner (burr clover) ; Claytonia {Montia) perjoliata 

 Howell (miner's lettuce or winter purslane) ; Phoradendron villosum Nuttall 

 (California mistletoe) ; Rumex pidcher L. (fiddleleaf dock) ; Schinus molle L. 

 (California pepper tree) ; Siymphoricarpos albus Blake (snowberry) ; 

 Tropaeolum ma jus L. (nasturtium); Zauschneria calif ornica Presl. (Cali- 

 fornia fire-chalice); and Cladophora spp. (fresh-water alga). Another 

 series of leaves were shown to contain principally /3-carotene, although 

 a-carotene was also present in small concentration. In this group, leaves 

 from the following species are included : Mahonia {Berberis) nervosa Pursh 

 (Cascades barberry or Oregon grape) ; Brachychiton popidneus Brown 

 (kurrajong bottle-tree, sterculia); Calycanthus occidentalis Hooker and 

 Arnott (California sweet-shrub) ; Cupressus macrocarpa Hartweg (Monterey 

 cypress) ; Erioboirya japonica Lindley (loquat) ; Hydrangea paniculata 

 Siebold (panicle hydrangea) ; Phaseolus vulgaris L. (kidney bean) ; and 

 Photinia serrulata Lindley (Chinese photinia, shining shrub). Spinach 

 and nettles contain /3-carotene free from a-carotene, ^''■^^ while chestnut 

 leaves have a certain proportion of a-carotene associated with the /3-caro- 

 tene.^* Medicago saliva (lucerne grass) was found to contain /3-carotene 

 and phytoxanthin.^* 



Strain^^ later reported that |S-carotene is found in most higher plants, in a 



'" R. Yamamoto,, Y. Osima, and T. Goma, Sci. Papers Inst. Phys. Chem. Research 

 Tokyo, 19, 122-126 (1932). 



«i G. MacKinnev, J. Biol. Chem., Ill, 75-84 (1935). 



s2 H. H. Strain, J. Biol. Chem., Ill, 85-93 (1935). 



95 H. Willstaedt and T. K. With, Z. physiol. Chem., 253, 40-46 (1938). 



s^ H. H. Strain, Ann. Rev. Biochem., 13, 591-610 (1944). 



