CAROTENOIDS 



is the characteristic carotenoid (see p. 132). Fucoxanthin is certainly 

 absent from Chlorella vulgaris. ^ ^ ' 



The recent work of Karrer and his coileagues^^^ on Chara cerato- 

 phylla and on Nitella syncarpa is most interesting for they find the 

 carotenoid distribution to be differential. The vegetative parts contain 

 principally a- and p-carotene, whereas the antherida contain mostly 

 -^-carotene together with small amounts of lutein (xanthophyll) 

 and still smaller amounts of ^-carotene. Strain ^^^ has stated that 

 a- carotene is the major carotene of certain Siphonales and that 

 £-carotene {see p. 137) occurs in Bryopsis corticulans. He also reports the 

 presence of a carotenoid very similar to, but chromatographically 

 different from, fucoxanthin ; about 50 per cent, of this pigment, which 

 has been named siphonaxanthin, occurs as an ester which has been 

 named siphonein. 



Carotenoids occur in Lyngbya perelegans. ^ '* ^ 



Seybold and Egle^'^^ have investigated quantitatively the carotene 

 and xanthophyll fractions of a number of Chlorophyceae. Representa- 

 tive values, obtained on Ulva lactuca, were 4-4 and 21-8 mg. per 100 g. 

 wet weight, of carotenes and xanthophylls respectively (see also Table 

 22). For all the species examined the xanthophylls : carotenes ratio 

 was between 5 : 1 and 6:1. The same ratio was obtained for fresh 

 water algae. ^ * ^ 



Xanthophyceae 



Little is known of the carotenoids of this class of alga. Poulton ^ * ^ 

 indicated the presence of an hydroxy carotenoid which gave a blue 

 colour with concentrated HCl. Carter et al.^^^ were able to examine 

 only one member of this group, the mud alga Botrydium granulatum. 

 ^-carotene and Poulton's carotenoid were detected ; there is good 

 reason to beheve that the latter is flavoxanthin, for it had the same 

 absorption spectrum as a sample of flavoxanthin isolated from green 

 leaves.^** The only other pigment giving the same type of colour 

 reaction with HCl is violaxanthin which has a very different absorption 

 spectrum (Table 2). 



p-carotene has been detected in the fresh water Tribonema bombyci- 

 num which also contains a number of xanthophylls none of which 

 appears to be a known pigment. ^ * ^ 



Bacillariophyceae (Diatoms) 



In nearly all diatoms examined ^-carotene has been identified (see 

 e.g. Strain, Manning and Hardin). ^ ^ ^ An apparently new carotene, 

 z-carotenSj has been detected in Nitzschia closterium and Navicula 



130 



