90 SOME MISCELLANEOUS UNSAPONIFLABLE LIPIDS 



a-- 



C— C^C — CH=CHCH3 



Several of these highly unsaturated, conjugated compounds show light absorption in the 

 visible region and may therefore be classed as plant pigments which are similar in color 

 and other properties to some carotenoids. 



Long-chain aliphatic alcohols and ketones are also frequent constituents of plant 

 waxes. The alcohols almost always have an even number of carbons like the fatty acids, 

 whereas the ketones have an odd number like the hydrocarbons. Long-chain alcohols 

 which occur in the form of esters are discussed in Chapter 5. The unesterified alcohols 

 are particularly common in the leaf waxes of monocots but also appear in other types of 

 plant waxes. Unsaturated, long chain alcohols are uncommon in plants, but a few have 

 been reported. Sugar cane wax is unusual in containing polymeric, long chain aldehydes 

 (7). Some examples of the occurrence of these compounds are summarized in Table 1. 

 Long-chain acetylenic alcohols and ketones are of interest because of their pronounced 

 pharmacological effects. The first acetylenic compound to be isolated from plants, 

 car Una oxide from Carlina acaulis, is strongly toxic to animals and also bacteriocidal. 



^]^CH2C=C-Iljl 



It appears related to an acetylenic alcohol found as an acetate in Coreopsis: 



i Vc^C—C^C— CH=CHCH20H 



Both of these aromatic compounds could be derived by rir^ closure from a C13 alcohol 

 also found as an acetate in Carlina acaulis: 



CHj = CHCH = CH - C =C - C^C - C^CCH = CHCHjOH 



The roots of several umbelliferous plants owe their great toxicity to long-chain acetylenic 

 alcohols, of which the following are examples: 



OH 



I 

 HOCHjCHaCHaC^C - C = C(CH = CH)3 CHCH2CH2CH3 



cicutoxin (Cicuta virosa) „„ 



I 

 HOCH2CH = CHC^C - C^CCH = CHCH = CHCH2CH2CHCH2CH2CH3 



oenanthotoxin (Oenanthe crocata) 



