SAPONIFIABLE LIPIDS 75 



Macrocyclic lactones with a musk-like odor are exaltolide from Angelica roots and ambret- 

 tolide from seeds of Hibiscus abelnioschus. 



(CH2)|2 C^ 



I \rt exaltolide 



CH, C' 



y(CH2)7 CH2 



CH \ 



^^ . ^ / ambrettolide 



^CH(CH2)5-C; 



Waxes containing polymeric esters formed by the linking of several o) -hydroxy acids to 

 each other are especially prominent in the waxy coatings of conifer needles. The two 

 most common acids found in such waxes are sabinic and juniperic: 



HOCHzCCHaJwCOOH juniperic acid 



HOCH2(CH2)ioCOOH sabinic acid 



The polymers may be linear or cyclic. The general term used for this type of wax con- 

 stituent is "etholide" or "estolide". 



The lipid constituents of cork and cuticle are known respectively as suberin and 

 cutin. Cutin is tightly bound to other constituents within the cuticle layer and is therefore 

 distinguished from easily-removed outer deposits of wax. The exact chemical nature of 

 cutin and suberin remains obscure partly because the drastic chemical measures used in 

 obtaining them may have caused serious degradation to occur. However, what evidence 

 there is indicates that it is reasonable to group these substances with the high molecular 

 weight esters. Hydrolysis of suberin yields a little glycerol but cutin does not. Cutin is 

 also more resistant than suberin to attack by chemical reagents or enzymes. Suberin 

 has been considered to be an impure form of cutin. Saponification of both substances 

 yields several hydroxy fatty acids whose structures are not yet well established although 

 they have been given names. Phloionic, phloionolic, phellonic and phellogenic acids 



