54
F. B. SHORLAND
The seed fat of Simmondsia californica (Buxaceae) is unique in
that it consists of wax esters of higher unsaturated alcohols with higher
unsaturated fatty acids, glycerides being entirely absent. The main
fatty acid constituent is eicos-11-enoic acid (263).
In the animal kingdom, waxes are of sporadic and infrequent occurrence. Perhaps the best-known wax is the sperm oil obtained from the
head and blubber of the sperm whale, Physeter macrocephalus, the
fatty acids of which consist of Ci 0 -Ci 8 n-saturated and C 14—L>22 unsaturated acids. The fatty acid composition (cf. Section IV,B,2) resembles that of a typical marine fish oil, but the average molecular
weight of the fatty acids, which are largely monoethenoid, is lower
(167).
The lipid secretions of the skin and hair, including wool, as well as
those of the preen glands of birds, appear to consist largely of waxlike
substances, though glycerides may also be present in some cases. The
presence in the waxlike secretions of a wide range of straight-chain, oddand even-numbered carbon fatty acids, saturated and unsaturated, as
well as branched-chain acids has been shown. As will be discussed in
Section VI, the presence of this unusual range of straight- and branchedchain acids, which varies in different species, serves to distinguish these
waxlike substances from those found elsewhere.
The evidence considered in the present section points to some differentiation of fatty acid distribution in waxes in the different forms of
life. In the acid-fast bacteria, the waxes are characterized by the presence of the unique mycolic acids, the mycolic acids varying perhaps in
the different strains and types of acid-fast bacteria. In the plant and
insect world, the waxes contain the higher n-saturated acids as well as,
in some cases at least, the corresponding ω-hydroxy acids. However, in
the seed wax of Simmondsia californica, the occurrence of an unsaturated fatty acid, eicos-11-enoic acid, forms a striking exception. In the
higher animals the formation of a wax with the fish oil type of fatty
acids in the main fatty depots of the sperm whale provides a parallel in
the animal kingdom. The waxlike secretions of the hair, skin, and preen
glands of the higher animals afford a fatty acid distribution that is not
paralleled by the waxes occurring in other forms of life.
Related to the waxes are the cholesterol esters, which are of widespread occurrence, usually in minor amounts, in animal tissues. However,
in blood plasma they are a major lipid constituent. The fatty acids present in cholesterol esters in blood plasma (276, 277) and in liver (278)
are characterized by their exceptionally high content (approximately
90%) of unsaturated acids consisting chiefly of linoleic acid. However,
when di- and polyenoic acids are restricted in the diet, the amounts of
F. B. SHORLAND
The seed fat of Simmondsia californica (Buxaceae) is unique in
that it consists of wax esters of higher unsaturated alcohols with higher
unsaturated fatty acids, glycerides being entirely absent. The main
fatty acid constituent is eicos-11-enoic acid (263).
In the animal kingdom, waxes are of sporadic and infrequent occurrence. Perhaps the best-known wax is the sperm oil obtained from the
head and blubber of the sperm whale, Physeter macrocephalus, the
fatty acids of which consist of Ci 0 -Ci 8 n-saturated and C 14—L>22 unsaturated acids. The fatty acid composition (cf. Section IV,B,2) resembles that of a typical marine fish oil, but the average molecular
weight of the fatty acids, which are largely monoethenoid, is lower
(167).
The lipid secretions of the skin and hair, including wool, as well as
those of the preen glands of birds, appear to consist largely of waxlike
substances, though glycerides may also be present in some cases. The
presence in the waxlike secretions of a wide range of straight-chain, oddand even-numbered carbon fatty acids, saturated and unsaturated, as
well as branched-chain acids has been shown. As will be discussed in
Section VI, the presence of this unusual range of straight- and branchedchain acids, which varies in different species, serves to distinguish these
waxlike substances from those found elsewhere.
The evidence considered in the present section points to some differentiation of fatty acid distribution in waxes in the different forms of
life. In the acid-fast bacteria, the waxes are characterized by the presence of the unique mycolic acids, the mycolic acids varying perhaps in
the different strains and types of acid-fast bacteria. In the plant and
insect world, the waxes contain the higher n-saturated acids as well as,
in some cases at least, the corresponding ω-hydroxy acids. However, in
the seed wax of Simmondsia californica, the occurrence of an unsaturated fatty acid, eicos-11-enoic acid, forms a striking exception. In the
higher animals the formation of a wax with the fish oil type of fatty
acids in the main fatty depots of the sperm whale provides a parallel in
the animal kingdom. The waxlike secretions of the hair, skin, and preen
glands of the higher animals afford a fatty acid distribution that is not
paralleled by the waxes occurring in other forms of life.
Related to the waxes are the cholesterol esters, which are of widespread occurrence, usually in minor amounts, in animal tissues. However,
in blood plasma they are a major lipid constituent. The fatty acids present in cholesterol esters in blood plasma (276, 277) and in liver (278)
are characterized by their exceptionally high content (approximately
90%) of unsaturated acids consisting chiefly of linoleic acid. However,
when di- and polyenoic acids are restricted in the diet, the amounts of