1. FATTY ACID OCCURRENCE AND DISTRIBUTION
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Examples of marked deviations in the composition of the saturated
acids include those of the stearic-rich seed fats (Section IV,D,4,h),
with up to 60% stearic acid as in Garcinia indica (270), the seed oils
rich in myristic acid as in Myristica fragrans with 76.6% myristic acid
(Section IV,D,4,i), the seed oils rich in lauric acid, as in Cocos nucifera
(272) with 45.2% lauric acid and the Ulmaceae with 50-73% decanoic
acid (Section IV,D,4,j). The amounts of higher saturated acids (Section IV,D,4,g) in seed fats seldom exceeds 10%, but in Adhatoda vasica
(269) these acids become major constituents with 22.2% behenic and
10.7% lignoceric.
In the cryptogams, the n-saturated acids usually consist mainly of
palmitic acid with lesser amounts of stearic acid. In yeasts and molds
the amounts are often like those of mammals.
In the fats of aquatic plants and animals there is, as a rule, about
10-15% of palmitic acid with lesser amounts of myristic and stearic
acids, but in the liver oils of some sharks the amounts of palmitic and
stearic acid may rise, respectively, to 25 and 15%. In amphibians and
reptiles (see Table III) a somewhat similar situation prevails. The
composition of their saturated acids approaches that of nonruminant
mammals in which palmitic acid comprises usually 25-30% and stearic
acid 3-10%. In a few nonruminants, however, the amounts of stearic acid
may rise to 20%, and in ruminants it commonly reaches this amount and
may even exceed that of palmitic acid.
The distribution and amounts of n-saturated acids in the depot fats
provides a limited basis for the classification of species.
The Palmae, Myristicaceae, and Ulmaceae are characterized by the
high contents in their seed fats of lauric, myristic, and decanoic acids,
respectively. Land mammals are characterized by the presence of 2530% palmitic acid in their depot fats, which serves, as a rule, to distinguish them from the seed fats as well as from fats of aquatic origin,
in which the amounts of palmitic acid are typically less than 20%. However, yeast and mold fats, which sometimes contain larger amounts of
palmitic acid, cannot thus be distinguished from mammalian fats.
2. n-Unsaturated Acids
The importance of these constituents in lipids may be seen from
the fact that in seeds oleic and linoleic acids are estimated to form 80%
of the total fatty acids, while oleic acid probably accounts for not less
than 40% of all the fatty acids synthesized (348).
The endogenous unsaturated acids of land mammals are almost exclusively oleic, with lesser amounts of palmitoleic acid.
In aquatic plants and animals, polyethenoid acids of the Ci 8 , C 20 ,
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Examples of marked deviations in the composition of the saturated
acids include those of the stearic-rich seed fats (Section IV,D,4,h),
with up to 60% stearic acid as in Garcinia indica (270), the seed oils
rich in myristic acid as in Myristica fragrans with 76.6% myristic acid
(Section IV,D,4,i), the seed oils rich in lauric acid, as in Cocos nucifera
(272) with 45.2% lauric acid and the Ulmaceae with 50-73% decanoic
acid (Section IV,D,4,j). The amounts of higher saturated acids (Section IV,D,4,g) in seed fats seldom exceeds 10%, but in Adhatoda vasica
(269) these acids become major constituents with 22.2% behenic and
10.7% lignoceric.
In the cryptogams, the n-saturated acids usually consist mainly of
palmitic acid with lesser amounts of stearic acid. In yeasts and molds
the amounts are often like those of mammals.
In the fats of aquatic plants and animals there is, as a rule, about
10-15% of palmitic acid with lesser amounts of myristic and stearic
acids, but in the liver oils of some sharks the amounts of palmitic and
stearic acid may rise, respectively, to 25 and 15%. In amphibians and
reptiles (see Table III) a somewhat similar situation prevails. The
composition of their saturated acids approaches that of nonruminant
mammals in which palmitic acid comprises usually 25-30% and stearic
acid 3-10%. In a few nonruminants, however, the amounts of stearic acid
may rise to 20%, and in ruminants it commonly reaches this amount and
may even exceed that of palmitic acid.
The distribution and amounts of n-saturated acids in the depot fats
provides a limited basis for the classification of species.
The Palmae, Myristicaceae, and Ulmaceae are characterized by the
high contents in their seed fats of lauric, myristic, and decanoic acids,
respectively. Land mammals are characterized by the presence of 2530% palmitic acid in their depot fats, which serves, as a rule, to distinguish them from the seed fats as well as from fats of aquatic origin,
in which the amounts of palmitic acid are typically less than 20%. However, yeast and mold fats, which sometimes contain larger amounts of
palmitic acid, cannot thus be distinguished from mammalian fats.
2. n-Unsaturated Acids
The importance of these constituents in lipids may be seen from
the fact that in seeds oleic and linoleic acids are estimated to form 80%
of the total fatty acids, while oleic acid probably accounts for not less
than 40% of all the fatty acids synthesized (348).
The endogenous unsaturated acids of land mammals are almost exclusively oleic, with lesser amounts of palmitoleic acid.
In aquatic plants and animals, polyethenoid acids of the Ci 8 , C 20 ,