60
F. B. SHORLAND
differences in the distribution of dienoic and trienoic acids between the
phospholipid and glyceride fractions have been found. The ratios of
Cis triene: diene in the depot glycerides, liver glycerides, and liver
phospholipids of the horse were reported as 4.22, 2.39, and 0.13, respectively (183). Similar, but not so marked, differences are found also
in the lipids of the rabbit (287).
2. Phospholipids of Phnts
In general the range and types of fatty acids in the plant phospholipids (see Table XVII) are similar to those of the corresponding glycerides. The amounts of unsaturated C 2 o-C 2 2 shown in Table XVII have
been calculated from the saponification equivalents of the residual fractions obtained during ester fractionation. Klenk and Debuch (291) reexamined the phospholipids of soybean oil and rapeseed oil but were
unable to substantiate these findings. The acids from the ether-insoluble
polybromides from the phospholipid fatty acids, when hydrogenated,
yield pure stearic acid. It is therefore unlikely that the highly unsaturated C 20 and C 22 acids characteristic of animal phospholipids are
present in plant phospholipids.
In plants, the seed and leaf phospholipids are shown to contain the
same fatty acids as are present in the corresponding glycerides, albeit
in slightly different proportions. The phospholipids as compared with the
glycerides tend to contain more saturated acids, particularly palmitic
acid. There is more linoleic acid in phospholipids than in glycerides but,
linolenic acid, when present, is concentrated in the glycerides.
3. The Fatty Acid Composition of Specific Phospholipids and Related
Substances
Earlier work in this field involved the separation and purification of
individual phospholipids by precipitation methods. The purified phospholipid thus obtained, often in low yield, was probably not representative in its fatty acid composition of the material as it existed in the
tissues. However, the more recent work involving the use of chromatography and countercurrent extraction is perhaps less defective in this
respect.
In connection with studies on the flesh lipids of ijsh, Lovern and
Olley (292, 293) have shown that the phospholipids οΐ haddock flesh,
which contains very little glyceride, have a high content of highly unsaturated C 20 and C 22 acids, but no hexadecenoic acid. This acid is, of
course, usually found in quantity in fish oils. The fatty acid composition of the main phospholipid component—lecithin—is compared in
Table XVIII with that of the main depot fat.
F. B. SHORLAND
differences in the distribution of dienoic and trienoic acids between the
phospholipid and glyceride fractions have been found. The ratios of
Cis triene: diene in the depot glycerides, liver glycerides, and liver
phospholipids of the horse were reported as 4.22, 2.39, and 0.13, respectively (183). Similar, but not so marked, differences are found also
in the lipids of the rabbit (287).
2. Phospholipids of Phnts
In general the range and types of fatty acids in the plant phospholipids (see Table XVII) are similar to those of the corresponding glycerides. The amounts of unsaturated C 2 o-C 2 2 shown in Table XVII have
been calculated from the saponification equivalents of the residual fractions obtained during ester fractionation. Klenk and Debuch (291) reexamined the phospholipids of soybean oil and rapeseed oil but were
unable to substantiate these findings. The acids from the ether-insoluble
polybromides from the phospholipid fatty acids, when hydrogenated,
yield pure stearic acid. It is therefore unlikely that the highly unsaturated C 20 and C 22 acids characteristic of animal phospholipids are
present in plant phospholipids.
In plants, the seed and leaf phospholipids are shown to contain the
same fatty acids as are present in the corresponding glycerides, albeit
in slightly different proportions. The phospholipids as compared with the
glycerides tend to contain more saturated acids, particularly palmitic
acid. There is more linoleic acid in phospholipids than in glycerides but,
linolenic acid, when present, is concentrated in the glycerides.
3. The Fatty Acid Composition of Specific Phospholipids and Related
Substances
Earlier work in this field involved the separation and purification of
individual phospholipids by precipitation methods. The purified phospholipid thus obtained, often in low yield, was probably not representative in its fatty acid composition of the material as it existed in the
tissues. However, the more recent work involving the use of chromatography and countercurrent extraction is perhaps less defective in this
respect.
In connection with studies on the flesh lipids of ijsh, Lovern and
Olley (292, 293) have shown that the phospholipids οΐ haddock flesh,
which contains very little glyceride, have a high content of highly unsaturated C 20 and C 22 acids, but no hexadecenoic acid. This acid is, of
course, usually found in quantity in fish oils. The fatty acid composition of the main phospholipid component—lecithin—is compared in
Table XVIII with that of the main depot fat.