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LECITHINS. 243
The various lecithins stand close to each other in regard to constitu-
tion. The amount of phosphorus varies between 3.7-3.97 per cent and
the amount of nitrogen between 1.7-1.9 per cent. The so-called
di-stearyl-lecithin studied by Hoppe-Seyler and Diacoxow,1
which
probably has a different structure, has the formula C44H90XPO9. Erlaxd-
sex gives the formula C^HsoNPOj for the lecithin isolated by him from
the heart muscles.
On saponification with alkalies or baryta-water, lecithin yields fatty
acids, glycerophosphoric acid, and choline. It is remarkable that in
the cleavage of lecithins a smaller amount of nitrogen than corresponds
to the choline is obtained. Mac Lean 2
who has especially investigated
this could not re-obtain the total nitrogen in the lecithins as choline but
only a part thereof—from heart muscle lecithin, 42 per cent, and from egg-
yolk lecithin, G5 per cent. He is therefore of the opinion that the choline
group is not the only nitrogenous group in the lecithins and that there-
fore the generally accepted formula for lecithin is incorrect. Trier 3
has indeed obtained aminoethyl alcohol as a cleavage product from sev-
eral phosphatides, which he calls lecithins, but because of the difficulty
in preparing phosphatides in a pure condition we are not sure that he was
"working with pure substances. Lecithin is slowly decomposed by
dilute acids. Besides small quantities of glycerophosphoric acid we
have large quantities of free phosphoric acid split off. The lecithins
are also decomposed by enzymes (lipase) with the splitting off of fatty
acids.
Lecithin is optically active, and as the glycerophosphoric acid which
can be split off is also active, Willstatter and Ludecke 4
claim that the
phosphoric acid is not bound on the middle unsymmetric CH group, but
rather at the end CH2 group of glycerin.
Lecithin, according to Hoppe-Seyler,5
is found in nearly all animal
and vegetable cells thus far studied, and also in nearly all animal fluids.
It is especially abundant in the brain, nerves, fish eggs, yolk of the egg,
electrical organs of the Torpedo electricus, semen, and pus, and also in
the muscles and blood-corpuscles, blood-plasma, lymph, milk, especially
woman’s milk, and bile. Lecithin is also found in different pathological
tissues or liquids. As the presence of lecithin is only indirectly deter-
mined by the detection of phosphorus in organic combinations, it must
be borne in mind that the above assertions relate chiefly to the occur-
rence of phosphatides.
1
Hoppe-Seyler, Med. chem. Unters., Heft 2 and 3.
2
Zeitschr. f. physiol. Chem., 59 and Bioch. Centralbl., 9.
3
1. c, Zeitschr. f. physiol. Chem., 73, 76 and 80.
4
Ber. d. d. chem. Gesellsch., 37.
5
Physiol. Chem. Berlin, 1877-81, p. 57.
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