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246 ANIMAL FATS AND PHOSPHATIDES.
Various methods have been suggested by Strecker, Hoppe-Seyler
and Diaconow, Thudichum, Gilson, Zuelzer and Bergell x
for the
preparation of the lecithins. As none of these yield a positively pure
product we will here only mention them. According to Erlandsen’s
experience all methods which are based upon the precipitation of the
lecithin as a metallic compound should be avoided. The best method
depends upon the solubility of the lecithin in alcohol and in ether in
the cold and its precipitation by acetone (Erlandsen, H. E. Roaf and
E. Edie 2
). The work of Erlandsen is especially referred to in the
preparation of lecithins.
For the present we have no quantitative method for estimating
lecithin. The methods used in the past, when the amount of lecithin
was calculated from the amount of phosphorus contained in the alcohol-
ether extract is useless, as in this case the phosphorous content of all
the phosphatides is determined and not alone of the lecithins. Even
the detection of choline is not evidence, as this base probably occurs also
in other phosphatides. In the detection of choline the double platinum
compound is ordinarily prepared, and this can be done as described
below. In special determinations of lecithin and cephalin Koch used
to heat with hydroiodic acid, and determined the methyl groups split
off below 240° and those at about 300°. Instead of this he recommends
with Woods 3
to separate the two by precipitation in alcoholic solution,
while boiling, with alcoholic lead acetate solution and a little ammonia,
which precipitates only the cephalin.
Of the cleavage products of the lecithins choline is of especially
great interest.
Choline (trimethyloxyethyl ammonium hydroxide),
/CH2 .CH2 .(OH)
C5H15 N02 ,
= HO.N<
X(CH3) 3 ,
stands in close "relation to the poisonous base neurine (trimethylvinyl
/(CH3 ) 3
ammonium hvdroxide), HO.N<^ , which according to Brieger
XCH:CH2
can be formed from choline by the action of bacteria, and also to mus-
/(CH3 ) 3
carine, HO.N<y , which is the aldehyde of choline and occurs in
XH2 CHO
/ ° \
the fly agaric, and also to betaine, trimethyl glycocoll, (CH3 ) 3 N<( /CO,
XCH-/
1
Strecker, Annal. d. Chem. u. Pharm., 148; Hoppe-Seyler and Diaconow, 1. c;
Thudichum, 1. c; Gilson, Zeitschr. f. physiol. Chem., 12; Zuelzer, ibid., 27; Bergell,
Per. d. d. chem. Gesellsch., 33.
2
Erlandsen. 1. c; Roaf and Edie, Thompson Yates Laboratory Reports, Vol. 6
part I, 1905.
3
Koch and Woods, Journ. of biol. Chem., 1.
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