Process for the preparation of a new-type active substance selectively inhibiting food intake

DETAILED DESCRIPTION What we claim is: 1.
A process for isolating a food intake suppressant from human or animal blood serum which comprises subjecting the human and/or animal blood serum to ultrafiltration on a membrane or hollow fiber ultrafilter passing a filtrate containing substances of a molecular weight of at most 50,000 daltons, partially evaporating the filtrate, removing the insoluble part from the concentrate obtained, adding trichloroacetic acid up to a concentration of 5 to 25 weight/volume percent to the liquid phase at a temperature of 0.
degree.
C.
to 10.
degree.
C.
, removing the proteins precipitated, subjecting the obtained solution to chromatography on a gel with an elution solution of pH 6.
0 to 7.
0, concentrating the biologically active fractions, chromatographing again on a gel with a void volume having a molecular weight of 3000 to 4000 daltons, fractionating by elution with water, lyophilizing the active fractions, dissolving the lyophilized fractions in a buffer of pH 8.
1 to 8.
2, adding trypsin and chymotrypsin to the solution in substantially identical amounts of 0.
01 to 0.
2 by weight as calculated for the total weight of the lyophilized product, subjecting the mixture to digestion at a temperature of 36.
degree.
C.
to 39.
degree.
C.
for 20 to 30 hours, adding after the first 5 hours an equal quantity of trypsin and chymotrypsin in a substantially half amount as calculated for the original enzyme quantity and continuing the digestion, then adding trichloroacetic acid to the reaction mixture up to a concentration of 4 to 6 weight/vol.
% at a temperature between 0.
degree.
C.
and 10.
degree.
C.
, keeping the mixture at a temperature between -15.
degree.
C.
and 5.
degree.
C.
for 1 to 24 hours, removing the insoluble part, subjecting the reaction mixture to chromatography on a gel with a void volume having a molecular weight of 3000 to 4000 daltons, fractionating by elution with water and lyophilizing the biologically active fractions to yield said food intake suppressant having a molecular weight between 40,000 and 50,000 daltons