GB715821A - Improvements relating to the manufacture of sulphuric esters of dextran - Google Patents

Abstract

A solution containing dextran sulphate of varying molecular weight is treated with a precipitating agent whereby the large toxic molecules are precipitated first; fractional precipitation then gives one or more fractions of lower molecular weight suitable as blood anticoagulants. The final solution contains molecules too small to have therapeutic activity and is discarded. The fractions retained are those having intrinsic viscosities between 0.01 and 0.035. It is preferable to fractionate the dextran before sulphation also, discarding those fractions of intrinsic viscosity above 0.12. In the examples: (1) a solution of raw dextran is partially degraded with acid, neutralized with lime and fractionally precipitated with acetone; the desired fraction is dried and esterified with chlorsulphonic acid and pyridine, the pyridine salt of the sulphate ester being converted into the sodium salt and the latter freed from pyridine and most of the inorganic salts by successive passage through cation-exchange and anion-exchange resins; the resulting solution is treated with a small quantity of acetone and the precipitate discarded; five further fractions are then precipitated with acetone, the supernatant liquor being discarded; (2) a solution of the sodium salt of dextran sulphate is treated with ethanol until a turbidity appears; the mixture is then warmed until it clears and allowed to cool, when a syrup separates; this is triturated with ethanol to give a powder (first fraction); five further fractions are obtained similarly. Tables are given of the properties of the various fractions obtained in each example. The first Provisional Specification refers to the similar treatment of polysaccharide sulphates in general. Specification 695,787 is referred to.