GB754885A - Recovery of heparin - Google Patents

Abstract

Heparin is recovered from an alkaline or substantially neutral aqueous solution containing also a protein by adding a soluble salt of an alkali metal, or of ammonium, or of an alkaline earth metal to said solution, acidifying the solution to precipitate the protein, removing the protein and recovering the heparin from the remaining solution. The solution of the proteinheparin mixture may have a pH between 7 and 10. Sufficient soluble salt may be added to produce an anion concentration of at least about one mol. per litre. Suitable salts which may be used are alkali metal and ammonium citrates, halides, acetates, sulphates and thiocyanates, and alkaline earth metal halides, acetates and citrates, e.g. sodium chloride, sodium thiocyante, calcium chloride and acetate, and ammonium sulphate and citrate may be used. When sodium chloride is used, the solution may be acidified to a pH of less than 4, e.g. when between about 100 grams and about 150 grams of sodium chloride is used, the solution may be acidified to a pH of about 2.5 to precipitate the protein. The heparin solution containing protein may be obtained by autolyzing heparinbearing animal tissue, extracting the autolyzed tissue with an aqueous solution of alkali, e.g. ammonium sulphate and sodium hydroxide, heating the mixture, filtering to remove the coagulated substance, acidifying to precipitate a protein-heparin complex which is dissolved in water at a pH of at least 7 to form the solution for the above process. The process is applicable to heparin mixtures containing denatured or native proteins. The temperature at which protein coagulation is effected may vary from about 0 DEG C. to about 100 DEG C.-heating during or after the acidification being particularly useful. Suitable acids which may be used for the acidification are strong inorganic and strong organic acids such as sulphuric, hydrochloric and trichloroacetic acids. The heparin is preferably precipitated from the protein-free solution by adding a water-miscible organic solvent such as methyl or ethyl alcohol or acetone. When the soluble salt used in the above process is not very soluble in ethyl alcohol or acetone, it is desirable to subject the filtrate to dialysis to remove the salt before the heparin is precipitated. Alternatively, the precipitated heparin containing the salt may be dissolved in water, the solution subjected to dialysis to remove the salt, and reprecipitating the heparin with alcohol or acetone. The process is suitable for the purification of heparin, e.g. impure heparin can be mixed with an acid precipitable protein such as casein, the mixture is acidified and the resulting precipitated heparin-protein complex can then be treated by the above process. A number of detailed examples are given. U.S.A. Specification 2,623,001 is referred to.