The invention provides a method for preparing a biologically active complex, said method comprising dissolving a mixture of a polypeptide element, such as alphalactalbumin or fragments thereof, in powder form and oleic acid or a pharmaceutically acceptable salt thereof also in solid form, in an aqueous solvent comprising a mixture of at least two and preferably three salts, wherein the method is carried out at moderate temperatures. The preparation does not require extensive heating and so is simple and efficient to carry out.
