Insulin

Uses

Primary

• Pharm: WHO LEM treatment for diabetes mellitus
• Precursor for WHO LEM component NPH insulin

Natural occurrence

• Insulins do occur naturally. Various forms exist in many land vertebrates and some fish. Bovine versions are remarkably similar to Human insulin.

Hazards

• Overdose is potentially lethal via hypoglycemia

Production

Extraction

Several sketches of the extraction process appear in The Chemistry of the Hormones

Preparations

• One USP Insulin Unit is equivalent to 0.0342 mg of pure insulin derived from beef or 0.0345 insulin derived from pork.
• Insulin, as extracted, is considered short-acting (or immediate-acting) insulin
• A preservative such as phenol is commonly included (at 0.1%) and enough sodium chloride is included to make the solution isotonic.
• Zinc salts are also occasionally included (~2mg per 1000 units) in order to stabilize the physical structure of insulin.

Purification

Various methods of purification are discussed in The Chemistry of the Hormones, including this final one, which is quite explicit:

Equal volumes of fresh minced pancreas and 95 per cent alcohol are allowed to stand for several hours, with occasional shaking, and then filtered. Two volumes of 95 per cent alcohol are added to the filtrate. At this stage much of the protein is precipitated, but the insulin still remains in solution. The precipitate is allowed to settle for several hours, the mixture is filtered, and the filtrate is evaporated to a small volume by distillation in vacuo at a temperature of from 100 to 300°. The lipoids(sic) are now removed by means of ether, and the aqueous extract which remains is further evaporated (in vacuo) to a pasty consistency. Eighty per cent alcohol is now added to the mixture, which is then centrifuged. Four layers separate out: a bottom layer of salt crystals; a saturated aqueous solution of salt above it; above this a flocculent layer of protein; and on top a layer of alcohol containing the insulin in solution. The alcohol layer is removed with a pipette and added to several volumes of 95 per cent (or, still petter, absolute) alcohol. After standing for several hours, the precipitate, containing the insulin, is dissolved in water and concentrated in vacuo to the desired volume. The product is passed through a Berkefeld filter and is then ready for use. The extract is practically free from proteins, salts and alcohol-soluble substances and can be made isotonic and injected subcutaneously without local reaction. 

Storage

• All modern sources agree that storage of sufficiently pure insulin at room temperature is possible for up to four weeks, while storage beyond that time should be refrigerated (2-7°C)
• Older sources say that insulin can be stored indefinitely at room temperature, but caution that even lightly heating the solution at non-neutral pH can destroy its potency.

See Also

• Epinephrine
• US patent 1469994 "Extract obtainable from the mammalian pancreas or from the related glands in fishes, useful in the treatment of diabetes mellitus, and a method of preparing it"
  Link courtesy Google original
• US patent 2449076 "Process of extracting antidiabetic substance from pancreas"
  Link courtesy Google
• US patent 2466487 "Process of obtaining insulin from pancreas glands"
  Link courtesy Google
• DODDS, E. C.; DICKENS. (1924.) "SOME OBSERVATIONS ON THE PROPERTIES AND PREPARATION OF INSULIN, WITH SPECIAL REFERENCE TO THE PICRATE-ACETONE METHOD OF PREPARATION."
  From the Biochemical Department, the Bland-Sutton Institute of Pathology,