Indospicine is an

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...

not found in proteins, which occurs in ''

Indigofera ''Indigofera'' is a large genus of over 750 species of flowering plants belonging to the pea family Fabaceae. They are widely distributed throughout the tropical and subtropical regions of the world. Description Species of ''Indigofera'' are mo ...

'' species. The chemical resembles

arginine Arginine is the amino acid with the formula (H2N)(HN)CN(H)(CH2)3CH(NH2)CO2H. The molecule features a guanidino group appended to a standard amino acid framework. At physiological pH, the carboxylic acid is deprotonated (−CO2−) and both the am ...

. It is toxic to mammals and causes

liver damage Liver disease, or hepatic disease, is any of many diseases of the liver. If long-lasting it is termed chronic liver disease. Although the diseases differ in detail, liver diseases often have features in common. Signs and symptoms Some of the si ...

and

abortion Abortion is the termination of a pregnancy by removal or expulsion of an embryo or fetus. An abortion that occurs without intervention is known as a miscarriage or "spontaneous abortion"; these occur in approximately 30% to 40% of pregn ...

. Dogs are particularly sensitive to the toxic effect and can sicken or die after eating a grazing animal that has eaten ''Indigofera''.

History

For years it was known that '' Indigofera spicata'' was toxic to cows, rabbits and sheep. Both leaves and seeds are poisonous. Leaves were shown to contain ''β''-nitropropionic acid, which affected chickens, but it was not found in the seeds. M. P. Hegarty, and A. W. Pound performed experiments to isolate the toxin by examining its effect on mouse livers. They used absorption dialysis and

paper chromatography Paper chromatography is an analytical method used to separate coloured chemicals or substances. It is now primarily used as a teaching tool, having been replaced in the laboratory by other chromatography methods such as thin-layer chromatography ...

to separate chemical components from seeds, focusing on strong bases. Ninhydrin revealed where the different chemicals were on the paper used for chromatography. Bands were cut out of the paper, the substances extracted and then tested on the mice. Only one band was

hepatotoxic Hepatotoxicity (from ''hepatic toxicity'') implies chemical-driven liver damage. Drug-induced liver injury is a cause of acute and chronic liver disease caused specifically by medications and the most common reason for a drug to be withdrawn fro ...

. The substance was crystallised as a hydrochoride. The hydrochloride melted between 131 and 134°C. (α) + 18°. The ratio of elements was established and a rough molecular weight. From the degradation products, the structure was determined.

Properties

Between pH 2 and 10.5 indospicine is an ion with a single positive charge. In stronger alkaline conditions, it decomposes to ammonia and an amide. In strong acid L- α-amino-pimelic acid is formed. With ninhydrin, indospicine gives a purple colour. With nitroprusside-alkaline ferricyanide reagent a yellow colour is produced, indicating it is not a guanidine derivative.

References

Toxic amino acids Amidines {{Improve categories, date=August 2021