Indospicine is an

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 a ...

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 ''Indigofera'' is a varied genu ...

'' 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 guanidinium, guanidino group appended to a standard amino acid framework. At physiological pH, the carboxylic acid is deprotonated (−CO2−) a ...

. It is toxic to mammals and causes liver damage and

abortion Abortion is the early termination of a pregnancy by removal or expulsion of an embryo or fetus. Abortions that occur without intervention are known as miscarriages or "spontaneous abortions", and occur in roughly 30–40% of all pregnan ...

. 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 ''Indigofera spicata'', the creeping indigo or trailing indigo, is a species of flowering plant in the family Fabaceae. It is native to SubSaharan Africa, Madagascar, Mauritius, Réunion, and Yemen, and has been introduced to the southeastern Uni ...

'' 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 colored chemicals or substances. It can also be used for colorless chemicals that can be located by a stain or other visualisation method after separation. It is now primarily used as ...

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. 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

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