Succinic acid

Overview
Succinic acid (IUPAC systematic name: butanedioic acid; historically known as spirit of amber) is a dicarboxylic acid which plays a biochemical role in the citric acid cycle.

Physical properties
At room temperature, pure succinic acid is a solid that forms colorless, odorless crystals. It has a melting point of 185 °C and a boiling point of 235  °C. It is a diprotic acid. The carboxylate anion is called 'succinate and esters of succinic acid are called alkyl succinates.

Biochemical role
Succinate is a component of the citric acid cycle and is capable of donating electrons to the electron transfer chain via the following reaction:


 * succinate + FAD → fumarate + FADH2

This is catalysed by the enzyme succinate dehydrogenase (or complex II of the mitochondrial ETC). The complex is a 4 subunit membrane-bound lipoprotein which couples the oxidation of succinate to the reduction of ubiquinone. Intermediate electron carriers are FAD and three Fe2S2 clusters part of subunit B.

Mark Donnelly from Argonne National Laboratory developed one of the best strains (AFP 184) to convert raw hydrolysates from biomass to succinate.

History
Spirit of amber was procured from amber by pulverising and distilling it using a sand bath. It was chiefly used externally for rheumatic aches and pains, and internally in inveterate gleets.

Safety
The acid is combustible and corrosive, capable of causing burns. "Harmful by inhalation, ingestion and through skin absorption. Wash after handling. Eye contact may cause serious damage."

In nutraceutical form as a food additive and dietary supplement, is safe and approved by the FDA.

Oxidition reaction
Succinic acid can be converted to fumaric acid by oxidation.