Camalexin

Camalexin is a simple indole alkaloid found in the plant Arabidopsis thaliana and other crucifers. The secondary metabolite functions as a phytoalexin to deter bacterial and fungal pathogens.

Structure

The base structure of camalexin consists of an indole ring derived from tryptophan. The ethanamine moiety attached to the 3 position of the indole ring is subsequently rearranged into a thiazole ring.

Biosynthesis

While the biosynthesis of camalexin in planta has not been fully elucidated, most of the enzymes involved in the pathway are known and involved in a metabolon complex. The pathway starts with a tryptophan precursor which is subsequently oxidized by two cytochrome P450 enzymes. The indole-3-acetaldoxime is then converted to indole-3-acetonitrile by another cytochrome P450, CYP71A13. A glutathione conjugate followed by a subsequent unknown enzyme is needed to form dihydrocamalexic acid. A final decarboxylation step by cytochrome P450 CYP71B15, also called phytoalexin deficient4 results in the final product, camalexin.

Biological activity

Camalexin is cytotoxic against aggressive prostate cancer cell lines in vitro.