Rhodotorulic acid is the smallest of the 2,5-diketopiperazine family[1] of hydroxamate siderophores which are high-affinity chelating agents for ferric iron, produced by bacterial and fungal phytopathogens for scavenging iron from the environment.

[2] It is a tetradentate ligand, meaning it binds one iron atom in four locations (two hydroxamate and two lactam moieties), and forms Fe2(siderophore)3 complexes to fulfill an octahedral coordination for iron.

[3] Rhodotorulic acid occurs in basidiomycetous yeasts[4] and was found to retard the spore germination of the fungus Botrytis cinerea.

In combination with yeast Rhodotorula glutinis it was found to be effective in the biocontrol[5] of iprodione-resistant B. cinerea of apple wounds caused by the disease.