Secondary compounds is a generic term to describe some molecules produced by organisms using different metabolic pathways. These metabolites have different functions but the most commonly studied ones have antibiotic, allelopathic or bioactive/toxic properties.
Allelopathic compounds include alkaloids, cyclic peptides, terpens and volatile organic compounds.
(Cyano-)toxins include alkaloids, polyethers, esters, cyclic peptides and lipopolysaccharides.