The cyanobacterium Nodularia PCC 7804, of freshwater origin, produces [L-Har2]nodularin.

The cyanobacterium Nodularia PCC 7804, an axenic, non gas-vacuolate strain from a freshwater source, produces several metabolites with cyanobacterial hepatotoxin characteristics. The most abundant is a cyclic pentapeptide, [L-Homoarginine2]nodularin. [L-Har2]nodularin is of similar toxicity, in terms of bioassay in vivo, and the inhibition of protein phosphatase-1 in vitro to nodularin, which was present in lesser amounts in the cultures.