Dioctatin A hydrochloride is a metabolite of Streptomyces and acts as an inhibitor of human dipeptidyl aminopeptidase II. It curtails aflatoxin production in Aspergillus parasiticus with an IC50 of 0.4 μM. The compound reduces the mRNA levels of genes associated with aflatoxin biosynthesis and the regulatory gene aflR, inhibits conidiation, and decreases the mRNA levels of the brlA gene, while also promoting kojic acid production. Additionally, Dioctatin A hydrochloride inhibits the production of sterigmatocystin. It exerts multifaceted regulatory effects on the production and differentiation of fungal secondary metabolites.