Methylspinazarin is a naphthoquinone bacterial metabolite that has been found in Streptomyces and is an inhibitor of catechol O-methyltransferase (COMT; IC50 = 0.8 μg/ml).1 It is selective for COMT over tyrosine hydroxylase, DOPA decarboxylase, and dopamine-β-hydroxylase at 100 μg/ml. Methylspinazarin decreases blood pressure in spontaneously hypertensive rats when administered at a dose of 50 mg/kg.