Dopastin (Inhibitor for dopamine β-hydroxylase), FNK-00381, Dopastin produced by a Pseudomonus No.BAC-125 is a potent inhibitor of dopamine β-hydroxylase of beef adrenals, and its IC50 value is 4.7 × 10-6 M.1) Dopastin shows a significant hypotensive effect to spontaneously hypertensive rats and a phytotoxicity to barley germination.2) Structure and synthesis method is described.3) Dopastin has low toxicity (oral LD50:750 mg/kg, i.p. LD50:460 mg/kg in mice)