3‐ n ‐Butylphthalide

3‐ n ‐Butylphthalide (NBP) is one of the chemical constituents in celery oil. It exhibits pharmacological properties that are useful in the treatment of hypertension. The metabolism and excretion of NBP were studied in four healthy Chinese male volunteers after a single oral administration of 200 mg. A total of 23 metabolites were observed in human plasma and urine. Pharmacokinetics data revealed the presence of four major side‐chain hydroxylated metabolites in human plasma. The biological activities of these metabolites were higher than that of NBP. Other minor phase I metabolic reactions were opening of the lactone ring, aryl hydroxylation, and β‐oxidation. Numerous phase II metabolites (glucuronide and sulfate conjugates) were also identified. About 82% of the administered dose was excreted in human urine. Predominant metabolic pathways of NBP were ω‐carboxylation followed by acyl glucuronide conjugation and glucuronide conjugation of monohydroxylated NBP.