Captopril Captopril is an angiotensin-converting enzyme (ACE) inhibitor used to treat high blood pressure, heart failure, and certain kidney conditions. · Captopril is a sulfhydryl-containing analogue of proline with antihypertensive activity & antineoplastic activity. · Captopril is a specific competitive inhibitor of angiotensin I-converting enzyme (ACE) that enzyme responsible for the conversion of angiotensin I to angiotensin II. Captopril is a white to off-white crystalline powder that may have a slight sulphurous odour; it is soluble in water, methanol, & ethanol and sparingly soluble in chloroform and ethyl acetate. Discovery of Captopril · One of the first drugs marketed for lowering blood pressure was found by studying the venom from Bothrops jararaca, a poisonous snake. Captopril, an analog of the snake venom's ACE-inhibiting peptide, was first synthesized in 1975 by three researchers at the U.S. drug company E.R....