(R)-Lisinopril Sodium Salt is the R,S,S-Isomer of Lisinopril. Lisinopril is a potent inhibitor of angiotensin-converting enzyme (ACE). Lisinopril prevents the conversion of angiotensin I to angiotensin II, which acts as a potent vasoconstrictor and also signals the release of aldosterone, which modulates sodium absorption. ACE inhibition has the net result of vasodilation and increased sodium and water excretion. Lisinopril, (2S)-1-[(2S)-6-amino-2-[[(1S)-1-carboxy-3-phenylpropyl]amino] hexanoyl]pyrrole-2-carboxylic acid is an angiotensin-converting enzyme (ACE) inhibitor, used for the treatment of hypertension, heartfailure andacutemyocardial infarction. The RSS isomer of lisinopril ((2S)-1-[(2S)-6-amino-2-[[(1R)-1-carboxy- 3-phenylpropyl]amino]hexanoyl]pyrrole-2-carboxylic acid) is an impurity (impurity E) resulting from the synthesis of lisinopril. The impurity profile of a drug substance is critical to its safety assessment and is important for monitoring the manufacturing process.