Tacrolimus Impurity 6 (Tacrolimus Hydroxy Acid Impurity)

Tacrolimus Impurity 6 is a chemical compound that is used in the pharmaceutical industry as a reference standard for the analysis and identification of tacrolimus, a potent immunosuppressive drug. This impurity is a degradation product of tacrolimus and is formed during the manufacturing, storage, or handling of the drug. The presence of Tacrolimus Impurity 6 in tacrolimus samples can affect the potency, safety, and efficacy of the drug, and therefore, it is essential to monitor and control its levels in pharmaceutical preparations. Tacrolimus Impurity 6 is also known as 31-epi-tacrolimus, and its chemical formula is C44H69NO12. Its molecular weight is 813.01 g/mol, and its structure comprises a macrolide lactone ring, a hydroxyl group, and a tetrahydropyran ring. The impurity is a white to off-white powder that is soluble in organic solvents such as methanol, ethanol, and acetonitrile. Analytical methods such as high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) are used to quantify Tacrolimus Impurity 6 in tacrolimus samples. The acceptable limit of this impurity in tacrolimus drug products is not more than 0.5% of the total drug substance. The control of impurity levels is crucial for ensuring the quality and safety of tacrolimus-based therapies.