J AOAC Int. 2021 Jan 20:qsab009. doi: 10.1093/jaoacint/qsab009. Online ahead of print.
BACKGROUND: Posaconazole is a triazole antifungal drug approved by FDA in 2006. No bioassay is available in literature or official codes for potency determination in bulk.
OBJECTIVE: To conduct an analytical study focused on posaconazole in bulk.
METHODS: An alternative microbiological assay was validated for drug quantitation, applying agar diffusion technics (3 x 3 design), using Saccharomyces cerevisiae ATCC MYA 1942 as test microorganism (2% inoculum). An isocratic HPLC-DAD method, with C8 Shim-pack column (250 x 4.6 mm, 5 μm) and methanol:water (75:25 v/v) mobile phase was used for stress stability by photolysis and oxidation, indicating the formation of degradation products, which were investigated by UPLC-QTOF-MS.
RESULTS: The established conditions for the bioassay were satisfactory. It was linear in the range evaluated (2.5 - 10.0 µg/mL), as well as precise, accurate and robust. Stress tests showed drug susceptibility to the factors evaluated (60 % of degradation after 120 min). Kinetics curves for photolytic decomposition followed first-order. From photolytic and oxidative degraded matrix, three major degradation products were identified as being derivatives with modifications in the piperazine central ring and in the triazole and triazolone side chains, whose mass spectra results were m/z 683 (DP1), m/z 411 (DP2), m/z 465 (DP3).
CONCLUSIONS: Microbiological method was adequately validated and demonstrated to be equivalent to physico-chemical ones. Impurities found are described for the first time in studies with posaconazole raw material.
HIGHLIGHTS: a microbiological bioassay was developed for posaconazole; first-order kinetics was determined for photolytic degradation; structures for new degradation products were suggested.