Stereoselective determination of midodrine and desglymidodrine in culture medium: application to a biotransformation study employing endophytic fungi.

A CE method was developed and validated for the stereoselective determination of midodrine and desglymidodrine in Czapek culture medium to be applied to a stereoselective biotransformation study employing endophytic fungi. The electrophoretic analyses were performed using an uncoated fused-silica capillary and 70 mmol/L sodium acetate buffer solution (pH 5.0) containing 30 mmol/L heptakis (2, 3, 6-tri-O-methyl)-β-CD as running electrolyte. The applied voltage and temperature used were 15 kV and 15°C, respectively. The UV detector was set at 200 nm. The sample preparation was carried out by liquid–liquid extraction using ethyl acetate as extractor solvent. The method was linear over the concentration range of 0.1–12 μg/mL for each enantiomer of midodrine and desglymidodrine (r≥0.9975). Within-day and between-day precision and accuracy evaluated by RSDs and relative errors, respectively, were lower than 15% for all analytes. The method proved to be robust by a fractional factorial design evaluation. The validated method was used to assess the midodrine biotransformation to desglymidodrine by the fungus Phomopsis sp. (TD2), which biotransformed 1.1% of (−)-midodrine to (−)-desglymidodrine and 6.1% of (+)-midodrine to (+)-desglymidodrine.