Direct HPLC separation of enantiomers of main moguisteine metabolite: comparison of different stationary phases.

Moguisteine is a new non-narcotic antitussive agent. The molecule contains a chiral centre, which is maintained in the metabolite structure. The unchanged drug is not found in the plasma of treated animals or humans. The main moguisteine metabolite, M1, is the free racemic acid generated by hydrolysis of the ethyl-ester group of moguisteine. HPLC separation of M1 enantiomers was attempted using various chiral stationary phases. Separation of the enantiomers was achieved with alpha-1-AGP and beta-cyclodextrin columns, which showed similar enantioselectivity and good resolution. However, the routine application of alpha-1-AGP columns turned out to be difficult, due to the limiting low flow rate which displayed baseline problems and progressive loss of resolution. beta-Cyclodextrin columns showed greater efficiency than alpha-1-AGP columns, as the former allows reproducible separation and can easily be applied to biological sample analysis in pharmacokinetic studies.