Study of the Oscillatory In-vitro Transenantiomerization of the Antimers of Flurbiprofen and Their Enantioseparation by Thin-layer Chromatography (tlc)

In our earlier studies on the spontaneous in-vitro oscillatory transenantiomerization of profens we investigated optically pure S-(+)-ibuprofen and S-(+)-naproxen and the racemic mixtures S,R-(±)-2-phenylpropionic acid and S,R-(±)-ketoprofen, which remained in a state of dynamic equilibrium between the two antimers yet also had the ability to transenantiomerize. In this study we have demonstrated, for the first time, the spontaneous oscillatory in-vitro transenantiomerization of S-(+)-flurbiprofen (an important non-steroidal anti-inflammatory drug, NSAID) and R-(−)-flurbiprofen, as monitored by polarimetry. It is also noteworthy that – as far as we are aware – this is the first report of separation of the enantiomers of flurbiprofen by TLC. This separation was achieved by two-dimensional development using a simple chromatographic system comprising a commercial silica gel layer impregnated with L-arginine as stationary phase and ethanol containing a few drops of glacial acetic acid as mobile phase. Unfortunately, this chromatographic system resulted in catalysis of structural conversion of the optically pure flurbiprofen enantiomer, either S-(+), or R-(−), to the scalemic or racemic mixture of the two antimers. This is an interesting contribution to general knowledge about the reactivity of this particular profen, although the spontaneous and rapid conversion observed prevents use of this TLC system for identification and quantification of individual flurbiprofen enantiomers.