Different stereoselectivity in the reduction of pulegone by Mentha species

Aqueous solutions of [H-2]-labeled pulegone enantiomers were fed to Mentha spicata ssp. spicata L. and Mentha spicata ssp. crispata L. shoot tip and f irst leaf pair. After solid phase microextraction the essential oil was ana lysed with enantioselective multidimensional gas chromatography/mass spectr ometry. Both Mentha spicata species were able to convert labelled (1R)- and (1S)-pulegone at the same rate into the corresponding menthone and isoment hone, indicating an unspecific process. The reduction of both pulegone enan tiomers preferably led to the cis-stereoisomers. The observed stereoselecti vity is completely different from those of pulegone reduction by Mentha x p iperita L.