Enzymic reduction of [6]-gingerol,a major pungent principle of ginger,in the cell-free preparation of rat liver

A reductive metabolism of S-(+)-6]-gingerol 1-(4'-hydroxy-3'-methoxyphenyl)-5-hydroxydecan-3-one], the major pungent principle of ginger, was investigated in vitro with phenobarbital-induced rat liver 10,000 x g supernatant containing the NADPH-generating system. The ethyl acetate-extractable products were isolated and two metabolites were identified as diastereomers of 6]-gingerdiol by gas chromatrography/mass spectrometry. The ratio of two isomers formed in the above reaction was about 1:5, suggesting the stereospecific reduction of S-(+)-6]-gingerol by carbonyl reductase activity present in the postmitochondrial supernatant fraction of rat liver. The enzymic reduction of S-(+)-6]-gingerol thus introduces the second asymmetric carbon center in the molecule with concomitant production of S,S- and R,S-isomers of 6]-gingerdiol in different proportions. This stereospecific reduction of 6]-gingerol may be relevant to the clinical use of the compound.