Stereo-selective oxidations of terpinolene by cytochrome P450 monooxygenases in the microsomal fraction of Cupressus lusitanica cultured cells

Abstract

We showed previously that in Cupressus lusitanica (Mexican cypress), the first two steps of terpinolene oxidation, beginning at hydroxylation at the aryl position and then forming epoxide at the double bond, were driven by cytochrome P450s. The significance of enantio differences, in general, has received attention because those enantiomers often have their own biological activities. We, therefore, investigated the stereo-specificity of the substrate and the enantio-selectivity of these reactions. The hydroxylation of terpinolene by cytochrome P450 in the microsomal fraction from C. lusitanica cells gave a single product with an S configuration of 5-isopropylidene-2-methylcyclohex-2-enol. Next, epoxidizing enzyme accepted only the S-configuration substrate and produced a single enantiomer product, (1R, 2S, 6S)-(+)-1,6-epoxy-4(8)-p-menthen-2-ol. No isomer was detected at our gas chromatography/mass spectrometry sensitivity; therefore, the calculated enantiomeric excess values were 100 %. These results indicate that the cytochrome P450s involved in terpinolene metabolism in C. lusitanica cells have very strict stereo-selective ability. Our findings may be helpful in the stereo-selective synthesis of fine chemicals, although the physiological meanings of these chiral products are still not unclear.