Transformation of terpenes using a Picea abies suspension culture

When subjected to a Picea abies suspension cell culture, β-pinene, either one of the pure enantiomers or the racemate, was transformed mainly to trans-pinocarveol along with the minor products myrtenol, α-terpineol, pinocarvone, myrtenal and cis-pinocarveol. The absolute configuration of the major products corresponded to that of the starting β-pinene enantiomer. Some of the primary transformation products, i.e. (1 S)- cis- and (1 S)- trans-pinocarveol, (1 R)-myrtenol and (4 S)-α-terpineol, were also tested as substrates of the P. abies suspension culture. They reacted more slowly than β-pinene but, except for (4 S)-α-terpineol, they were all transformed. Thus, (1 R)-myrtenol was converted into both (1 R)-myrtenal and (1 R)-myrtanol, whereas (1 S)- trans-pinocarveol was converted into (1 S)-pinocarvone. (4 R)-Limonene was slowly transformed by the suspension culture into limonene-(1,2)-epoxide as the major product, with carveol, perillyl alcohol and 1,8-cineole as minor products. Autoxidation of terpenes in cell-free nutrient medium was investigated in detail. α-Pinene and β-pinene were both autoxidized to a certain extent, while limonene remained unaffected. The rate of the autoxidation was more than one order of magnitude slower than that of the biotransformation. Moreover, different products were formed by autoxidation than by biotransformation.