Biotransformation of sesquiterpenes by cultured cells of Curcuma zedoaria

The transformation of a 10-membered ring sesquiterpene, germacrone, into guaiane-type sesquiterpenes by suspension cultured cells of Curcuma zedoaria was investigated. Germacrone was converted into several sesquiterpenes, some of which were isolated from the Curcuma spp. plants through, the key intermediate, (4 R,5 R)-germacrone 4,5-epoxide, and their structures were determined by spectral and chemical evidence. The configurations of some of the derivatives were opposite to those of the sesquiterpenes isolated from the Curcuma sp plants, C. aromatica, C. longa and C. zedoaria. An eudesmane-type product was also isolated and its structure was determined. From the structure, the transformation of germacrone through the intermediate, (1 S, 10 S)-germacrone 1,10-epoxide, was supposed and further confirmed by the transformation of germacrone 1,10-epoxide into the same product by acid treatment. The structures of two new products were also determined and their transformation mechanism through curcumenone and dihydrocurcumenone was deduced.