Biotransformation of dihydro-epi-deoxyarteannuin B by suspension-cultured cells of Averrhoa carambola

The biotransformation of dihydro-epi-deoxyarteannuin B (compound 1) was investigated by using suspension-cultured cells of Averrhoa carambola. One novel sesquiterpene, 7α-hydroxy-dihydro-epideoxyarteannuin B (compound 2, 29.02%), and one known sesquiterpene, 3-α-hydroxy-dihydro-epideoxyarteannuin B (compound 3, 23.26%), were obtained upon the addition of the substrate (compound 1). All the biotransformation products were obtained for the first time by using suspension-cultured cells of A. carambola as a new biocatalytic system, and their structures were identified based on nuclear magnetic resonance and mass spectral analyses. The results indicate that the cultured cells of A. carambola have the abilities to hydroxylate sesquiterpene compounds in a regioand stereoselective manner. Moreover, antitumor activities of compounds 2 and 3 were investigated against K562 and HeLa cell lines. These data demonstrate that 7-hydroxyl product (compound 2) exhibited stronger antitumor activity than the 3-hydroxyl product (compound 3) against the K562 and HeLa cell lines.