Three sesquiterpene compounds biosynthesised from artemisinic acid using suspension-cultured cells of Averrhoa carambola (Oxalidaceae).

A new sesquiterpene glycoside, artemisinic acid 3-β-O-β-D-glucopyranoside (3, 31.24%) and other two biotransformation products, 3-β-hydroxyartemisinic acid (2, 36.69%) and 3-β-hydroxyartemisinic acid β-D-glucopyranosyl ester (4, 7.03%), were biosynthesised after artemisinic acid (1) was administered to the cultured cells of Averrhoa carambola. The three biotransformation products were obtained for the first time by using the suspension-cultured cells of A. carambola as a new biocatalyst system, and their structures were identified on the basis of the physico-chemical properties, NMR and mass spectral analyses. The results indicate that the cultured cells of A. carambola have the abilities to hydroxylate and glycosylate sesquiterpene compounds in a regio- and stereoselective manner. Furthermore, the anti-tumour activity of compounds 3 and 4 was evaluated against K562 and HeLa cell lines. Compound 4 showed strong activity against HeLa cell line, with the IC₅₀ value of 0.56 µmol mL⁻¹.