Biotransformation of chinensiolide B and the cytotoxic activities of the transformed products

Biotransformation of chinensiolide B, 10α-hydroxy-1α,5α,15-H-3-oxoguaia-11(13)-en-6α,12-olide (1), yielded three selectively reduced products, 3β,10α-dihydroxy-1α,5α,15α-H-guaia-11(13)-en-6α,12-olide (2), 3α,10α-dihydroxy-1α,5α,15α-H-guaia-11(13)-en-6α,12-olide (3), and 3β,10α-dihydroxy-1α,5α,11β,15α-H-guaia-6α,12-olide (4) by the cell suspension cultures of Catharanthus roseus. 2 and 3 were also obtained from 1 incubated with cell cultures of a fungus Abisidia coerulea IFO 4011 and Platycodon grandiflorum, respectively. Among them, 2, 3 are two new compounds. The three products, 2-4, along with 1 were preliminarily evaluated for their in vitro cytotoxic activity against 3 cell lines (HepG2, WI-38 and VA-13) and all showed potent inhibitory effects on the cell proliferation. Of the four compounds, 3 was the most toxic to the three cell lines tested with IC50 values of 22.7, 0.33 and 3.30 μM, respectively.