Biotransformation of α- and 6β-santonin by fungus and plant cell cultures

Abstract

One fungus, Abisidia coerulea IFO 4011, and suspended cell cultures of one plant, Asparagus officinalis, were employed to bioconvert α- and 6β-santonin. Incubation of α-santonin with the cell cultures of the fungus afforded two products, 11β-hydroxy-α-santonin (1, in 76.5% yield) and 8α-hydroxy-α-santonin (2, in 2.0% yield). And from 6β-santonin, four major products (3, 4, 5 and 6) and four minor products (7, 8, 9 and 10) were obtained, including 8α-hydroxylated products in trace yields. Very interestingly, a skeletal rearrangement occurred and a guaiane product (13) formed in a very low yield when α-santonin incubating with A. officinalis cell cultures, while not in the case of 6β-santonin as substrate. Among the obtained 15 products, 2, 7, 8, 9, 10 and 12 are new compounds. The fact of 8α hydroxylation of santonin enables the formation of 8,12-eudesmanolide instead of 6,12-eudesmanolide and some useful modification at C-8 position. In addition, these reactions would provide evidence for the biogenesis between different types of eudesmane and/or guaiane compounds in the plants in nature.

Keywords:

• α-Santonin
• 6β-Santonin
• Biotransformation
• Abisidia coerulea IFO 4011
• Cell suspension cultures
• Asparagus officinalis

Acknowledgements

We are grateful to the Japan Society for the Promotion of Science (JSPS) postdoctoral fellowship for J.D. (ID No. P-01274) and Grant-in-Aid (No. 1300127). This work was also supported by the National Natural Science Foundation of China (No. 30100230).