Microbial transformation of dehydroandrographolide by Cunninghamella echinulata

The capabilities of 24 strains of filamentous fungi (from 11 genera) to transform dehydroandrographolide (1) were screened. The highly region-specific hydroxylation of 1 at C-9 by Cunninghamella echinulata AS 3.3400 was observed. Five products were obtained, and they were identified as 9β-hydroxydehydroandrographolide (2), 3-oxo-hydroxydehydroandrographolide (3), 3-oxo-9β-hydroxydehydroandrographolide (4), 7α-hydroxydehydroandrographolide (5) and 8β,17α-epoxydehydroandrographolide (6), respectively. Among them, products 2, 4 and 5 were novel compounds.