Biotransformation of gambogenic acid by Chaetomium globosum CICC 2445

Microbial transformation of gambogenic acid (1), a caged polyprenylated xanthone isolated from the resin of Garcinia hanburyi, was carried out with Chaetomium globosum CICC 2445, after screening forty-six strains of filamentous fungi. A new caged polyprenylated xanthone, 16,17-dihydroxygambogenic acid (2), was specifically obtained, as a result of hydroxylation at C-16, and C-17. Its structure was elucidated on the basis of spectroscopic methods. The cytotoxicity of compounds 1 and 2 against HeLa tumor cell line was evaluated, with both of them being modestly active.