Biotransformation of Bergapten and Xanthotoxin by Glomerella cingulata

The biotransformation of bergapten (1) by the fungus Glomerella cingulata gave the corresponding reduced acid, 6,7-furano-5-methoxy hydrocoumaric acid (2), a new compound. Xanthotoxin (3) was also converted to the corresponding reduced acid cnidiol b (4) and demethylated metabolite xanthotoxol (5) by G. cingulata. The structure of the new compound 2 was elucidated by high-resolution mass spectrometry, extensive NMR techniques, including (1)H NMR and (13)C NMR, (1)H-(1)H correlation spectroscopy, heteronuclear multiple quantum coherence, and heteonuclear multiple bond coherence. The methyl ester or methyl ether or methyl ester and ether derivatives of 2 and 4 were synthesized. All compounds were tested for the beta-secretase (BACE1) inhibitory activity in vitro. The methyl ester and ether derivative 8 was shown to possess BACE1 inhibitory activity, and a IC(50) value was 0.64 +/- 0.04 mM.