Biosynthesis of β-substituted furan skeleton in the lower furanoterpenoids: A model study

Furanoterpenes are widely distributed in the plant kingdom. In this study we have carried out enzymatic synthesis of simple furan compounds from the molecules containing an alpha-isopropylidene ketone unit and the role of cytochrome P450 in this biotransformation has been conclusively established. Eight model compounds (acyclic, monocyclic, and bicyclic, 1-8), having an alpha-isopropylidene ketone unit, were synthesized and incubated with PB-induced rat liver microsomes in the presence of NADPH and O-2. GC-MS and NMR analyses of the product(s) indicated the formation of corresponding furano derivatives (11-18). Cytochrome P450 inhibitors, metyrapone, SKF-525, and carbon monoxide, inhibited the formation of furan (8) to 76, 62, and 97%, respectively. Incubation of dehydrofukinone (7), a aturally occurring terpene, with purified cytochrome P450, NADPH-cytochrome P450 reductase, and dilaurylphosphatidylcholine in the presence of NADPH and O-2 resulted in the formation of 10 and furanodehydrofukinone (19). Based on these observations, we propose one of the probable biosynthetic routes for lower furanoterpenoids in higher plants.