Novel carotenoids produced on the interaction of the foreign carotenoid ketolase CrtW and endogenous epoxycarotenoids unique to sweetpotato tubers

Bacterial genes that include the crtW gene encoding carotenoid 4,4′-ketolase were expressed in the tubers (tuberous roots) of sweetpotato, Ipomoea batatas (L.) Lam. Consequently, three novel carotenoids with epoxy and keto groups 1, 2, and 3 were found to be produced there. The structures of 1, 2, and 3 were determined as 5′,8′-epoxy-5′,8′-dihydro-β,β-caroten-4-one (named echinenone 5′,8′-epoxide), 5′,6′-epoxy-5′,6′-dihydro-β,β-caroten-4-one (named echinenone 5′,6′-epoxide), and 3′-hydroxy-5′,6′-epoxy-5′,6′-dihydro-β,β-caroten-4-one (named 3′-hydroxyechinenone 5′,6′-epoxide), respectively, based on spectral data.