Formation of novel flavonoids in apple (Malus x domestica) treated with the 2-oxoglutarate-dependent dioxygenase inhibitor prohexadione-Ca

Novel flavonoids were formed in young leaves of apple (Malus x domestica) after treatment with the dioxygenase inhibitor pro-hexadione-Ca. which is known to reduce the incidence and severity of fire blight caused by Erwinia amylovora and other plant diseases. The compounds were isolated and identified as luteoliflavan, luteoliflavan 5-glucoside, eriodictyol 7-glucoside and 6-O-trans-p-coumaroyleriodictyol 3'-glucoside. These flavonoids represent a novel biosynthetic pathway in apple leading to the formation of 3-deoxyflavans. Concomitantly, the content of regularly occurring phenylpropanoids is also influenced by prohexadione-Ca with increasing amounts of hydroxycinnamic acids and decreasing flavan-3-ols and flavonols. The altered flavonoid metabolism may be related to the lowered pathogen incidence though the isolated novel flavonoids do not exhibit antibacterial activity. (C) 2003 Elsevier Ltd. All rights reserved.