Flavonoid O-Methyltransferases in Eucalyptus—Biosynthesis of Alpinetin via a Methylated Chalcone Precursor

Abstract

Methylated flavonoids are abundant phytochemicals in Eucalyptus and are of interest because methylation can alter flavonoid diversity, bioactivity, and stability. However, the enzymes responsible for flavonoid methylation in eucalypts remain largely uncharacterised. We used comparative leaf transcriptomics of two species with contrasting flavanone profiles, together with protein-structure-guided candidate selection, to identify prospective O-methyltransferases involved in methylated flavonoid biosynthesis. Five candidate methyltransferases from E. eugenioides were cloned, heterologously expressed, and assayed against a panel of flavonoids and a chalcone precursor. The enzymes showed distinct..