A forty-year journey in plant research: original contributions to flavonoid biochemistry

Abstract

This review highlights original contributions by the author to the field of flavonoid biochemistry during his research career of more than four decades. These include elucidation of novel aspects of some of the common enzymatic reactions involved in the later steps of flavonoid biosynthesis, with emphasis on methyltransferases, glucosyltransferases, sulfotransferases, and an oxoglutarate-dependent dioxygenase, as well as cloning, and inferences about phylogenetic relationships, of the genes encoding some of these enzymes. The three-dimensional structure of a flavonol O-methyltransferase was studied through homology-based modeling, using a caffeic acid O-methyltransferase as a template, to explain their strict substrate preferences. In addition, the biological significance of enzymatic prenylation of isoflavones, as well as their role as phytoanticipins and inducers of nodulation genes, are emphasized. Finally, the potential application of knowledge about the genes encoding these enzyme reactions is discussed in terms of improving plant productivity and survival, modification of flavonoid profiles, and the search for new compounds with pharmaceutical and (or) nutraceutical value.Key words: flavonoid enzymology, metabolite localization, gene cloning, 3-D structure, phylogeny.

The Roles of a Flavone-6-Hydroxylase and 7-O-Demethylation in the Flavone Biosynthetic Network of Sweet Basil

“…Thus, the three distinct types of F6Hs studied to date at the molecular level present an interesting case of convergent evolution (42). Because the respective compounds produced by both saxifrage and soybean (43,44) belong to different flavonoid subclasses than the basil and mint flavones, the independent origins of analogous catalytic capacities are not quite unexpected. It remains intriguing what type of catalyst mediates the 6-hydroxylation of the same flavonoid subclass, the flavones, in distantly related species and genera accumulating identical compounds, such as, for example, Tamarix, Citrus, Ononis, and others (7,45,46).…”

A systematic review on biological activities of prenylated flavonoids

“…The common 2,2-dimethylchromeno substituent is often termed a pyran ring. C-prenylation at positions 6 and/or 8, as well as 3 0 and/or 5 0 , appears to be generally preferred (Figure 1) (Ibrahim, 2005).…”

“…Most of the prenylated isoflavonoids are considered to be the products of inducible metabolites (Ibrahim, 2005;Wang et al, 2001) and comes from the Leguminosae subfamily Papilionoideae (Botta et al, 2005;Yazaki et al, 2009). Recently the research on prenylated flavanones becomes a hot pot due to their promising and diverse bioactivities on multitarget tissues.…”

Polymethylated Myricetin in Trichomes of the Wild Tomato Species Solanum habrochaites and Characterization of Trichome-Specific 3′/5′- and 7/4′-Myricetin O-Methyltransferases

“…The great structural diversity of flavonoids stems from the possible substitution on up to 10 carbons of the core structure. Some common functional group substitutions include hydroxylation, methylation, sulfonation, methylation, and (iso)prenylation (Ibrahim and Anzellotti, 2003;Ibrahim, 2005). In addition to these core substitutions, hydroxyl functional groups can be further modified by the addition of a wide range of different sugar moieties, which can be further modified themselves.…”