Chemistry, Occurrence and Biosynthesis ofC-Glycosyl Compounds in Plants

Abstract

compounds with glucuronic acid have been found in mammals, which are probably analogous to C-glycosylated compounds in plants. C-Glucuronides of drugs in man [10] and other mammals [11, 12] represent a novel type of drug metabolite. As regards the biosynthetic pathway which leads to the formation of the carbon-carbon bond in C-glycosides, very little is known. In some cases it is thought that the attachment of the sugar moiety takes place during an early stage of the aglycone formation but definite proof is still missing and cannot be generalized for all groups of the C-glycosides. The aim of this article is to present a short review of the principal structural features and occurrence of the different classes of C-glycosides and further, to discuss the few biosynthetic findings of the C-glycosyl attachment which have been published so far. C-Glycosyl Flavonoids Chemistry of C-glycosyl Flavonoids As it has been pointed out, this group of C-glycosides has been the subject of a still increasing number of reports, which mainly deal with the occurrence and structural investigation of these compounds. Since they have been the subject of several review articles [3, 6, 7, 13, 14] only the main features are given here. At the present over one hundred C-glycosyl flavonoids have been shown to exist in the plant kingdom. The model compound and one of the first to be isolated was vitexin (8-C-3-D-glucopyranosylapigenm) (Fig. 2), the structure of which was established

New type of linkage between a carbohydrate and a protein: C-glycosylation of a specific tryptophan residue in human RNase Us

“…Although aromatic C-glycosides in proteins have not been reported before, low molecular weight C-glycosides are very abundant in plants. At least five major classes can be distinguished on the basis of the aglycon involved (Franz & Griin, 1983); attachment of the carbohydrate in all cases occurs to a carbon atom of nucleophilic character, and it has been shown in one case that the sugar donor is UDP-glucose (Franz & Griin, 1983). Activation of sugars by the formation of diphosphate derivatives is also used in the biosynthesis of N-and 0-glycosylated proteins.…”

The Occurrence, Fate and Biological Activities ofC-glycosyl Flavonoids in the Human Diet

“…The flavonoids are a highly diverse class of polyphenolic organic compounds formed principally as secondary plant metabolites with broad functional roles in planta, acting as siderophores, colourants, antioxidants and attractants, whilst providing protection against UV-radiation, insects, fungi and bacteria (Franz and Grun, 1983). Their wide distribution throughout the plant kingdom results in their inevitable presence in diets rich in plant-derived foods or beverages, where they appear to contribute to the overall health benefits of consuming such a diet.…”

“…C-glycosyl flavonoids, the subject of this review, are a less well understood sub-class of (Franz and Grun, 1983).…”

Production of <i>C</i>-glucosides of flavonoids and related compounds by <i>Escherichia coli</i> expressing buckwheat <i>C</i>-glucosyltransferase

“…C-Glycosides are characterized by the carbon-carbon bond that forms between the anomeric carbon of sugar moieties and the carbon atom of aglycon (Franz and Grün 1983). Because of this bond, C-glycosides are extremely stable against enzyme or acid hydrolysis compared with other glycosides that can be hydrolyzed.…”

“…Because of this bond, C-glycosides are extremely stable against enzyme or acid hydrolysis compared with other glycosides that can be hydrolyzed. Many kinds of plant C-glycosides have been reported (Franz and Grün 1983), and the most common are the flavonoid C-glycosides that have been found in mosses, liverworts, ferns, gymnosperms, monocots, and dicots (Jay 1994;Talhi and Silva 2012). These C-glycosides are known to show various biological activities in planta, such as antioxidant, antifungal, insecticide, and allelochemical activities (Byrne et al 1996;Hooper et al 2010;Jay 1994;McNally et al 2003).…”