Flavonoid C-glycosides in Fabaceae seeds: From structural diversity and functional significance to human health benefits

Flavonoid C-glycosides (FCGs) are a distinct class of plant secondary metabolites characterized by stable carbon-carbon glycosidic bonds that confer resistance to hydrolysis. Although less frequent than flavonoid O-glycosides, FCGs occur across numerous plant families and tissues and display multiple biological activities, including antioxidant, anti-inflammatory, hepatoprotective, and anticancer effects. Recent studies report exceptional abundance and molecular diversity of FCGs in fenugreek seeds and in the germ of other Fabaceae species, such as carob, Neltuma spp., and tara. This review critically summarizes current knowledge on the occurrence, structural variability, analytical approaches, physiological roles, and functional relevance of FCGs, with emphasis on Fabaceae seeds. Evidence for their nutraceutical and pharmacological potential is discussed, particularly their capacity to modulate glycaemia through inhibition of pancreatic α-amylase and intestinal α-glucosidases and synergic mechanisms improving glucose metabolism. Fabaceae seeds thus emerge as strategic and sustainable sources of functional phytochemicals, supporting dietary approaches to human metabolic health.