title: Natural flavonoids are potent inhibitors of glycogen phosphorylase.
abstract: There is little known about effects to be expected from high intake of flavonoids with respect to regulation of glucose/glycogen homeostasis. Glucose/glycogen homeostasis is mainly regulated by glycogen synthase (GS) and glycogen phosphorylase (GP). We investigated effects of naturally occurring flavonoids with varying substitution pattern on the activity of isolated muscle GP. Almost all flavonoids tested inhibited phosphorylated, active GPa, as well as unphosphorylated, adenosine monophosphate-activated GPb. However, inhibition of GPa was two-to-fourfold stronger than that of GPb. The flavonol quercetin and the anthocyanidins cyanidin and delphinidin turned out to be the most potent inhibitors of GPa, with concentration values where enzymatic activity is 50% of the respective control in the low micromolar range (<5 microM). Furthermore, by comparing GPa inhibitory activity of typical representatives from all known flavonoid classes, structural elements of flavonoids required for effective GP inhibition could be identified.
authors.affiliation: Department of Chemistry, Division of Food Chemistry and Environmental Toxicology, University of Kaiserslautern, Kaiserslautern, Germany.
authors.forename: Sandra
authors.initials: S
authors.lastname: Jakobs
authors.forename: Diana
authors.initials: D
authors.lastname: Fridrich
authors.forename: Sabine
authors.initials: S
authors.lastname: Hofem
authors.forename: Gudrun
authors.initials: G
authors.lastname: Pahlke
authors.forename: Gerhard
authors.initials: G
authors.lastname: Eisenbrand
mesh_terms: D000818:Animals; D000872:Anthocyanins / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005419:Flavonoids / Q000737:chemistry / Q000494:pharmacology*; D024981:Glycogen Phosphorylase / Q000037:antagonists & inhibitors*; D024982:Glycogen Phosphorylase, Muscle Form / Q000037:antagonists & inhibitors / Q000302:isolation & purification; D009132:Muscles / Q000201:enzymology; D011794:Quercetin / Q000494:pharmacology; D011817:Rabbits; D013329:Structure-Activity Relationship
chemical_list: D000872:Anthocyanins; D004791:Enzyme Inhibitors; D005419:Flavonoids; C017154:cyanidin; D011794:Quercetin; D024981:Glycogen Phosphorylase; D024982:Glycogen Phosphorylase, Muscle Form; C017185:delphinidin