cyanidin-3-o-beta-glucopyranoside and epigallocatechin-gallate

Flavonoids are commonly abundant, plant-derived polyphenolic compounds which are responsible for color, taste, and antioxidant properties of certain plant based foods. Glucosylation by glucansucrases or other glycosyltransferases/glycoside hydrolases has been described to be a promising approach to modify stability, solubility, bioavailability, and taste profile of flavonoids and other compounds. In this study, we modified and applied a recombinant dextransucrase from Lactobacillus reuteri TMW 1.106 to glucosylate various flavonoids and flavonoid glycosides. The glucoconjugates were subsequently isolated and characterized by using two-dimensional NMR spectroscopy. Efficient glucosylation was achieved for quercetin and its glycosides quercetin-3-O-β-glucoside and rutin. Significant portions of α-glucose conjugates were also obtained for epigallocatechin gallate, dihydromyricetin, and cyanidin-3-O-β-glucoside, whereas glucosylation efficiency was low for naringin and neohesperidin dihydrochalcone. Most of the flavonoids with a catechol or pyrogallol group at the B-ring were predominantly glucosylated at position O4'. However, glycosyl substituents such as β-glucose, rutinose, or neohesperidose were glucosylated at varying positions. Therefore, mutant dextransucrase from L. reuteri TMW 1.106 can be applied for versatile structural modification of flavonoids.

Topics: Anthocyanins; Bacterial Proteins; Catechin; Flavonoids; Glucosides; Glucosyltransferases; Glycosides; Glycosylation; Limosilactobacillus reuteri; Magnetic Resonance Spectroscopy; Molecular Structure; Mutation; Quercetin; Rutin

Natural food sources constitute a promising source of new compounds with neuroprotective properties, once they have the ability to reach the brain. Our aim was to evaluate the brain accessibility of quercetin, epigallocatechin gallate (EGCG) and cyanidin-3-glucoside (C3G) in relation to their neuroprotective capability. Primary cortical neuron cultures were exposed to oxidative insult in the absence and presence of the selected compounds, and neuroprotection was assessed through evaluation of apoptotic-like and necrotic-like cell death. The brain accessibility of selected compounds was assessed using an optimised human blood-brain barrier model. The blood-brain barrier model was crossed rapidly by EGCG and more slowly by C3G, but not by quercetin. EGCG protected against oxidation-induced neuronal necrotic-like cell death by ~40%, and apoptosis by ~30%. Both quercetin and C3G were less effective, since only the lowest quercetin concentration was protective, and C3G only prevented necrosis by ~37%. Quercetin, EGCG and C3G effectively inhibited α-synuclein fibrillation over the relevant timescale applied here. Overall, EGCG seems to be the most promising neuroprotective compound. Thus, inclusion of this polyphenol in the diet might provide an affordable means to reduce the impact of neurodegenerative diseases.

Topics: alpha-Synuclein; Animals; Anthocyanins; Antioxidants; Apoptosis; Brain; Catechin; Cells, Cultured; Dose-Response Relationship, Drug; Drug Evaluation, Preclinical; Drug Stability; Endothelial Cells; Flavonoids; Glucosides; Humans; Necrosis; Neurons; Neuroprotective Agents; Oxidative Stress; Protein Multimerization; Quercetin; Rats, Wistar; Recombinant Proteins