THERMAL INTERACTION OF QUERCETIN AND GLUCOSE. INFLUENCE OF MECHANO-CHEMICAL TREATMENT. QUANTUM-CHEMISTRY EVALUATION OF REACTION ROUTES

10.25712/ASTU.1811-1416.2022.03.004

Abstract

Quercetin is one the best-studied natural antioxidants flavonoids. Meanwhile, there are only a few studies focused on interactions with quercetin occurring during its “industrial” treatment (e.g., tablet molding, heating within mixtures, long-term storage, etc.). Formation of a quercetin product containing a glycosidic bond (isoquercitrin) can alter the effectiveness and biological activity profile of the end product. Earlier, the interaction between quercetin and glucose occurring during mechanochemical activation was shown. The reaction proceeded only in the mechanically activated mixtures. In this paper, the reaction was studied by thermal analysis. Thermal analysis demonstrated that quercetin was stable at temperatures 393-603 K, the glucose decomposition involves several stages. The route of direct (thermal) interaction was evaluated by quantum chemical modeling using the Gaussian 09 software package (B3LYP/6-31G*). According to the modeling results, a conclusion was drawn that direct interaction is unlikely to proceed in the temperature range of reagent existence. Removal of a water molecule from glucose yields anhydroglucopyranose as an intermediate product. Different variants of anhydroglucopyranose structures are suggested. The 1,6-, 2,6-, 3,6-, and 4,6-anhydroglucopyranoses were chosen for further consideration. A hypothesis was put forward that mechanochemical activation affects the quercetin-glucose interaction by reducing the activation barrier.