Computational study of chemical phenol glycosylation mechanism in the gas phase for modeling direct glycoconjugate formation in raw plant material

Abstract

Glycosylation in a broad sense is commonly considered a chemical reaction between a carbohydrate and another molecule with any functional group which can act as a glycosyl acceptor forming covalent bond. Such modification of small natural biologically active molecules (e.g., flavonols) is of significant importance for drug delivery and dietary supplements due to the increase in their bioavailability. Nevertheless, classical chemical synthesis is complicated by the oxidation of flavonols and requires multiple stages to prevent its degradation. Thus, the idea of direct solid-state chemical synthesis in raw plant material arises. To evaluate such a possibility, we provide a computational gas phase study of this process based on the model system of reaction between glucose and phenol. This investigation is based on the assumption that water and flavonol (here phenol as a model) molecules are deficient in raw plant material and do not form liquid phase, whereas dielectric constant (Ɛ = 2–5) is close to 1 in vacuo, and absence of regular-crystals structure. The reaction mechanism and particular path of phenol direct chemical glycosylation are calculated as well as all intermediate products, transition states, and energy barriers tacking into account molecular symmetry. This work proves a concept of the possibility of such reaction in the raw plant material, including flavonol direct glycosylation using mechanochemistry.