Mechanism of Dihydromyricetin-Induced Reduction of Furfural Derived from the Amadori Compound: Formation of Adducts between Dihydromyricetin and Furfural or Its Precursors.

Dihydromyricetin (DMY) was employed to reduce the yield of furfural derived from the Amadori rearrangement product of l-threonine and d-xylose (Thr-ARP) by trapping Thr-ARP, 3-deoxyxyosone (3-DX), and furfural to form adducts. The effect of different concentrations of DMY at different pH values and temperatures on the reduction of furfural production was studied, and the results showed that DMY could significantly reduce furfural production at higher pH (pH 5-7) and lower temperature (110 °C). Through the surface electrostatic potential analysis by Gaussian, a significant enhancement of the C6 nucleophilic ability at higher pH (pH ≥ 5) was observed on DMY with hydrogen-dissociated phenol hydroxyl. The nucleophilic ability of DMY led to its trapping of Thr-ARP, 3-DX, and furfural with the generation of the adducts DMY-Thr-ARP, DMY-3-DX, and DMY-furfural. The formation of the DMY-Thr-ARP adduct slowed the degradation of Thr-ARP, caused the decrease of the 3-DX yield, and thereby inhibited the conversion of 3-DX to furfural. Therefore, DMY-Thr-ARP was purified, and the structure was identified by nuclear magnetic resonance (NMR). The results confirmed that C6 or C8 of DMY and carbonyl carbon in Thr-ARP underwent a nucleophilic addition reaction to form the DMY-Thr-ARP adduct. In combination with the analysis results of Gaussian, most of the DMY-Thr-ARP adducts were calculated to be C6-DMY-Thr-ARP. Furthermore, the formation of DMY-furfural caused furfural consumption. The formation of the adducts also shunted the pathway of both Thr-ARP and 3-DX conversion to furfural, resulting in a decrease in the level of furfural production.

Exogenous Alanine Promoting the Reaction between Amadori Compound and Deoxyxylosone and Inhibiting the Formation of 2-Furfural during Thermal Treatment.

The involvement of exogenous alanine was observed to inhibit the generation of 2-furfural during the thermal degradation of the Amadori rearrangement product (ARP). To clarify the reason for the reduced yield of 2-furfural triggered by exogenous alanine, the evolution of the precursors of 2-furfural formed in the ARP model and ARP-alanine model was investigated, and a model including ARP and 15N-labeled alanine was used to differentiate the role of endogenous and exogenous alanine in the degradation of ARP. It was found that the condensation between ARP and 3-deoxyxylosone could occur during thermal treatment. Nevertheless, the interaction of ARP with 3-deoxyxylosone exhibited an accelerated pace in the presence of exogenous alanine. In this way, exogenous alanine blocked the recovery of endogenous alanine while simultaneously enhancing the consumption of ARP and 3-deoxyxylosone during the Maillard reaction. Hence, the yield of 2-furfural was diminished with the interference of exogenous alanine. Furthermore, the promotion of the reaction between ARP and deoxyxylosone induced by exogenous alanine blocked their retro-aldolization reaction to short-chain α-dicarbonyls (α-DCs) and consequently resulted in a lack of pyrazine formation during the ARP degradation. The present study provided a feasible method for the controlled formation of 2-furfural during the thermal treatment of ARP derived from alanine.