Purification and thermochemical properties of dihydromyricetin

This work reports the purification of dihydromyricetin (abbreviation: DMY) by the recrystallization method, with a yield of secondary recrystallization of up to 77 %. The products were confirmed by element and spectral analysis. The results showed a sharp R-bond absorption peak located around the near-ultraviolet band, which is close to K-bond absorption, illustrating the occurrence of a large conjugation of carbonyl with adjacent phenol and hydroxyl. This was further confirmed by the infrared (IR) spectrum, i.e., the carbonyl stretching vibration peaks were red-shifted from 1700 to 1641 cm−1. The standard thermodynamic energy was determined to be ΔcUmθ[DMY(s), 298.15 K] = −(5437.44 ± 5.14) kJ mol−1 by an oxygen bomb calorimeter. Furthermore, the standard molar enthalpy of combustion was calculated to be ΔcHmθ[DMY(s), 298.15 K] = −(5434.96 ± 5.14) kJ mol−1, and the standard molar formation enthalpy of DMY was estimated to be ΔfHmθ[DMY(s), 298.15 K] = −(2182.67 ± 5.33) kJ mol−1.