Configurational transformation of dihydromyricetin during thermal processing and its implications for quality evaluation

Thermal processing is a critical under-evaluated factor influencing the stereochemical stability of bioactive flavonoids. This study demonstrates that natural 2R, 3R-dihydromyricetin (DMY) undergoes a configurational evolution during heating, yielding two previously overlooked non-natural diastereomers (2S, 3R- and 2R, 3S-). The transformation was proposed to proceed through a quinone methide (QM)-mediated pathway. Bioactivity assays revealed differences in antibacterial activity between the natural and non-natural isomers at the tested concentration (32 μg/mL). This disparity in activity suggests that processing-induced isomerization may represent an overlooked factor contributing to variations in biological properties. Consequently, monitoring the emergence of these isomers during thermal processing may complement conventional content-based assays by incorporating stereochemical information, thereby providing a more comprehensive framework for quality evaluation.