The material basis of bitter constituents in Carbonized Typhae Pollen, based on the integration strategy of constituent analysis, taste sensing system and molecular docking

The discovery of bitter constituents is of great significance to the exploration of medicinal substances for they have potential physiological effects. Carbonized Typhae Pollen (CTP), which is a typical example of carbonized Traditional Chinese Medicine (TCM), has a bitter taste and hemostatic effect after carbonized processing. The objective of this study is to elucidate the material basis of bitter constituents in CTP. Firstly, the constituents of CTP extracts with 7 different solvents were characterized by UPLC-Q-TOF-MS. Then, multivariate statistical analysis was used to visualize the CTP extracts from 7 solvents. A total of 37 constituents were tentatively identified and 17 constituents were considered as the key constituents in differentiating 7 different solvent extracts. Subsequently, the bitter evaluation of extracts from different polar parts was investigated by using an electronic tongue. As a result, the order of bitterness of the extracts was as follows: ethanol > methanol > water >n-butyl alcohol > petroleum ether > butyl acetate > isopropanol. There were statistically significant differences in the bitter degree of extracts. By correlation analysis of bitter information and chemical constituents with partial least squares regression (PLSR), 8 potential bitterness constituents were discovered, including phenylalanine, valine, chlorogenic acid, isoquercitrin, palmitic acid, citric acid, quercetin-3-O-(2-alpha-L-rhamnosyl)-rutinoside, and typhaneoside. Additionally, molecular docking analysis was conducted to reveal the interaction of these constituents with the bitter taste receptor. The docking result showed that these constituents could be embedded well into the active pocket of T2R46 and had significant affinity interactions with critical amino acid residues by forming hydrogen bonds. This study provided a reliable theoretical basis for future research on biological activity of bitterness substances.