Metabolite Profiling and Identification of Sweet/Bitter Taste Compounds in the Growth of Cyclocarya paliurus Leaves Using Multiplatform Metabolomics

Cyclocarya paliurus tea, also known as "sweet tea", a health substitute tea with Cyclocarya paliurus leaves as raw material, is famous for its unique nutritional benefits and flavor. However, due to the unique "bittersweet" of Cyclocarya paliurus tea, it is still unable to fully satisfy consumers' high-quality taste experience and oral pleasure. The taste and sensory quality of Cyclocarya paliurus tea are mainly determined by secondary metabolites. Therefore, this study aimed to explore the metabolites in Cyclocarya paliurus leaves during their growth process, particularly the composition and variation of sweet and bitter taste compounds, by combining multi-platform metabolomics analysis with an electronic tongue system and molecular docking simulation technology. The results indicated that there were significant differences in the contents of total phenols, flavonoids, polysaccharides and saponins of C. paliurus leaves in different growing months, among which the bioactive components in leaves harvested in July were the highest, and the best balance between sweetness and bitterness was achieved. A total of 575 secondary metabolites were identified as potential active metabolites related to sweet/bitter taste using nontargeted metabolomics based on UHPLC-MS/MS analysis. Molecular docking technology was utilized to study the interactions between candidate metabolites and the sweet receptor T1R2/T1R3 and the bitter receptor T2R4/T2R14. Six key compounds with high sweetness and low bitterness were successfully identified by using computational simulation analysis, including cis-Anethole, Gluconic acid, beta-D-Sedoheptulose, Asparagine, Proline, and Citrulline, which may serve as candidates for taste modification in Cyclocarya paliurus leaves. These findings provide a new perspective for understanding the sweet and bitter taste characteristics metabolites that contribute to the distinctive sensory quality of Cyclocarya paliurus leaves.