Correlation analysis of taste phenotype and Gynostemma pentaphyllum saponins using computer virtual screening and UPLC-(HR)MS/MS metabolomics.

Gynostemma pentaphyllum, a popular tea ingredient, can be categorized into bitter, sweet, and tasteless varieties based on flavor. However, the metabolic causes of these disparities remain unclear. In this paper, sensory evaluation, untargeted metabolomic analysis using UPLC-QTOF-MS/MS, molecular docking and e-tongue testing were conducted to reveal and verify the structural characteristics and mechanisms underlying these different flavor substances. Component analysis indicated sweet saponins were characterized by glucose chains and protopanaxadiol-type aglycones featuring diagnostic ions m/z 459/475/491 in MS2- spectra; whereas bitter saponins typically featured at least one terminal rhamnose and the higher unsaturated sapogenins with diagnostic ions m/z 473/489/521. Virtual screening on T2R14 and e-tongue testing consistently validated gypenosides with more terminal rhamnoses or higher unsaturated aglycone tended to be more bitter. Docking analysis revealed PHE 172, TYR 159 and ALA 77 were the key amino residue sites in bitterness conduction via hydrophobic and hydrogen bonding interactions.