ABSTRACT
We report on activity-guided investigation of the key antisweet principles of Gymnema sylvestre. Orosensory-guided fractionation by means of solid phase extraction, preparative 2D-LC, and semipreparative HPLC followed by accurate MS and 1D/2D NMR experiments revealed six known and three previously unknown gymnemic acids as the key constituents of seven highly sensory-active fractions. Localized via a modified comparative taste dilution analysis (cTDA) and taste modulation probability (TMP) based screening techniques, a strong intrinsic bitterness was also observed for gymnemic acids. In addition, the suppressive effects of the most abundant acids on the response of the human sweet taste receptor to sucrose were verified by means of a functional hTAS1R2/hTAS1R3 sweet taste receptor assay. This in vitro screening revealed large differences in antisweet activity among the isolated compounds, where gymnemic acids XV and XIX showed the highest sweet suppressing activity. This broad-based molecular characterization of the sweet taste inhibiting activity of Gymnema sylvestre will enable further insight into the molecular basis of sweet taste modulation at the receptor level.
Subject(s)
Gymnema sylvestre , Saponins , Triterpenes , Chromatography, High Pressure Liquid , Humans , Magnetic Resonance Spectroscopy , Plant ExtractsABSTRACT
This is the first application of fully automated, preparative, two-dimensional HPLC combined with sensory analysis for taste compound discovery using a sweet and licorice-like bitter-tasting aniseed extract as an example. Compared to the traditional iterative fractionation of food extracts by sensory-guided sequential application of separation techniques, the fully automated 2D-HPLC allowed the comprehensive separation of the aniseed extract into 256 subfractions and reduced the fractionation time from about 1 week to <1day. Using a smart sensory strategy to locate high-impact fractions, e.g., by evaluating first-dimension fractions by reconstituting them from second-dimension subfractions, followed by straightforward application of the taste dilution analysis on the individual second-dimension subfractions revealed the sweet-tasting trans-anethole and the bitter-tasting trans-pseudoisoeugenol 2-methylbutyrate, showing recognition thresholds of 70 and 68 µmol/L, respectively, as the primary orosensory active compounds in aniseed. 2D-HPLC combined with smart sensory analysis seems to be a promising strategy to speed the discovery of the key players imparting the attractive taste of foods.
