Identification of 4'-Demethyl-3,9-dihydroeucomin as a Bitter-Masking Compound from the Resin of Daemonorops draco.

Masking the bitter taste of foods is one of the key strategies to improve their taste and palatability, particularly in the context of clean labeling, where natural compounds are preferred. Despite the demand, the availability of natural bitter-masking compounds remains limited. Here, we identified the bitter-masking compound 4'-demethyl-3,9-dihydroeucomin (DMDHE) isolated from the resin of Daemonorops draco by means of an activity-guided in vivo (sensory bitterness rating of quinine) and in vitro (cell-based bitter response assays) approach. First, a mean bitter-masking effect of -29.6 ± 6.30% on the bitterness perceived from quinine [10 ppm] was demonstrated for an organic solvent extract of the resin of D. draco (= DD [500 ppm]) in a sensory trial. The results were verified in a cell-based bitter assay in which the bitter taste receptor (TAS2R)-dependent proton secretion serves as an outcome measure of the cellular bitter response in parietal HGT-1 cells. By means of preparative RP-18 high-performance liquid chromatography (HPLC) analysis combined with activity-guided sensory evaluations, the most potent bitter-masking fractions were identified. Subsequent quantitative liquid chromatography/high-resolution mass spectrometry/charged aerosol detection/ultraviolet (LC-HRMS/CAD/UV), NMR analysis, followed by gram-scale synthesis, led to the characterization of DMDHE as bitter-masking homoisoflavanone. DMDHE decreased the sensory bitterness of quinine by 14.8 ± 5.00%. Functional involvement of TAS2R14 was demonstrated by means of a CRISPR-Cas9 approach, which revealed a reduction of the DMDHE-evoked bitter-masking effect by 40.4 ± 9.32% in HGT-1 TAS2R14ko versus HGT-1 wt cells.