Comprehensive analyses of the bitterness of alkaloids and simulated taste mechanism of theacrine from Jianghua Kucha tea (<i>Camellia sinensis</i> var. assamica cv. Jianghua)

Jianghua Kucha (JHKC) is a special tea germplasm that has a certain degree of bitterness. Alkaloids (theacrine, caffeine, theobromine, and theophylline) are one of the bitter substances in tea. However, simultaneous comparison of bitterness thresholds at different temperatures and taste active values (TAVs) of alkaloids in JHKC are unclear. Furthermore, as a special purine alkaloid of JHKC, the interaction between theacrine and bitter taste receptors is not clear. In this study, comprehensive analysis of bitterness thresholds and TAVs of alkaloids in JHKC as well as theacrine-bitter taste receptor interaction were carried out. These results showed that thresholds of caffeine, theobromine, theophylline, and theacrine at 15°C were significantly lower than those at 25°C and 45°C. Docking simulation results showed that theacrine had the best binding capability with TAS2R14. TAS2R14 amino acid residues Q2667.38, S652.60, and W893.32 may play a key role in docking simulation of theacrine, and hydrogen bonding and π-π interaction was the main interaction.