Discovery of N-l-Lactoyl-l-Trp as a Bitterness Masker via Structure-Based Virtual Screening and a Sensory Approach

Abstract

N-Lactoyl-amino acid derivatives (N-Lac-AAs) are of increasing interest as potential taste-active compounds. The complexity and diversity of N-Lac-AAs pose a significant challenge to the effective discovery of taste-active N-Lac-AAs. Therefore, a structure-based virtual screening was used to identify taste-active N-Lac-AAs. Virtual screening results showed that N-lactoylhydrophobic amino acids had a higher affinity for taste receptors, specifically N-L-Lac-L-Trp. And then, N-L-Lac-L-Trp was synthesized in yields of 22.3% by enzymatic synthesis in the presence of L-lactate and L-Trp, and its chemical structure was confirmed by MS/MS and one-dimensional (1D) and two-dimensional (2D) NMR. Sensory evaluation revealed that N-L-Lac-L-Trp had a significant taste-masking effect on quinine, D-salicin, caffeine, and L-Trp, particularly L-Trp and caffeine. N-L-Lac-L-Trp had a better masking effect on the higher concentration of bitter compounds. It reduced the bitterness of caffeine (500 mg/L) and L-Trp (1000 mg/L) by approximately 20 and 26%, respectively. The result of the ligand−receptor interaction and a quantum mechanical analysis showed that N-L-Lac-L-Trp increased the binding affinity to the bitter receptor mainly through hydrogen bonding and lowering the electrostatic potential.

Kokumi-Enhancing Mechanism of N-l-lactoyl-l-Met Elucidated by Sensory Experiments and Molecular Simulations

“…Figure A reveals that N - l- Lac- l- Met solutions exhibit a complex taste profile with the detection thresholds observed at 100 mg/L for kokumi-like perception, 100 mg/L for astringency, and 400 mg/L for bitterness. Similar phenomena have been reported for the lactylation of polar or hydrophobic amino acids, such as Phe and Trp. , N - l- Lac- l- Gly in aqueous solution imparted astringent and bitter flavors, while N - l- Lac- l- Ala, N - l- Lac- l- Glu, N - l- Lac- l- Gln, N - l- Lac- l- Asp, and N - l- Lac- l- Asn have found to possess a palate-enveloping taste, with detection thresholds ranging from 86 to 1404 mg/L. These amino acid derivatives are known to exhibit a taste-modifying effect .…”

“…On the other hand, the crystal structure of umami receptors T1R1/T1R3, a heterodimer, remains elusive. Hence, homology modeling was employed to construct a high-quality umami protein receptor model (T1R1/T1R3) as shown in Figure A . The 3D structure of the kokumi protein receptor (entry id: 5K5S) is presented in Figure B.…”

“…Similar phenomena have been reported for the lactylation of polar or hydrophobic amino acids, such as Phe and Trp. 8,22 N-L-Lac-L-Gly in aqueous solution imparted astringent and bitter flavors, while N-L-Lac-L-Ala, N-L-Lac-L-Glu, N-L-Lac-L-Gln, N-L-Lac-L-Asp, and N-L-Lac-L-Asn have found to possess a palateenveloping taste, with detection thresholds ranging from 86 to 1404 mg/L. These amino acid derivatives are known to exhibit a taste-modifying effect.…”

“…Hence, homology modeling was employed to construct a high-quality umami protein receptor model (T1R1/T1R3) as shown in Figure 4A. 22 The 3D structure of the kokumi protein receptor (entry id: 5K5S) is presented in Figure 4B. Subsequently, molecular docking using Autodock Vina was performed to assess the binding affinity of N-L-Lac-L-Met, glutamate (representing the umami substance), and glutathione (representing the kokumi substance) with the taste receptor.…”

Enhancing Kokumi Sensation and Reducing Bitterness in Acid-Hydrolyzed Vegetable Proteins through Lactate and Thermal Processing

“…According to the above results, among the identified N-L-Lac-L-AAs, N-L-Lac-L-Met, N-L-Lac-L-Ile, N-L-Lac-L-Leu, N-L-Lac-L-Val, and N-L-Lac-L-Phe were identified as the most significant contributors for the observed differences (VIP > 1). and N-L-Lac-L-Met have already indicated a kokumi effect, 11,23 while the taste-modulating effects of N-L-Lac-L-Leu, N-L-Lac-L-Ile, and N-L-Lac-L-Val remained unknown. Therefore, sensory evaluations were conducted to assess the taste modulating of these three N-L-Lac-L-AAs.…”