title: The combination effect of L-arginine and NaCl on bitterness suppression of amino acid solutions.
abstract: The purpose of the present study was to quantify the degree of suppression of the bitterness of two amino acids (L-isoleucine (L-Ile), and L-phenylalanine (L-Phe)) which could be achieved by the addition of various test chemicals, and to examine the mechanism of this bitterness suppression. The test chemicals used were two sweeteners (sucrose, aspartame), NaCl, various acidic (L-aspartic acid, L-glutamic acid), or basic (L-histidine, L-lysine and L-arginine) amino acids, tannic acid and phosphatidic acid. The combination of L-arginine (L-Arg) and NaCl together was the most effective in reducing the bitterness of 100 mM L-Ile and L-Phe solutions in human gustatory sensation tests. Even in bitterness of 0.1 mM quinine solution, L-Arg was also successful in reducing the bitterness. This bitterness-suppression effect was specific to L-Arg and not to the other basic amino acids. No comparable taste-masking effect was observed for the acidic amino acids. The artificial taste sensor failed to predict completely the bitterness-suppressing effect of L-Arg. It seems likely that the bitterness-suppressing effect of L-Arg is mediated not only by binding at the receptor site, but also elsewhere in the process of bitterness perception, such as a direct effect on the sodium channel. It is conjectured that the guanidinium group of L-Arg may interact with sodium channels in taste bud membranes.
authors.affiliation: School of Pharmaceutical Sciences, Mukogawa Women's University, Nishinomiya, Japan.
authors.forename: Tazuko
authors.initials: T
authors.lastname: Ogawa
authors.forename: Tomoko
authors.initials: T
authors.lastname: Nakamura
authors.forename: Eriko
authors.initials: E
authors.lastname: Tsuji
authors.forename: Yohko
authors.initials: Y
authors.lastname: Miyanaga
authors.forename: Hiroyo
authors.initials: H
authors.lastname: Nakagawa
authors.forename: Hitomi
authors.initials: H
authors.lastname: Hirabayashi
authors.forename: Takahiro
authors.initials: T
authors.lastname: Uchida
mesh_terms: D001120:Arginine / Q000737:chemistry / Q000494:pharmacology*; D004347:Drug Interactions; D006801:Humans; D007532:Isoleucine / Q000737:chemistry / Q000494:pharmacology*; D010649:Phenylalanine / Q000737:chemistry / Q000494:pharmacology*; D011803:Quinine / Q000737:chemistry / Q000494:pharmacology; D012965:Sodium Chloride / Q000737:chemistry / Q000494:pharmacology*; D013549:Sweetening Agents / Q000737:chemistry / Q000494:pharmacology; D013649:Taste / Q000187:drug effects*; D013652:Taste Threshold / Q000187:drug effects
chemical_list: D013549:Sweetening Agents; D007532:Isoleucine; D012965:Sodium Chloride; D010649:Phenylalanine; D001120:Arginine; D011803:Quinine