Rubemamine and Rubescenamine, Two Naturally Occurring <i>N</i>‑Cinnamoyl Phenethylamines with Umami-Taste-Modulating Properties

Sensory screening of a series of naturally occurring <i>N</i>-cinnamoyl derivatives of substituted phenethylamines revealed that rubemamine (<b>9</b>, from Chenopodium album) and rubescenamine (<b>10</b>, from Zanthoxylum rubsecens) elicit strong intrinsic umami taste in water at 50 and 10 ppm, respectively. Sensory tests in glutamate- and nucleotide-containing bases showed that the compounds influence the whole flavor profile of savory formulations. Both rubemamine (<b>9</b>) and rubescenamine (<b>10</b>) at 10–100 ppm dose-dependently positively modulated the umami taste of MSG (0.17–0.22%) up to threefold. Among the investigated amides, only rubemamine (<b>9</b>) and rubescenamine (<b>10</b>) are able to directly activate the TAS1R1-TAS1R3 umami taste receptor. Moreover, both compounds also synergistically modulated the activation of TAS1R1-TAS1R3 by MSG. Most remarkably, rubemamine (<b>9</b>) was able to further positively modulate the IMP-enhanced TAS1R1-TAS1R3 response to MSG ∼1.8-fold. Finally, armatamide (<b>11</b>), zanthosinamide (<b>13</b>), and dioxamine (<b>14</b>), which lack intrinsic umami taste in vivo and direct receptor response in vitro, also positively modulated receptor activation by MSG about twofold and the IMP-enhanced MSG-induced TAS1R1-TAS1R3 responses approximately by 50%. In sensory experiments, dioxamine (<b>14</b>) at 25 ppm in combination with 0.17% MSG exhibited a sensory equivalent to 0.37% MSG.