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BSTRACT The mechanism of action of tastants has been under investigation for many years. For the sweet taste several models have been developed to describe the nature and topological arrangement of the glucophores of ideal sweet compounds and/or the recognition sites of the sweet taste receptor. In less than a decade our knowledge about the mechanism of sweet taste chemoreception has grown enormously, following the identification and cloning of T1Rs. The observation that receptor cells co-expressing T1R2 and T1R3 respond to a great variety of sweet compounds has been generally interpreted as an inference that there is a single heterodimeric receptor for sweet taste. The three-dimensional structure of the receptor is not known and alternative methodologies are required to model the binding of sweet compounds. Therefore homology modelling and molecular modelling become indispensable tools to suggest point mutations which further define the binding regions. Only their cooperative effect allowed researchers to determine several molecular mechanisms of the sweet taste receptors, including the modality of action of blockers and positive allosteric modulators. For umami taste, despite the general appreciation of the meaty, mouth filling and rich taste found in many foods (and the great interest of the food industry thereof), the existence of an umami receptor has been accepted only after its cloning. Probably because of this, no umami taste receptor models have been developed, while the molecular mechanism for its synergism has been unravelled before that of the sweet taste receptor. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

BSTRACT The chemistry of sweet compounds has been an ideal training ground for researchers in the field of taste for a very long time. Sweeteners have a huge importance in the food and pharmaceutical industries, but they have also attracted much interest in connection with their biological function and the general mechanism of action of sweet compounds. Several factors contributed to a large and varied production of scientific data in this field: among these the existence of several active compounds in the plant kingdom, the diversity of structural, stereochemical and conformational hallmarks, the intriguing aspects related to their modulation, inhibition and synergy. Among all molecules that have been isolated and synthesized, only a few have successfully reached the final goal of commercial development while some have been used to derive models and structure-activity relationships. Nevertheless, there is a number of very interesting compounds of natural or synthetic origin that - after a short period of popularity - were apparently lost or forgotten, without any further development. The article will give an overview on some of these compounds and discuss, in the light of current knowledge, the contribution that chemistry still could give in the sweeteners area. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]