Structure sweet substance

In this section, the presently known highly sweet substances of natural origin are described. Sweet-tasting compounds are listed in Table 1, with information published subsequent to an earlier chapter [16] then discussed in more detail. The structures of the compounds mentioned will be interspersed in the text, with the following abbreviations used to designate the sugar units of glycosides api = D-apiofuranosyl ara = L-... 

Shigemura N, Miura H, Kusakabe Y, Hino A, Ninomiya Y (2003) Expression of leptin receptor (Ob-R) isoforms and signal transducers and activators of transcription (STATs) mRNAs in the mouse taste buds. Arch Histol Cytol 66 253-260 Shigemura N, Ohta R, Kusakabe Y, Miura H, Hino A, Koyano K, Nakashima K, Ninomiya Y (2004) Leptin modulates behavioral responses to sweet substances by influencing peripheral taste structures. Endocrinology 145 839-847... 

They can also be obtained from the hydrolysis of starch with dilute acid at low temperature. Dextrins are mixtures of polysaccharides having 5-15 glucose units in their structure. They are sticky, sweet substances used in the manufacture of adhesives and soft drinks. 

For a molecule to taste sweet, it must fit into a taste bud site where a nerve impulse can carry the message of sweetness from the tongue to the brain. Not all natural sugars, however, trigger an equivalent neural response. Some sugars, such as glucose, have a relatively bland taste, and others, such as fructose, taste very sweet. Fructose, in fact, has a sweeter taste than common table sugar or sucrose. Furthermore, individuals vary in their ability to perceive sweet substances. The relationship between perceived sweetness and molecular structure is very complicated, and, to date, it is rather poorly understood. 

The interpretation of taste in terms of molecular interactions of taste-active compounds with biopolymers in taste receptors is probably analogous to the general scheme of pairs of interactions of the type of enzyme-substrate, hormone-receptor or antigen-antibody. These interactions and relationships between the chemical structure of a substance and its taste are best known (relatively) for sweet substances, but information on other substances is still largely incomplete. 

The newest frontier in sweetener research is the area of sweet enhancers. These substances, while tasteless themselves, cause sweetness receptors to respond more strongly to sweet substances. For example, the simple experimental molecule dubbed SE-2 enhances the sweetness of sucralose up to eightfold. It is thought that SE-2 and related structures bind to the Venus flytrap complex at a remote site from the sweetener itself, causing the trap to stay shut for longer periods of time. Sucrose and sucralose enhancers are beginning to be commercialized around the... 

Sweet Taste. The mechanism of sweetness perception has been extensively studied because of its commercial importance. Many substances that vary in chemical structure have been discovered which are similar to the taste of sucrose. Commercial sweeteners include sucralose, acesulfame-K, saccharin, aspartame, cyclamate (Canada) and the protein thaumatin 4), Each sweetener is unique in its perceived sensation because of the time to the onset of sweetness and to maximum sweetness, ability to mask other sensations, persistence, aftertaste and intensity relative to sucrose [TABLE IT. For example, the saccharides, sorbitol and... 

CHOH.(CHOH)2.CH2, (CHOH)2 mw 164.16 monoclinic crysts with a sweet taste mp 234— 35° sol in w si sol in hot, almost insol in cold ale practically insol in eth. Found in the acoms of various species of Quercus Fagaceae (Refs 2, 3 6). Its structure was detd by Kiliani (Ref 7), Postemak (Ref 8), and others (Ref 1, p [1151]). On nitration, it forms an expl compd Quercitol Pentenitrate (Nitroquercite). C6H7(0N02)s, mw 389.16, N 18.00%, OB to CO —2.1% nearly colorl, transparent, resinous substance mp, explds... 

Shown below are the structures of 10 compounds, all of which taste sweet to humans. The MRS and AG° for binding to the sweet receptor are given for each substance. 

A first requirement for a substance to produce a taste is that it be water soluble. The relationship between the chemical structure of a compound and its taste is more easily established than that between structure and smell. In general, all acid substances are sour. Sodium chloride and other salts are salty, but as constituent atoms get bigger, a bitter taste develops. Potassium bromide is both salty and bitter, and potassium iodide is predominantly bitter. Sweetness is a property of sugars and related compounds but also of lead acetate, beryllium salts, and many other substances such as the artificial sweeteners saccharin and cyclamate. Bitterness is exhibited by alkaloids such as quinine, picric acid, and heavy metal salts. 

Chemically, these intense sweeteners are a very diverse group of substances. The early forms available were discovered serendipitously, usually by an experimenter accidentally tasting some. All of the intense sweeteners appear to be able to fit onto a particular receptor on the human tongue, and quite small chemical changes in their structures can convert a substance from sweet to bitter or vice versa. 

Human taste response is modified by several plant-derived substances. The detergent sodium dodecyl sulfate, as well as triterpene saponins from the leaves of several plant species (most notably Gymnema sylvestre and Ziziphus jujuba) will temporarily inhibit the sweet taste sensation in man the duration of the effect being about one hour for G. sylvestre and about fifteen minutes for Z. jujuba. The mechanism of action seems to be related, in part, to the surfactant properties of the materials. Structures of the modifiers and possible mechanisms of action are discussed. 

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