Stevioside

Steviol
IUPAC name	Kaur-16-en-18-oic acid, 13-hydroxy-, (4.alpha.)-
Identifiers
CAS number	[471-80-7]
PubChem	452967
SMILES	CC12CCCC(C1CCC34C2CCC(C3)(C(=C)C4)O)(C)C(=O)O
InChI	1/C20H30O3/c1-13-11-19-9- 5-14-17(2,7-4-8-18(14,3) 16(21)22)15(19)6-10- 20(13,23)12-19/h14- 15,23H,1,4-12H2,2-3H3, (H,21,22)/t14-,15-,17+, 18+,19+,20-/m0/s1/f/h21H
Properties
Molecular formula	C20H30O3
Molar mass	318.4504 g/mol
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

The steviol glycosides are responsible for the sweet taste of the leaves of the stevia plant (Stevia rebaudiana bertoni). These compounds range in sweetness from 40 to 300 times sweeter than sucrose.The sweetness multiplier "300 times" comes from subjective evaluations by a panel of test subjects tasting various dilutions compared to a standard dilution of sucrose. Sources referenced in this article say steviosides have up to 250 times the sweetness of sucrose, but others, including stevioside brands such as SweetLeaf, claim 300 times. 1/3 to 1/2 teaspoon (1.6–2.5 ml) of stevioside powder is claimed to have equivalent sweetening power to 1 cup (240 ml) of sugar. They are heat stable, pH stable, and do not ferment.Brandle, Jim (2004-08-19). FAQ - Stevia, Nature\'s Natural Low Calorie Sweetener (HTML). Agriculture and Agri-Food Canada. Retrieved on 2006-11-08. They also do not induce a glycemic response when ingested, making them attractive as natural sweeteners to diabetics and others on carbohydrate-controlled diets.

Structure

The diterpene known as Steviol is the aglycone of stevia\'s sweet glycosides, which are constructed by replacing the bottom hydrogen atom (see figure) with glucose (forming an ester), and replacing the top hydrogen atom with combinations of glucose and rhamnose. The two primary compounds, stevioside and rebaudioside A, use only glucose: stevioside has two linked glucose molecules at the top hydrogen site, where rebaudioside A has three, with the middle glucose of the triplet connected to the central steviol structure.

In terms of weight fraction, the four major steviol glycosides found in the stevia plant tissue are:

• 5–10% stevioside (250–300X of sugar)
• 2–4% rebaudioside A — most sweet (350–450X of sugar) and least bitter
• 1–2% rebaudioside C
• ½–1% dulcoside A

Rebaudioside B, D, and E may also be present in minute quantities; however, it is suspected that rebaudioside B is a byproduct of the isolation technique. The two majority compounds stevioside and rebaudioside, primarily responsible for the sweet taste of stevia leaves, were first isolated by two French chemists in 1931.Bridel, M.; Lavielle, R. (1931). "Sur le principe sucre des feuilles de kaa-he-e (stevia rebaundiana B)". Academie des Sciences Paris Comptes Rendus (Parts 192): 1123-1125. 

Availability

Rebiana is the tradename for a patent-pending, calorie-free, food and beverage sweetener derived from stevia and developed jointly by The Coca-Cola Company and Cargill. In May 2007, Coca-Cola announced plans to obtain approval for its use as a food additive within the United States by 2009. Coca-Cola has also announced plans to market rebiana-sweetened products in 12 countries that allow stevia\'s use as a food additive. The two companies are conducting their own studies in an effort to gain regulatory approval in the United States and the European Union.Stanford, Duane D.. "Coke and Cargill teaming on new drink sweetener", Atlanta Journal-Constitution, 2007-05-31. Retrieved on 2007-05-31. Etter, Lauren and McKay, Betsy. "Coke, Cargill Aim For a Shake-Up In Sweeteners", Wall Street Journal, 2007-05-31. Retrieved on 2007-06-01. 

Recently Blue California a US ingredient manufacturer claims to have developed an economical industrial production process for the \'natural sweetener\' stevia, which promises lower prices for manufacturers. The ingredient firm said it has completed the isolation of Rebaudioside A, a sweet compound derived from stevia, using a "more economical and proprietary process". The company expects to go into industrial scale production in 2008. The isolation process for Rebaudioside A results in a product that delivers the desired sweetness without the bitter aftertaste.Lorraine Heller. "US firm claims cheap, industrial stevia production", Food Navigator USA, 2007-11-15. Retrieved on 2007-11-01. 

Toxicity

A 1985 study reporting that steviol may be a mutagenPezzuto, JM; Compadre CM, Swanson SM, Nanayakkara D, Kinghorn AD (April 1985). "Metabolically activated steviol, the aglycone of stevioside, is mutagenic". Proc Natl Acad Sci U.S.A. 82 (8): 2478-82.  has been criticized on procedural grounds that the data were mishandled in such a way that even distilled water would appear mutagenic.Procinska, E; Bridges BA, Hanson JR (March 1991). "Interpretation of results with the 8-azaguanine resistance system in Salmonella typhimurium: no evidence for direct acting mutagenesis by 15-oxosteviol, a possible metabolite of steviol". Mutagenesis 6 (2): 165-7.  – full article text is reproduced here. More recent studies appear to establish the safety of steviol and its glycosides. In 2006, the World Health Organization (WHO) performed a thorough evaluation of recent experimental studies of stevia extracts conducted on animals and humans, and concluded that "stevioside and rebaudioside A are not genotoxic in vitro or in vivo and that the genotoxicity of steviol and some of its oxidative derivatives in vitro is not expressed in vivo." Benford, D.J.; DiNovi, M., Schlatter, J. (2006). "Safety Evaluation of Certain Food Additives: Steviol Glycosides" (PDF – 18 MB). WHO Food Additives Series 54: 140. World Health Organization Joint FAO/WHO Expert Committee on Food Additives (JECFA).  The report also found no evidence of carcinogenic activity. The report also suggested the possibility of health benefits, in that "stevioside has shown some evidence of pharmacological effects in patients with hypertension or with type-2 diabetes", but concluded that further study was required to determine proper dosage.

See also

• Stevia
• Glycoside
• Sugar substitute

References

External links

• PubChem summary of steviol molecule

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