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.[1] They are heat-stable, pH-stable, and do not ferment.[2] They also do not induce a glycemic response when ingested, making them attractive as natural sweeteners to diabetics and others on carbohydrate-controlled diets.
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The diterpene known as steviol is the aglycone of stevia's sweet glycosides, which are constructed by replacing steviol's carboxyl hydrogen atom (at the bottom left of the figure) with glucose to form an ester, and replacing the hydroxyl hydrogen (at the top of the figure) with combinations of glucose and rhamnose to form an ether. The two primary compounds, stevioside and rebaudioside A, use only glucose: Stevioside has two linked glucose molecules at the hydroxyl site, whereas 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:
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.[2] The two majority compounds stevioside and rebaudioside, primarily responsible for the sweet taste of stevia leaves, were first isolated by two French chemists, Bridel and Lavielle (1931).[3]
Steviol glycosides were first commercialized as a sweetener in 1971 by the Japanese firm Morita Kagaku Kogyo Co., Ltd., a leading stevia extract producer in Japan.
Rebiana is the trade name[4] for a zero-calorie sweetener containing mainly rebaudioside A (also called Reb A).[5] Truvia is the consumer brand for Rebiana marketed by Cargill and developed jointly with The Coca-Cola Company.[6] PureVia is PepsiCo's brand of Reb A sweetener. Enliten is Corn Products International's brand of Reb A sweetener.
A 1985 study reporting that steviol may be a mutagen[7] has been criticized on procedural grounds that the data were mishandled in such a way that even distilled water would appear mutagenic.[8] 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.”[9] 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”,[9] but concluded that further study was required to determine proper dosage.
The European Food Safety Authority evaluated the safety of steviol glycosides, extracted from the leaves of the Stevia rebaudiana Bertoni plant, as sweetener and expressed its opinion on 10 March 2010. The authority concluded an Acceptable Daily Intake (ADI) for steviol glycosides, expressed as steviol equivalents, of 4 mg/kg bodyweight/day.[10]
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