Stevia rebaudiana Steviol, Stevioside

The leaves of Stevia rebaudiana (Compositae) are a source of several sweet glycosides of steviol (26) (Fig. 15) [1, 61]. The major glycoside, stevioside (27), is used in oriental countries as a food sweetener and the second major glycoside named rebaudioside (28), which is sweeter and more delicious than stevioside, is utilized in beverages. 

Stevia species are members of the family of Asteraceae. Stevia rebaudiana contains steviol glycosides, such as stevioside and rebaudioside A, used as artificial sweeteners and 100-300 times sweeter than sucrose [72, 73 ]. Their clinical pharmacology and therapeutic actions have been reviewed [74, 75 ]. 

Figure 4A.21 Steviarebaudiana. (a) Stevia plant (b) Stevia field (Picture (a) and (b) Foundation of Humanity and Development "F.H.D." Guido Herrera, with kind permission) (c) Dry leaves of Stevia rebaudiana (d) chemical structure Stevioside (e) chemical structure Steviol (f) chemical structure Rebaudioside A.

Steviol glycosides are derived from the mevalonic acid pathway. The ent-kaurene skeleton of stevioside is formed via 2-C-methyl-D-erythritol-4-phosphate (MEP) pathway [59, 60]. High activity of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase in chloroplasts of Stevia rebaudiana has been reported [61]. Hence, the investigators anticipated mevalonic acid (MVA) as an intermediate of steviol biosynthetic route on the basis of the fact that HMG-CoA reductase is a key enzyme of the MVA route to isopentenyl-diphosphate (IPP). 

In Japan, the largest market for the S. rebaudiana sweeteners to date, three different forms of stevia sweetener products are commercially available, namely, stevia extract , sugar-transferred stevia extract , and rebaudioside A-enriched stevia extract . Stevia extract is a powder or granule made by several industrial steps and standardized so as to contain more than 80% of steviol glycosides, inclusive of dulcoside A (3-5%), rebaudioside A (20-25%), rebaudioside C (5-10%), and stevioside (50-55%) [31]. Sugar-transferred stevia extract is made by... 

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