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IWAMURA, Jun-ichi; KOMAKI, Kyosuke; KOMAI, Koichiro; Hirao, Nenokichi

doi:10.1246/nikkashi.1979.255

Cited by 6 publications

(5 citation statements)

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“…While it was not possible to isolate the sweet constituents in the limited amounts of plant material available, the positive glycoside identifications proposed here for the S. rebaudiana and S. phlebopbylla samples were based on a combination of tic and hplc data, backed up by the unequivocal generation of isosteviol methyl ester from both plants by acid hydrolysis and methylation, as demonstrated by gc/ms. Isosteviol, a known product of stevioside on acid hydrolysis (26,27), was also shown here to be produced after reflux of rebaudiosides A-E, delcoside A, and steviolbioside, a treatment undergone by all of the Stevia samples examined in this study. The failure to detect isosteviol on acid hydrolysis of the other 108 Stevia species studied not only confirms the negative results obtained after analytical tic, but also strongly suggests that steviol glycosides, whether sweet or nonsweet, were absent from the samples studied of these species.…”

Section: Resultssupporting

confidence: 57%

A Phytochemical Screening Procedure for Sweet Ent-Kaurene Glycosides in the Genus Stevia

Kinghorn¹,

Soejarto²,

Nanayakkara³

et al. 1984

J. Nat. Prod.

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Altogether, 110 species of the genus Stevia, comprising both herbarium and fresh leaf samples, were screened for the presence of sweet ent-kaurene glycosides, using a combination of tlc and hplc, followed by gc/ms. Stevioside and rebaudiosides A and C were detected in a Stevia rebaudiana herbarium specimen collected in Paraguay in 1919, and stevioside was observed as a constituent of a Stevia phlebophylla herbarium specimen collected in Mexico in 1889. Steviol glycosides were not detected in any of the other 108 Stevia species studied. The phytochemical results obtained in this study are correlated with those of preliminary organoleptic tests on the sweetness of these Stevia samples, and the chemotaxonomic implications of the present findings are discussed.

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Section: Resultssupporting

confidence: 57%

A Phytochemical Screening Procedure for Sweet Ent-Kaurene Glycosides in the Genus Stevia

Kinghorn¹,

Soejarto²,

Nanayakkara³

et al. 1984

J. Nat. Prod.

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“…In the context of results presented in this communication, the questions of imminent importance are the chemical stability and metabolic disposition of this substance. Considering the former, a variety of chemical reaction conditions have been shown to result in the production of isosteviol (18,28). Refluxing stevioside for 5 hr in aqueous methanol/1.5% HCl gives isosteviol in 78% yield (28).…”

Section: Resultsmentioning

confidence: 99%

“…Considering the former, a variety of chemical reaction conditions have been shown to result in the production of isosteviol (18,28). Refluxing stevioside for 5 hr in aqueous methanol/1.5% HCl gives isosteviol in 78% yield (28). In a comprehensive study in which stevioside was incubated for up to 3 months at pH values ranging from 2 to 8 and §In separate experiments using incubation conditions known to mediate bacterial mutagenesis, the enzymic generation of approximately 10 …”

Section: Resultsmentioning

confidence: 99%

Metabolically activated steviol, the aglycone of stevioside, is mutagenic.

Pezzuto¹,

Compadre²,

Swanson³

et al. 1985

Proc. Natl. Acad. Sci. U.S.A.

108

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Stevioside, a constituent of Stevia rebaudiana, is commonly used as a noncaloric sugar substitute in Japan. Consistent with reports in the literature, we have found that stevioside is not mutagenic as judged by utilization of Salmonella typhimurium strain TM677, either in the presence or in the absence of a metabolic activating system. Similar negative results were obtained with several structurally related sweet-tasting glycosides. However, steviol, the aglycone of stevioside, was found to be highly mutagenic when evaluated in the presence of a 9000 X g supernatant fraction derived from the livers of Aroclor 1254-pretreated rats. Expression of mutagenic activity was dependent on both pretreatment of the rats with Aroclor 1254 and addition of NADPH; unmetabolized steviol was not active. The structurally related species, isosteviol, was not active regardless of metabolic activation. Similarly, chemical reduction of the unsaturated bond linking the carbon-16 and -17 positions of steviol resulted in the generation of two isomeric products, dihydrosteviol A and B, that were not mutagenic. In addition, ent-kaurenoic acid was found to be inactive. It is therefore clear that a metabolite of an integral component of stevioside is mutagenic; structural features of requisite importance for the expression of mutagenic activity include a hydroxy group at position 13 and an unsaturated bond joining the carbon atoms at positions 16 and 17. A potential metabolite of steviol, steviol-16a,17-epoxide, was synthesized chemically and found to be ineffective, as. a direct-acting mutagen. Thus, although stevioside itself 'appears innocuous, it would seem prudent to expeditiously and unequivocally establish the human metabolic disposition of this substance.Stevia rebaudiana Bertoni (Compositae) is a sweet herb indigenous to elevated terrain in the northeastern corner of Paraguay, adjacent to its frontier with Brazil (1). Extracts of this plant and stevioside, its major sweet constituent, are commercially available in Japan, where they have been used for nearly a decade to sweeten a variety of foods including sea foods, pickled vegetables, dessert items, soft drinks, and confectionery (2-4). Recently, S. rebaudiana products were cleared for sale in Brazil (5, 6), and they are also used in Paraguay for the treatment of hyperglycemia (1).Stevioside is one of eight known sweet ent-kaurene glycoside constituents of S. rebaudiana, with the others being steviolbioside, rebaudiosides A-E, and dulcoside A (7). The results of several studies to assess the safety for human consumption of certain of these compounds and S. rebaudiana extracts have appeared in the literature. For example, neither stevioside nor two different S. rebaudiana extracts were found to be significantly active during acute toxicity tests in mice and subacute toxicity tests in rats (8). Also, no dose-related abnormalities in an extensive range of blood chemistry values were observed after subacute oral administration to rats of a S. rebaudiana extract containing 50% ...

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“…Its absolute configuration was resolved by the chemical correlation through its hydrogenation product that was identical to a material derived from 129 by dehydration with POCl 3 and hydrogenation [352, 353] . The (−)‐enantiomer of 138 was later isolated from several other plants [177, 349, 354–367] . Full 1 H‐ and 13 C‐NMR data in CDCl 3 and C 6 D 6 have been reported [367, 368] …”

Section: Cyclised and Rearranged Guaianesmentioning

confidence: 96%

Germacrene A–A Central Intermediate in Sesquiterpene Biosynthesis

Dickschat

2020

Chemistry A European J

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This review summarises known sesquiterpenes whose biosyntheses proceed through the intermediate germacrene A. First, the occurrencea nd biosynthesis of germacrene Ai nN ature and its peculiar chemistry will be highlighted , followed by ad iscussion of 6-6 and 5-7 bicyclic compounds and their more complex derivatives. For each compound the absolutec onfiguration, if it is known,a nd the reasoning for its assignment is presented. 2. Germacrene A 2.1. Occurrence in Nature (À)-Germacrene A(1,S cheme 2) was first isolated in 1970 from the gorgonian Eunicea mammosa. [7] Its absolute configuration was established as (S)-(À)-1 through its Cope rearrangement to (+ +)-b-elemene (2)f or which the configurational assignment was performed by chemical correlation of (À)-elemol(3)t o (À)-2. [8, 9] Compound (À)-1 is also believed to occur in the soft coral Lobophytum, [10] andi st he alarm pheromone of the aphid Terioaphis maculata. [11, 12] In the course of this work it was noticed that the optical rotation([ a] D 25 = À26.8, c 1.0, CCl 4)w as significantly highert han initially reported ([a] D 25 = À3.2, c 14.4, CCl 4), [7] which is explainableb yapartial rearrangement of purified (À)-1 to (+ +)-2,o ra lternatively, 1 isolated from E. mammosa was not enantiomerically pure. However,the opticalrotation of (+ +)-2 ([a] D 25 =+15.1, neat) reported in this initial study [7] matches the reported value for (À)-2 ([a] D 25 = À15.8, c 0.50, CHCl 3)o btainedb yC ope rearrangement of (+ +)-1, [13] thus disfa-Scheme1.Te rpene cyclisation modes for FPP. Scheme2.Structure of 1 and its absolute configurationbyc hemicalcorrelation.

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Cited by 6 publications

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A Phytochemical Screening Procedure for Sweet Ent-Kaurene Glycosides in the Genus Stevia

A Phytochemical Screening Procedure for Sweet Ent-Kaurene Glycosides in the Genus Stevia

Metabolically activated steviol, the aglycone of stevioside, is mutagenic.

Germacrene A–A Central Intermediate in Sesquiterpene Biosynthesis

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