Chemistry Reference
In-Depth Information
sweetener,andlavorcompanieshavebeentryingtoindwaystomaskitwithoutdetractingfrom
theperceivedbeneitsofitsnaturalstatus.Asaresultofresearchinvestigatingthebittercomponent,
wenowreportonanewwater-solubleiminosugaralkaloidin
Stevia
.Alkaloidshavenotbeenprevi-
ouslyreportedfrom
Stevia
species.Inanongoingsearchfornewiminosugars,
Veltheimia capensis
Hyacinthaceae(SandLily),anativetoWesternCape,SouthAfrica,wasalsofoundcoincidentally
tocontainthesamealkaloid.
Steviamine(1)hasamolecularformulaC
10
H
20
NO
3
.Thepositiveresponsetochlorine-
o
-tolidine
reagent suggested that steviamine was an alkaloid. The
13
C nuclear magnetic resonance (NMR)
spectroscopicdatarevealedthepresenceofasinglemethyl(δ19.2),fourmethylenes(δ23.7,29.2,
33.3,and56.5),andivemethine(δ52.8,61.3,66.7,69.1,and73.8)carbonatoms.Theconnectivity
ofthecarbonandhydrogenatomswasdeinedfromCOSYandHMBCspectroscopicdata.Three
methinesignals(δ52.8,61.3,and66.7)withrelativelydown-ieldchemicalshiftsweresuggestive
ofbeingbondedtothenitrogenoftheindolizidinering.Themethylenesignalatδ56.5(C-1)was
attributedtothehydroxymethylcarbon,andthisshowedHMBCcorrelationstoδ61.3(C-2)and
69.1(C-3).Themethinesignalatδ61.3showedHMBCcorrelationstoδ69.1(C-3),73.8(C-4),and
66.7(C-5),suggestingaive-memberedring.
Iminosugarindolizidinealkaloidssuchasswainsonineandcastanosperminehavestrongbio-
logicalactivities(Watsonetal.2001),includingglycosidaseinhibition,immunemodulation,and
antiviral and anticancer activity. The biological activity of steviamine and the synthesis of other
5-methyl-indolizidinealkaloidsareunderinvestigation.Nostudyhasbeenreportedabouttheeffect
ofiminosugarsontasteinhumans,butweconsideritpossiblethatpolyhydroxylatediminosugars
likesteviamine mayhave an effect on thesweet tasteof steviosideand rebaudosides. Since imi-
nosugars are dificult to resolve and detect by most commonly used analytical systems and have
similarsolubilitytothesteviolglycosides,itisverylikelythattheyoccurinsome
Stevia
products.
4.12 SUCraLOSe
Sucralose,1,6-dichloro-1,6-dideoxy-β-d-fructofuranosyl4-chloro-4-deoxy-α-d-galacto-pyranoside,
or 4,1ʹ,6ʹ-trichloro-4,1ʹ,6ʹ-trideoxy-
galacto
-sucrose (Figure 4.10), is a chlorinated derivative of
sucrose, discovered in 1976 by carbohydrate research chemists at Queen Elizabeth College and
TateandLyle,U.K.Itisderivedfromapatentedmultistepprocess,involvingselectivechlorina-
tion of sugar at the 4, 1ʹ, and 6ʹ positions substituting three hydroxyl groups on the sucrose mol-
ecule.Itistheresultofastudyonalargenumberofrelatedcompounds,carefullysynthesizedand
evaluated to determine the spatial structure and molecular coniguration required for sweetness
perception.
IngredientsandtabletopformsofsucralosearebeingmarketedunderthebrandnameSplenda.
ItschemicalformulaisC
12
H
19
O
8
Cl
3
(MW397.35).Sucraloseisawhite,odorlesscrystallinepowder
andisreadilydispersibleandsolubleinwater,methanol,andethanol.At20°C,a280g/Lsolutionof
sucraloseinwaterispossible.SucralosepresentsNewtonianviscositycharacteristics,anegligible
Cl
HO
OH
CI
O
O
OH
HO
O
Cl
OH
Figure 4.10
Chemical structure of sucralose.
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