1. Temhedron Letters, Vol32, No 6, pp 783-792 1991 w40-4039191 $3 00 + 00
Prmcd m Great Britam Pergamon Press plc
A NEW TYPE OF ANTISWEET PRINCIPLES OCCURRING IN GYMNEMA SYLVESTREl)
Kazuko YoshlkawaxFa Shlgenobu Anharaa and KOUJ~ Matsuura b
aFaculty of Pharmaceutical Sciences. Tokushlma-Bunr1 Umverslty. Tokushlma-sin,
Tokushlma. 770, Japan
bTeikoku Seiyaku Co, Ouchi-cho, Ookawa-gun, Kagawa 769-26, Japan
Summary A New type of antisweet pnnc1ples. gymnemasapomns I-V has been Isolated
fro1n Gymnema sylvestre Their structures were established as novel D-glucosldes of 3p.
16@,23,28-tetrahydroxyolean-12-ene on the basis of spectroscopic analysis The
antisweet activity of these compounds 1s discussed 1n relation to another type of active
components, gymnemlc acids I-VI
To date the only known antlsweet substances are gymnemic acids I-VI from the
leaves of Gvmnema svlvestre R Br (Asclepladaceae)2),3) and z1z1ph1n from the leaves
of Zlz1Dhus Ju_mba4) They dll contain acyl group(s) like acetIc, tlgl1c and 2-methylbutync
acid 1n genm or sugar parts and 1t has been pomted out that acyl group(s) play an
important role 1n the occurrence of ant1sweet activity Continuing studies of the title
plant resulted 1n the isolation of five novel glucosldes of oleanene, designated as
gymnemasaponln I(i), II@), III(a), IV($) and V(5) These new compounds have a
different gemn from that of gymnemlc acids I-VI and have no acyl groups On the
activity assay, 2, 4, and 5 showed the antlsweet actlvlty This paper deals with their
chemical structures and the activity of this new type of ant1sweet principles
The aq SO%EtOH extract( at 60°C ) of the dned leaves(3 Okg) of G svlvestre was
successively chromatographed on Amberhte XAD-2 and Toyopearl HW-40 to give
fr I-V Gymnennc acids I-VI had been isolated from fr IV2) Fr I and II were
further separated by ordinary-phase S102 and reversed-phase HPLC(ODS) column
chromatography to furnish five new saponlns. gymnemasaponm I(l, 180mg), II(2,
80mg), IIl(z. 30mg), IV($, 50mg) and V(Z 400mg)
On acid hydrolysis, gymnemasaponlns I-V(i-2) afforded 23-hydroxylonglsymogemn
(_6)5), amorph, [a]~ +32 O”(c=2 8, MeOH), FAB-MS m/z 497(M+Na)” as the same
aglycone and only D-glucose as a sugar component, respectively
Gymneinasaponln I(L), 1np 184-185”C, [a]D +9 3’(c=3 5, MeOH). C36H6009 showed
a molecular 1on peak at m/z 659(M+Na)+ 1n the posltlve FAB-MS The lH- and l3C-NMR
spectra of l_ Indicated the presence of one P-glucopyranosyl unit [ H-l’ 6 4 92( d,
J=8 OHz ), C-l’ i? 105 8 ] Comparison of 13C-NMR spectrum of L w1tk that of 5 showed
glycosylat1on sh1ft6) for the C-28 s1gnal( +9 lppm ), demonstrahng that
789

2. 790
RI R2
- LH2UK2
2 -gk -glc~glc
i -gdglc -g1c -
CX-I 6 -gl&c -gl&lc
HO
7
-, -g&lc -H
5 -H -H
a fi-glucopyranosyl group 1s located at the C-28-OH Therefore. L was formulated as
28-O-~-D-glucopyranosyl-23-hydroxylonglspinogen~n
The posltlve FAB-MS of gymnemasaponln Il(I$_ mp 190-192°C la]D +l 9”(c=2 6,
MeOH), C42H70014 revealed a molecular ion peak at m/z 821(M+Na)+ The lH- and
13C-NMR spectra mdlcated the presence of two p-gluLopyranosy1 units [ H-l’ 6 492
( d, J=8 OHz ) and 4 95( d, J=8 OHz ). C-l’ 6 105 8 and 105 2 ] In the same way as J,
glycosylatlon shifts were observed for the C-23 slgnal( +7 Oppm ) as well as the C-28
slgnal( +9 lppm ), indicating that both the C-23- and C-28-OH were glycosylated
Hence, 2 was formulated as 7.28~dl-O-~-D-glucopyranosyl-23-hydroxylongisp~nogenin
Gymnemasaponm V(z), mp 186-188”C, [a]D -62”(c=l 9, MeOH), C54H90024
revealed the molecular Ion peak at m/z 114S(M+Na)+ m the posltlve FAB-MS The 1H-
and 13C-NMR spectra showed the presence of four fi-glucopyranosyl units [ H-l’ 6 4 84,
4 87( each d, J=8 5Hz ), 5 06 5 lO( each d, J=8 OHz ), C-l’ 6 104 9, 105 4, 105 4 dnd
105 9 ] It also suggested the mode of glycosldlc linkages have two 136 lmkages( 6 69 8
and 70 2 ) The signals at 675 1 and 77 9 indicated the presence of glycosldlc linkage at
the C-23- and C-28-OH From these spectrum data, the followmg three cases could be
consldered as the posslblllty of the sugar linkage a) C-23-0-glchglc and C-28-0-gl&glc,
b) C-23-0-glc6glcfiglc and C-2%0-glc, c) C-23-0-glc and C-28-O-glcfiglchglc
In order to determme the lmkage between sugars, 2 was subjected to cellulase
hydrolysis to give three products, V-enz-l(z), V-enz-2(3 and V-enz-3(>
Compound 7, mp 173-175”C, [a]D +I 2 I”(c=l 1, MeOH) revealed a molecular ion
peak at m/z 821(M+Na)+ In the posrtlve FAB-MS, quggestmg that 2 waq a dlglucoslde
Comparison of the 13C-NMR spectrum of 7 with those of 6 and 2_ showed that the
chemical shifts at the C-23 and the C-5’ and C-6’ of the glucosyl moleties in 1 were
shifted by +7 lppm, +l 2ppm and +7 2ppm, respectively, mdlcatmg two
o-glucopyranosyl groups being Joined to the C-23-OH though 1+6 linkage Hence, 1 was
represented as 23-0-P-gentlbloslde of 5
Compound 2, mp 203-205”C, [a]D -11 6”(c=l 1, MeOH) and 4, mp 201-203°C. [a]D
-1 l”(c=l 9, MeOH) have the same molecular formula C48H80019 [ FAB-MS m/z 983
(M+Na)+ 1, demonstrating 2 and 4, to be a tnglucoslde and the l3C-NMR spectra Indicated
that the sugar moieties were attached to both the C-23- and C-28-OH Detailed
comparisons of the 13C-NMR spectrum of the sugar moiety of 5 with that of ,2+ showed
glycosylatlon shift for the C-6’ slgnal( +7 2ppm ) of the C-23 glucosyl moletles, while

3. 791
that of the C-28 glucosyl moiety rematned unshlfted( 6 62 8 ) The C-23 sugar carbons
signals of 5 were In good agreement with those of 1 It IS clear that one 8-gentlblosyl
group was bound to the C-23-OH Consequently, 5 was represented as 23-O-@-
gentlblosyl-28-O-B-D-glucopyranosyl-23-hydroxylong~sp~nogenln In the case of 3,
the glycosylatlon shift was observed for the C-6’ slgnal( +7 Oppm ) of the C-28 glucosyl
moletle?. while that of the C-23 glucosyl moiety remamded unshlfted( 6 63 0 ) It
Indicated that the additIona &glucopyranosyl resrdue was attached to the C-6’ of the
C-28 glucose moletIes Therefore, 2 was determined as 23-0-fl-D-glucopyranosyl-28-O.
fl-gentlblosyl-23-hydroxylonglsptnogenm Compounds 2 and 4, were also Isolated from
this plant and designated as gymnemasaponm III and IV, respectively
Based on the above evidence, 2 was established as 23,28-dl-O-fl-gentlblosyl-23-
hydroxylonglspmogenm These five gymnemasapomns are the first examples of
23-hydroxylongisplnogenm glucoslGes
One mM solution of 2, 4, and 5 reduced completely sweetness perception induced
by 0 1M sucrose, it corresponds to l/2 of the activity of gymnemic acids I-VI
Compounds l_ and 2 were not active at all Kurlhara et a13),4) have reported acyl
group(s) In gymnemlc acids and zlzlphm play an important role in the generation of the
antisweet activity However, our present results suggest that the acyl group(s) only
increase the antisweet actlvlty rather than playing the essential role This mvestlgatlon
could lead to be better knowledge of the mechanism of antisweet sensations
Acknowledgments
This work was supported by a Grant-m-Aid from the Ministry of Education,
Science and Culture of Japan( Grant No 02771677. 1990 )
References
1) This work was presented at The 110th Annual Meeting of The Pharmaceutical Society
of Japan, Sapporo, Auguest 1990
2) K Yoshlkawa. K Amlmoto, S Arlhara and K Matsuura, Tetrahedron Lett . 30, 1103
(1989) , K Yoshikawa, K Amlmoto. S Anhara and K Matsuura, Chem Pharm Bull,
37, 852, (1989)
3) M Maeda, T Iwashlta and Y Kunhara, Tetrahedron Lett , 30, 1547 (1989)
4) Y Kunhara. K Ookubo, H Tasakl, H Kodama, Y Akryama, A Yagl and B Halpem,
Tetrahedron, 44, 61 (1988)
5) S B Mahato and B C Pal, J Chem Sot Perkm Trans I, 629 (1987)
6) R Kasal, M Oklhara, J Asakawa, K Mlzutam and 0 Tanaka, Tetrahedron Lett , 35,
1427 (1979)

4. 792
Table I 13C-NMR Data for 1, 2, 3, 4, , 2, 1 and 6, ( lOOMHz, pyrtdme-d5 )
C No
Aglycone molty
L‘
..
z 3, 4,: z 5
2 27 7 27 4 27 4 27 4 27 4 27 4 27 6
3 73 4 72 3 72 3 72 2 72 1 72 2 73 4
4 42 9 42 9 42 9 43 0 43 0 42 9 42 8
15 37 0 36 9 36 9 36 9 36 9 37 0 36 7
16 66 3 66 1 66 3 66 2 66 3 66 7 66 6
‘7 41 3 41 3 41 4 41 3 41 4 41 0 41 0
23 67 9 7.5 0 75 1 75 1 7.5 1 75 1 68 0
24 ‘ 1
3 13 2 ‘3 2 13 2 13 3 ‘3 2 ‘3 0
28 78 0 78 0 77 9 78 0 77 9 68 8 68 9
C-23 sugars
glc 1’ I05 2 105 2 105 3 105 4 105 3
2 75 3 75 3 75 2 75 2 75 2
3’ 78 7 78 7 78 7 78 6 78 6
4’ 7’ 8 7’ 9 7’ 7 71 6 71 7
5’ 78 4 78 4 77 2 77 2 77 2
6’ 63 0 63 0 70 2 70 2 70 2
glc 1” 104 9 104 9 104 9
(l&i) 2” 74 6 74 6 74 7
3” 78 4 78 4 78 5
4” 7’ 7 71 6 7’ 6
5” 78 4 78 4 78 5
6” 62 8 62 7 62 8
C-28 sugars
glc 1’ 105 8 105 8 105 7 105 9 I05 9
2 75 0 75 0 75 1 75 1 75 2
3’ 78 7 78 7 78 6 78 7 78 5
4 71 7 7’ 7 71 6 71 7 71 6
5’ 78 6 78 7 77 3 78 6 77 3
6’ 62 8 62 8 69 8 62 8 69 8
glc 1” 105 4 105 4
(1*6) 2” 74 8 74 8
3” 78 4 78 4
4” 7’ 4 71 3
5” 78 4 78 4
6” 62 8 62 7
Assmgment of 13C-NMR spectrum of L-1 were based on the
ZD-NMR ( ‘H-lH , 13C-‘H ) spectra
(Received m Japan 24 November 1990)