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Two prenylflavanones from Euchresta japonica
0031-9422/82/122959-05$03.00/O @ 1982 PergamonPress Ltd.
Phytochemistry,Vol. 21, No. 12. pp. 2959-2963, 1982. Printedin Great Britain.
TWO PRENYLFLAVANONES YOSHIAKI
SHIRATAKI,
AKIHIKO
FROM EUCHRESTA MANAKA,
ICHIRO YOKOE
JAPONK’A”
and MANKI KOMATSU
Faculty of Pharmaceutical Sciences, Josai University, Keyakidai l-1, Sakado, Saitama 350-02, Japan
(Received I April 1982) Key Word Index-Euchresta japonica; Leguminosae; euchrestaflavanone B; euchrestaflavanone 5, 7, 4’-trihydroxy-6, I-diprenylisoflavone; warangalone; osajin; prenylflavonoids.
Abstract-Two new prenylflavanones, Euchresta japonica. Their structures
C;
named eucbrestaflavanone B and C were isolated from the roots of have been confirmed by spectroscopic and chemical evidence, respec-
tively.
RESULTS AND
INTRODUCTION
Previously we reported the isolation and the structural elucidation of euchrestaflavanone A from the roots of Euchresta japonica Hook. f. ex Regel which have been used as a substitute for a Chinese drug, Shan-Dou-Gen [ 11. In our further studies on this drug, two new prenylflavanones, euchrestaflavanone B (1) and C (2), together with 5,7,4’-trihydroxy6,8_diprenylisoflavone (3), warangalone (4) and osajin (5) have been isolated. This paper deals with the isolation and structural determination of these compounds.
Euchrestaflavanone B (1) (M’ 424, [cr]~-31.0° in EtOH, Cz5H,,06) was isolated as colorless needles, mp 188-190” from the ether-soluble fraction of the methanol extract of the roots of E. juponica. It gave a greenish-brown color in the ferric chloride test, a dark blue color in the Gibbs test and a positive magnesium-hydrochloric acid test. The IR spectrum of 1 showed strong absorptions at 1630 cm-’ (chelated C=O) and 34OOcm-’ (OH). The UV spectrum (A%:” 294, 334(sh)nm) suggested a flavanone structure. It formed a tetra-acetate (la) indicating the presence of
2
I EuchrestafLavanone
Euchrestaflovonone
A
DISCUSSION
Euchrestaflovonone
6
C
OH
5,7,4’-Trihydroxy6,6-diprenyllsoflavone
Warangolone (scandenone)
L- Maackioin R=H Trlfolirhizm R: glucose
*Part 17 in the series “Studies on the Constituents of Sophoru Species”. For Part 16 see ref. [l].
Medlcagol
Prenylflavanones
2961
from Euchresta japonica
PPm 200
I50
I
100
I *
ss.5
I sd,,
*
I
d,,
s
.
-.
c-2’/‘.” .* /.
c-4
dd
c-&i.
C-8
’ t
d
OH
i c-z : .
0
Naringenm
c-3
I
s
sss
ss
s
sss
s
-.._ -.
: : :
r’....ssdddss
d
t
EuchrestafLavanone ssdd
d
ss
d
d
t
ssdx*
tqtq x*
A
l.2
Fig . 1. “C NMR spectrum of 1 (in DMSO-d&. Off-resonance decoupling (SFORD). s, Singlet; d, doublet; t,
triplet; 4, quartet.* The position of C-2’ in 1 corresponds to C-6’ of euchrestaflavanone A.
positive Cotton effect at 339 nm (Ae - 0.14) and the negative Cotton effect at 295 nm (A.E- 3.01) allows the assignment of the S-configuration at C-2 in 1. Euchrestaflavanone C (2) (M’ 422, [a]‘, - 103.1” in ethanol, Cz5HZ606) was obtained as pale yellow needles, mp 198-200”. It gave a greenish-brown color in the ferric chloride test, a blue color in the Gibbs test and a positive magnesium-hydrochloric acid test. The IR spectrum of 2 showed a strong absorptions at 1640cm-’ (chelated C=O) and 3350cm-’ (OH). The UV spectrum (A$$r = 293, 342(sh) nm) suggested a flavanone structure. It formed a triacetate (2a) indicating the presence of three hydroxyl groups. The ‘H NMR spectrum of 2 (CD,COCD,) showed 6 5.68 (1 H, dd, J = 11.6 and 3.8 Hz) and 2.6-3.2 (2H, m), attributed to the C-ring protons (H-2, Hz-3) of the flavanone. It also indicated the presence of one 3,3dimethylallyl group [6 1.63 (6 H, s, Me x 2), 3.25 (2 H, brd, J = 7.4 Hz, Ar-C&CH:), 5.22 (1 H, brt, J = 7.4 Hz, -CHr-CH=C=)I,
one 2,2_dimethylchromene
ring [S 1.40 (6 H, s, Me x 2), 5.61 (1 H, d, J = 10.0 Hz), 6.36 (1 H, d, J = 10.0 Hz)], three hydroxyl groups [S 9.0 (2 H, brs) and 12.2 (1 H, s, chelated with C-4 carbonyl); both of which disappeared on the addition of DzO] and three aromatic protons [S 6.04 (1 H, s, H-6 or H-8), 6.38 (1 H, s, H-3’), 7.22 (1 H, s, H-6’)].
The mass spectrum of 2 showed major ion peaks at m/z 407 (17.6), 404 (32.9), 389 (6.9), 220 (4.0) and 202
(0.7). The ion peaks at m/z 220 and 202 were derived from a retro-Diels-Alder fragmentation. In view of the ‘H NMR spectral data, the ion peak at m/z 220 must include the A-ring. This ion loses C4H7 to yield the ion peak at m/t 165 (46.8) and therefore the A-ring contains one 3,3-dimethylallyl group. On the other hand, the ion peak at m/z 202 arises from the B-ring. It loses Me to yield the ion peak at m/z 187 (100). Therefore the B-ring contains one 2,2-dimethylchromene ring. Since the 13CNMR spectrum of 2 showed signals at 6 106.9 (C-6) and 95.3 (C-8) which are the same as those of 1, the 3,3-dimethylallyl group was shown to be located at C-6. The substitution pattern of B-ring was determined to be 2’,4’-dihydroxy-5’-C-substituted by comparison of the chemical shifts of 1 and 2 (Table 1). From these spectral data and biogenetic considerations, the structure of euchrestaflavanone C (2) to be 5,7,2’-trihydroxy-6-(3,3concluded was dimethylallyl) - 2”,2” - dimethylpyrano - (5”,6” : 4’,5’) flavanone. The absolute configuration of 2 was determined as (- )-2S-flavanone by the CD spectra as well as 1. Other compounds (3-5) are referred to in the Experimental.
Table 1. “C NMR spectral data of 1 and 2 (B-ring, in DMSO-d,) Compound 1
2
PHYTO
Vol. 21, No. 12-M
C-l’
C-2’
C-3’
C-4’
C-5’
C-6
118.1 117.6
153.2 153.5
102.3 102.9
155.5 155.5
115.5 112.8
127.3 127.7
Prenylflavanones
2%3
from Euchresro joponica
C-4). This was identified by direct comparison (mmp, HPLC, TLC and IR) with an authentic sample [4]. w~ru~gfff~~e (~cu~de~one) (4) [S, 61. Pale yellow needles (from n-C6Hr4), mp 165-166”. Found: M’ 404.1622; C2,H2d05 requires 404.1609. HPLC R,: 17.2 min. Osajjn [7]. Pale yellow needles (from n-C6Hu). mp 194195”. Found: M’ 484.1622; C25H2405 requires 404.1620. HPLC R,: 15.8 min. ~u~~geni~. 13C.NMR (DMSO-d& 95.0 (C-8), 95.8 (C-6). Euchrestaf?aoanone A. ‘“C NMR (DMSO-d,): 95.2 (C-8), 106.8 (C-6). Ackn~wfedgemen~s-We are very grateful to Dr. Y. Hamada, Kumamoto University and to Miss K. Higuchi and Mr. M. Endo of our University for collecting the plant material. Thanks are also due to Dr. A. K. Singhal, Regional Research Laboratory, India, for a generous gift of an authentic sample of 5,7,4’-trihydroxy-6,8-diprenylisoflavone and Dr. Y. Komoda, Tokyo Medical and Dental University,
for the “C NMR spectral measurements. Y. S. is grateful to President Z. Horii, Josai University for a grant to support a part of this work. REEERENCES 1. Shirataki, Y., Komatsu, M., Yokoe, 1. and Manaka, A. (1981) Chem. Phnrm. Bull. 29,3033. 2. Gaflield, W. (1970) ~ef~ahedr~~ X,4093. 3. Clark-Lewis, J. W. (1968) Aust. J. Chem. 21, 2059. 4. Singhal, A. K., Sharma, R. P., Thyagarajan, G., Herz, W. and Govindan, S. V. (1980) Phytochemfstry 19, 929. 5. Falshaw, C. P., Harmer, R. A., Ollis, W. D., Wheeler, R. E., Lalitha, V. R. and Subba Rao, N. V. (1969) J. Chem. SM. C 374. 6. Pelter, A. and Stainton, P. (1%6) J. Chem. Sac. C 701.
7. Wolfrom, M. L., Harris, W. D., Johnson, G. F., Mahan, J. E., Moffets, S. M. and Wildi, B. (1946) L Am. Chem. Sot. 68,406.
Phytochemistry,Vol. 21, No. 12. pp. 2959-2963, 1982. Printedin Great Britain.
TWO PRENYLFLAVANONES YOSHIAKI
SHIRATAKI,
AKIHIKO
FROM EUCHRESTA MANAKA,
ICHIRO YOKOE
JAPONK’A”
and MANKI KOMATSU
Faculty of Pharmaceutical Sciences, Josai University, Keyakidai l-1, Sakado, Saitama 350-02, Japan
(Received I April 1982) Key Word Index-Euchresta japonica; Leguminosae; euchrestaflavanone B; euchrestaflavanone 5, 7, 4’-trihydroxy-6, I-diprenylisoflavone; warangalone; osajin; prenylflavonoids.
Abstract-Two new prenylflavanones, Euchresta japonica. Their structures
C;
named eucbrestaflavanone B and C were isolated from the roots of have been confirmed by spectroscopic and chemical evidence, respec-
tively.
RESULTS AND
INTRODUCTION
Previously we reported the isolation and the structural elucidation of euchrestaflavanone A from the roots of Euchresta japonica Hook. f. ex Regel which have been used as a substitute for a Chinese drug, Shan-Dou-Gen [ 11. In our further studies on this drug, two new prenylflavanones, euchrestaflavanone B (1) and C (2), together with 5,7,4’-trihydroxy6,8_diprenylisoflavone (3), warangalone (4) and osajin (5) have been isolated. This paper deals with the isolation and structural determination of these compounds.
Euchrestaflavanone B (1) (M’ 424, [cr]~-31.0° in EtOH, Cz5H,,06) was isolated as colorless needles, mp 188-190” from the ether-soluble fraction of the methanol extract of the roots of E. juponica. It gave a greenish-brown color in the ferric chloride test, a dark blue color in the Gibbs test and a positive magnesium-hydrochloric acid test. The IR spectrum of 1 showed strong absorptions at 1630 cm-’ (chelated C=O) and 34OOcm-’ (OH). The UV spectrum (A%:” 294, 334(sh)nm) suggested a flavanone structure. It formed a tetra-acetate (la) indicating the presence of
2
I EuchrestafLavanone
Euchrestaflovonone
A
DISCUSSION
Euchrestaflovonone
6
C
OH
5,7,4’-Trihydroxy6,6-diprenyllsoflavone
Warangolone (scandenone)
L- Maackioin R=H Trlfolirhizm R: glucose
*Part 17 in the series “Studies on the Constituents of Sophoru Species”. For Part 16 see ref. [l].
Medlcagol
Prenylflavanones
2961
from Euchresta japonica
PPm 200
I50
I
100
I *
ss.5
I sd,,
*
I
d,,
s
.
-.
c-2’/‘.” .* /.
c-4
dd
c-&i.
C-8
’ t
d
OH
i c-z : .
0
Naringenm
c-3
I
s
sss
ss
s
sss
s
-.._ -.
: : :
r’....ssdddss
d
t
EuchrestafLavanone ssdd
d
ss
d
d
t
ssdx*
tqtq x*
A
l.2
Fig . 1. “C NMR spectrum of 1 (in DMSO-d&. Off-resonance decoupling (SFORD). s, Singlet; d, doublet; t,
triplet; 4, quartet.* The position of C-2’ in 1 corresponds to C-6’ of euchrestaflavanone A.
positive Cotton effect at 339 nm (Ae - 0.14) and the negative Cotton effect at 295 nm (A.E- 3.01) allows the assignment of the S-configuration at C-2 in 1. Euchrestaflavanone C (2) (M’ 422, [a]‘, - 103.1” in ethanol, Cz5HZ606) was obtained as pale yellow needles, mp 198-200”. It gave a greenish-brown color in the ferric chloride test, a blue color in the Gibbs test and a positive magnesium-hydrochloric acid test. The IR spectrum of 2 showed a strong absorptions at 1640cm-’ (chelated C=O) and 3350cm-’ (OH). The UV spectrum (A$$r = 293, 342(sh) nm) suggested a flavanone structure. It formed a triacetate (2a) indicating the presence of three hydroxyl groups. The ‘H NMR spectrum of 2 (CD,COCD,) showed 6 5.68 (1 H, dd, J = 11.6 and 3.8 Hz) and 2.6-3.2 (2H, m), attributed to the C-ring protons (H-2, Hz-3) of the flavanone. It also indicated the presence of one 3,3dimethylallyl group [6 1.63 (6 H, s, Me x 2), 3.25 (2 H, brd, J = 7.4 Hz, Ar-C&CH:), 5.22 (1 H, brt, J = 7.4 Hz, -CHr-CH=C=)I,
one 2,2_dimethylchromene
ring [S 1.40 (6 H, s, Me x 2), 5.61 (1 H, d, J = 10.0 Hz), 6.36 (1 H, d, J = 10.0 Hz)], three hydroxyl groups [S 9.0 (2 H, brs) and 12.2 (1 H, s, chelated with C-4 carbonyl); both of which disappeared on the addition of DzO] and three aromatic protons [S 6.04 (1 H, s, H-6 or H-8), 6.38 (1 H, s, H-3’), 7.22 (1 H, s, H-6’)].
The mass spectrum of 2 showed major ion peaks at m/z 407 (17.6), 404 (32.9), 389 (6.9), 220 (4.0) and 202
(0.7). The ion peaks at m/z 220 and 202 were derived from a retro-Diels-Alder fragmentation. In view of the ‘H NMR spectral data, the ion peak at m/z 220 must include the A-ring. This ion loses C4H7 to yield the ion peak at m/t 165 (46.8) and therefore the A-ring contains one 3,3-dimethylallyl group. On the other hand, the ion peak at m/z 202 arises from the B-ring. It loses Me to yield the ion peak at m/z 187 (100). Therefore the B-ring contains one 2,2-dimethylchromene ring. Since the 13CNMR spectrum of 2 showed signals at 6 106.9 (C-6) and 95.3 (C-8) which are the same as those of 1, the 3,3-dimethylallyl group was shown to be located at C-6. The substitution pattern of B-ring was determined to be 2’,4’-dihydroxy-5’-C-substituted by comparison of the chemical shifts of 1 and 2 (Table 1). From these spectral data and biogenetic considerations, the structure of euchrestaflavanone C (2) to be 5,7,2’-trihydroxy-6-(3,3concluded was dimethylallyl) - 2”,2” - dimethylpyrano - (5”,6” : 4’,5’) flavanone. The absolute configuration of 2 was determined as (- )-2S-flavanone by the CD spectra as well as 1. Other compounds (3-5) are referred to in the Experimental.
Table 1. “C NMR spectral data of 1 and 2 (B-ring, in DMSO-d,) Compound 1
2
PHYTO
Vol. 21, No. 12-M
C-l’
C-2’
C-3’
C-4’
C-5’
C-6
118.1 117.6
153.2 153.5
102.3 102.9
155.5 155.5
115.5 112.8
127.3 127.7
Prenylflavanones
2%3
from Euchresro joponica
C-4). This was identified by direct comparison (mmp, HPLC, TLC and IR) with an authentic sample [4]. w~ru~gfff~~e (~cu~de~one) (4) [S, 61. Pale yellow needles (from n-C6Hr4), mp 165-166”. Found: M’ 404.1622; C2,H2d05 requires 404.1609. HPLC R,: 17.2 min. Osajjn [7]. Pale yellow needles (from n-C6Hu). mp 194195”. Found: M’ 484.1622; C25H2405 requires 404.1620. HPLC R,: 15.8 min. ~u~~geni~. 13C.NMR (DMSO-d& 95.0 (C-8), 95.8 (C-6). Euchrestaf?aoanone A. ‘“C NMR (DMSO-d,): 95.2 (C-8), 106.8 (C-6). Ackn~wfedgemen~s-We are very grateful to Dr. Y. Hamada, Kumamoto University and to Miss K. Higuchi and Mr. M. Endo of our University for collecting the plant material. Thanks are also due to Dr. A. K. Singhal, Regional Research Laboratory, India, for a generous gift of an authentic sample of 5,7,4’-trihydroxy-6,8-diprenylisoflavone and Dr. Y. Komoda, Tokyo Medical and Dental University,
for the “C NMR spectral measurements. Y. S. is grateful to President Z. Horii, Josai University for a grant to support a part of this work. REEERENCES 1. Shirataki, Y., Komatsu, M., Yokoe, 1. and Manaka, A. (1981) Chem. Phnrm. Bull. 29,3033. 2. Gaflield, W. (1970) ~ef~ahedr~~ X,4093. 3. Clark-Lewis, J. W. (1968) Aust. J. Chem. 21, 2059. 4. Singhal, A. K., Sharma, R. P., Thyagarajan, G., Herz, W. and Govindan, S. V. (1980) Phytochemfstry 19, 929. 5. Falshaw, C. P., Harmer, R. A., Ollis, W. D., Wheeler, R. E., Lalitha, V. R. and Subba Rao, N. V. (1969) J. Chem. SM. C 374. 6. Pelter, A. and Stainton, P. (1%6) J. Chem. Sac. C 701.
7. Wolfrom, M. L., Harris, W. D., Johnson, G. F., Mahan, J. E., Moffets, S. M. and Wildi, B. (1946) L Am. Chem. Sot. 68,406.