P. Mann et al. / Phytochemistry 50 (1999) 267±271
269
molecule and sodium is the counter ion. Acid hydroly-
sis of 5 yielded quercetin 7-methyl ether and sulfate.
The UV spectral data obtained with standard shift
reagents (see Section 3) indicated substitutions of the
¯avonoid at C-7, C-3 and C-30 (Mabry, Markham, &
Thomas, 1970). After addition of hydrochloric acid to
a methanolic solution of 5, a bathochromic shift of 25
nm (band I) was observed, therefore the positions 3
and 30 had to be sulfated (Barron & Ibrahim, 1988a).
measurable signal enhancement of any proton was
observable, supporting the placement of this methoxy
group at C-3. Finally the position of the sulfate moiety
was determined by methylation of 6, followed by
hydrolysis with hydrochloric acid. The product of the
hydrolysis, a trimethylated quercetin derivative, exhib-
1
ited one additional methoxy singlet at d 3.98 in the H
NMR spectrum. Irradiation at d 7.76 (H-20) showed
an NOE enhancement of the methoxy signal at d 3.98.
On the basis of these data compound 6 was shown to
be quercetin 3,7-dimethyl ether-40-sulfate.
1
The H NMR spectrum of compound 5 showed sig-
nals for a pair of meta coupled protons at d 6.36 (1 H,
d, J= 2.1 Hz, H-6) and d 6.73 (1 H, d, J= 2.1 Hz, H-
8), a one proton doublet at d 6.92 (J= 8.7 Hz, H-50),
a one proton doublet at d 7.91 (J= 1.8 Hz, H-20), a
one proton double doublet at d 8.12 (J=1.8, 8.7 Hz,
H-60), a methoxy group at d 3.88 (s) and a one proton
singlet at d 12.67. The position of this methoxy group
was established by NOE dierence experiments.
Irradiation of the methoxy singlet at d 3.88 led to
enhancement of the H-6 (d 6.36) and H-8 (d 6.73) sig-
nals, indicative of the position of the methoxy group
at C-7. A comparison with the corresponding quercetin
7-methyl ether spectrum showed that the signals of
H-20 and H-60 of ¯avonoid 5 were signi®cantly shifted
The EIMS of compound 8 showed a base peak at
m/z 344 [M 80], the formula of which was deter-
mined as C18H16O7. The FABMS showed a quasi-mol-
ecular ion peak at m/z 423 [M±H] as well as peaks at
m/z 445 [(M±2H) +Na] and at m/z 343 [M±H-80] .
The UV spectral data indicated, as in compound 6,
substituted hydroxy groups at C-3, C-7 and C-40
(Mabry et al., 1970). Addition of hydrochloric acid to
a methanolic solution of 8 led to a distinctive batho-
chromic shift (band I), indicating an attachment of the
sulfate moiety to C-3 (Barron & Ibrahim, 1988a).
1
The H NMR spectrum of 8 (Table 2) showed the
signals of
a
trimethylated quercetin derivative.
down®eld (Barbera, Sanz, Sanchez-Parareda,
&
Irradiation at d 3.84, d 3.85 and d 3.87 led to NOE
enhancements at the signals of H-6 and H-8, H-20 and
H-50, respectively, showing that the methoxy groups
were attached to C-7, C-30 and C-40. Compound 8 is
therefore quercetin 30,40,7-trimethyl ether-3-sulfate.
Prior to this work, no sulfated ¯avonoids have been
reported in convolvulaceous species at all. Such com-
pounds have also neither been described in the
Solanaceae nor in any other family closely related to
the Convolvulaceae so far. The ability to synthesize
¯avonoid sulfates is not a universal feature for the
convolvulaceous species, though. This is evident from
the fact that no such compounds could be detected in
the following species: Ipomoea alba L., I. muricata (L.)
JACQ. (syn. I. turbinata LAG.), Merremia medium
(L.) HALL. and M. umbellata (L.) HALL.
Marco, 1986). Correspondingly, in the 13C NMR spec-
trum the carbon signals of C-20 at d 124.4 and C-60 at
d 128.2, as well as the signal of C-4 at d 178.7 were
signi®cantly shifted down®eld, when compared to the
corresponding carbon signals of quercetin 7-methyl
ether (Markham & Chari, 1982; Barron & Ibrahim,
1988b; Barron & Ibrahim, 1987). Consequently 5 is
quercetin 7-methyl ether-3,30-disulfate.
The compounds 6 and 8 were obtained from an
n-butanolic extract of the aerial vegetative parts of I.
regnellii. The EIMS of compound 6 exhibited a base
peak at m/z 330 [M-80] and its formula was deter-
mined as C17H14O7 by HRMS. The FABMS (negative
mode) gave a quasi-molecular ion peak at m/z 409
[M±H]
and signi®cant peaks at m/z 431 [(M±
2H) +Na] as well as m/z 329 [M±H-80] , indicative
of the loss of one molecule of SO3. The UV spectral
data indicated substitutions of the hydroxy groups at
3. Experimental
1
C-3, C-7 and C-40 (Mabry et al., 1970). The H NMR
spectrum of compound 6 exhibited singlets from a
chelated hydroxy group (d 13.08) and two methoxy
groups (d 3.85 and 3.87) as well as two meta coupled
aromatic proton signals at d 6.36 (1 H, d, J =2.0 Hz,
H-6) and 6.69 (1 H, d, J =2.0 Hz, H-8), an aromatic
proton doublet at d 7.02 (J= 9.0 Hz, H-50), a one pro-
ton doublet at 7.62 (J =2.0 Hz, H-20) and an aromatic
proton double doublet at 7.78 (J= 2.0; 9.0 Hz, H-60).
Irradiation of the methoxy resonance at d 3.85 gave an
enhancement of the doublet at d 6.36 (H-6) and the
doublet at 6.69 (H-8) indicating the positioning at C-7.
On irradiation of the methoxy signal at d 3.87 no
3.1. Spectroscopic methods
EIMS, HRMS and FABMS spectra were obtained
using MAT-711 and CH5-DF Finnigan spectrometers.
1
All H NMR and 13C NMR spectra were recorded in
DMSO-d6 on a Bruker AC-400 spectrometer, using
TMS as internal standard.
3.2. Plant material
Roots and aerial vegetative parts were obtained
from plants cultivated in our greenhouse from seeds,