MAGNETIC RESONANCE IN CHEMISTRY
Magn. Reson. Chem. 2006; 44: 727–730
Published online 20 April 2006 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/mrc.1830
Spectral Assignments and Reference Data
0
Complete assignments of 1H and 13C NMR
data for seven arylnaphthalide lignans from
Justicia procumbens
followed by preparative reverse-phase C HPLC to yield 6 -hydroxy
18
0
0
justicidin A (1), 6 -hydroxy justicidin B (2), 6 -hydroxy justicidin C
(3), neojusticin A (4), chinensinaphthol methyl ester (5), isodiphyllin
6) and taiwanin C (7) (Figs 1 and 2).
(
The structures of the known compounds 4–7 were determined
1
by comparison of mass spectrometric (MS) and H NMR data with
those in the literature and reconfirmed by 2D NMR experiments. The
C NMR data of these compounds, which have not been reported
1
2∗
3
3
Meihua Yang, Jun Wu, Fan Cheng and Yuan Zhou
1
3
1
Institute of Medicinal Plant Development, Chinese Academy of Medical
Sciences and Peking Union Medical College, Beijing, 100094, P.R. China
Guangdong Key Laboratory of Marine Materia Medica, South China
Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West
Xingang Road, Guangzhou 510301, P.R. China
Chemistry and Life Science College, China Three Gorges University, 8
so far, were first assigned unambiguously by HSQC and HMBC
correlations, as shown in Tables 1–2.
2
0
6 -Hydroxy justicidin A (1) was isolated as a pale yellow
amorphous powder. Its molecular formula was determined as
C22H18O8 by the HR-TOF-MS spectrum (m/z 410.1000, calcd for
C
3
[M] 410.1002). The UV maxima at 203, 256, 307 nm and the IR (KBr)
absorption bands at 3290, 2936, 1727, 1508, 1485, 1262, 1220, 1177,
University Road, Yichang 443002, P.R. China
ꢀ
1
1
162 and 928 cm suggested that it was an arylnaphthalide lignan
1
with a ꢀ-lactone. The H NMR data (Table 1) of 1 contained the
signals of four singlet aromatic protons (υ 6.59, 6.67, 6.91, 7.49 ppm),
a methylenedioxy group (υ 5.981 ppm, broad s; 5.987 ppm, broad s),
Received 9 February 2006; revised 4 March 2006; accepted 7 March 2006
ꢀ
Three new arylnaphthalide lignans named 6 -hydroxy
a ꢀ-lactone methylene group (υ 5.67 ppm, 2H, broad s) and three
ꢀ
ꢀ
justicidin A (1), 6 -hydroxy justicidin B (2) and 6 -hydroxy
justicidin C (3) have been isolated from the whole
plant of Justicia procumbens, together with four known
ones, neojusticin A (4), chinensinaphthol methyl ester
1
methoxy groups (υ 3.65 ppm, s; 3.92 ppm, s; 4.11 ppm, s). The
H
1
NMR data of 1 were similar to those of Justicidin A except for
the absence of an aromatic proton that led to the disappearance
1
of an ABX system seen in the H NMR spectrum of Justicidin A.
(
5), isodiphyllin (6) and taiwanin C (7). The complete
assignments of H and C NMR chemical shifts for the
new lignans and the C NMR chemical shifts for the
known lignans were obtained for the first time by means
of 2D NMR techniques, including HSQC and HMBC.
Copyright 2006 John Wiley & Sons, Ltd.
1
13
The above observation suggested that an oxygenated group might
0
1
3
be substituted at the 6 -C of the 1-aryl group of 1. Considering
the elemental composition of 1, this group was characterized as
a hydroxyl. On the basis of these results, the structure of 1
0
13
was identified as 6 -hydroxy justicidin A and its C NMR data
were assigned unambiguously by the HSQC and HMBC (Fig. 3)
KEYWORDS: NMR; 1H NMR; 13C NMR; 2D NMR; arylnaphthalide
lignan; Justicia procumbens; complete NMR assignments
correlations, as shown in Table 2.
0
6
-Hydroxy justicidin B (2), a pale yellow amorphous powder,
had a molecular formula of C21H16O7 established by the HR-TOF-
C
1
MS spectrum (m/z 380.0899, calcd for [M] 380.0896). The H and
1
3
C NMR data of 2 were almost the same as those of 1, except
INTRODUCTION
for the absence of a methoxy group (υH 4.11 ppm, s; υC 59.6 ppm,
q; 1-OCH3 in 1) and the presence of one more aromatic proton
(υH 7.86 ppm, s). It was indicated that 1-methoxy group in 1 was
replaced by an aromatic proton. This result was further confirmed by
the HMBC correlation from this proton to C-2 (υC 139.9 ppm) and C-9
(υC 128.1 ppm) (Fig. 3). Therefore, the structure of 2 was identified as
1-demethoxy 6 -hydroxy justicidin A, namely 6 -hydroxy justicidin
B. Its C NMR data were assigned unambiguously by the HSQC
and HMBC (Fig. 3) correlations, as shown in Table 2.
The whole plant of Justicia procumbens L. (Acanthaceae) is used
as a herbal remedy for the treatment of fever, pain due to
laryngopharyngeal swelling and cancer in China. In Taiwan, the
juice of this plant has also been used as a fish-killing material
for many hundred years. Previous phytochemical studies on this
plant have afforded 10 diarylbutane lignans, 12 arylnaphthalide
lignans and 7 arylnaphthalide lignan glycosides.
was reported that justicidin A, isolated from the same plant, not
only decreased the level of cytosolic Ku70 leading to apoptosis in
1
2
0
0
2
–8
13
Recently, it
0
6 -Hydroxy justicidin C (3) was isolated as a pale yellow
9
amorphous powder. Its molecular formula was determined as the
human colorectal cancer cells but also inhibited LPS-stimulated
TNF-˛ release from RAW 264.7 macrophages in a concentration-
and time-dependent manner.10 In the continuing search for potential
drug leads from acanthaceae plants, three new arylnaphthalide
0
0
lignans, named 6 -hydroxy justicidin A (1), 6 -hydroxy justicidin
0
B (2) and 6 -hydroxy justicidin C (3), have been isolated from
the whole plant of J. procumbens, together with four known ones,
2
2,11
neojusticin A (4), chinensinaphthol methyl ester (5),
isodiphyllin
6) and taiwanin C (7). Though the H NMR data of the
above four known lignans 4–7 are well described in the literature,
1
2
13
1
(
1
3
no completely assigned C NMR data have been published.
1
13
Here we give the exact and unambiguous H and C NMR
assignments of these arylnaphthalide lignans for the first time,
achieved with the aid of 2D NMR techniques, including HSQC
and HMBC.
RESULTS AND DISCUSSION
The ethanolic extract of the whole plant of J. procumbens was subjected
to sequential extraction with petroleum ether and ethyl acetate as
described in the Experimental section. The resulting ethyl acetate
extract was chromatographed on silica gel, Sephadex LH-20 gel, and
Ł
Correspondence to: Jun Wu, Guangdong Key Laboratory of Marine Materia
Medica, South China Sea Institute of Oceanology, Chinese Academy of
Sciences, 164 West Xingang Road, Guangzhou 510301, P.R. China.
E-mail: wwujun2003@yahoo.com
Figure 1. Structures of compounds 1–2 and 5–7.
Copyright 2006 John Wiley & Sons, Ltd.