Antioxidant lignans from the roots of vladimiria muliensis

Article abstract of DOI:10.1055/s-0033-1350801

Three new lignans (1, 2, and 8) and ten known ones (3-7, 9-13) were isolated from the roots of Vladimiria muliensis. Their structures and configurations were elucidated by means of spectroscopic techniques (IR, MS, NMR, and CD) and chemical methods. The i

Full text of DOI:10.1055/s-0033-1350801

1470 Letters
Antioxidant Lignans from the Roots of
Vladimiria muliensis
Jian-Jun Chen, Hong-Bo Wei, Yuan-Zhen Xu, Jun Zeng, Kun Gao
State Key Laboratory of Applied Organic Chemistry, College of
Chemistry and Chemical Engineering, Lanzhou University, Lanzhou,
Peopleʼs Republic of China
Abstract
!
Three new lignans (1, 2, and 8) and ten known ones (3–7, 9–13)
were isolated from the roots of Vladimiria muliensis. Their struc-
tures and configurations were elucidated by means of spectro-
scopic techniques (IR, MS, NMR, and CD) and chemical methods.
The isolated compounds were evaluated for their antioxidant and
antibacterial activities. The antioxidant activity was the greatest
for lignans 7 and 10 with IC50 values of 11.2 and 7.3 µM against
DPPH radical, and of 1.6 and 1.7 µM against ABTS+ radical, respec-
tively. Moreover, 7 also displayed broad-spectrum antibacterial
activity with MIC values around 7.25 µg/mL.
Fig. 1 Structures of compounds 1–13.
spectroscopic data of 1 were similar to those of the known com-
pound 5 which is co-occurring in this species, indicating that 1
was a highly oxygenated 7,7′-diaryl-8,8′-dihydroxy-7,9′:7′,9-di-
epoxylignan derivative.
Key words
Vladimiria muliensis · Compositae · lignans · antioxidant activ-
ity · antibacterial activity
"
This conclusion was confirmed by HMBC spectrum (l Fig. 2). The
HMBC experiment showed the correlations of H-7/C-9, H-7′/C‑9′,
H2-9/C‑8, and H2-9′/C‑8′, and determined the 8,8′-dihydroxy-
7,9′:7′,9-diepoxylignan structure [10]. Moreover, the HMBC data
revealed the correlations of H-7/C-1, C-2, C-6 and H-7′/C‑1′, C-2′,
C-6′, establishing that the benzyl group A was attached to C-7 and
group B to C-7′. The most significant difference between 1 and 5
was that the 1,3,4,5-tetrasubstituted phenyl group in 1 replaced
the 1,3,4-trisubstituted phenyl group in 5. With a careful analysis
of the NMR spectra of 1, three O-methyl groups were observed.
Two of these O-methyl groups were connected with C-3 and C-
3′, as in 5, thus the other one must be attached to C-5 to form
the 1,3,4,5-tetrasubstituted phenyl group. The HMBC correla-
tions between the O-methyl signals and C-3, C-3′, and C-5 sup-
Abbreviations
!
DPPH:
ABTS+:
1,1′-diphenyl-2,2′-picrylhydrazyl
2,2′-azinobis-3-ethylbenzothiazoline-6-sulfonic acid
Supporting information available online at
http://www.thieme-connect.de/ejournals/toc/plantamedica
Vladimiria is a highly diversified genus and belongs to the family
Compositae. The roots of many species in this genus have effects
on the treatment of dysentery, indigestion, nausea, and arresting
vomiting [1]. Sesquiterpenoids, lignans, triterpenoids, and phe-
nylpropanoids have been reported from this genus [2–7]. Howev-
er, relevant studies are few on Vladimiria muliensis (H.-M.) Ling
which is commonly used for the treatment of the symptoms
mentioned above as a folk medicine in China [1]. Previously, phy-
tochemical studies on V. muliensis collected in Muli in China by
our group have reported that steroids and triterpenoids isolated
from this plant showed antimicrobial and cytotoxic activity [8,9].
In our continuing research into this genus, three new (1, 2, and 8)
and ten known (3–7, 9–13) lignans were obtained from the roots
of V. muliensis collected in Yajiang in China (l Fig. 1). Herein, the
isolation, structural elucidation, and antioxidant and antibacteri-
al activities of these lignans are described.
Compound 1 was obtained as a colorless amorphous powder. Its
molecular formula was determined as C21H24O9 by HRESIMS as-
sociated with NMR data (l Table 1). The 13C and DEPT NMR spec-
"
ported the above conclusion (l Fig. 2). Consequently, the planar
structure of 1 was assigned as 5-methoxyprinsepiol.
The specific rotation of 1 was determined to be [α]2D0 − 36 (c 1.1,
CH3OH), which was similar to the value of [α]2D0 − 20 (c 1.0,
CH3OH) observed for 5. Also, a negative Cotton effect was ob-
served for 1 at λmax = 234 nm, Δε = − 1.61, similar to that of 5
(λmax = 235 nm, Δε = − 1.76) [11]. Taken together, these results in-
dicated that 1 and 5 had the same absolute configurations. There-
fore, the absolute configuration of 1 was determined as (7R,8S,7′
R,8′S)-5-methoxyprinsepiol.
"
Compound 2 was obtained as a colorless oil. Its molecular formu-
la was determined as C27H34O14 by HRESIMS and NMR data. The
13
"
C NMR data (l Table 1) of 2 were analogous to those of 1 except
for six more signals due to a sugar moiety and the corresponding
downfield shift of the ortho-related C-3 and C-5 (+ 6.8 ppm), and
the para-related C-1 (+ 8.6 ppm). The sugar moiety was identified
as β-glucopyranosyl by comparison to reported NMR data of
(−)-massoniresinol-4′′-O-β-D-glucopyranoside [12]. These obser-
vations strongly suggested that compound 2 differed from 1 in
that the hydroxyl at C-4 was replaced by a glucopyranosyl group.
The assignment was further supported by the correlation be-
"
tra showed 21 carbon signals including two aromatic rings, three
methoxys, two oxygenated methylenes, two oxygenated meth-
ines, and two oxygenated quaternary carbons. The 1H NMR spec-
trum showed the presence of a 1,3,4-trisubstituted phenyl group
and a 1,3,4,5-tetrasubstituted phenyl group [10]. Besides, it also
showed the presence of two benzylic oxymethines, two oxygen-
"
tween H-1′′ and C-4 in the HMBC spectrum (l Fig. 2). Acidic hy-
"
ated methylenes, and three O-methyl protons (l Table 1). These
drolysis of 2 in HCl-methanol (9%) yielded 1 and glucose, identi-
Chen J-J et al. Antioxidant Lignans from… Planta Med 2013; 79: 1470–1473

Letters 1471
Table 1 1H‑NMR (300 MHz) and 13C‑NMR (75 MHz) data of 1, 2, and 8.
1
2
8
no.
δ
H (J in Hz)
δC
δ
H (J in Hz)
δC
δ
H (J in Hz)
δC
1
126.7
103.8
147.2
134.9
147.2
103.8
87.1
135.3
106.9
154.0
136.0
154.0
106.9
89.2
130.1
112.6
153.7
149.3
116.1
120.8
200.3
50.4
2
6.62, s
6.77, s
7.54, br s
3
4
5
6.90, d, (7.8)
6
6.62, s
5.00, s
6.77, s
5.01, s
7.56, br d, (7.8)
7
8
87.4
89.3
3.33, m
4.18, m
4.20, m
9a
4.13, d, (9.4)
4.18, d, (9.4)
76.8
3.98, d, (9.3)
4.15, d, (9.3)
77.0
72.2
9b
1′
127.6
109.7
145.8
146.7
114.5
120.0
87.0
129.7
113.0
147.7
148.8
115.8
121.8
88.9
137.4
112.3
151.0
147.7
117.8
125.2
85.1
2′
6.93, br s
7.04, br s
7.08, br s
3′
4′
5′
6.92, d, (8.1)
6.84, br d, (8.1)
4.99, s
6.78, d, (8.1)
6.83, br d, (8.1)
5.00, s
6.83, d, (8.1)
7.07, br d, (8.1)
4.64, d, (7.8)
2.63, m
6′
7′
8′
87.5
89.6
54.9
9′a
9′b
Glu
1′′
2′′
3′′
4′′
5′′
6′′a
6′′b
3-OCH3
5-OCH3
3′-OCH3
4.13, d, (9.4)
4.18, d, (9.4)
76.8
3.99, d, (9.3)
4.16, d, (9.3)
76.9
3.64, m
61.5
3.64, m
4.86, d, (7.5)
3.55, dd, (9.5, 7.5)
3.48, t, (9.5)
3.44, t, (9.5)
3.45, m
105.5
75.9
78.0
71.5
78.5
62.7
4.84, d, (7.2)
3.53, m
102.9
75.0
78.2
71.5
77.9
62.6
3.47, m
3.41, m
3.43, m
3.65, dd, (12.1, 4.5)
3.84, dd, (12.1, 3.5)
3.86, s
3.63, dd, (12.1, 4.2)
3.82, dd, (12.1, 3.5)
3.83, s
3.88, s
3.88, s
3.88, s
56.3
56.3
55.9
57.2
57.2
56.5
56.9
56.6
3.86, s
3.86, s
3.86, s
Note: 1 in CDCl3, 2 and 8 in CD3OD
Fig. 2 Important HMBC (H→C) correlations of
compounds 1, 2, and 8.
1
fied as D-(+)-glucose by TLC comparison with an authentic sam-
ple and by its specific rotation value [12]. The structure of 2 was
therefore assigned as (7R,8S,7′R,8′S)-5-methoxyprinsepiol-4-O-
β-D-glucopyranoside.
copyranosyl unit [12]. Close analysis of H-1H COSY, HMQC, and
HMBC data confirmed this assignment. Acidic hydrolysis of 8 in
HCl-methanol (9%) afforded vladinol D and D-(+)-glucose which
were identified by the method mentioned above. Accordingly,
the structure of 8 was assigned as (8S,7′S,8′R)-vladinol D-4′-O-β-
D-glucopyranoside.
On the basis of HRESIMS and NMR data, the molecular formula of
compound 8 was determined to be C26H32 O12. The 1H and 13C
"
NMR spectra (l Table 1) of compound 8 presented similar signals
By comparison of our spectroscopic data with those reported in
the literature, the following known compounds were identified
as: 8′-hydroxypinoresinol (3) [10], 5-methoxypinoresinol (4)
[13], prinsepiol (5) [14], syringaresinol (6) [15], pinoresinol (7)
[16], massoniresinol (9) [17], berchemol (10) [18], lariciresinol
(11) [19], vladinol D (12) [13], and olivil (13) [17].
to those of vladinol D (12) co-occurring in this species, indicating
that 8 was a 7,7′-diaryl-7′,9-epoxylignan derivative. The big dif-
ferences were that 8 included one more glucopyranosyl unit,
and the downfield shifts (about 3.8 ppm, 3.1 ppm, and 2.8 ppm,
respectively) of C-1′, C-3′, and C-5′ (compared to those of 12).
These observations strongly suggested that compound 8 differed
from 12 in that the C-4′ hydroxyl group was replaced by a β-glu-
Chen J-J et al. Antioxidant Lignans from… Planta Med 2013; 79: 1470–1473

1472 Letters
Comparison of the structure of 1 with that of 2, or the structure of
8 with that of 12, showed that the antioxidant activity declined
sharply when a hydroxyl on the benzene ring was replaced by a
glucopyranosyl. So the phenolic hydroxyl was crucial to the anti-
oxidant activity, consistent with the previous observation [23].
Table 2 Free radical scavenging activities of compounds 1–13 (IC50, µM)a.
Compoundb
DPPH radical
ABTS+ radical
1
105.0
171.9
73.7
35.8
70.2
32.7
11.2
280.3
59.4
7.3
4.5
12.6
2.9
2
3
4
3.3
Materials and Methods
!
5
4.5
6
6.7
Plant material
7
1.6
The rhizome of V. muliensis was collected from Yajiang of Si-
chuan, China (29°30′N; 100°26′E; elevation 2982 m), in August
2010, and authenticated by Prof. Guoliang Zhang (the School of
Life Science, Lanzhou University) according to the Flora of China
[24]. A voucher specimen (No. 20100822) was deposited at the
Natural Product Laboratory of College of Chemistry and Chemical
Engineering, Lanzhou University.
8
55.0
4.0
9
10
1.7
11
21.3
162.0
26.5
20.7
11.3
8.5
12
13
Vitamin Cc
5.5
21.0
a IC50 (in µM) is defined as the concentration required to achieve 50% inhibition over
control free radicals; b Purity (%) of tested compounds was > 95%. c This compound
was used as a positive control (≥ 99%)
Extraction and isolation
The air-dried rhizome of V. muliensis (4.5 kg) was pulverized and
extracted with methanol (3 × 5 L) at room temperature, filtered
and concentrated to give a crude extract (426 g). The EtOAc-solu-
ble fraction (162.3 g) was subjected to Si gel column chromatog-
raphy (Φ 90 × 1000, 1000 g) with a gradient of petroleum ether-
acetone as the eluent, and seven fractions (A–G) were collected.
Fraction F (22.3 g) was further separated on Si gel, RP‑C 18 Si gel,
and Sephadex LH-20 columns to give pure compounds 1–13
(Supporting Information).
Compared with the common 7,7′-diaryl-7,9′:7′,9-diepoxylignans
from Valdimiria species [4–7], compounds 8–13 with a 7,7′-dia-
ryl-7′,9-epoxy skeleton were more unusual.
The antibacterial activities of the isolated compounds against
Escherichia coli, Bacillus cereus, Staphyloccocus aureus, Erwinia
carotovora, and Bacillus subtilis were tested using a microbroth
dilution method [20]. Ampicillin (98%) was used as the positive
control. Compound 7 was the most active metabolite and dis-
played broad-spectrum inhibitory activity on these bacteria with
MIC values of 15.5, 7.25, 7.25, 7.25, and 7.25 µg/mL, respectively.
Compound 11 exhibited moderate activity against B. cereus and S.
aureus with MIC values of 31.25 and 125 µg/mL, whereas com-
pound 10 only exhibited moderate activity against B. cereus with
an MIC value of 31.25 µg/mL. All of the tested bacteria were less
sensitive to the other ten compounds, with MIC values above
250 µg/mL. Comparing the antibacterial activities of compounds
1–7, it seemed that the hydroxyl group at C-8 or C-8′ and one
more methoxy group in the A ring or B ring might cause a de-
crease in antibacterial activity.
Isolates
(7R,8S,7′R,8′S)-5-Methoxyprinsepiol (1): colorless amorphous
powder; [α]2D0 = − 36.36 (MeOH, c 1.10); IR (KBr) νmax: 3502,
1711, 1648, 1518, 1424, 1362, 1224, 1092, 904 cm−1; UV (MeOH)
λmax (log ε): 205 (3.82), 228 (3.48), 273 (3.22) nm; 1H‑(CDCl3,
13
"
300 MHz) and C‑NMR (CDCl3, 75 MHz) data: see l Table 1;
HRESIMS m/z 443.1325 [M
21H24O9Na).
+
Na]+ (443.1313 calcd. for
C
(7R,8S,7′R,8′S)-5-Methoxyprinsepiol-4-O-β‑D-glucopyranoside
(2): colorless oil; [α]D20 = − 50.01 (MeOH, c 1.00); IR (KBr) νmax
:
3458, 1710, 1665, 1514, 1423, 1363, 1225, 1091, 905 cm−1; UV
(MeOH) λmax (log ε): 209 (3.76), 225 (3.48), 273 (3.18) nm;
1H‑(CD3OD, 300 MHz) and 13C‑NMR (CD3OD, 75 MHz) data: see
The antioxidant activities of 1–13 were evaluated by their ability
of scavenging the DPPH and ABTS+ radicals [21,22]. Vitamin C
+
"
l Table 1; HRESIMS m/z 605.1847 [M + Na] (605.1841 calcd. for
C27H34O14Na).
"
(≥ 99%) was used as the positive control (l Table 2). Most of the
isolated compounds showed significant antioxidant activity, with
compound 7 (IC50 values of 11.2 µM against the DPPH radical and
1.6 µM against the ABTS+ radical, respectively) and compound 10
(IC50 values of 7.3 µM against the DPPH radical and 1.7 µM
against the ABTS+ radical, respectively) being the most potent.
Compounds 4, 6, 11, and 13 were also active with IC50 value
ranges of 21.3–35.8 µM and 3.1–11.3 µM against DPPH and ABTS+
radicals, respectively.
(8S,7′S,8′R)-Vladinol D-4′-O-β‑D-glucopyranoside (8): colorless
amorphous powder; [α]D20 = − 31.82 (MeOH, c 2.20); IR (KBr) νmax
:
3359, 2917, 2849, 1734, 1598, 1512, 1461, 1422, 1369, 1226,
1121, 1068, 785 cm−1; UV (MeOH) λmax (log ε): 204 (3.82), 224
(3.58), 275 (3.68), 301 (3.09) nm; 1H‑(CD3OD, 300 MHz) and
13
"
C‑NMR (CD3OD, 75 MHz) data: see l Table 1; HRESIMS m/z
559.1788 [M + Na]+ (559.1786 calcd. for C26H32O12Na).
The fact that compound 7 showed better activity than 3 and 5
suggested that the additional hydroxyl groups on the positions 8
and 8′ might cause the decrease in antioxidant activity for the
7,7′-diaryl-7,9′:7′,9-diepoxylignans. Interestingly, in 7,7′-diaryl-
7′,9-epoxylignans, the scavenging activity against ABTS+ and
DPPH radicals of 10 with a hydroxyl on position 8 was 7-fold
and 3-fold higher than those of 11, respectively. However, its
8,8′-dihydroxyl derivative (9) showed a lower level of inhibitory
activity against both radicals than 10. These results suggested
that the presence of a hydroxyl on position 8 was a structure re-
quirement for the radical inhibitory activity of this kind of lignan.
Antibacterial assay
The method described in the literature was used for the measure-
ment of antibacterial activities against E. coli (CGMCC1.1636), B.
cereus (CGMCC1.1846), S. aureus (CGMCC1.89), E. carotovora,
and B. subtilis (CGMCC1.88) [20]. For detailed protocols, see Sup-
porting Information.
Assay of DPPH radical scavenging activity
Reaction mixtures containing a methanol solution of 200 µM
DPPH (100 µL) and two fold serial dilutions of the sample were
placed in a 96-well microplate and incubated at 30°C for 30 min
Chen J-J et al. Antioxidant Lignans from… Planta Med 2013; 79: 1470–1473

Letters 1473
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The ABTS+ radical cation (ABTS+) stock solution was diluted with
methanol to get an absorbance of 0.70 0.02 at 734 nm. Then
100 µL of the diluted ABTS+ solution and two fold serial dilutions
of the sample were placed in a 96-well microplate and incubated
at 30°C for 6 min. After incubation, the absorbance was read at
734 nm with a Tecan Infinite 200 Pro microplate reader, and the
means of three readings were calculated.
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Acknowledgements
!
The research work was financially supported by the National Nat-
ural Science Foundation of China (No. 31270396, No. 21002046),
Fundamental Research Funds for the Central Universities
(lzujbky-2013–51), and National Science Foundation for Foster-
ing Talents in Basic Research of the National Natural Science
Foundation of China (J1103307).
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PK, Nazemiyeh H, Sarker SD. Americanin, a bioactive dibenzylbutyro-
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Conflict of Interest
!
24 Chen SK, Chen BY, Li H. Flora of China (Zhongguo Zhiwu Zhi). Beijing:
Science Press; 1997: 78, 141–147
The authors of the present manuscript have declared that no
competing interests exist.
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DOI http://dx.doi.org/10.1055/s-0033-1350801
Published online September 17, 2013
Planta Med 2013; 79: 1470–1473
© Georg Thieme Verlag KG Stuttgart · New York ·
ISSN 0032‑0943
Correspondence
Prof. Kun Gao
State Key Laboratory of Applied Organic Chemistry
College of Chemistry and Chemical Engineering
Lanzhou University
Tianshui South Road 222
Lanzhou 730000
Peopleʼs Republic of China
Phone: + 86 931 891 2592
Fax: + 86 931 891 2582
npchem@lzu.edu.cn
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