Bioactive constituents from the rhizomes of Dioscorea septemloba Thunb

Article abstract of DOI:10.1016/j.fitote.2016.10.011

Eight new compounds, dioscorosides G (1), H₁ (2), H₂ (3), dioscorol B (4), dioscorosides I (5), J (6), K₁ (7), and K₂ (8), together with twelve known ones (9–20) were obtained from the rhizomes of Dioscorea sept

Full text of DOI:10.1016/j.fitote.2016.10.011

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Fitoterapia 115 (2016) 165–172
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Fitoterapia
journal homepage: www.elsevier.com/locate/fitote
Bioactive constituents from the rhizomes of Dioscorea septemloba Thunb
Yi Zhang a,b, Liping Chao a, Jingya Ruan a, Chang Zheng a, Haiyang Yu a,b, Lu Qu b, Lifeng Han a,b, Tao Wang a,b,
⁎
a
Tianjin State Key Laboratory of Modern Chinese Medicine, Tianjin University of Traditional Chinese Medicine, 312 Anshanxi Road, Nankai District, Tianjin 300193, China
b
Tianjin Key Laboratory of TCM Chemistry and Analysis, Institute of Traditional Chinese Medicine, Tianjin University of Traditional Chinese Medicine, 312 Anshanxi Road, Nankai District, Tianjin
300193, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 4 October 2016
Received in revised form 21 October 2016
Accepted 26 October 2016
Available online 28 October 2016
Eight new compounds, dioscorosides G (1), H1 (2), H2 (3), dioscorol B (4), dioscorosides I (5), J (6), K1 (7), and K2
(8), together with twelve known ones (9–20) were obtained from the rhizomes of Dioscorea septemloba. Their
structures were elucidated by chemical and spectroscopic methods. Among the known isolates, 12–14, 18, and
20 were isolated from the Dioscoreae genus for the first time. While, 9–11, 15, and 16 were firstly obtained
from the plant. Moreover, all the isolates were evaluated for in vitro anti-inflammatory potential using LPS-stim-
ulated RAW 264.7 murine macrophages, and compounds 7, 11, 15, and 16 were found to display significant in-
hibition of nitrite production.
Keywords:
Dioscorea septemloba Thunb
RAW 264.7 cells
© 2016 Published by Elsevier B.V.
Anti-inflammatory activity
1. Introduction
477.1053 [M − H]−, calcd for C22H21O12, 477.1038). Its IR spectrum sug-
gested the presences of hydroxyl (3356 cm−1), α,β-unsaturated car-
In the process of continuing to study anti-inflammatory constituents
from the 70% EtOH extract of Dioscorea spongiosa rhizomes [1], eight
new compounds, named as dioscorosides G (1), H1 (2), H2 (3), dioscorol
B (4), dioscorosides I (5), J (6), K1 (7), and K2 (8), together with twelve
known ones, albiflorin (9) [2], benzoyl paeoniflorin (10) [3], isopsoralen
(11) [4], isodemethylfuropinarine (12) [5], annulatomarin (13) [6,7],
icariside E5 (14) [8], (+)-syringaresinol 4-O-β-D-glucopyranoside (15)
boxyl group (1673 cm−1), aromatic ring (1634, 1504, 1458 cm−1), O-
glycoside linkage (1072 cm−1), and methylenedioxyl (927 cm−1).
Acid hydrolysis of 1 with 1 M HCl afforded D-glucose, whose absolute
configuration was determined by HPLC analysis [1]. The analysis of the
1H, 13C (Table 1) and 2D (1H 1H COSY, HSQC, HMBC) spectra revealed
the presences of one ABX-type aromatic ring [δ 6.74 (1H, dd, J = 3.0,
8.5 Hz, H-4′), 6.94 (1H, d, J = 3.0 Hz, H-6′), 7.18 (1H, d, J = 8.5 Hz, H-
3′)], one pentasubstituted aromatic ring [δ 6.42 (1H, s, H-5)], one oxy-
genated methine [δ 6.03 (1H, dd, J = 3.0, 12.0 Hz, H-3)], one
methylenedioxyl [δ 6.04 (2H, s, H2–9)], one methylene group [δ 3.05
(1H, dd, J = 12.0, 16.0 Hz, H-4ax), 3.36 (1H, dd, J = 3.0, 16.0 Hz, H-
4eq)], together with one β-D-glucopyranosyl [δ 4.75 (1H, d, J = 7.0 Hz,
H-1″)]. The 1H 1H COSY experiment on 1 indicated the presences of
three partial structure written in bold bonds (Fig. 3). The planar struc-
ture of its aglycone was determined based on the key HMBC correla-
tions from H-3 to C-1, 4, 4a, 1′, 2′, 6′; H2-4 to C-4a, 5, 8a, C-1′; H-5 to
C-1, 4a, 6, 7, 8a; H2-9 to C-6, C-7; H-3′ to C-1′, 5′; H-4′ to C-2′, C-6′; H-
6′ to C-2′, 4′ (Fig. 3), which was a dihydroisocoumarin. Furthermore,
the absolute configuration at C-3 of 1 was elucidated to be R by compar-
ing its Cotton effect with those of (+)-phyllodulcin [7]. Finally, accord-
ing to the long-range correlation from H-1″ to C-2′ observed in the
HMBC spectrum, the linkage position of β-D-glucopyranosyl was eluci-
dated to be C-2′.
[9,10], dioscorealide
B
(16) [11], zizyvoside
I
(17) [12],
gusanlungionoside D (18) [13], 2,5,6-trihydroxy-3,4-dimethoxy-9,10-
dihydrophenanthrene (19) [14], 5,7-dihydroxy-2-heneicosyl chromone
(20) [15] were obtained. Here, the isolation and identification of these
compounds, along with their inhibitory effect evaluations on nitrite pro-
duction are reported.
2. Results and discussion
The 70% EtOH extract from the rhizomes of D. spongiosa was subject-
ed to D101 macroporous resin column chromatography (CC) and eluted
with H2O, 95% EtOH, and acetone, successively. Then 95% EtOH eluted
fraction was isolated by Silica gel, Sephadex LH-20 and preparative
HPLC to obtain compounds 1–20 (Figs. 1 and 2).
Dioscoroside G (1) was obtained as a white powder with positive
optical rotation ([α]2D5 + 52.5°, in MeOH). The molecular formula,
C22H22O12, of 1 was established by negative-ion HRESI-TOF-MS (m/z
Dioscoroside H1 (2), white powder, its molecular formula was
C26H32O11 [m/z 519.1874 [M − H]− (calcd for C26H31O11, 519.1872)].
D-glucose was yielded after treated 2 with 1 M HCl [1]. The 13C NMR
spectrum (Table 2) displayed twenty-six carbon signals. In addition to
the carbon signals represented by the above mentioned β-D-
glucopyranosyl and two methoxy groups, the other eighteen ones
⁎
Corresponding author at: Tianjin State Key Laboratory of Modern Chinese Medicine,
Tianjin University of Traditional Chinese Medicine, 312 Anshanxi Road, Nankai District,
Tianjin 300193, China.
E-mail address: wangtao@tjutcm.edu.cn (T. Wang).
http://dx.doi.org/10.1016/j.fitote.2016.10.011
0367-326X/© 2016 Published by Elsevier B.V.

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Y. Zhang et al. / Fitoterapia 115 (2016) 165–172
Fig. 1. Structures of new compounds 1–8.
indicated 2 was a lignan. The 1H, 13C, 1H 1H COSY, HSQC, and HMBC NMR
spectra suggested the presences of one ABX-type aromatic ring [δ 6.57
(1H, d, J = 8.0 Hz, H-5), 6.61 (1H, d, J = 2.0 Hz, H-2), 6.49 (1H, dd,
J = 2.0, 8.0 Hz, H-6)]; one 1,3,4,5-tetrasubstituted aromatic ring [δ
7.19 (1H, d, J = 1.5 Hz, H-6′), 7.21 (1H, d, J = 1.5 Hz, H-2′)]; one 1-hy-
droxypropyl {δ [2.76 (1H, dd, J = 9.0, 14.0 Hz), 2.97 (1H, dd, J = 6.0,
14.0 Hz), H2-7], [3.73 (1H, dd, J = 9.0, 10.5 Hz), 3.80 (1H, dd, J = 6.0,
10.5 Hz), H2-9], 3.99 (1H, m, H-8)}, along with one acryl [6.74 (1H, dd,
Fig. 2. Structures of known compounds 9–20.

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Y. Zhang et al. / Fitoterapia 115 (2016) 165–172
167
Table 1
Table 2
1H and 13C NMR data for 1 in CD3OD.
1H and 13C NMR data for 2 in CD3OD.
No.
δC
δH (J in Hz)
No.
δC
δH (J in Hz)
No.
δC
δ
H (J in Hz)
No.
δC
δH (J in Hz)
1
3
4ax
4eq
4a
5
6
7
8
8a
9
171.5
77.3
35.2
–
2′
3′
4′
5′
6′
1″
2″
3″
4″
5″
6″
148.9
119.6
117.0
154.3
113.8
104.5
75.0
78.2
71.4
78.3
62.6
–
1
2
3
4
5
6
7
132.9
113.7
148.5
145.5
115.7
122.6
39.1
–
4′
5′
6′
7′
8′
9′
148.0
139.9
110.7
155.3
129.0
196.0
56.5
104.9
75.9
77.8
–
–
6.03 (dd, 3.0, 12.0)
3.05 (dd, 12.0, 16.0)
3.36 (dd, 3.0, 16.0)
–
6.42 (s)
–
–
–
7.18 (d, 8.5)
6.74 (dd, 3.0, 8.5)
–
6.94 (d, 3.0)
4.75 (d, 7.0)
3.40 (dd, 7.0, 8.0)
3.42 (dd, 8.0, 8.0)
3.36 (m, overlapped)
3.36 (m, overlapped)
3.68 (dd, 4.5, 11.5)
3.87 (br. d, ca. 12)
6.61 (d, 2.0)
–
–
7.19 (d, 1.5)
7.63 (d, 16.0)
6.74 (dd, 8.0, 16.0)
9.64 (d, 8.0)
3.87 (s)
4.82 (d, 8.0)
3.48 (dd, 8.0, 9.0)
3.41 (dd, 9.0, 9.0)
3.39 (dd, 8.5, 9.0)
3.13 (m)
3.67 (dd, 6.0, 12.0)
3.74 (dd, 2.5, 12.0)
138.0
101.5
155.6
134.4
147.0
105.6
103.9
131.1
6.57 (d, 8.0)
6.49 (dd, 2.0, 8.0)
2.76 (dd, 9.0, 14.0)
2.97 (dd, 6.0, 14.0)
3.99 (m)
3.73 (dd, 9.0, 10.5)
3.80 (dd, 6.0, 10.5)
3.73 (s)
3′-OCH3
1″
2″
3″
4″
5″
6″
8
9
42.9
66.4
–
6.04 (s)
–
71.2
78.1
62.4
1′
4-OCH3
56.3
132.4
122.6
154.0
1′
2′
3′
–
7.21 (d, 1.5)
–
J = 8.0, 16.0 Hz, H-8′), 7.63 (1H, d, J = 16.0 Hz, H-7′), 9.64 (1H, d, J =
8.0 Hz, H-9′)]. According to the long-range correlations from H-2 to C-
4, 6; H-5 to C-1, 3; H-6 to C-2, 4; 4-OCH3 to C-4 observed in the HMBC
spectrum, the ABX-type aromatic ring was elucidated, which was
substituted with hydroxyl and methoxyl at C-3 and C-4, respectively.
Using the same method, 1,3,4,5-tetrasubstituted aromatic ring and its
substituted groups were clarified, too. On the other hand, the linkage
positions of above mentioned moieties were determined by the correla-
tions observed from H-7 to C-1, 2, 6, 5′; H-8 to C-1, 4′, 6′; H-9 to C-5′; H-
7′ to C-2′, 6′; H-8′ to C-1′; H-1″ to C-4′. The structure of 2 was similar to
that of icariside E5, except for the substitution position of hydroxyl and
methoxyl at ABX-type aromatic ring. Meanwhile, the optical rotation
value ([α]2D5–105.5° for 2; [α]D22–109.0° for icariside E5 [8], both in
MeOH) and 13C NMR data at C-7 and 8 [δC 39.1 (C-7), 42.9 (C-8) for 2;
Dioscoroside H2 (3), [α]2D5–54.9° (in MeOH). Its molecular formula
was revealed to be C34H46O17 by HRESI-TOF-MS [m/z 725.2668 [M −
H]− (calcd for C34H45O17, 725.2662)]. The 1H, 13C (Table 3) and 2D (1H
1H COSY, HSQC, HMBC) NMR spectra suggested the following moieties
presented in 3: two methoxyl signals [δ 3.83 (6H, s, 3,5-OCH3), 3.85
(6H, s, 3′,5′-OCH3)]; one β-D-glucopyranosyl [δ 4.85 (1H, d, J = 7.5 Hz,
H-1″)], one α-L-rhamnopyranosyl [δ 5.21 (1H, br. s, H-1‴)], together
with one 7,9′:7′,9-diepoxylignane aglycone [δ 3.12 (2H, m, H-8 and
8′), 3.92, 4.29 (2H each, both m, H2-9 and 9′), 4.76 (2H, d, J = 3.0 Hz,
H-7 and 7′), 6.68 (2H, s, H-2′,6′), 6.71 (2H, s, H-2,6)]. Furthermore, the
planar structure of 3 was elucidated by the long-range correlations
from H-2,6 to C-1, 3,5, 4, 7; H-2′,6′ to C-1′, 3′,5′, 4′, 7′; H-1″ to C-4, H-
1‴ to C-4′; 3,5-OCH3 to C-3,5; 3′,5′-OCH3 to C-3′,5′ found in its HMBC
spectrum. Its NMR data of C-7–9, 7′–9′ were almost the same as those
δC 39.1 (C-7), 42.7 (C-8) for icariside E5 [8], both in CD3OD] were very
similar to each other. Then, the absolute configuration at C-8 was eluci-
dated to be R.
Fig. 3. The main 1H 1H COSY and HMBC correlations of 1–8.

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Y. Zhang et al. / Fitoterapia 115 (2016) 165–172
Table 3
8.0 Hz, H-3,5)]; one (O)CH-CH3 moiety [δ 1.41 (3H, d, J = 6.5 Hz, H3-8),
4.78 (1H, q, J = 6.5 Hz, H-7)], along with one β-D-glucopyranosyl [δ 4.88
(1H, d, J = 7.0 Hz, H-1′)] were observed. Furthermore, its planar
structure was elucidated by the long-range correlations from H3-8
to C-4; H-1′ to C-1 observed in the HMBC spectrum. Finally, the
aglycone (5a) of 5 was yielded by enzymatic hydrolysis with β-glu-
cosidase, whose absolute configuration was clarified as 7R by com-
parison its optical rotation ([α]2D5–20.6°, in MeOH) with those of
diethyl 2-hydroxypropylphosphonate (R configuration: [α]0D–6.0°; S
configuration: [α]0D + 7.5°, in MeOH) [16].
1H and 13C NMR data for 3 in CD3OD.
No.
δC
δ
H (J in Hz)
No.
δC
δH (J in Hz)
1
2,6
3,5
4
7
8
9
1′
2′,6′
3′,5′
4′
7′
8′
9′
139.5
–
3′,5′-OCH3
57.1 3.85 (s)
104.9 6.71 (s)
1″
2″
3″
105.4 4.85 (d, 7.5)
75.7 3.48 (dd, 7.5, 9.0)
77.8 3.41 (dd, 9.0, 9.0)
71.3 3.41 (dd, 9.0, 9.0)
78.3 3.20 (m)
62.6 3.66 (dd, 5.0, 12.0)
3.77 (dd, 2.0, 12.0)
103.6 5.21 (br. s)
72.1 4.10 (br. d, ca. 4)
72.3 3.89 (dd, 3.5, 9.0)
73.8 3.42 (dd, 9.0, 9.0)
71.1 4.29 (m)
154.4
135.6
–
–
87.3 4.76 (d, 3.0) 2.35 (m) 4″
55.7 3.12 (m)
73.0 3.92 (m), 4.29 (m)
5″
6″
139.2
–
104.0 6.68 (s)
1‴
2‴
3‴
4‴
5‴
6‴
The molecular formula, C32H52O14, of dioscoroside J (6) was
established by negative-ion HRESI-TOF-MS [m/z 705.3348
[M + COOH]− (calcd for C33H53O16, 705.3339)]. The 13C NMR (Table
6) spectrum displayed thirty-two carbon signals, consisting of five qua-
ternary carbons, fourteen methines, ten methylenes, together with
three methyls. Combining with its 1H NMR spectrum, the presences of
two β-D-glucopyranosyl groups [δ 4.84 (1H, d, J = 8.0 Hz, H-1″), 5.55
(1H, d, J = 8.0 Hz, H-1′)] were deduced. In addition to the carbon signals
represented by the above mentioned sugars, the other twenty ones in-
dicated 6 was a diterpenoid glycoside. The 1H 1H COSY spectrum of 6
suggested the presence of five partial structures written in bold lines
(Fig. 3). The planar structure of the aglycone was determined based
on the key HMBC correlations from H2-15 to C-7–9, 16; H3-17 to C-13,
15, 16; H3-18 to C-3–5, 19; H3-20 to C-1, 5, 9, 10. On the other hand,
the 1H and 13C NMR data on A, B rings in 6 were superimposable on
those of 7β,17-dihydroxy-16α-ent-kauran-19-oic acid 19-O-β-D-
glucopyranoside ester [17], which indicated 7-OH of compound 6 was
in β configuration, which was further clarified by the NOE correlations
observed from H-5 to H-9, H3-18; H-6α to H-7, H3-20 in the NOESY
spectrum. Furthermore, the NOE correlations observed between H-
14α to H-7, H-13; H-13 to H3-17 suggested 16-OH was in β configura-
tion, too. Furthermore, the connectivity of oligoglycoside moiety to the
aglycone part was characterized by HMBC experiment, in which long-
range correlations were found from H-1′ to C-19; H-1″ to C-2′. On the
basis of above mentioned evidences, the structure of 6 was elucidated
to be 7β,16β-dihydroxy-ent-kauran-19-oic acid 19-O-β-D-
glucopyranosyl(1 → 2)-β-D-glucopyranoside ester.
Dioscoroside K1 (7) was isolated as a white powder with negative
optical rotation ([α]2D5–42.9°, in MeOH). The IR spectrum of 7 showed
absorption bands at 3364, 1647, 1069 cm−1 ascribable to hydroxyl,
α,β-unsaturated carbonyl, and ether functions. Its molecular formula,
C25H42O12, was determined from negative-ion HRESI-TOF-MS [m/z
579.2664 [M + COOH]−, calcd for C26H43O14, 579.2658)]. Acid
hydroxysis of 7 with 1 M HCl liberated D-glucose and L-rhamnose [1].
The 1H, 13C NMR (Table 7) spectra indicated the presences of one β-D-
glucopyranosyl [δ 4.40 (1H, d, J = 8.0 Hz, H-1′)] and one α-L-
rhamnopyranosyl [δ 5.23 (1H, d, J = 1.5 Hz, H-1″)], together with the
characteristic signals for megastigmane aglycone [δ 1.02, 1.11 (3H
each, both s, H3-12 and 11), 1.22 (3H, d, J = 6.0 Hz, H3-10), 2.06 (3H,
d, J = 1.5 Hz, H3-13), 2.16, 2.62 (1H each, both d, J = 18.0 Hz, H2-2),
5.87 (1H, br. s, H-4)]. The side chain structure was determined by the
correlations between H2-8 and H2-7, H-9; H-9 and H3-10 observed its
1H 1H COSY spectrum. Furthermore, the long-range correlations from
the proton to carbon pairs were observed in the HMBC spectrum: H2-
2 to C-3, 4, 11, 12; H2-7 to C-1, 5, 6; H2-8 to C-6; H3-11 to C-1, 2, 6, 12;
H3-12 to C-1, 2, 6, 11; H3-13 to C-4-6; H-1′ to C-9; H-1″ to C-2′. Then,
the planar structure of 7 was elucidated, which was similar to that of
dihydrovomifoliol-O-β-D-glucopyranoside [18], the difference was that
C-2′ was substituted by α-L-rhamnopyranosyl in 7. Meanwhile, the CD
154.8
135.2
–
–
87.2 4.76 (d, 3.0)
55.7 3.12 (m)
73.0 3.92 (m), 4.29 (m)
56.6 3.83 (s)
17.9 1.21 (d, 6.0)
3,5-OCH3
of (−)-(7R,7′R,8S,8′S)-4′-hydroxy-3,3′,4,5,5′-pentamethoxy-7,9′:7′,9-
diepoxylignane (a) [10]. But the Cotton effects of them [Δε (nm):
+1.7 (277), +14.5 (240), +95.7 (209) for 3; −0.72 (274), −0.86
(239), −3.79 (214) for a, both in MeOH] were just opposite. On the
basis of above mentioned evidence, the absolute configuration
dioscoroside H2 (3) was determined as 7S,7′S,8R,8′R.
Dioscorol B (4) was isolated as a white powder with positive optical
rotation ([α]2D5 + 97.7°, in CHCl3). The molecular formula of it, as sug-
gested by its HRESI-TOF-MS spectra, was deduced to be C17H14O7 [m/z
329.0667 [M − H]− (calcd for C17H13O7, 329.0667)]. The 1H, 13C NMR
(Table 4) spectra indicated the presences of two aromatic spin systems
{One was two ortho protons of a tetrasubstituted benzene ring [δ 7.58
(1H, d, J = 8.0 Hz, H-2), 7.82 (1H, d, J = 8.0 Hz, H-3)], and the other
was one proton of another pentasubstituted benzene [δ 7.39 (1H, br. s,
H-4)]}, together with one hemiacetal group [δ 5.80 (1H, s, H-8)]. The
above mentioned moieties were connected with each other by the
long-range correlations observed in the HMBC spectrum (Fig. 3).
Which indicated it was a naphthofuranoxepin. On the other hand,
there were three methoxy groups [δ 3.51, 3.99, 4.11 (3H each, all s, 8,
5, 9-OCH3)] in 4, whose linkage positions with aglycone were elucidated
by the long-range correlations from 5-OCH3 to C-5; 8-OCH3 to C-8; 9-
OCH3 to C-9 and NOE correlations (Fig. 4) between H-4 and 5-OCH3;
H-8 and 8-OCH3, 9-OCH3 observed in the HMBC and NOESY spectra, re-
spectively. The structure of 4 was similar to that of dioscorealide A [11].
The main difference lay in C-6 was substituted by hydroxyl in com-
pound 4. On the other hand, the Cotton effects of them were similar to
each other, which suggested the oxepin ring actually adopted the M
conformation [11]. Furthermore, 4 displayed positive optical rotation
in CHCl3, which indicated it possessed 8S configuration [11].
Dioscoroside I (5) was obtained as a white powder. Its molecular for-
mula was proposed to be C14H20O7 as rationalized from the negative
HRESI-TOF-MS determination [m/z 301.1043 [M − H]− (calcd for
C14H19O7, 301.1035)] of it. After treating it with 1 M HCl, D-glucose
was yielded [1]. In its 1H NMR spectrum (Table 5), one AA′BB′ aromatic
spin coupling system [δ 7.07 (2H, d, J = 8.0 Hz, H-2,6), 7.29 (2H, d, J =
Table 4
1H and 13C NMR data for 4 in DMSO-d6.
No.
δC
δ
H (J in Hz)
No.
δC
δH (J in Hz)
1
167.0
115.0
134.1
117.4
127.9
129.6
116.8
103.6
152.3
–
–
–
6
6a
8
9
139.8
133.4
100.9
139.8
130.9
56.0
–
–
1a
1b
2
spectral data for
7
was essentially identical to that of
5.80 (s)
–
–
3.99 (s)
3.51 (s)
4.11 (s)
dihydrovomifoliol-O-β-D-glucopyranoside [18], which suggested the
absolute configuration at C-6 was S. On the other hand, the 1H NMR
data for 11- and 12-position were deduced from NOE correlation be-
tween H-7 and H-11 observed in the NOESY spectrum. Finally, the abso-
lute configuration at C-9 was elucidated to be R by the comparison of its
13C NMR data (δC 75.9) with that of dihydrovomifoliol-O-β-D-
7.58 (d, 8.0)
7.82 (d, 8.0)
–
–
7.39 (br. s)
–
3
9a
3a
3b
4
5-OCH3
8-OCH3
9-OCH3
57.0
60.0
5