802
Q.-G. Ma et al. / Bioorg. Med. Chem. Lett. 26 (2016) 799–803
Table 2
1H NMR (300 MHz, CD3OD), 13C NMR (125 MHz, CD3OD), and HMBC correlations of compounds (3–4)
No.
3
4
dH
dC
HMBC (1H–13C)
dH
dC
HMBC (1H–13C)
1
2
3
4
5a
5b
6
7
8
9a
9b
10
11
12
13
14
15
16
17
18
8.19(s)
—
—
8.32(s)
5.97(d,6.3)
5.97(d,6.3)
4.75(t,12.0,6.0)
4.34(m)
153.5
157.6
150.0
142.0
91.3
91.3
75.5
72.7
88.2
63.5
63.5
—
—
—
—
—
—
—
—
—
C-2,C-3
—
—
C-3
C-4,C-6
C-4,C-6
C-5,C-8
C-5,C-8,C-9
0.97(t,15.0,7.5)
2.07(m)
5.44(d,15.9)
5.46(d,15.9)
2.36(m)
2.14(m)
3.46(m)
5.68(d,16.0)
5.75(d,16.0)
3.96(m)
3.96(m)
4.06(m)
3.93(m)
1.32(m)
1.33(m)
1.34(m)
1.60(m)
1.52(m)
14.6
21.7
134.3
126.4
31.6
31.6
75.9
136.5
131.1
75.8
75.8
73.0
76.5
30.6
30.3
30.4
26.5
38.3
71.4
26.4
C-2,C-3
C-1,C-3,C-4
C-1,C-5
C-2
C-3,C-4,C-6
C-3,C-4,C-6
C-4,C-5,C-8
C-8
C-6,C-10
C-7,C-8
C-7,C-8
C-8
C-9
C-14
—
C-15
C-13
C-14,C-15
—
4.18(m)
3.92(dd,12.6,2.7)
3.77(dd,12.6,2.7)
C-7
C-7,C-8
C-7,C-8
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
3.65(m)
1.34(d,7.2)
—
Table 3
H-7), 5.75 (1H, d, J = 16.0 Hz, H-8) in the middle field. Moreover,
there were two methyl signals at dH 0.97 (3H, t, J = 15.0, 7.5 Hz,
H-1), 1.34 (3H, d, J = 7.2 Hz, H-18) in the 1H NMR of compound 4
(Table 2). Based above spectral data, the skeleton of compound 4
was concluded to be alkene by the degrees of unsaturation of com-
pound 4. In the HMBC spectrum of compound 4, correlations of
H-1/C-2, C-3; H-2/C-1, C-3, C-4; H-3/C-1, C-5; H-4/C-2; H-5/C-3,
C-4, C-6; H-6/C-4, C-5, C-8; H-7/C-8; H-8/C-6, C-10; H-9/C-7, C-8;
H-10/C-8; H-11/C-9; H-12/C-14; H-14/C-15; H-15/C-13; H-16/
C-14, C-15 (Fig. 2) indicating the planar construction of compound
4. According to the correlations of H-1/H-2; H-4/H-5; H-6/H-7;
H-8/H-9; H-11/H-12; H-17/18-CH3 of 2D-NOESY spectrum, the
relative configuration of compound 4 was identified. The absolute
configuration of compound 4 was established by Mosher’s method.
Two aliquots (1.0 mg) of pure compound were treated with (+)-(R)-
Antioxidative activities of selective compounds
Compound
IC50 (lM)
1
2
4
7
38.4
23.5
25.4
40.2
56.4
Chlorogenic acid
as the reference compound (IC50 = 56.4 lM) in the DPPH assay
(Table 3), and its IC50 value was greater than those of selective
compounds. Among them, compounds 2 and 4 showed the stron-
gest antioxidative activities with IC50 values of 23.5 and 25.4
respectively. Compounds 1 and 7 with IC50 values of 38.4 and
40.2 M, which showed moderate antioxidative activities. How-
lM,
l
MTPA-Cl and (ꢀ)-(S)-MTPA-Cl (MTPA =
a-methoxy-a-(trifluo-
ever, the other compounds exhibited no antioxidative activities.
Based the chemical structures and bioactivities of the active com-
pounds, the fact showed that the active compounds contained ter-
minal alkenyl and trans double bonds played positive roles in the
mediating their antioxidative activities. Moreover, the antioxida-
tive activities would decrease if the active compounds contained
the glucosyl unit. The study of Structure-Activity Relationship of
the active compounds from M. koenigii which needed further
research.
In conclusion, we had isolated and identified four new alkenes
(1–4) and eight known alkenes (5–12) from M. koenigii. The known
compounds (5–12) were isolated from this plant for the first time.
Meanwhile, we had evaluated the antioxidative activities of com-
pounds (1–12). Among them, compounds 1, 2, 4, and 7 exhibited
significant antioxidative activities using 2,2-diphenyl-1-picrylhy-
romethyl)phenylacetyl), respectively. Assignment of the H-atoms
vicinal to CH–OH groups of the two diasterotopic diesters was
obtained by related spectra.17 According to above spectral data
and reference,16 the structure of compound 4 was identified as
(3E,6S,7E,9R,10S,11S,17R)-octadeca-3,7-diene-6,9,10,11,17-
pentaol.
Additionally, eight known compounds (5–12) belonging to alke-
nes, which were isolated and identified as (2E,6R)-2,6-dimethyl-
2,7-octadiene-1,6-diol (5),18 (6R,7E,9S,10R)-6,9,10-trihydroxy-7-
octadecenoic
acid
(6),19
capsianoside
V
(7),20
(9S,10R,11R,12Z,15Z)-9,10,11-trihydroxy-octadeca-12,15-dienoic
acid (8),21 oxylipin (9),20 (8R,9R,10S,6Z)-trihydroxyoctadec-6-enoic
acid (10),21 (9S,10R,11E,13S)-9,10,13-trihydroxyoctadec-11-enoic
acid (11),17 (8S,9R,10E,12S,14Z)-heptadeca-10,14-diene-1,8,9,12-
tetraol (12)17 by comparison of their physical and spectroscopic
data with those reported in the references. To the best of our
knowledge, the known compounds (5–12) were isolated from this
plant for the first time.
drazyl (DPPH) assay with IC50 = 21.4–49.5 lM.
Acknowledgments
Compounds (1–12) were evaluated for their antioxidative activ-
ities using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, and
the chlorogenic acid was included for comparison.22,23 According
the screening results of all the compounds (1–12), we found that
some compounds exhibited significant antioxidative activities
This work was supported by the Key Scientific Research Project
of Colleges and Universities in Henan Province (No. 15A350009),
the Special Project of Nanyang Normal University (No.
ZX2014044), the Scientific and Technological Project of Nanyang
(No. KJGG23), the Ideological and Political Education Project of
Nanyang Normal University (No. SZ2014015), the Graduate
Students’ Case Teaching Course Construction Project of Nanyang
using
2,2-diphenyl-1-picrylhydrazyl
(DPPH)
assay
with
IC50 = 21.4–49.5
lM. Moreover, the chlorogenic acid was served