Sesquiterpene quinones from a viet nam sea sponge Spongia sp.

Full text of DOI:10.1007/s10600-011-9858-8

Chemistry of Natural Compounds, Vol. 47, No. 1, March, 2011 [Russian original No. 1, January–February, 2011]
SESQUITERPENE QUINONES FROM
A VIET NAM SEA SPONGE Spongia SP.
*
N. K. Utkina and V. A. Denisenko
UDC 547.567+547.913.5+593.4
The CHCl extract from a Viet Nam sea sponge Spongia species (Order Dictyoceratida) that was collected during the
3
fifth cruise of the RS Akademik Oparin was investigated in a search for antioxidants in marine organisms.
The sea sponge (100 g) was extracted with CHCl . The extract was separated over a column of Sephadex LH-20
3
using CHCl :MeOH (3:1) to afford 1 (35 mg), which was active for trapping DPPH radicals (2,2-diphenyl-1-picrylhydrazyl).
3
Inactive compounds 2 (300 mg) and 3 (35 mg) were also isolated. These were readily identified as ilimaquinone [1, 2] and
smenospongiarin [3].
O
O
O
O
O
21
HO
HO
R
1
19
17
15
OH
OH
R
2
O
13
14
7
H
H
1
9
10
5
3
12
11
1 - 4
6
5
1: R = R = OH
1
2
2: R = OH, R = OCH
1
2
3
3: R = OH, R = NHCH CH CH(CH )
1
2
2
2
3 2
4: R = R = OCH
1
2
3
20
Compound 1, orange crystals, mp >350°C (CHCl :EtOH), [ꢀ] –9.8° (c 0.46, CHCl ), showed a peak for the molecular
3
D
3
ion with m/z 344.1991 (HR-EI-MS) that corresponded to the empirical formula C H O . The PMR spectrum of 1 (Table 1)
21 28
4
was very reminiscent of that of 2. The difference was the lack of a methoxyl resonance in the spectrum of 1. However, the
13
C NMR spectrum showed resonances for only 17 C atoms. 2D NMR spectroscopy experiments (HSQC, HMBC) enabled all
resonances of the sesquiterpenoid part to be assigned. These agreed fully with the corresponding resonances of 2 [1, 4].
20
Methylation of 1 by diazomethane in Et O gave the corresponding dimethyl ether 4, [ꢀ] –27° (c 0.59, CHCl ), the
2
D
3
spectral properties of which agreed with the literature for the synthetic methyl ether of 2 [5] and the dimethyl ether of
smenoquinone (1), which was isolated from a sea sponge Smenospongia species [3]. Thus, it was confirmed that 1 was
smenoquinone. Table 1 presents the full assignment of proton and carbon resonances in smenoquinone and its dimethyl ether
[3, 5] because these have not been reported.
13
A comparison of the PMR and C NMR spectra of 1 taken in CD OD with the published spectra for smenoquinone
3
13
[3] showed that the resonances in the quinoid parts of the molecules were different. Thus, the C NMR spectrum of 1 showed
only the resonance for C-16 (ꢁ 117.7) for the quinoid ring C atoms, in contrast with the published spectrum for the same
C atoms in smenoquinine [ꢁꢂ114.45 (C-16), 182.82 (C-17), 179.65 (C-18), 101.79 (C-19), 174.72 (C-20), 166.80 (C-21)] in
CD OD [3]. The PMR spectrum of 1 lacked a resonance for quinoid proton H-19, in contrast with the published value for this
3
proton at ꢁꢂ5.71 [3].
Pacific Institute of Bioorganic Chemistry, Far-East Branch, Russian Academy of Sciences, 690022, Vladivostok, fax:
(4232) 31 40 50, e-mail: utkinan@mail.ru. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 120–121, January–
February, 2011. Original article submitted June 25, 2010.
©
0009-3130/11/4701-0135 2011 Springer Science+Business Media, Inc.
135

13
Table 1. C NMR (125 MHz), PMR (500 MHz), and HMBC Spectra of 1 and 4 (CDCl )
3
1
4
C atom
HMBC
3, 5, 9
4, 10
1, 5, 11
HMBC
ꢁC
ꢁ
ꢁC
ꢁ
H (J/Hz)
H (J/Hz)
1
2
3
4
23.3 (CH2)
28.7 (CH2)
32.9 (CH2)
160.2 (C)
40.5 (C)
2.08 m, 1.47 m
1.87 m, 1.16 m
2.33 m, 2.08 m
23.2 (CH2)
28.5 (CH2)
32.9 (CH2)
160.3 (C)
40.6 (C)
2.08 m, 1.47 m
1.86 m, 1.16 m
2.32 m, 2.08 m
3, 5, 9
4, 10
1, 5, 11
5
6
7
8
9
36.7 (CH2)
27.9 (CH2)
38.2 (CH)
43.3 (C)
1.53 m, 1.37 m
1.41 m
1.16 m
4, 8, 10, 12
5, 9, 13
6, 10, 14, 15
36.6 (CH2)
28.1 (CH2)
38.3 (CH)
43.6 (C)
1.53 m, 1.39 m
1.42 m
1.17 m
4, 8, 10, 12
5, 9, 13
6, 10, 14, 15
10
11
12
13
14
15
50.2 (CH)
102.8 (CH2)
20.6 (CH3)
17.9 (CH3)
17.3 (CH3)
32.6 (CH2)
0.75 (d, J = 11.7)
4.45 m
1.05 s
0.97 (d, J = 6)
0.85 s
2.54 (d, J = 14),
2.45 (d, J = 14)
2, 5, 9, 12, 14, 15
3, 4, 5
4, 5, 6, 10
7, 8, 9
8, 9, 10, 15
8, 9, 10, 14, 16
50.7 (CH)
102.7 (CH2)
20.6 (CH3)
18.0 (CH3)
17.3 (CH3)
32.8 (CH2)
0.74 (d, J = 11.7)
4.44 m
1.04 s
0.93 (d, J = 6.5)
0.83 s
2.53 (d, J =13.3),
2.46 (d, J = 13.3)
2, 5, 9, 12, 14, 15
3, 4, 5
4, 5, 6, 10
7, 8, 9
8, 9, 10, 15
8, 9, 10, 14, 16, 17, 21
16
17
18
19
20
21
22
23
OH
114.9 (C)
170 (C)à
170 (C)à
102.1 (CH)
170 (C)à
170 (C)à
128.9 (C)
182.7 (C)
159.3 (C)
105.2 (CH)
183.4 (C)
157.5 (C)
56.5 (CH3)
60.9 (CH3)
6.02 s
5.72 s
17, 18, 21
3.80 s
4.01 s
18
21
7.87 br.s
_______
a
Observed as a very broad resonance in the processed spectrum (LB = 30 Hz).
13
The C NMR spectrum of 1 taken in CDCl lacked resonances for four C atoms of the quinoid ring (C-17, C-18,
3
13
C-20, and C-21) that were bonded to O atoms. The lack of these resonances in C NMR spectra (CDCl ) was noted earlier for
3
acid-rearrangement products of ilimaquinone, i.e., 5 [ꢁꢂ115.1 (C-16), 102.1 (C-19)] [6] and 6 [ꢁꢂ115.8 (C-16), 102.3 (C-19)]
13
[6]. The C NMR spectrum (CDCl ) of natural dihydroxyavarone 5 [ ꢁꢂ121.8 (C-16), 185.4 (C-17), 152.7 (C-18), 130.6
3
(C-19), 181.8 (C-20), 144.5 (C-21)] that was isolated from the sea sponge Dysidea cinerea [7] had chemical shifts for the
quinoid C atoms that did not agree with those for smenoquinone isolated from the sea sponge Smenospongia sp. [3], 5 [6],
6 [6], and 1.
A literature search for other examples of 3-substituted 2,5-dihydroxy-1,4-benzoquinones revealed a series of
13
2,5-dihydroxy-3-alkyl-1,4-benzoquinones isolated from plants of the genus Embelia [8, 9]. The C NMR spectra of these
compounds gave resonances for O-containing quinoid C atoms as a very broad peak at ꢁ 170 and chemical shifts for the other
C atoms (ꢁꢂ117.0, 102.2) that agreed with those of C-16 and C-19 in 1. Expansion of the resonance lines by processing the
13
C NMR spectrum of 1 (use of exponential window function LB = 30 Hz) showed in the spectrum also a broad resonance at
ꢁꢂ170. The lack of a resonance for H-19 in the PMR spectrum (CD OD) of 1 was due to replacement of quinoid H-19 with
3
deuterium. In fact, adding CD OD to the CDCl solution of 1 caused the resonance of not only the hydroxyl protons at ꢁ 7.87
3
3
but also that of quinoid H-19 at ꢁ 6.02 to disappear. Replacement of H-19 with deuterium also explained the lack of a
13
resonance for C-19 in the C NMR spectrum taken in CD OD.
3
•+
The antioxidant activity of 1 was tested using bleaching of solutions of DPPH radical [10] andABTS [2,22-azinobis
(3-ethylbenzothiazolin-6-sulfonic acid)] [11]. Compound 1 exhibited moderate activity for trapping DPPH radicals
–4
–4
(IC 3.7 ꢃ 10 M) that was comparable with that of ionol (IC 3.6 ꢃ 10 M). The antioxidant activity of 1 for reduction of
50
50
•+
ABTS radical cations corresponded to 0.15 mmol/L of trolox equivalents (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic
acid).
136

ACKNOWLEDGMENT
The work was supported by Grant 09-III-A-05-145 (FEB RAS) and the RAS Presidium Program “Molecular and
Cellular Biology.”
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