Parasitenone, a new epoxycyclohexenone related to gabosine from the marine-derived fungus Aspergillus parasiticus

Article abstract of DOI:10.1021/np010450k

Bioassay-guided fractionation of an organic extract of the broth from the marine-derived fungus culture of Aspergillus parasiticus led to the isolation and subsequent structural elucidation of a new gabosine derivative, parasitenone (1), and two known benzyl alcohols, 3-chloro-4,5-dihydroxybenzyl alcohol (2) and gentisyl alcohol (3). The benzyl alcohols (2, 3) were identified as the principal free radical scavenging components. Parasitenone (1) also showed moderate activity in the free radical scavenging assay.

Full text of DOI:10.1021/np010450k

7
94
J . Nat. Prod. 2002, 65, 794-795
P a r a siten on e, a New Ep oxycycloh exen on e Rela ted to Ga bosin e fr om th e
Ma r in e-Der ived F u n gu s Asper gillu s pa r a siticu s
,
†
†,§
†
‡
§
⊥
Byeng Wha Son,* J in Seok Choi, J ung Chul Kim, Ki Wan Nam, Dong-Soo Kim, Hae Young Chung,
|
3
J ung Sook Kang, and Hong Dae Choi
Department of Chemistry and Department of Marine Biology, Pukyong National University, Busan 608-737, Korea,
Department of Food Science and Technology, Kyungsung University, Busan, Korea, College of Pharmacy and College of
Dentistry, Pusan National University, Busan, Korea, and Department of Chemistry, Dongeui University, Busan, Korea
Received September 12, 2001
Bioassay-guided fractionation of an organic extract of the broth from the marine-derived fungus culture
of Aspergillus parasiticus led to the isolation and subsequent structural elucidation of a new gabosine
derivative, parasitenone (1), and two known benzyl alcohols, 3-chloro-4,5-dihydroxybenzyl alcohol (2) and
gentisyl alcohol (3). The benzyl alcohols (2, 3) were identified as the principal free radical scavenging
components. Parasitenone (1) also showed moderate activity in the free radical scavenging assay.
As part of an effort to discover biologically active natural
products from marine organisms, we investigated bioactive
constituents of the marine algicolous fungus Aspergillus
parasiticus and isolated a fairly unstable epoxycyclohex-
enone chromophore [203 nm (ꢀ 5300), 237 (4800)]. Since
1a showed six degrees of unsaturation from HREIMS
analysis, it was implied that 1a contains two rings. In the
1
1
H NMR spectrum, two proton signals [δ 5.79 (1H, d, J )
enone, parasitenone (1), and two known benzyl alcohols,
6.2 Hz, 4-OH), 5.01 (1H, t, J ) 5.5 Hz, 7-OH)] were
2
3
-chloro-4,5-dihydroxybenzyl alcohol (2) and gentisyl al-
2
exchanged by D O, suggesting that 1 had two hydroxyl
3
groups. The 1H and C NMR spectra of 1 show signals
attributable to one ketone (δ 193.9, C-1), one trisubstituted
double bond [(δ 6.39, H-2), (δ 141.4, C-2), (δ 133.8, C-3)],
13
cohol (3).
2
one oxygenated methylene [(δ 4.07, 3.96, H -7), (δ 57.3,
C-7)], and three oxygenated methines [(δ 4.70, H-4), (δ 63.7,
C-4), (δ 3.40, H-5), (δ 52.9, C-5), (δ 3.76, H-6), (δ 54.0, C-6)]
bearing oxygen. The upfield oxygenated 13C NMR signals
(δ 52.9, C-5; δ 54.0, C-6) were assigned to an epoxy group.
Interpretation of 2D NMR (COSY, HMQC, HMBC)
confirmed the presence of functional groups noted above
and led to structure 1.
The physicochemical data of 1 were not consistent with
the data for the 4-epimer of 1, which was previously
reported as a synthetic intermediate in the synthesis of
4
(
-)-phyllostine (1b). So, we elucidated the stereostructure
of 1.
The relative stereochemistry of 1 was determined by
coupling constants (J 4,5 ) 0, J 5,6 ) 4.2 Hz, J 4,6 ) 2.8 Hz)
and NOESY data. Key NOE correlations from H-4 to H-6
and from H-5 to H-6 indicated that H-4, H-5, and H-6 were
all of the cis configuration. The three stereocenters in
parasitenone (1) were assigned S configurations by inter-
pretation of its CD data. Parasitenone (1) showed a positive
first Cotton effect at 338 nm (∆ꢀ + 0.95), which from the
5
octant rule indicated 4S, 5S, and 6S configurations for 1.
The absolute configuration of 1 was further supported by
chemospecific oxidation of the secondary allylic hydroxyl
of 1 with pyridinium dichromate (PDC) in DMF to 1b,
which was identified by direct comparison of its spectral
data with those of natural (-)-phyllostine (1b). On the
basis of the above evidence, the structure of parasitenone
was determined to be (4S,5S,6S)-5,6-epoxy-4-hydroxy-3-
hydroxymethylcyclohex-2-en-1-one (1).
Parasitenone (1) was isolated as a very unstable colorless
oil, which was deduced to have the molecular formula
from the HREIMS of its diacetate (1a ) and 13
C
7
H
8
O
4
C
NMR data of 1 and 1a . The IR spectrum of 1 suggested
4
,6
-
1
the presence of hydroxyl (3356 cm ), enone (1680, 1027
-
1
-1
cm ), and epoxy (1236, 903, 867 cm ) groups. The UV
spectrum of 1 showed the presence of a ââ-disubstituted
*
To whom correspondence should be addressed. Tel: +82-51-620-6378.
The polyoxygenated cyclohexenone derivatives known as
gabosines have been previously reported from natural
sources.7 Since they are biologically interesting for their
phytotoxic, antibiotic, antitumor, and antigermination
activities, they have been used as targets or intermediates
Fax: +82-51-628-8147. E-mail: sonbw@pknu.ac.kr.
†
Department of Chemistry, Pukyong National University.
Department of Marine Biology, Pukyong National University.
Kyungsung University.
College of Pharmacy, Pusan National University.
College of Dentistry, Pusan National University.
Dongeui University.
,8
‡
§
⊥
|
3
8,9
for the synthesis of biologically active compounds.
1
0.1021/np010450k CCC: $22.00
© 2002 American Chemical Society and American Society of Pharmacognosy
Published on Web 05/03/2002

Notes
There is considerable recent evidence that free radicals
J ournal of Natural Products, 2002, Vol. 65, No. 5 795
2.7, 2.6, 2.2, 2.1 Hz, H-2), 4.70 (1H, ddddd, J ) 6.2, 2.8, 2.8,
2.6, 2.6 Hz, H-4), 5.79 (1H, d, J ) 6.2 Hz, 4-OH), 3.40 (1H, d,
J ) 4.2 Hz, H-5), 3.76 (1H, ddd, J ) 4.2, 2.8, 2.7 Hz, H-6),
induce oxidative damage to biomolecules. This oxidative
damage is considered to play a causative role in aging and
several degenerative diseases such as Alzheimer’s disease,
rheumatoid arthritis, cancer, and atherosclerosis.10 So far,
a number of free radical scavengers have been found by
using various screening systems.1
3
.96 (1H, dddd, J ) 15.2, 5.5, 2.8, 2.2 Hz, H-7), 4.07 (1H, dddd,
J ) 15.2, 5.5, 2.6, 2.1 Hz, H-7), 5.01 (1H, t, J ) 5.5 Hz, 7-OH);
1
3
C NMR (100 MHz, DMSO-d
33.8 (s, C-3), 63.7 (d, C-4), 52.9 (d, C-5), 54.0 (d, C-6). 57.3 (t,
C-7).
Acetyla tion of P a r a siten on e (1). Acetylation of 1 (10 mg)
6
) δ 193.9 (s, C-1), 141.4 (d, C-2),
1
0-12
Parasitenone (1) and benzyl alcohols (2, 3) showed
scavenging activities toward free radicals, 1,1-diphenyl-2-
in the usual manner (acetic anhydride-pyridine) furnished the
-
picrylhydrazyl (DPPH), peroxy nitrite (ONOO ), superoxide
diacetate (1a ) (6 mg).
•
-
•
1a : colorless oil; IR (neat) νmax 1737, 1367, 1208, 1023 cm-1
;
1
radical ( O
1) exhibited mild activity against DPPH and ONOO , with
IC50 values of 57.0 and 52.6 µM, respectively. In contrast,
and 3 showed strong activity, and the corresponding IC50
2
), and nitric oxide radical ( NO). Parasitenone
-
H NMR (400 MHz, DMSO-d ) δ 6.49 (1H, dddd, J ) 2.5, 2.2,
(
6
1
.5, 1.5 Hz, H-2), 5.90 (1H, dddd, J ) 2.5, 2.2, 1.5, 1.5 Hz,
H-4), 3.58 (1H, d, J ) 4.2 Hz, H-5), 3.93 (1H, ddd, J ) 4.2,
.5, 2.5 Hz, H-6), 4.65, 4.59 (each 1H, ddd, J ) 13.5, 1.5, 1.5
Hz, H
-7), 2.15, 2.03 (each 3H, s, 4- and 7-OAc); 13C NMR (100
MHz, DMSO-d ) δ 192.1 (s, C-1), 139.6 (d, C-2), 130.9 (s, C-3),
6.5 (d, C-4), 51.6 (d, C-5), 54.9 (d, C-6), 59.9 (t, C-7), 169.9,
69.8 (each s, 4- and 7-OAc), 20.8, 20.7 (each q, 4- and 7-OAc);
2
2
values (µM) for each radical are as follow: 2, DPPH (0.6),
2
-
•
-
•
-
ONOO (3.1), O
2
(11.0), NO (0.5); 3, DPPH (1.4), ONOO
6
•
-
•
(
2.2), O
2
(50,, inactive), NO (0.4). Among the assay
6
1
results obtained, gentisyl alcohol (3) exhibited more potent
activity (300-fold) than the positive control (carboxy-PTIO),
with an IC50 value of 137.7 µM against nitric oxide radical
+
+
EIMS m/z 240 [M] (5), 180 [M - AcOH] (15), 138 [M - AcOH
+
- CH
2
dCdO] (100); HREIMS m/z 240.0641 (calcd for
•
C H O , 240.0634).
(
NO). Details of the radical scavenging activity of com-
11 12
6
Oxid a tion of P a r a siten on e (1). Pyridinium dichromate
67 mg, 0.17 mmol) was added to a solution of 1 (13 mg, 0.08
pounds 1-3 and its mode of action are currently under
investigation and will be reported in due course.
(
mmol) in DMF (1 mL) at 0 °C, and the mixture was stirred
for 3 h at the same temperature, then at room temperature
for 3 h. The reaction mixture was filtered through a Celite
pad. The filtrate was reduced under vacuum, and the residue
was chromatographed on a Si gel column eluted with n-hex-
anes-EtOAc (1:1) to afford (-)-phyllostine (1b) (2.7 mg).
(-)-P h yllostin e (1b): reddish solid. The compound exhibits
Exp er im en ta l Section
Gen er a l Exp er im en ta l P r oced u r es. Melting points were
determined on a Electrothermal model IA 9100 micro-melting
point apparatus and are uncorrected. Optical rotation was
determined on a Perkin-Elmer model 341 polarimeter. The IR
spectrum was recorded on a Bruker FT-IR model IFS-88
1
spectral data (mp, [R] , IR, H NMR) comparable to published
D
1
13
4,6
spectrometer. H (400 MHz) and C NMR (100 MHz) spectra
were obtained on a J EOL J NM-ECP 400 NMR spectrometer,
using TMS or solvent peaks as reference standard. MS spectra
were obtained on a J EOL J MS-700 spectrometer. UV/visible
spectra were measured on a Hitachi U-2001 UV/vis spectrom-
eter. CD spectra were taken on a J ASCO J -715 spectropola-
rimeter.
values.
Ack n ow led gm en t. NMR and mass spectral data were
kindly provided by the Korea Basic Science Institute, Taejeon,
and The Cooperative Laboratory Center of Pukyong National
University. This study was supported by a grant of the Korea
Health 21 R&D Project, Ministry of Health & Welfare,
Republic of Korea (HMP-00-B-21600-0121).
F u n ga l Isola tion a n d Cu ltu r e. The fungal strain (culture
#
MFA 153) was isolated from the surface of the marine red
Su p p or tin g In for m a tion Ava ila ble: The physicochemical data
of 3-chloro-4,5-dihydroxybenzyl alcohol (2) and methods of the radical
scavenging assay. This material is available free of charge via the
Internet at http://pubs.acs.org.
alga Carpopeltis cornea collected in the Golmae village, Ulsan
City, in 1999 and identified as a Aspergillus parasiticus on
the basis of fatty acid methyl ester analysis (Korean Culture
Center of Microorganisms, Seoul, Korea), similarity index
0
2
Refer en ces a n d Notes
.858. The fungus was cultured (20 L) for 30 days (static) at
9 °C in SWS medium: soytone (0.1%), soluble starch (1.0%),
(1) Son, B. W.; Kim, J . C.; Choi, H. D. Lipids 2001, 36, 427-429.
(
2) Neilson, A. H.; Allard, A.-S.; Hynning, P.-A.; Remberger, M. Appl.
Environ. Microbiol. 1988, 54, 2226-2236.
agar (1.5%), and seawater (100%).
Isola tion of P a r a siten on e (1) a n d Ben zyl Alcoh ols (2,
). The resulting broth and mycelium were separately ex-
(
3) Sakamura, S.; Chida, T.; Ito, J .; Sakai, R. Agric. Biol. Chem. 1971,
35, 1810-1811.
3
tracted with EtOAc and CH Cl -MeOH (1:1) to afford crude
2
2
(4) Yoshida, N.; Konno, H.; Kamikubo, T.; Takahashi, M.; Ogasawara,
K. Tetrahedron: Asymmetry 1999, 10, 3849-3857.
extracts of 0.6 and 2.2 g, respectively. The broth extract
showed strong radical scavenging activity against DPPH, and
the active components were purified by assay-guided isolation
using repeated silica gel (n-hexane-EtOAc) and HPLC (10:1
EtOAc-MeOH) methods to yield a new gabosine derivative,
parasitenone (1, 8 mg), as well as the known benzyl alcohols,
(
5) Imahori, K. Optical Activity-The Theory and Application; Tokyo
Kagaku Dojin: Tokyo, 1979; pp 67-76.
(6) Sakamura, S.; Ito, J .; Sakai, R. Agric. Biol. Chem. 1971, 35, 105-
1
10.
(
7) Bach, G.; Breiding-Mack, S.; Grabley, S.; Hammann, P.; H u¨ tter, K.;
Thiericke, R.; Uhr, H.; Wink, J .; Zeeck, A. Liebigs Ann. Chem. 1993,
2
41-250.
(8) Kamikubo, T.; Hiroya, K.; Ogasawara, K. Tetrahedron Lett. 1996, 37,
99-502, and references therein.
3
-chloro-4,5-dihydroxybenzyl alcohol (2, 22 mg) and gentisyl
4
alcohol (3, 12 mg).
(
9) Lubineau, A.; Billault, I. J . Org. Chem. 1998, 63, 5668-5671.
10) Chung, H. Y.; Choi, H. R.; Park, H. J .; Choi, J . S.; Choi, W. C. J .
P a r a siten on e (1): unstable colorless oil; [R] + 71.6° (c 0.3,
D
(
MeOH); IR (neat) νmax 3356, 1680, 1400, 1236, 1027, 903, 867
cm ; UV (MeOH) λmax (log ꢀ) 203 (3.72), 237 (3.68) nm; CD
Agric. Food Chem. 2001, 49, 3614-3621, and references therein.
-
1
(11) Pietta, P.-G. J . Nat. Prod. 2000, 63, 1035-1042.
(12) Hwang, B. Y.; Kim, H. S.; Lee, J . H.; Hong, Y. S.; Ro, J . S.; Lee, K.
S.; Lee, J . J . J . Nat. Prod. 2001, 64, 82-84, and references therein.
+
(
MeOH) (∆ꢀ) 338 (+0.95), 245 (-1.76) nm; CIMS m/z 156 [M]
+
+
(100), 138 [M - H
2
O] (7), 122 [M - H
2
O - O] (2), 110(3),
1
8
6(3); H NMR (400 MHz, DMSO-d ) δ 6.39 (1H, dddd, J )
6
NP010450K