Cytotoxic sesterterpenes, 6-epi-ophiobolin G and 6-epi-ophiobolin N, from marine derived fungus Emericella variecolor GF10

Article abstract of DOI:10.1016/j.tet.2004.05.021

Two new sesterterpenes, 6-epi-ophiobolin G (1) and 6-epi-ophiobolin N (3), and six known ophiobolins were isolated from the extracts of the fungus, Emericella variecolor GF10, which was separated from marine sediment. The planar structures of the new comp

Full text of DOI:10.1016/j.tet.2004.05.021

Tetrahedron 60 (2004) 6015–6019
Cytotoxic sesterterpenes, 6-epi-ophiobolin G and 6-epi-ophiobolin
N, from marine derived fungus Emericella variecolor GF10
Hong Wei,a Takuya Itoh,a Masahiro Kinoshita,a Yasuhide Nakai,a Mineko Kurotakib
and Motomasa Kobayashia
,
*
aGraduate School of Pharmaceutical Sciences, Osaka University, Yamada-oka 1-6, Suita, Osaka 565-0871, Japan
bR&D Division, Nippon Kayaku Co., Ltd, Shimo 3-31-12, Kitaku, Tokyo 115-8588, Japan
Received 22 March 2004; accepted 6 May 2004
Available online 5 June 2004
Abstract—Two new sesterterpenes, 6-epi-ophiobolin G (1) and 6-epi-ophiobolin N (3), and six known ophiobolins were isolated from the
extracts of the fungus, Emericella variecolor GF10, which was separated from marine sediment. The planar structures of the new compounds
were deduced from analysis of the 2D NMR spectra, and the stereochemistry was determined by extensive examination of the NOESY
spectrum. Additionally, the configuration of the C-6 proton in ophiobolin G (2) was revised from a to b, and the unsolved stereochemistry of
ophiobolin H (4) was determined by its physicochemical evidence and the chemical correlation with ophiobolin K (8). Ophiobolin K (8)
showed cytotoxic activity against various tumor cell lines, including adriamycin-resistant mouse leukemia cells (P388), with IC50 of
0.27–0.65 mM.
q 2004 Elsevier Ltd. All rights reserved.
1. Introduction
marine derived fungus, Emericella variecolor GF10. This
paper presents the isolation of these compounds and the
structural elucidation of 6-epi-ophiobolin G (1), ophiobolin
G (2), 6-epi-ophiobolin N (3), and ophiobolin H (4).
Ophiobolins are a group of naturally occurring sester-
terpenes with an unusual tricyclic or tetracyclic structure
showing a broad spectrum of inhibitory activity against
nematodes, fungi, and bacteria, and cytotoxic activity
against cancer cells.1 Ophiobolin A (9) is the first known
member of this family, and its absolute structure was
determined by X-ray crystallography of the bromo-methoxy
derivative.2 This compound was reported to inhibit
calmodulin-activated cyclic nucleotide phosphodiesterase3
and induce apoptotic cell death in the L1210 cell line.4
Although the mechanisms of these activities remain unclear,
these findings imply ophiobolin’s potential for biological
and pharmaceutical uses.
2. Results and discussion
The fungus strain of E. variecolor GF10 was separated from
marine sediment collected at 70 m depth in the Gokasyo
Gulf, Mie Prefecture, Japan. The GF10 strain was cultured
at 30 8C for 2 weeks in MG medium (malt extract 20 g,
glucose 20 g, bact peptone 1 g, artificial seawater 1000 mL)
or barley solid medium (barley 15 g, artificial seawater
25 mL). The EtOAc soluble portion of the 2-butanone
extracts of these cultures were fractionated by silica gel
column chromatography and purified by reversed-phase
HPLC to obtain two new sesterterpenes named 6-epi-
ophiobolin G (1) and 6-epi-ophiobolin N (3) together with
six known sesterterpenes. The structures of the six known
sesterterpenes were identified as ophiobolin G (2),7
ophiobolin H (4),7 6-epi-ophiobolin C (5),8 ophiobolin C
(6),8,9 6-epi-ophiobolin K (7),10 and ophiobolin K (8)10 by
comparison of the MS and NMR data with those of the
authentic compounds.
During our search for bioactive substances from marine
microorganisms, we previously reported a novel anthra-
cycline, komodoquinone A, from the solid-state fermenta-
tion of a marine Streptomyces sp. KS3.5,6 Further study led
us to the isolation of two new ophiobolins, 6-epi-ophiobolin
G (1) and 6-epi-ophiobolin N (3), and six known
ophiobolins, ophiobolin G (2),7 ophiobolin H (4),7 6-epi-
ophiobolin C (5),8 ophiobolin C (6),8,9 6-epi-ophiobolin K
(7),10 and ophiobolin K (8)10 from the culture broth of the
Keywords: Ophiobolin; Marine fungus; Emericella variecolor; Cytotoxic;
Sesterterpene.
The molecular formula of compound 1 was determined as
C25H34O2 by HRFABMS in conjunction with NMR
analysis. The H NMR spectrum of 1 showed the signals
*
Corresponding author. Tel.: þ81-6-6879-8215; fax: þ81-6-6879-8219;
1
e-mail address: kobayasi@phs.osaka-u.ac.jp
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.05.021

6016
H. Wei et al. / Tetrahedron 60 (2004) 6015–6019
and HMBC spectral data of 1 revealed that 1 is a
sesterterpene having a tricyclic ophiobolane skeleton,1
which consists of one each of ketone and aldehyde, eight
olefinic carbons (five of them are carbons bearing a proton,
and other three are quaternary carbons), one quaternary
carbon, five methine carbons, four methylene carbons, and
five methyl carbons. The 1H and 13C NMR data of
compound 1 closely resembled those of ophiobolin G (2).
These evidences indicated that compound 1 is a stereo-
isomer of ophiobolin G (2). The stereostructure of 1 was
elucidated by detailed analysis of the NOESY spectra of 1
and 2. Thus, the NOESY spectrum of 1 showed the NOE
correlations from H-6 (dH 3.38, brs) to H-10 (dH 2.61, m)
and H-1a (dH 1.15, t); H3-22 (dH 0.85, s) to H-2 (dH 2.65,
m), H-8 (dH 6.79, d), and H-9b (dH 2.20, m), and the lack of
NOE from H-6 to H-2 gave a clear indication that the A/B
ring is trans-fused and the H-2 proton is on the same side
with the C-22 methyl group (Fig. 1). On the other hand, the
A/B-cis ring structure in ophiobolin G (2) was deduced from
the strong NOESY correlation between H-2 (dH 3.11, brs)
and H-6 (dH 4.16, brs) (Fig. 2). These evidences indicated
that compound 1 is the 6-epi isomer of ophiobolin G (2). It
has been reported that the C-1 carbon of ophiobolin having
an A/B-cis ring structure resonates at higher field in
comparison with the A/B-trans ophiobolin11 and the proton
signal at C-2 of the 6-epi isomer having H-6a is shielded by
ca. 0.2–0.3 ppm in comparison with the A/B-cis isomer
having H-6b.12 These phenomena were also observed in this
study (Tables 1 and 2); thus, the C-1 carbon and the H-2
proton of compound 1 and ophiobolin G (2) were observed
at dC 46.1 and dC 35.7; dH 2.65 (m) and dH 3.11 (brs),
respectively. The orientation of H-6 in ophiobolin G (2) has
been previously reported to be a. Based on the above
findings, the orientation of the H-6 proton in ophiobolin G
Figure 1. Key NOE correlations of 6-epi-ophiobolin G (1).
Figure 2. Key NOE correlations of ophiobolin G (2).
due to one aldehyde proton, five olefinic protons, four
singlet methyl protons (three for vinylic methyls and one for
angular methyl), and one doublet methyl protons. Detailed
1
interpretation of a combination of H–1H COSY, HMQC,
Table 1. 1H NMR data for 6-epi-ophiobolin G (1), ophiobolin G (2), 6-epi-ophiobolin N (3), ophiobolin H (4), 6-epi-ophiobolin C (5), ophiobolin C (6), 6-epi-
ophiobolin K (7), and ophiobolin K (8). (600 MHz in CDCl3, dH (mult., J (Hz)))
1
2
3
4
5
6
7
8
1a
1b
2
1.15 (t, 13.2)
2.03 m
2.65 m
1.34 m
1.16 (t, 13.0)
2.04 m
2.68 m
1.42 m
1.52 m
2.24 m
2.06 (d, 13.5)
2.15 (d, 13.5)
3.15 m
5.62 m
2.46 m
1.69 m
1.59 m
1.36 m
1.42 m
1.27 m
1.73 m
2.06 m
2.67 m
5.19 m
1.56 m
1.76 m
2.15 m
2.42 (d, 16.5)
3.08 (d, 16.5)
3.35 (d, 10.3)
6.89 (d, 5.5)
2.61 m
2.21 m
2.61 m
1.47 m
1.47 m
1.16 m
1.56 m
1.76 m
1.47 m
0.98 m
1.47 m
1.23 m
1.78 m
2.36 m
2.47 (d, 20.1)
2.77 (d, 20.1)
3.24 (d, 9.6)
7.18 (t, 8.5)
2.28 m
2.42 m
2.63 m
1.39 m
1.43 m
1.43 m
1.52 m
2.36 m
1.62 m
1.15 m
1.23 m
1.51 m
1.83 m
2.13 m
2.44 (d, 16.4)
3.04 (d, 16.4)
3.24 (d, 11.0)
6.80 (d, 4.9)
2.79 m
2.36 (d, 17.1)
2.49 m
1.40 m
1.45 m
1.18 m
1.21 m
1.77 m
2.36 m
2.51 (d, 18.9)
2.78 (d, 18.9)
3.26 (d, 10.3)
7.11 (t, 8.5)
2.11 m
2.95 m
1.59 m
1.40 m
1.40 m
1.25 m
1.61 m
2.07 m
2.71 m
5.18 (t, 9.7)
1.89 m
3.11 brs
6.05 s
4
6.02 s
6.04 s
6
8
9a
9b
10
12
3.38 brs
6.79 (d, 6.1)
2.92 (d, 20.6)
2.20 m
2.61 m
1.44 m
1.52 m
1.28 m
1.67 m
1.88 m
4.16 brs
7.06 m
2.88 (d, 19.1)
2.30 m
1.90 m
1.34 m
1.40 m
1.27 m
1.66 m
1.83 m
2.51 m
5.11 m
3.45 (d, 4.3)
6.84 (d, 4.4)
2.71 m
2.23 m
2.71 m
1.43 m
1.51 m
1.25 m
1.61 m
1.74 m
1.43 m
0.99 m
1.43 m
13a
13b
14
15
16
1.61 m
1.82 m
2.47 m
5.06 (t, 11.2)
2.58 m
5.10 (t, 10.5)
17
6.09 (t, 10.5)
5.98 m
1.93 m
1.93 m
5.98 m
1.91 m
2.07 m
1.95 m
2.07 m
6.02 (t, 11.2)
6.01 m
18
20
21
6.00 (d, 10.5)
2.06 s
9.27 s
5.98 m
2.21 s
9.38 s
5.12 (t, 6.9)
2.07 s
9.31 s
5.98 m
1.22 s
4.59 (d, 12.1)
4.78 (d, 12.1)
0.89 s
0.87 (d, 6.6)
1.72 s
1.80 s
5.12 (t, 6.9)
1.44 s
9.20 s
5.07 (t, 6.9)
1.33 s
9.20 s
5.95 (d, 11.2)
1.37 s
9.09 s
5.97 m
1.34 s
9.21 s
22
23
24
25
0.85 s
0.78 s
0.86 s
0.84 s
0.88 s
0.76 s
0.95 s
0.96 (d, 6.6)
1.76 s
1.82 s
0.86 (d, 6.6)
1.74 s
1.82 s
0.90 (d, 6.6)
1.61 s
1.69 s
0.89 (d, 6.6)
1.60 s
1.69 s
0.76 (d, 6.6)
1.58 s
1.66 s
0.91 (d, 6.6)
1.69 s
1.76 s
0.92 (d, 6.6)
1.74 s
1.81 s

H. Wei et al. / Tetrahedron 60 (2004) 6015–6019
6017
Table 2. 13C NMR data for 6-epi-ophiobolin G (1), ophiobolin G (2), 6-epi-
ophiobolin N (3), ophiobolin H (4), 6-epi-ophiobolin C (5), ophiobolin C
(6), 6-epi-ophiobolin K (7), and ophiobolin K (8) (150 MHz in CDCl3, dC)
(2) should be revised to be b and compound 1 should be
6-epi-ophiobolin G having H-6a.
Compound 3 named 6-epi-ophiobolin N has a molecular
formula of C25H36O2 as determined by HRFABMS. The
proton and carbon signals ascribable to the A and B rings in
3 were closely similar to those of 1, while other signals were
almost identical to those of 6-epi-ophiobolin C (5) (Tables 1
and 2). This suggested that 3 has a hybrid structure of 1 and
5. NOE correlations from H-6 (dH 3.45, d) to H-10 (dH 2.71,
m) and H-1a (dH 1.16, t); H3-22 (dH 0.86, s) to H-1b (dH
2.04, m), H-2 (dH 2.68, m), H-8 (dH 6.84, d), and H-9b (dH
2.23, m) in the NOESY spectrum of 3 indicated that 1 and 3
share the same stereostructure. Consequently, the structure
of compound 3, 6-epi-ophiobolin N, was clarified to be a
16,17-dihydro analogue of 6-epi-ophiobolin G (1), and also
the 6-epi isomer of the previously reported congener named
anhydrozizanin A.8
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
46.1
49.3
35.7
48.8
45.8
49.0
35.9
50.9
80.0
50.8
41.6
49.7
76.7
55.2
36.1
50.9
76.8
54.8
41.4
49.6
76.7
55.0
35.1
50.3
76.9
54.9
177.6 177.4 177.5
130.5 130.7 130.2
207.7 207.1 207.4 116.5 217.1 217.4 216.9 217.2
50.2 48.3 50.0 52.8 49.1 48.5 48.9 48.6
140.2 137.7 140.4 138.8 142.0 141.5 141.4 141.4
158.1 160.3 156.9 123.3 159.8 164 160.5 163.9
31.1
44.0
45.6
44.5
27.9
52.3
32.9
9
29.6
46.4
46.0
40.3
27.8
46.4
35.3
31.0
43.1
45.0
44.6
27.1
51.5
31.8
24.9
55.0
43.5
42.9
26.6
47.1
35.5
31.2
43.3
44.6
45.7
27.4
51.8
32.2
37.2
26.0
24.8
53.5
43.9
42.6
22.9
45.3
32.8
37
30.8
43.8
44.7
45.7
27.7
52.1
32.6
25.5
53.6
43.9
42.6
26.5
47.2
35.3
10
11
12
13
14
15
16 135.9 137.4
17 124.2 122.3
37.2 137.9
25.7 121.7
135.6 137.1
26.0 124.0 122.5
18 120.1 120.2 124.4 120.3 124.7 124.5 120.0 120.0
19 136.7 135.7 131.6 135.0 131.7 131.4 136.4 136.1
The physical data of compound 4 were identical with those
of ophiobolin H.7 The unsolved stereochemistry of
ophiobolin H (4) led us to do further structural examination
of this compound. The NOESY spectrum of 4 exhibited
NOE correlations from H-6 (dH 3.15, m) to H-2 (dH 2.24,
m), H-9b (dH 1.69, m), and H3-22 (dH 0.89, s); H-10 (dH
1.59, m) to H-1a (dH 1.42, m) and H-14 (dH 2.06, m)
indicating a cis fusion of the ring A/B. Further observation
of the NOE correlations from H3-20 (dH 1.22, s) to H-2 (dH
2.24, m) and H-1b (dH 1.52, m) suggested that the methyl
group at C-3 is b-orientation (Fig. 3). This was corroborated
by the fact that the reduction of ophiobolin K (8)10 with
CeCl3/6H2O and NaBH4 afforded a single product, which
was identical with ophiobolin H (4) on the basis of HPLC,
20
17.4
18.7
21 193.2 194.9 193.0
17.2
25.6
26.1
25.5
25.9
25.7
71.5 194.5 196.2 194.7 196.2
22
23
24
25
23.1
21.4
18.2
26.7
24.5
20.6
18.1
26.4
23.1
18.6
17.7
25.7
18.7
20.2
18.1
26.4
23.7
18.9
18.0
25.9
19.0
16.5
17.6
25.7
23.3
21.3
18.2
26.5
18.7
20.4
18.1
26.6
1
TLC, H NMR, and HRFABMS comparison. Furthermore,
the orientation of the hydroxyl group at C-5 could be
deduced as b, since the stereostructure having 5b-hydroxyl
group, which was shown in Figure 3, is only reasonable
one to be able to explain the presence of the above
NOE correlations. Based on these findings, the unsolved
Figure 3. Key NOE correlations of ophiobolin H (4).
Chart 1.

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H. Wei et al. / Tetrahedron 60 (2004) 6015–6019
Table 3. Cytotoxic activity of ophiobolin K (8) against various cultured tumor cells
Compound
IC50 value (mM)
T-47D
MDA-MB-231
HOP18
NCI-H460
HCT116
ACHN
P388
P388/ADRa
Adriamycin
Ophiobolin K (8)
0.048
0.35
0.095
0.57
0.11
0.65
0.0061
0.57
0.055
0.33
0.048
0.27
0.012
0.51
2.56
0.36
a
Adriamycin-resistant cells.
stereochemistry at C-3, C-5, and C-6 of ophiobolin H (4)
was determined to be as depicted in Chart 1.
MG medium (malt extract: 20 g, glucose: 20 g, bact
peptone: 1 g, artificial seawater: 1000 mL) was used as
seed medium and liquid medium. Rice solid medium (rice:
25 g, artificial seawater: 50 mL, in a 500 mL flask), barley
solid medium (barley: 15 g, artificial seawater: 25 mL, in a
500 mL flask), soybean solid medium (soybean: 50 g,
artificial seawater: 75 mL, in a 500 mL flask), corn solid
medium (canned corn: 100 g, solid Aquamarine: 1.4 g,
liquid Aquamarine: l mL, in a 500 mL flask), and potato
solid medium (sliced fresh potato: 100 g, solid Aquamarine:
1.4 g, liquid Aquamarine: l mL, in a 500 mL flask) were
used as solid medium. They were all autoclaved before use.
The GF10 strain was cultured in the seed medium at 30 8C
for 5 days. Then, the broth of the strain was inoculated into
the production medium and cultured under static conditions
at 30 8C for 2 weeks. The culture of the MG medium was
filtered, and then the filtrate was partitioned with 2-buta-
none, and the residue was extracted with acetone. The
organic extracts were combined and evaporated under
reduced pressure to give an extract, which was further
partitioned into an EtOAc–H2O mixture. The EtOAc layer
was evaporated under reduced pressure to give an EtOAc
extract. For solid-state fermentation, the culture was
extracted with acetone and a mixed solvent (EtOAc–
MeOH–acetone, 1:2:4), and then the organic solvent was
combined and evaporated under reduced pressure to give an
extract. The extract was partitioned into an EtOAc–H2O
mixture, and the EtOAc layer was evaporated under reduced
pressure to afford an EtOAc extract.
The compounds obtained here are well correlated, and all
can be considered as congeners of ophiobolin A (9). The
stereochemistry at C-14 and C-15 and the absolute
stereostructure were deduced from those of ophiobolin
A,2,11 whose absolute stereostructure was determined by
X-ray crystallography of its bromo-methoxy derivative, and
ophiobolin C,9 of which asymmetric total synthesis has been
accomplished.
These compounds showed cytotoxicity against the neuro-
blastoma cell line, Neuro 2A. The treatment of 1–3 mM of
these compounds induced cell death accompanied by
shrinkage in cell soma and chromatin condensation at 12
or 24 h after drug application. Ophiobolin K (8) was further
tested with various cultured cell lines. As showed in Table 3,
8 showed seven times stronger cytotoxic activities against
P388/ADR tumor cells than adriamycin.
The liquid culture of the GF10 strain in the MG medium
produced ophiobolins in poor yield (0.1–0.6 mg/L for
compounds 1–4, 2–3 mg/L for compounds 5–8). On the
other hand, the culture in the solid-state medium based on
cereals produced ophioblins in higher yield. In the case of
the rice medium or soybean medium, 0.5–1.5 mg of 1–4
and 5–10 mg of 5–8 were produced in both 100 g medium,
while in the cases of the barley medium, corn medium, or
potato medium, 1–5 mg of 1–4 and 10–30 mg of 5–8 were
produced in each 100 g medium, respectively.
3.3. Isolation of ophiobolins (1–8)
The EtOAc extract (4.5 g) of the MG medium culture
(1 L£10) was fractionated by SiO2 column chromatography
(n-hexane–EtOAc) to give five fractions (A–E). The active
fraction C (70 mg) was further separated by reversed-phase
HPLC (Cosmosil 5C18-AR, 10£250 mm, MeOH–
H2O¼85:15) to furnish 6-epi-ophiobolin K (7, 12 mg),
ophiobolin K (8, 11 mg), 6-epi-ophiobolin C (5, 9 mg),
6-epi-ophiobolin G (1, 2 mg), 6-epi-ophiobolin C (6,
10 mg), and 6-epi-ophiobolin N (3, 3 mg). The purification
of the EtOAc extract (3.4 g) of the barley solid medium
culture (barley 40 g£20) by the same procedure gave
ophiobolin G (2, 15 mg), 6-epi-ophiobolin G (1, 9 mg),
ophiobolin H (4, 8 mg), and 6-epi-ophiobolin N (3, 9 mg).
For quantitative analyses, the EtOAc extracts were
fractionated by SiO2 column chromatography (n-hexane–
EtOAc) and the fractions containing ophiobolins were
analyzed by HPLC (Cosmosil 5C18-AR, 10£250 mm,
MeOH–H2O¼80:20, UV 230 nm).
3. Experimental
3.1. General experimental procedures
NMR spectra were recorded on a Varian Unity Inova 600
(600 MHz) spectrometer using the solvent peak as the
internal standard. Spots on TLC were detected by spraying
1% Ce(SO4)2/10% H2SO4 [1 g Ce(SO4)2, 100 mL 10% aq.
H2SO4] with subsequent heating. Artificial seawater was
prepared by Aquamarine (Yashima Pure Chemical Co.
LTD, Japan). Other instruments used to obtain physical data
and the experimental conditions for chromatography were
the same as in our previous paper.5
3.2. Fungus material, culture conditions, and extraction
The E. variecolor GF10 strain was separated from the
marine sediment collected from a depth at 70 m in Gokasyo
Gulf, Mie Prefecture, Japan, in 2002 and deposited in our
laboratory. The GF10 strain was classified as E. variecolor
from its cultural characteristics and 16S rDNA sequence.
3.3.1. 6-epi-Ophiobolin G (1). Amorphous powder;
[a]D23¼þ1178 (c 1.05, MeOH); IR (KBr) nmax cm21: 2965,
1705, 1680; UV (CHCl3) lmax (1): 228 nm (27000); 1H and

H. Wei et al. / Tetrahedron 60 (2004) 6015–6019
6019
13C NMR data: shown in Tables 1 and 2; FABMS: m/z 389
[(MþNa)þ]; HRFABMS: found m/z 389.2466. Calcd for
C25H34O2Na: 389.2456.
‘renal carcinoma), HCT116 (human colon carcinoma), P388
(mouse leukemia cells) and P388/ADR (adriamycin
resistant cells) were cultured in RPMI-1640 medium
supplemented with 10% FBS. All cells were maintained at
37 8C with 5% CO2. Cells were seeded into 96-well plates
(1£104 cells/well) and incubated for 24 h. The test sample,
dissolved in DMSO, was added in serial dilutions and the
cells were further incubated for 72 h. In vitro cytotoxic
activity was evaluated by MTT [3-(4,5-dimethylthiazol-2-
yl)-2,5-diphenyltetrazolium bromide] assay or WST-1
[5-(2,4-disulfophenyl)-2-(4-iodophenyl)-2H-tetrazolium,
inner salt, sodium salt] assay.
3.3.2. Ophiobolin G (2). Amorphous powder; [a]2D3¼þ268
(c 0.88, MeOH); UV (CHCl3) lmax (1): 227 nm (29700); 1H
and 13C NMR: data shown in Tables 1 and 2; FABMS: m/z
367 [(MþH)þ]; HRFABMS: found m/z 367.2642. Calcd for
C25H35O2: 367.2637.
3.3.3. 6-epi-Ophiobolin N (3). Amorphous powder;
[a]D23¼þ888 (c 0.34, MeOH); IR (KBr) nmax cm21: 2970,
1702, 1670; UV (CHCl3) lmax (1): 226 nm (19000); 1H and
13C NMR: data shown in Tables 1 and 2; FABMS: m/z 391
[(MþNa)þ]; HRFABMS: found m/z 391.2634. Calcd for
C25H36O2Na: 391.2613.
Acknowledgements
This study was financially supported by Grants-in-Aid for
Scientific Research from the Ministry of Education,
Science, Sports, and Culture of Japan.
3.3.4. Ophiobolin H (4). Amorphous powder; [a]2D3¼þ448
(c 0.12, MeOH); UV (CHCl3) lmax (1): 240 nm (16800); 1H
and 13C NMR: data shown in Tables 1 and 2; FABMS: m/z
409 [(MþNa)þ]; HRFABMS: found m/z 409.2717. Calcd
for C25H38O3Na: 409.2719.
References and notes
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NCI-H460, HOP18 (human lung carcinoma), MDA-MB-
231, T-47D (human breast carcinoma), ACHN (human