structure with a long side chain that is rare in Nature, and it was also the first C-3pyranosyl 4-hydroxypyrone derivative to be isolated from a sponge-derived fungus.
The glucoside iso-D8646-2-6 (48) showed anti-influenza A viral (H1N1) activity
with an IC 50 value of 91.5 μM, while ribavirin as a positive control had an IC 50 value
of 114.8 μM. Compound 48 was also found to possess weak NF-κB inhibitory
activity with an IC 50 value of 40.0 μM [30].
Asteltoxins E and F (49 and 50) were isolated from the solid rice medium
fermentation of Aspergillus sp. SCSIO XWS02F40 that was obtained from the
sponge Callyspongia sp. collected from the sea area near Xuwen County, Guangdong Province. Asteltoxins E and F (49 and 50) showed significant activity against
H3N2 cells with IC 50 values of 6.2 and 8.9 μM. In addition, asteltoxin E (49) also
exhibited inhibitory activity against the H1N1 virus with an IC 50 value of 3.5 μM
[31]. The fungal strain Emericella variecolor XSA-07-2 was obtained from the
sponge Cinachyrella sp. collected from Yongxing Island in the South China Sea.
Chemical examination of the EtOAc extract of E. variecolor cultured on solid rice
medium yielded varioxiranols K and L (51 and 52). Cytotoxic activities of both
compounds were evaluated against different tumor cell lines including human colon
carcinoma (HCT-116), liver hepatocellular carcinoma (HepG2), gastric cancer
(BGC-823), lung cancer stem cells (NCI-H1650), and human ovarian cancer
(A2780) cells.
Varioxiranol K (51) showed significant effects against the tumor cell lines
HCT-116 (IC 50 3.5 μM ), HepG2 (IC 50 8.8 μM), BGC-823 (IC 50 4.2 μM), and
NCI-H1650 (IC 50 2.8 μM ), while varioxiranol L (52) showed selective inhibitory
activity toward HCT-116 (IC 50 2.0 μM ), BGC-823 (IC 50 5.0 μM), and NCI-H1650
cells (IC 50 2.2 μM ) [32]. Diethyl sulfate was added as a chemical mutagen to the
fungus E. variecolor XSA-07-2 in order to activate silent fungal metabolite pathways of this fungus. Fresh fungal spores in 50% (v/v) DMSO were treated with 1%
(v/v) diethyl sulfate at 4
C for 1 day, and single colony isolates resulting from the
treated spores were collected. A mutant of E. variecolor XSA-07-2-M3 that produced asteltoxin (absent in the wild strain) was obtained. Chromatographic separation following solid rice medium fermentation of the mutant resulted in the isolation
of three further novel asteltoxin-bearing dimers, diasteltoxins AÀC (53–55), which
were characterized structurally by a [2+2] cycloaddition of asteltoxin. This was the
first report of a [2+2] cycloaddition occurring in marine fungi. Diasteltoxins AÀC
(53–55) showed significant inhibition of thioredoxin reductase (TrxR) with IC 50
values of 12.8, 11.1, and 7.2 μM, respectively, suggesting that these compounds may
act as regulators of tumor progression and metastasis (Fig. 3) [33].
2.3 γ-Pyrones Including Xanthones and Chromones
The fungus Penicillium citrinum SCSGAF 0167 was obtained from the gorgonian
Echinogorgia aurantiaca collected from Sanya, Hainan Province. 2,11-Dihydroxy1-methoxycarbonyl-9-carboxylxanthone (56) (Fig. 4) was isolated following
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Z. Liu et al.
The glucoside iso-D8646-2-6 (48) showed anti-influenza A viral (H1N1) activity
with an IC 50 value of 91.5 μM, while ribavirin as a positive control had an IC 50 value
of 114.8 μM. Compound 48 was also found to possess weak NF-κB inhibitory
activity with an IC 50 value of 40.0 μM [30].
Asteltoxins E and F (49 and 50) were isolated from the solid rice medium
fermentation of Aspergillus sp. SCSIO XWS02F40 that was obtained from the
sponge Callyspongia sp. collected from the sea area near Xuwen County, Guangdong Province. Asteltoxins E and F (49 and 50) showed significant activity against
H3N2 cells with IC 50 values of 6.2 and 8.9 μM. In addition, asteltoxin E (49) also
exhibited inhibitory activity against the H1N1 virus with an IC 50 value of 3.5 μM
[31]. The fungal strain Emericella variecolor XSA-07-2 was obtained from the
sponge Cinachyrella sp. collected from Yongxing Island in the South China Sea.
Chemical examination of the EtOAc extract of E. variecolor cultured on solid rice
medium yielded varioxiranols K and L (51 and 52). Cytotoxic activities of both
compounds were evaluated against different tumor cell lines including human colon
carcinoma (HCT-116), liver hepatocellular carcinoma (HepG2), gastric cancer
(BGC-823), lung cancer stem cells (NCI-H1650), and human ovarian cancer
(A2780) cells.
Varioxiranol K (51) showed significant effects against the tumor cell lines
HCT-116 (IC 50 3.5 μM ), HepG2 (IC 50 8.8 μM), BGC-823 (IC 50 4.2 μM), and
NCI-H1650 (IC 50 2.8 μM ), while varioxiranol L (52) showed selective inhibitory
activity toward HCT-116 (IC 50 2.0 μM ), BGC-823 (IC 50 5.0 μM), and NCI-H1650
cells (IC 50 2.2 μM ) [32]. Diethyl sulfate was added as a chemical mutagen to the
fungus E. variecolor XSA-07-2 in order to activate silent fungal metabolite pathways of this fungus. Fresh fungal spores in 50% (v/v) DMSO were treated with 1%
(v/v) diethyl sulfate at 4
C for 1 day, and single colony isolates resulting from the
treated spores were collected. A mutant of E. variecolor XSA-07-2-M3 that produced asteltoxin (absent in the wild strain) was obtained. Chromatographic separation following solid rice medium fermentation of the mutant resulted in the isolation
of three further novel asteltoxin-bearing dimers, diasteltoxins AÀC (53–55), which
were characterized structurally by a [2+2] cycloaddition of asteltoxin. This was the
first report of a [2+2] cycloaddition occurring in marine fungi. Diasteltoxins AÀC
(53–55) showed significant inhibition of thioredoxin reductase (TrxR) with IC 50
values of 12.8, 11.1, and 7.2 μM, respectively, suggesting that these compounds may
act as regulators of tumor progression and metastasis (Fig. 3) [33].
2.3 γ-Pyrones Including Xanthones and Chromones
The fungus Penicillium citrinum SCSGAF 0167 was obtained from the gorgonian
Echinogorgia aurantiaca collected from Sanya, Hainan Province. 2,11-Dihydroxy1-methoxycarbonyl-9-carboxylxanthone (56) (Fig. 4) was isolated following
88
Z. Liu et al.