3334
Z. Chen et al. / Bioorg. Med. Chem. Lett. 22 (2012) 3332–3335
Figure 2. Key COSY and HMBC correlations of 2 and 3.
attention due to their vast array of biological activities. Among
these activities, the MPA scaffold was associated with antiviral
and immunosuppressive activities. However, there have been very
few reports on the isolation of MPA and derivatives from natural
sources12,13,19 and even fewer investigations aimed at understand-
ing the SAR of these compounds.20 We aim in this report to recon-
cile, in part, this scarcity of information by reporting three new
MPA analogues from a marine-derived fungus. Moreover, the 1–3
producer Penicillium sp. SOF07, is a previously unrecognized pro-
ducer of known compounds 4 and 5. On the basis of bioassays
exploiting isolated enzyme and intact cells we provide further in-
sight into MPA scaffold characteristics that may be applied to the
design of new MPA derivatives as drug leads particularly in the
context of immunosuppressives.
Table 2
Summary of IMPDH and mouse splenocyte proliferation inhibition assays for
compounds 1–5
a
a
Compounds IC50
(lM)
IC50 (lM)
Inosine monophosphate
dehydrogenase
Mouse splenocyte
proliferation
1
2
3
4
5
28.86 2.50
6.43 1.10
73.24 6.40
0.63 0.09
1.79 0.13
2.46 0.32
>20
>30
0.32 0.06
1.10 0.21
a
Data represent the mean SD of three triplicate experiments.
(30-Me) characteristic of 1, 2, 4 and 5 was down shifted to dC
18.1 ppm. H–1H COSY data revealed a H-10/H-20 spin system and
1
Acknowledgments
HMBC experiments revealed correlations of H-20/C-6, 30-Me/C-30,
C-20 (Fig. 2). Thus, the two olefinic side chain carbons characteristic
of the other penicacids are replaced in 3 with the oxygen-bearing
carbons C-20 and C-30. Limited amounts of 3, coupled with our
inability to obtain diffraction quality crystals have, thus far,
abrogated stereochemical assignments for C-20, C-30 and C-40
though efforts in this direction are ongoing. Consequently, 3 is
assigned as 20,30-dihydroxy-40-hydroxy-MPA.
We thank the analytical facility center of South China Sea Insti-
tute of Oceanology for recording NMR data. This work is supported,
in part, by grants from the Knowledge Innovation Programs of the
Chinese Academy of Sciences (KZCX2-YW-JC202, KZCX2-EW-G-12
and KSCX2-YW-G-065), ‘863’ Project (2012AA092104), Science
and Technology Planning Project of Guangdong Province
(2010B030600010), and Scientific Research Foundation for the Re-
turned Overseas Chinese Scholars of the State Education Ministry.
J.J. is a scholar of the ‘100 Talents Project’ of Chinese Academy of
Sciences (08SL111001).
To assess the biological activity of the penicacids we first eval-
uated 1–5 for their ability to inhibit IMPDH (type II) activity using
the method reported by Magasanik et al.17 Enzyme assays, in the
presence or absence of varying concentrations of 1–5, were carried
out in 96-well microtiter plates and rates of reaction determined
by monitoring absorbance at 340 nm resulting from enzymatic
NADH production. Compounds 1–5 were dissolved in DMSO and
serially diluted before being added to the initial assay mixture
for pre-incubation with the enzyme. Concentrations of DMSO to
dissolve compounds in assay mixtures were not allowed to exceed
2% (v/v). Data acquisition and processing revealed that 1–5 inhib-
ited IMPDH with IC50 values of 28.86, 6.43, 73.24, 0.63, and
Supplementary data
Supplementary data (1H and 13C NMR spectra of compounds 1–
3) associated with this article can be found, in the online version, at
References and notes
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differences among 1–5 compounds were then subjected to a
splenocyte T lymphocyte proliferation assay,18 the results of which
are shown in Table 2. With the exception of glycosylated 2, the
immunosuppresive activities of 1–5 at the cellular level paralleled
their IMPDH inhibitory activities. The collective SAR data from
both bioassays reveal the importance of the C-7 OH, the C-20/C-30
olefin, and the absence of the C-40 OH in the immunosuppresive
activities displayed by the MPA scaffold at both the enzymatic
and cellular levels.
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11. The strain Penicillium sp. SOF07 was cultured on PDA medium supplemented
with 3% sea salt at 25 °C for a week. The agar plugs containing strain SOF07
were inoculated into Erlenmeyer flasks containing 50 mL potato dextrose
liquid broth supplemented with 3% sea salt. Flask cultures were incubated at
28 °C on a rotary shaker at 200 rpm for 2 d as seed culture. Ten milliliter of the
seed culture was then inoculated to autoclaved solid medium (100 g rice,
MPA was discovered in 1893 by the Italian physician Bartolo-
meo Gosio.3 MPA and related derivatives attracted a great deal of