Heptaketides with antiviral activity from three endolichenic fungal strains Nigrospora sp., Alternaria sp. and Phialophora sp.
Graphical abstract
Two new heptaketides were isolated from three endolichenic fungal strains Nigrospora sp., Alternaria sp., and Phialophora sp. Their structures and antiviral activity are reported herein.
Introduction
Endolichenic fungi are microorganisms living in the thalli of lichens, which are analogous to the plant endophytic fungi inhabiting the intercellular spaces of the hosts [1]. Up to now, only a limited number of secondary metabolites have been previously reported from the endolichenic fungi, including Corynespora sp. [1], [2], Pestalotiopsis sp. [3], Neurospora sp. [4], Coniochaeta sp. [5], [6], Ulocladium sp. [7], Xylaria sp. [8], Preussia sp. [9], and Phaeosphaeria sp. [10]. In the search for bioactive secondary metabolites from microorganisms, the EtOAc extract of an endolichenic fungus Nigrospora sphaerica (No.83-1-1-2) showed (inhibition rate (IR), 67.1%) inhibition activity against HSV at the concentration of 12.5 μg/mL. Further chemical investigation on the EtOAc extract led to the isolation of eight secondary metabolites including two new heptaketides (1a and 2a) (Fig. 1). Interestingly, these metabolites were also obtained from the EtOAc extracts of other two endolichenic fungal strains Alternaria alternata (No.58-8-4-1) and Phialophora sp. (No.96-1-8-1). Herein, we report the isolation, structure elucidation, and antiviral activity of these compounds.
Section snippets
General
Optical rotations were measured on a JASCO P-1020 digital polarimeter at room temperature. IR spectra were recorded on a JASCO FT/IR-480 plus Fourier transform infrared spectrometer. UV spectra were recorded in CH3OH using a JASCO V-550 UV/VIS spectrophotometer. CD spectra were recorded in CH3OH using a JASCO J-810 spectrophotometer at room temperature. ESI-MS was performed on a Finigan LCQ Advantage MAX mass spectrometer and HR-ESI-MS was recorded on an Agilent 6200 ESI/TOF mass spectrometer,
Results and discussion
The molecular formula of 1 was assigned as C15H16O6 (eight degrees of unsaturation) on the basis of HR-ESI-MS at m/z 293.1019 [M + H]+ (calcd. for C15H17O6, 293.1019). The 1H NMR spectrum of 1 exhibited signals for one methyl group at δH 1.47 (s), one methoxy group at δH 3.86 (s), a pair of meta-positioned aromatic protons at δH 6.50 and 6.74 (each, d, J = 2.3 Hz), an olefinic proton at δH 6.30 (d, J = 3.3 Hz), and one phenolic hydroxyl group at δH 11.30 (s). The 13C NMR spectrum combined with DEPT-135
Acknowledgments
This work was financially supported by grants from the Ministry of Science and Technology of China (2009CB522300, and 2009ZX09302-004), by the Program for New Century Excellent Talents in University (NCET-10-0120) from the Ministry of Education of China, and by the Fundamental Research Funds for the Central Universities (21611203).
References (26)
- et al.
Fitoterapia
(2012) - et al.
J Nat Prod
(2012) - et al.
J Biomol Screen
(2010) - et al.
Biochem Syst Ecol
(2007) - et al.
Phytochemistry
(2003) - et al.
J Nat Prod
(2007) - et al.
J Nat Prod
(2010) - et al.
J Nat Prod
(2009) - et al.
J Nat Prod
(2009) - et al.
Org Lett
(2010)
J Nat Prod
J Nat Prod
J Nat Prod
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Authors contributed equally to this work.