Abstract
Two new coumarin derivatives, 4,4′-dimethoxy-5,5′-dimethyl-7,7′-oxydicoumarin (1), 7-(γ,γ-dimethylallyloxy)-5-methoxy-4-methylcoumarin (2), a new chromone derivative, (S)-5-hydroxy-2,6-dimethyl-4H-furo[3,4-g]benzopyran-4,8(6H)-dione (5), and a new sterone derivative, 24-hydroxylergosta-4,6,8(14),22-tetraen-3-one (6), along with two known bicoumarins, kotanin (3) and orlandin (4), were isolated from an endophytic fungus Aspergillus clavatus (collection No. R7), isolated from the root of Myoporum bontioides collected from Leizhou Peninsula, China. Their structures were elucidated using 1D- and 2D- NMR spectroscopy, and HRESIMS. The absolute configuration of compound 5 was determined by comparison of the experimental and calculated electronic circular dichroism (ECD) spectra. Compound 6 significantly inhibited the plant pathogenic fungi Fusarium oxysporum, Colletotrichum musae and Penicillium italicum, compound 5 significantly inhibited Colletotrichum musae, and compounds 1, 3 and 4 greatly inhibited Fusarium oxysporum, showing the antifungal activities higher than those of the positive control, triadimefon.
Highlights
Marine mangrove endophytic fungi are among the most productive sources of structurally unusual and biologically active natural products [1,2,3]
The fungal strain R7 was isolated from the root of M. bontioides, collected from the mangrove in Leizhou peninsula, China, in May 2014, and deposited at the College of Materials and Energy, South China Agricultural University, Guangdong Province, China
The calculated electronic circular dichroism (ECD) spectra were obtained by density functional theory (DFT) and time-dependent DFT (TD-DFT) using Gaussian 09 (Gaussian Inc., Wallingford, CT, USA) program package
Summary
Marine mangrove endophytic fungi are among the most productive sources of structurally unusual and biologically active natural products [1,2,3]. Gray collected from Leizhou Peninsula, China, had been screened to show antifungal activities against several plant pathogenic fungi [10]. This prompted us to investigate the corresponding metabolites. Two new coumarin derivatives, 4,40 -dimethoxy-5,50 -dimethyl-7,70 -oxydicoumarin (S)-5-hydroxy-2,6-dimethyl-4H-furo[3,4-g]benzopyran-4,8(6H)-dione (5), and a new sterone derivative, 24-hydroxylergosta-4,6,8(14),22-tetraen-3-one (6), along with two known bicoumarins, kotanin (3) and orlandin (4) [11], were isolated (Figure 1). We report their isolation, structural elucidation and bioactivity.
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