Six new cyclopentenone derivatives (+)-nigrosporione A (+)-1, (-)-nigrosporione A (-)-1, nigrosporione B (2), nigrosporione C (3), (+)-nigrosporione D (+)-4, and (-)-nigrosporione D (-)-4 were isolated from an endophytic fungus Nigrospora sphaerica ZMT05, collected from the rice grasshopper ( Oxya chinensis Thunberg), which is an insect pest in rice and which is also used as a food for people in some countries. Their planar and spatial structures were determined by spectroscopic analyses and eletronic circular dichroism (ECD) calculations. Compounds (+)-1, (-)-1, and 2 inhibited the plant pathogens Fusarium oxysporum, Colletotrichum musae, Penicillium italicum, and Fusarium graminearum, compounds 3 and (-)-4 inhibited F. oxysporum, C. musae, and P. italicum, and compound (+)-4 inhibited F. oxysporum, C. musae, and F. graminearum, showing antifungal activities stronger than triadimefon. Additionally, compounds (+)-1, (-)-1, 2, and 3 displayed moderate antibacterial activities against Staphyloccocus aureus and Escherichia coli.
Two novel cyclic hexadepsipeptides, fusarihexin A (1: ) and fusarihexin B (2: ), and two known compounds, cyclo-(L-Leu-L-Leu-D-Leu-L-Leu-L-Val) (3: ) and cyclo-(L-Leu-L-Leu-D-Leu-L-Leu-L-Ile) (4: ), were isolated from the marine mangrove endophytic fungus sp. R5. Their chemical structures were elucidated on the basis of spectroscopic data and Marfey's analysis. In an bioassay, fusarihexin A (1: ) remarkably inhibited three plant pathogenic fungi: (Penz.) Sacc., which causes anthracnose in many fruits and vegetables, (Berk. and M. A. Curtis) Arx, which causes crown rot and anthracnose in bananas, and Schlecht. f. sp. lycopersici (Sacc.) W. C. Snyder et H. N. Hansen, which causes Fusarium wilt and fruit rot in tomatoes. Fusarihexin B (2: ) strongly inhibited and . The compounds were more potent than carbendazim, which is widely used as an agricultural and horticultural fungicide worldwide.
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