Pseudomonas syringae pv. actinidiae (Psa) is a Gram-negative bacterium causing the kiwifruit canker disease, resulting in serious economic losses to the kiwifruit industry. This study investigated the use of an endophytic fungus, Fusarium tricinctum, obtained from the kiwi plant (Actinidia chinesis) as a potential biocontrol strain against the Psa. F. tricinctum showed an inhibition rate of 59.5% in vitro against Psa. Bioassay-guided isolation was conducted on the cultural broth of F. tricinctum and seven new imidazole alkaloids, (±)-fusaritricine J ((±)-1) and fusaritricines K-P (2−7), and four enniatins (8−11) were identified. Their absolute configurations were established through extensive spectroscopic methods, quantum chemical calculations, and X-ray single crystal diffraction. Compounds 1, 4, 5, and 8−11 showed comparable anti-bacterial activities against Psa as positive control, with MIC values of 25−50 μg/mL. Further cell membrane permeability assay suggested that the most active compound 4 could destroy the bacterial cell wall structure. Hence, F. tricinctum metabolites could be applied as potential anti-Psa agents, and F. tricinctum could be considered a biocontrol strain for the control of the kiwifruit canker disease.
In our ongoing study of fungal bioactive natural products,
12 previously
undescribed triquinane sesquiterpene glycosides, namely, antrodizonatins
A–L (1–12), and four known
compounds (13–16) have been obtained
from the fermentation of the basidiomycete Antrodiella zonata. The structures were established unambiguously via extensive spectroscopic
analysis and theoretical calculations of electronic circular dichroism
spectra. This is the first report of triquinane sesquiterpene glycosides.
Compounds 1, 5, and 12 displayed
antibacterial activity against Staphylococcus aureus with MIC50 values of 35, 34, and 69 μM, respectively.
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