Alzheimer’s disease (AD) is a progressive neurodegenerative disease for which no effective clinical therapies currently exist. The neuroprotective potential of Chaetoglobosin F (CF), a fungal secondary metabolite, was investigated in this study using a Caenorhabditis elegans ( C. elegans ) model of AD that are transgenic nematodes expressing amyloid-beta (Aβ). Key parameters evaluated included paralysis rate, lifespan, motor and cognitive functions, Aβ plaque aggregation, intracellular reactive oxygen species (ROS), and autophagosome formation. The transcriptional levels of genes were examined by real time PCR. Results showed that treatment with CF significantly delayed paralysis, extended lifespan, and ameliorated Aβ-induced deficits in locomotion and chemotaxis. CF markedly reduced Aβ plaque accumulation, suppressed intracellular ROS levels, and promoted autophagosome formation. Furthermore, CF had potent inhibitory effects on acetylcholinesterase (AChE) activity. These beneficial effects were correlated with the upregulation of crucial genes, including daf-16 , skn-1 , pmk-1 , mtl-1 , unc-51 , bec-1 , lgg-1 , sod-1 and sod-3 , which confirmed the improving antioxidant defenses and autophagy. Our findings demonstrate that CF confers strong neuroprotection against Aβ-induced toxicity in C. elegans by co-regulating oxidative stress and autophagy through the Insulin/IGF-1 (IIS) and p38 MAPK signaling pathways. These results suggest that CF is a promising natural compound for further investigation as a potential therapeutic agent for AD. Graphical
Two new metabolites, an α-pyridone derivative, 3-hydroxy-2-methoxy-5-methylpyridin-2(1H)-one (1), and a ceramide derivative, 3-hydroxy-N-(1-hydroxy-3-methylpentan-2-yl)-5-oxohexanamide (2), and a new natural product, 3-hydroxy-N-(1-hydroxy-4-methylpentan-2-yl)-5-oxohexanamide (3), along with 15 known compounds including chaetoglobosin C (7) and chaetoglobosin F (8) were isolated from the solid culture of the endophytic fungus Botryosphaeria dothidea KJ-1, collected from the stems of white cedar (Melia azedarach L). The structures were elucidated on the basis of spectroscopic analysis (1D and 2D NMR experiments and by mass spectrometric measurements), and the structure of 1 was confirmed by X-ray single-crystal diffraction. These metabolites were evaluated in vitro for antimicrobial, antioxidant, and cytotoxicity activities. Pycnophorin (4) significantly inhibited the growth of Bacillus subtilis and Staphyloccocus aureus with equal minimum inhibitory concentration (MIC) values of 25 μM. Stemphyperylenol (5) displayed a potent antifungal activity against the plant pathogen Alternaria solani with MIC of 1.57 μM comparable to the commonly used fungicide carbendazim. Both altenusin (9) and djalonensone (10) showed markedly DPPH radical scavenging activities. In addition, stemphyperylenol (5) and altenuene (6) exhibited strong cytotoxicity against HCT116 cancer cell line with a median inhibitory concentration (IC50) value of 3.13 μM in comparison with the positive control etoposide (IC50 = 2.13 μM). This is the first report of the isolation of these compounds from the endophytic B. dothidea.
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