Excessive glutamate damages neuronal cells via the accumulation of intracellular reactive oxygen species (ROS), calcium ion (Ca²⁺) influx, depolarization of mitochondrial membrane potential, and apoptosis, which may result in the development of chronic neurodegenerative diseases. In this study, we evaluated the effects of 4,6′-anhydrooxysporidinone isolated from endophytic fungus Fusarium lateritium SSF2 on glutamate-induced cytotoxicity, accumulation of intracellular ROS, increases in superoxide anion production, Ca²⁺, depolarization of mitochondrial membrane potential, and apoptotic cell death in hippocampal HT22 cells. 2′,7′-Dichlorofluorescin diacetate (H2DCFDA) staining was used to determine the intracellular reactive oxygen species concentration and dihydroethidine (DHE) staining was used to determine the superoxide radical. Expression of the nuclear factor-erythroid-2–related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) was analyzed by Western blot. Fluo-4 staining was used to determine the intracellular Ca²⁺ levels. In order to explore mitochondrial membrane potential, tetramethylrhodamine methyl ester (TMRM) staining was used. Apoptotic cell death was evaluated using Annexin-V/propidium iodide (PI) staining and TUNEL staining. Expression of the cytochrome c release and cleaved caspase-9, -3 was analyzed by Western blot. Here, we were able to isolate 4,6′-anhydrooxysporidinone from endophytic fungus, Fusarium lateritium SSF2, which was shown to protect HT22 cells from glutamate-induced cytotoxicity, accumulation of intracellular ROS, increases in superoxide anion production, Ca²⁺, and depolarization of mitochondrial membrane potential. In addition, 4,6′-anhydrooxysporidinone enhanced the expressions of Nrf2 and HO-1. It also inhibited the apoptotic cell death through the inhibition of cytochrome c release and cleaved caspase-9, -3 in glutamate-treated HT22 cells. Therefore, our results provide ample evidence of the neuroprotective properties of 4,6′-anhydrooxysporidinone.

Endophytes have been recognized as a source for structurally novel and biologically active secondary metabolites. Among the host plants for endophytes, some medicinal plants that produce pharmaceuticals have been reported to carry endophytes, which could also produce bioactive secondary metabolites. In this study, the medicinal plant Aconitum carmichaeli was selected as a potential source for endophytes. An endophytic microorganism, Aureobasidium pullulans AJF1, harbored in the flower of Aconitum carmichaeli, was cultured on a large scale and extracted with an organic solvent. Extensive chemical investigation of the extracts resulted in isolation of three lipid type compounds (1–3), which were identified to be (3R,5R)-3,5-dihydroxydecanoic acid (1), (3R,5R)-3-(((3R,5R)-3,5-dihydroxydecanoyl)oxy)-5-hydroxydecanoic acid (2), and (3R,5R)-3-(((3R,5R)-5-(((3R,5R)-3,5-dihydroxydecanoyl)oxy)-3-hydroxydecanoyl)oxy)-5-hydroxydecanoic acid (3) by chemical methods in combination with spectral analysis. Compounds 2 and 3 had new structures. Absolute configurations of the isolated compounds (1–3) were established using modified Mosher’s method together with analysis of NMR data for their acetonide derivatives. All the isolates (1–3) were evaluated for antibiotic activities against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, and their cytotoxicities against MCF-7 cancer cells. Unfortunately, they showed low antibiotic activities and cytotoxic activities.