Discovery of Tropolone Stipitaldehyde as a Potential Agent for Controlling Phytophthora Blight and Its Action Mechanism Research.

The fermentation of endophytic Nigrospora chinensis GGY-3 resulted in the isolation of tropolone stipitaldehyde (1), which exhibited broad-spectrum inhibition activity against fungi and bacteria, especially against Phytophthora capsici, with an EC50 value of 0.83 µg/mL and Xanthomonas oryzae pv. oryzicola, with a minimum inhibitory concentration value of 4.0 µg/mL. The in vitro and in vivo assays demonstrated that 1 had a significant protective effect on P. capsici. Furthermore, 1 inhibited the spore germination of P. capsici and damaged the plasma membrane structure. As observed by SEM and TEM, after exposure to 1, mycelia exhibited swelling, shrunken, branch-increasing phenomena, cell wall and membrane damage, and disordered content. Transcriptome analysis revealed that 1 might affect starch and sucrose metabolism and fatty acid biosynthesis by suppressing the expression of genes relevant to cell wall synthetases and cell membrane-associated genes. These findings indicate that 1 may be a potential agrochemical fungicide for controlling phytophthora blight.

Novel metabolites from the Cercis chinensis derived endophytic fungus Alternaria alternata ZHJG5 and their antibacterial activities.

BACKGROUND: Phytopathogenic bacteria, such as Xanthomonas oryzae pv. oryzae (Xoo) and Ralstonia solanacearum (Rs), seriously threaten crop production and are the cause of enormous yield losses. Endophytic fungi are abundant sources of bioactive metabolites that may be potential candidates in the development of new agrochemicals. This work emphasizes the discovery of bioactive polyketides from endophytic Alternaria alternata ZHJG5 and reports their structural elucidation and antibacterial activities in detail. RESULTS: Five novel polyketide derivatives, isotalaroflavone (2), (+/-)-5'-dehydroxytalaroflavone (3a/3b), (+)-talaroflavone (4b), and bialternacin G (7), along with five known compounds (1, 4a, 5, 6, and 8), were obtained from the Cercis chinensis-derived fungus A. alternata ZHJG5. The compounds' structures were characterized using spectroscopic methods and X-ray diffraction. Chiral high-performance liquid chromatography was used to separate the racemates 3 and 4, whose absolute configurations were unambiguously confirmed by comparing their experimental and calculated electron circular dichroism data. All isolated compounds were tested for antibacterial activity against the phytopathogenic bacteria Xoo, Xanthomonas oryzae pv. oryzicola (Xoc) and Rs. Compounds 1, 2 and 8 showed pronounced antibacterial activity against all tested bacteria, with minimal inhibitory concentrations ranging from 0.5 to 64 µg/ml. In addition, compound 1 showed a potent protective effect against rice bacterial leaf blight caused by Xoo with a protective efficacy of 75.1% at a concentration of 200 µg/ml. CONCLUSION: These findings highlight the practical potential of antibacterial compounds as candidates for the discovery of novel bactericides. © 2021 Society of Chemical Industry.

Antifungal meroterpenes and dioxolanone derivatives from plant-associated endophytic fungus Phyllosticta sp. WGHL2.

Four new meroterpenes named as guignardones U-X (1-4), along with eleven known meroterpenes (5-15) and three known dioxolanone derivatives (16-18), were obtained from the endophytic fungus Phyllosticta sp. WGHL2. The structural elucidation was conducted by HRESIMS, NMR, single crystal X-ray diffraction, along with ECD calculations and comparison. In antifungal tests, compound 16 possessed broad-spectrum antifungal activities against Rhizoctonia solani, Fusarium graminearum and Botrytis cinerea with inhibition ratio of 48.43%, 40.98%, and 49.53% at 50 µg/mL, respectively. Moreover, compound 16 showed moderate protective effect against B. cinerea in vivo at 200 µg/mL and exhibited effective inhibition on the spore germination of B. cinerea.

Enantiomeric Dibenzo-α-Pyrone Derivatives from Alternaria alternata ZHJG5 and Their Potential as Agrochemicals.

Three pairs of enantiomeric dibenzo-α-pyrone derivatives (1-3) including two pairs of new racemates (±)-alternaone A (1) and (±)-alternaone B (2) and one new enantiomer (-)-alternatiol (3), together with five known compounds (4-8) were isolated from the fungus Alternaria alternata ZHJG5. Their structures were confirmed by spectroscopic data and single-crystal X-ray diffraction analysis. All enantiomers were separated via chiral high-performance liquid chromatography, with their configurations determined by electronic circular dichroism calculation. Biogenetically, a key epoxy-rearrangement step was proposed for the formation of skeletons in 1-3; (+) 1, (-)-1, and 5 presented moderate antibacterial inhibition on phytopathogenic bacteria Xanthomonas oryzae pv. oryzae and Xanthomonas oryzae pv. oryzicola. In the antifungal test, compounds 7 and 8 showed a moderate protective effect against Botrytis cinerea in vivo.

Discovery of Natural FabH Inhibitors Using an Immobilized Enzyme Column and Their Antibacterial Activity against Xanthomonas oryzae pv. oryzae.

ß-Ketoacyl-acyl carrier protein synthase III (KAS III, FabH) is essential for bacterial fatty acid biosynthesis. Recent studies indicate that FabH can be a potential target for bactericide development. In the present study, an immobilized FabH column was developed and used to screen FabH inhibitors from complex natural product extracts. Combined with HPLC, four secondary metabolites, alternariol (1), altenuisol (2), alterlactone (3), and dehydroaltenusin (4), were site-directed, isolated, and identified from the crude extract of Alternaria alternata ZHJG5. These compounds showed inhibitory activities on FabH of Xanthomonas oryzae pv. oryzae (Xoo) with IC50 values from 29.5 to 74.1 µM and also displayed a varying degree of antibacterial activities against Xoo with minimal inhibitory concentration values from 4 to 64 µg/mL. Molecular modeling was then used to picture how the compounds interact with XooFabH. Two inhibitors, compounds 1 and 3, exhibited significant bactericidal activity against rice bacterial leaf blight with a protective efficiency of 66.2 and 82.5% at the concentration of 200 µg/mL, respectively, suggesting that they could be lead candidates to develop novel bactericides.

Topical Coenzyme Q10 demonstrates mitochondrial-mediated neuroprotection in a rodent model of ocular hypertension.

Coenzyme Q10 (CoQ10) is a mitochondrial-targeted antioxidant with known neuroprotective activity. Its ocular effects when co-solubilised with α-tocopherol polyethylene glycol succinate (TPGS) were evaluated. In vitro studies confirmed that CoQ10 was significantly protective in different retinal ganglion cell (RGC) models. In vivo studies in Adult Dark Agouti (DA) rats with unilateral surgically-induced ocular hypertension (OHT) treated with either CoQ10/TPGS micelles or TPGS vehicle twice daily for three weeks were performed, following which retinal cell health was assessed in vivo using DARC (Detection of Apoptotic Retinal Cells) and post-mortem with Brn3a histological assessment on whole retinal mounts. CoQ10/TPGS showed a significant neuroprotective effect compared to control with DARC (p<0.05) and Brn3 (p<0.01). Topical CoQ10 appears an effective therapy preventing RGC apoptosis and loss in glaucoma-related models.

Non-amyloidogenic effects of α2 adrenergic agonists: implications for brimonidine-mediated neuroprotection.

The amyloid beta (Aß) pathway is strongly implicated in neurodegenerative conditions such as Alzheimer's disease and more recently, glaucoma. Here, we identify the α2 adrenergic receptor agonists (α2ARA) used to lower intraocular pressure can prevent retinal ganglion cell (RGC) death via the non-amyloidogenic Aß-pathway. Neuroprotective effects were confirmed in vivo and in vitro in different glaucoma-related models using α2ARAs brimonidine (BMD), clonidine (Clo) and dexmedetomidine. α2ARA treatment significantly reduced RGC apoptosis in experimental-glaucoma models by 97.7% and 92.8% (BMD, P<0.01) and 98% and 92.3% (Clo, P<0.01)) at 3 and 8 weeks, respectively. A reduction was seen in an experimental Aß-induced neurotoxicity model (67% BMD and 88.6% Clo, both P<0.01, respectively), and in vitro, where α2ARAs significantly (P<0.05) prevented cell death, under both hypoxic (CoCl2) and stress (UV) conditions. In experimental-glaucoma, BMD induced ninefold and 25-fold and 36-fold and fourfold reductions in Aß and amyloid precursor protein (APP) levels at 3 and 8 weeks, respectively, in the RGC layer, with similar results with Clo, and in vitro with all three α2ARAs. BMD significantly increased soluble APPα (sAPPα) levels at 3 and 8 weeks (2.1 and 1.6-fold) in vivo and in vitro with the CoCl2 and UV-light insults. Furthermore, treatment of UV-insulted cells with an sAPPα antibody significantly reduced cell viability compared with BMD-treated control (52%), co-treatment (33%) and untreated control (27%). Finally, we show that α2ARAs modulate levels of laminin and MMP-9 in RGCs, potentially linked to changes in Aß through APP processing. Together, these results provide new evidence that α2ARAs are neuroprotective through their effects on the Aß pathway and sAPPα, which to our knowledge, is the first description. Studies have identified the need for α-secretase activators and sAPPα-mimetics in neurodegeneration; α2ARAs, already clinically available, present a promising therapy, with applications not only to reducing RGC death in glaucoma but also other neurodegenerative processes involving Aß.

S100A4 gene silencing in oxygen-induced ischemic retinopathy inhibits retinal neovascularization via down-regulation of CREB expression.

PURPOSE: To investigate the possible role of S100A4 in retinal neovascularization (RNV), as well as the underlying mechanism, in a mouse model of oxygen-induced retinopathy (OIR). METHODS: Retinas used in the experiments were obtained from a mouse model of OIR with and without treatment by intravitreal injection of adnoviral-S100A4-RNAi or adenoviral-green fluorescent protein at postnatal day 12 (P12). At P17, the efficacy of adenoviral gene transfer was assessed with fluorescence microscopy. RNV was evaluated by whole-mount immunofluorescent staining of the mouse retina with Griffonia simplicifolia isolectin B4 conjugated to Alexa Fluor 594 and quantified by counting the number of pre-retinal neovascular cells. Protein and mRNA expression levels of S100A4, cyclic AMP (cAMP) response element-binding protein (CREB), B-cell lymphoma 2 (Bcl-2), and caspase-3 were determined using Western blot analysis and real-time PCR. RESULTS: Retinal S100A4 levels were positively correlated with the progression of RNV. In the intravitreal Ad-S100A4-RNAi transfer mice, both S100A4 protein and mRNA expression levels in the retina were significantly decreased at P17. Ad-S100A4-RNAi transfer was clearly demonstrated by the green fluorescent protein (GFP) in many layers of the retina, including the ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform layer (OPL), and outer nuclear layer (ONL), 3 days after intravitreal injection. Whole-mount immunofluorescent staining of the retina and quantification of the pre-retinal neovascular cells demonstrated that RNV was significantly ameliorated. At the same time, the expression of CREB and Bcl-2 were significantly decreased at the transcriptional and translational levels in the OIR-S100A4 group, whereas caspase-3 expression was increased. CONCLUSIONS: Our results indicated that RNV was ameliorated by Ad-S100A4-RNAi transfer in a mouse model of OIR through mediation of the anti-apoptotic effect of Bcl-2 by reducing the expression of CREB, and that S100A4 may be a novel therapeutic target for ocular neovascularization diseases.

Current perspective of neuroprotection and glaucoma.

Glaucoma is the second leading cause of blindness worldwide and is most notably characterized by progressive optic nerve atrophy and advancing loss of retinal ganglion cells (RGCs). The main concomitant factor is the elevated intraocular pressure (IOP). Existing treatments are focused generally on lowering IOP. However, both RGC loss and optic nerve atrophy can independently occur with IOP at normal levels. In recent years, there has been substantial progress in the development of neuroprotective therapies for glaucoma in order to restore vital visual function. The present review intends to offer a brief insight into conventional glaucoma treatments and discuss exciting current developments of mostly preclinical data in novel neuroprotective strategies for glaucoma that include recent advances in noninvasive diagnostics going beyond IOP maintenance for an enhanced global view. Such strategies now target RGC loss and optic nerve damage, opening a critical therapeutic window for preventative monitoring and treatment.