Search Results (7)

The SARS-CoV-2 virus, which caused the COVID-19 infection, was discovered two and a half years ago. It caused a global pandemic, resulting in millions of deaths and substantial damage to the worldwide economy. Currently, only a few vaccines and antiviral drugs are available to combat SARS-CoV-2. However, there has been an increase in virus-related research, including exploring new drugs and their repurposing. Since discovering penicillin, natural products, particularly those derived from microbes, have been viewed as an abundant source of lead compounds for drug discovery. These compounds treat bacterial, fungal, parasitic, and viral infections. This review incorporates evidence from the available research publications on isolated and identified natural products derived from microbes with anti-hepatitis, anti-herpes simplex, anti-HIV, anti-influenza, anti-respiratory syncytial virus, and anti-SARS-CoV-2 properties. About 131 compounds with in vitro antiviral activity and 1 compound with both in vitro and in vivo activity have been isolated from microorganisms, and the mechanism of action for some of these compounds has been described. Recent reports have shown that natural products produced by the microbes, such as aurasperone A, neochinulin A and B, and aspulvinone D, M, and R, have potent in vitro anti-SARS-CoV-2 activity, targeting the main protease (M^pro). In the near and distant future, these molecules could be used to develop antiviral drugs for treating infections and preventing the spread of disease. Full article

Several natural products recovered from a marine-derived Aspergillus niger were tested for their inhibitory activity against SARS CoV-2 in vitro. Aurasperone A (3) was found to inhibit SARS CoV-2 efficiently (IC₅₀ = 12.25 µM) with comparable activity with the positive control remdesivir (IC₅₀ = 10.11 µM). Aurasperone A exerted minimal cytotoxicity on Vero E6 cells (CC₅₀ = 32.36 mM, SI = 2641.5) and it was found to be much safer than remdesivir (CC₅₀ = 415.22 µM, SI = 41.07). To putatively highlight its molecular target, aurasperone A was subjected to molecular docking against several key-viral protein targets followed by a series of molecular dynamics-based in silico experiments that suggested M^pro to be its primary viral protein target. More potent anti-SARS CoV-2 M^pro inhibitors can be developed according to our findings presented in the present investigation. Full article

A chemical investigation into endozoic fungus Aspergillus niger L14 derived from the marine sponge of Reniera japonica collected off Xinghai Bay (China) resulted in the isolation of two dimeric naphtho-γ-pyrones, fonsecinone A (1) and isoaurasperone A (2). Through a combination of ECD spectra and X-ray diffraction analysis, the chiral axes of compounds 1 and 2 were unambiguously determined as R_α-configurations. Bioassay results indicated that these substances exhibited remarkably inhibitory effects on human pathogens Helicobacter pylori G27 and 159 with MIC values of ≤4 μg/mL, which are similar to those of the positive control, ampicillin sodium. To the best of our knowledge, this is the first report on absolute configuration of 1 and crystallographic data of 2, as well as their potent anti-H. pylori activities. Full article

Bioassay-guided fractionation of a cytotoxic extract derived from a solid potato dextrose agar (PDA) culture of Teratosphaeria sp. AK1128, a fungal endophyte of Equisetum arvense, afforded three new naphtho-γ-pyrone dimers, teratopyrones A–C (1–3), together with five known naphtho-γ-pyrones, aurasperone B (4), aurasperone C (5), aurasperone F (6), nigerasperone A (7), and fonsecin B (8), and two known diketopiperazines, asperazine (9) and isorugulosuvine (10). The structures of 1–3 were determined on the basis of their spectroscopic data. Cytotoxicity assay revealed that nigerasperone A (7) was moderately active against the cancer cell lines PC-3M (human metastatic prostate cancer), NCI-H460 (human non-small cell lung cancer), SF-268 (human CNS glioma), and MCF-7 (human breast cancer), with IC₅₀s ranging from 2.37 to 4.12 μM while other metabolites exhibited no cytotoxic activity up to a concentration of 5.0 μM. Full article

The chemical investigation of one symbiotic strain, Aspergillus fumigatus D, from the coastal plant Edgeworthia chrysantha Lindl led to the isolation of eight compounds (1–8), which were respectively identified as rubrofusarin B (1), alternariol 9-O-methyl ether (2), fonsecinone D (3), asperpyrone A (4), asperpyrone D (5), fonsecinone B (6), fonsecinone A (7), and aurasperone A (8) by a combination of spectroscopic methods (1D NMR and ESI-MS) as well as by comparison with the literature data. An antimicrobial assay showed that these aromatic polyketides exhibited no remarkable inhibitory effect on Escherichia coli, Staphyloccocus aureus and Candida albicans. The genomic feature of strain D was analyzed, as well as its biosynthetic gene clusters, using antibiotics and Secondary Metabolite Analysis Shell 5.1.2 (antiSMASH). Plausible biosynthetic pathways for dimeric naphtho-γ-pyrones 3–8 were first proposed in this work. A non-reducing polyketide synthase (PKS) gene D8.t287 responsible for the biosynthesis of these aromatic polyketides 1–8 was identified and characterized by target gene knockout experiment and UPLC-MS analysis. Full article

Seven naphtho-gamma-pyrones (NγPs), including asperpyrone E, aurasperone A, dianhydroaurasperone C, fonsecin, fonsecinone A, fonsecin B, and ustilaginoidin A, were isolated from Aspergillus tubingensis G131, a non-toxigenic strain. The radical scavenging activity of these NγPs was evaluated using ABTS assay. The Trolox equivalent antioxidant capacity on the seven isolated NγPs ranged from 2.4 to 14.6 μmol L⁻¹. The toxicity and ability of the NγPs to prevent H₂O₂-mediated cell death were evaluated using normal/not cancerous cells (CHO cells). This cell-based assay showed that NγPs: (1) Are not toxic or weakly toxic towards cells and (2) are able to protect cells from oxidant injuries with an IC₅₀ on H₂O₂-mediated cell death ranging from 2.25 to 1800 μmol mL⁻¹. Our data show that A. tubingensis G131 strain is able to produce various NγPs possessing strong antioxidant activities and low toxicities, making this strain a good candidate for antioxidant applications in food and cosmetic industries. Full article

Bis-naphtho-γ-pyrones (BNPs) are an important group of aromatic polyketides derived from fungi, and asperpyrone-type BNPs are produced primarily by Aspergillus species. The fungal strain Aspergillus niger SCSIO Jcsw6F30, isolated from a marine alga, Sargassum sp., and identified according to its morphological traits and the internal transcribed spacer (ITS) region sequence, was studied for BNPs secondary metabolisms. After HPLC/MS analysis of crude extract of the fermentation broth, 11 asperpyrone-type BNPs were obtained directly and quickly by chromatographic separation in the extract, and those isolated asperpyrone-type BNPs were structurally identified by NMR and MS analyses. All of the BNPs showed weak cytotoxicities against 10 human tumor cells (IC₅₀ > 30 μM). However, three of them, aurasperone F (3), aurasperone C (6) and asperpyrone A (8), exhibited obvious COX-2–inhibitory activities, with the IC₅₀ values being 11.1, 4.2, and 6.4 μM, respectively. This is the first time the COX-2–inhibitory activities of BNPs have been reported. Full article