Search Results (8)

Four new sorbicillinoids, named trichodermolide E (1), trichosorbicillin J (2), bisorbicillinolide B (3), and demethylsorbiquinol (5), together with eight known compounds (4, 6–12), were isolated from the cultures of the mangrove-derived fungus Trichoderma reesei BGRg-3. The structures of the new compounds were determined by analyzing their detailed spectroscopic data, while the absolute configurations were further determined through electronic circular dichroism calculations. Snatzke’s method was additionally used to determine the absolute configurations of the diol moiety in 1. In a bioassay, compounds 7 and 10 performed greater inhibitory activities on interleukin-6 and interleukin-1β than the positive control (dexamethasone) at the concentration of 25 μM. Meanwhile, compounds 5 and 6 showed potent effects with stronger inhibition than dexamethasone on IL-1β at the same concentration. Full article

Two new proton-deficient metabolites, tandocyclinones A and B (1 and 2), were discovered via the chemical profiling of the Streptomyces sp. strain TDH03, which was isolated from a marine sediment sample collected from the intertidal mudflat in Tando Port, the Republic of Korea. The structures of 1 and 2 were elucidated as new ether-bridged C-glycosyl benz[a]anthracenes by using a combination of spectroscopic analyses of ultraviolet (UV) and mass spectrometry (MS) data, along with nuclear magnetic resonance (NMR) spectra, which were acquired in tetrahydrofuran (THF)-d₈ selected after an extensive search for a solvent, resulting in mostly observable exchangeable protons in the ¹H NMR spectrum. Their configurations were successfully assigned by applying a J-based configuration analysis, rotating-frame Overhauser enhancement spectroscopy (ROESY) NMR correlations, chemical derivatization methods based on NMR (a modified version of Mosher’s method) and circular dichroism (CD) (Snatzke’s method using Mo₂(OAc)₄-induced CD), as well as quantum-mechanics-based computational methods, to calculate the electronic circular dichroism (ECD). Tandocyclinones A and B (1 and 2) were found to have weak antifungal activity against Trichophyton mentagrophytes IFM40996 with an MIC value of 128 μg/mL (244 and 265 μM for 1 and 2, respectively). A further biological evaluation revealed that tandocyclinone A (1) displayed inhibitory activity against Mycobacterium avium (MIC₅₀ = 40.8 μM) and antiproliferative activity against SNU638 and HCT116 cancer cells, with IC₅₀ values of 31.9 µM and 49.4 µM, respectively. Full article

Three new dibenzo-α-pyrone derivatives, alternolides A–C (1–3), and seven known congeners (4–10) were isolated from the marine-derived fungus of Alternaria alternata LW37 assisted by the one strain-many compounds (OSMAC) strategy. The structures of 1–3 were established by extensive spectroscopic analyses, and their absolute configurations were determined by modified Snatzke′s method and electronic circular dichroism (ECD) calculations. Compounds 6 and 7 showed good 1,1-diphenyl-2-picrylhydrazyl (DPPH) antioxidant scavenging activities with IC₅₀ values of 83.94 ± 4.14 and 23.60 ± 1.23 µM, respectively. Additionally, 2, 3 and 7 exhibited inhibitory effects against α-glucosidase with IC₅₀ values of 725.85 ± 4.75, 451.25 ± 6.95 and 6.27 ± 0.68 µM, respectively. The enzyme kinetics study indicated 2 and 3 were mixed-type inhibitors of α-glucosidase with K_i values of 347.0 and 108.5 µM, respectively. Furthermore, the interactions of 2, 3 and 7 with α-glucosidase were investigated by molecular docking. Full article

As part of ongoing systematic research into the discovery of bioactive secondary metabolites with novel structures from Korean wild mushrooms, we investigated secondary metabolites from a poisonous mushroom, Omphalotus japonicus (Kawam.) Kirchm. & O. K. Mill. belonging to the family Marasmiaceae, which causes nausea and vomiting after consumption. The methanolic extract of O. japonicus fruiting bodies was subjected to the fractionation by solvent partition, and the CH₂Cl₂ fraction was analyzed for the isolation of bioactive compounds, aided by an untargeted liquid chromatography mass spectrometry (LC–MS)-based analysis. Through chemical analysis, five fatty acid derivatives (1–5), including two new fatty acid derivatives, omphalotols A and B (1 and 2), were isolated from the CH₂Cl₂ fraction, and the chemical structures of the new compounds were determined using 1D and 2D nuclear magnetic resonance (NMR) spectroscopy and high resolution electrospray ionization mass spectrometry (HR-ESIMS), as well as fragmentation patterns in MS/MS data and chemical reactions followed by the application of Snatzke’s method and competing enantioselective acylation (CEA). In the anti-Helicobacter pylori activity test, compound 1 showed moderate antibacterial activity against H. pylori strain 51 with 27.4% inhibition, comparable to that of quercetin as a positive control. Specifically, compound 3 exhibited the most significant antibacterial activity against H. pylori strain 51, with MIC₅₀ and MIC₉₀ values of 9 and 20 μM, respectively, which is stronger inhibitory activity than that of another positive control, metronidazole (MIC₅₀ = 17 μM and MIC₉₀ = 46 μM). These findings suggested the experimental evidence that the compound 3, an α,β-unsaturated ketone derivative, could be used as a moiety in the development of novel antibiotics against H. pylori. Full article

A chemical investigation on the EtOAc extracts from two marine-derived fungal strains of Aspergillus unguis resulted in the isolation of three previously undescribed phenolic polyketides including unguidepside C (1), aspersidone B (3), and agonodepside C (12), and their 14 known congeners. The structures of the new compounds were determined based on detailed analysis and comparison of their spectroscopic data with literature values, as well as Snatzke’s method. The new compounds (1, 3, and 12) displayed a significant anti-Gram-positive bacterial activity, with MIC values ranging from 5.3 to 22.1 µM. Additionally, the isolated compounds (1–11 and 13–16) were evaluated for their cytotoxicity against a panel of tumor cell lines. Most of them (except for 9) displayed cytotoxicity against all the tested cell lines, with IC₅₀ values ranging from 2.5 to 46.9 µM. Full article

Ginkgo biloba (Ginkgoaceae), well-known as the oldest living plant species and often referred to as a “living fossil,” is a famous medicinal plant that has been used in multiple countries to improve numerous illnesses, including anxiety, dementia, peripheral artery disease, and eye problems. We conducted a phytochemical exploration of G. biloba fruit, commonly consumed as a functional food as part of an ongoing natural product chemical research for the discovery of bioactive phytochemicals with novel structures. The natural product chemical analysis of the methanol extract of G. biloba fruit using column chromatography and high-performance liquid chromatography separation under the guidance of a liquid chromatography–mass spectrometry (LC/MS)-based analysis identified six phenylpropanoid glycosides (1–6), including one new compound, ginkgopanoside (1). The structures of the isolated compounds were elucidated by nuclear magnetic resonance spectroscopic data and LC/MS analysis, and the absolute configuration of compound 1 was established by chemical reactions followed by the application of Snatzke’s method. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activities of the isolated compounds 1–6 and the aglycone 1a of 1 were evaluated, and we found that compounds 1–5 exhibited antioxidant activities with IC₅₀ values in the range 32.75–48.20 μM, while the aglycone 1a exhibited greater radical scavenging activity (IC₅₀ = 5.23 μM) comparable to that of ascorbic acid (IC₅₀ = 2.54 μM), a positive control, implying that the present of glucose may decrease the DPPH scavenging activity. These findings provide experimental information that the active phenylpropanoid glycosides could represent natural antioxidants for use in pharmaceuticals and functional foods. Full article

Microbial transformation of licochalcones B (1), C (2), D (3), and H (4) using the filamentous fungi Aspergillus niger and Mucor hiemalis was investigated. Fungal transformation of the licochalcones followed by chromatographic separations led to the isolation of ten new compounds 5–14, including one hydrogenated, three dihydroxylated, three expoxidized, and three glucosylated metabolites. Their structures were elucidated by combined analyses of UV, IR, MS, NMR, and CD spectroscopic data. Absolute configurations of the 2″,3″-diols in the three dihydroxylated metabolites were determined by ECD experiments according to the Snatzke’s method. The trans-cis isomerization was observed for the metabolites 7, 11, 13, and 14 as evidenced by the analysis of their ¹H-NMR spectra and HPLC chromatograms. This could be useful in better understanding of the trans-cis isomerization mechanism of retrochalcones. The fungal transformation described herein also provides an effective method to expand the structural diversity of retrochalcones for further biological studies. Full article

Marine-derived fungi of the genera Aspergillus could produce novel compounds with significant bioactivities. Among these fungi, the strain Aspergillus flavus is notorious for its mutagenic mycotoxins production. However, some minor components with certain toxicities from A. flavus have not been specifically surveyed and might have potent biological activities. Our investigation of the marine-derived fungus Aspergillus flavus CF13-11 cultured in solid medium led to the isolation of four C-6′/C-7′ epimeric drimane sesquiterpene esters, asperienes A–D (1–4). Their absolute configurations were assigned by electronic circular dichroism (ECD) and Snatzke’s methods. This is the first time that two pairs of C-6′/C-7′ epimeric drimane sesquiterpene esters have successfully been separated. Aperienes A–D (1–4) displayed potent bioactivities towards four cell lines with the IC₅₀ values ranging from 1.4 to 8.3 μM. Interestingly, compounds 1 and 4 exhibited lower toxicities than 2 and 3 toward normal GES-1 cells, indicating more potential for development as an antitumor agent in the future. Full article