Toxic aromatic compounds from fruits of Narthecium ossifragum L

A novel bicyclic lactone and other polyphenols from the commercially important vegetable Anthriscus cerefolium

Garden chervil, Anthriscus cerefolium (L.) Hoffm. is an important herb commonly applied in Norwegian large-scale commercial kitchens. This species is a highly enriched source of phenolics, containing 1260 mg gallic acid equivalents (GAE) 100^-1 g DM, however, the individual phenolic compounds have been scarcely characterized. Here we report on the qualitative and quantitative content of phenolics in garden chervil. The structure of the main phenolic compound was elucidated to be the previously undescribed compound 1,3-dicaffeoyl-5-malonyl-δ-quinide (1) by means of 1D- and 2D NMR and high-resolution mass spectrometry. The known flavones apigenin 7-O-β-(2″-apiofuranosylglucopyranoside) (= apiin) (2), apigenin 7-(2″-apiosyl-6″-malonylglucoside) (3) and luteolin 7-glucoside (4) were also identified. Compound 3 is reported for the first time from this plant species. The main phenolic compound, 1,3-dicaffeoyl-5-malonyl-δ-quinide, exhibited moderate cytotoxicity towards acute monocytic leukaemia cells (MOLM-13) and rat kidney epithelial cells (NRK) with EC₅₀ between 400 and 600 µM.

New Polyketides With Anti-Inflammatory Activity From the Fungus Aspergillus rugulosa

Two new polyketide compounds, asperulosins A and B (1–2), and one new prenylated small molecule, asperulosin C (3), along with nine known compounds (4–12), were isolated and identified from a fungus Aspergillus rugulosa. Their structures were extensively elucidated via HRESIMS, 1D, and 2D NMR analysis. The absolute configurations of the new compounds were determined by the comparison of their electronic circular dichroism (ECD), calculated ECD spectra, and the detailed discussion with those in previous reports. Structurally, compounds 1 and 2 belonged to the polyketide family and were from different origins. Compound 2 was constructed by five continuous quaternary carbon atoms, which occur rarely in natural products. All of the isolates were evaluated for anti-inflammatory activity against the production of nitric oxide (NO) in lipopolysaccharide (LPS)-induced RAW264.7 cells. Among those, compounds 1 and 5 showed a significant inhibitory effect on NO production with IC₅₀ values of 1.49 ± 0.31 and 3.41 ± 0.85 μM, respectively. Additionally, compounds 1 and 5 markedly increased the secretion of anti-inflammatory cytokine IL10 while suppressing the secretion of pro-inflammatory cytokines IL6, TNF-α, IFN-γ, MCP-1, and IL12. Besides, 1 and 5 inhibited the transcription level of pro-inflammatory macrophage markers IL6, IL1β, and TNF-α while remarkably elevating the anti-inflammatory factor IL10 and M2 macrophage markers ARG1 and CD206. Moreover, 1 and 5 restrained the expression and nuclear translocation of NF-κB, as well as its downstream signaling proteins COX-2 and iNOS. All these results suggest that 1 and 5 have potential as anti-inflammatory agents, with better or comparable activities than those of the positive control, dexamethasone.

Anti-Inflammatory, Antiallergic, and COVID-19 Main Protease (Mpro) Inhibitory Activities of Butenolides from a Marine-Derived Fungus Aspergillus terreus

In December 2020, the U.K. authorities reported to the World Health Organization (WHO) that a new COVID-19 variant, considered to be a variant under investigation from December 2020 (VUI-202012/01), was identified through viral genomic sequencing. Although several other mutants were previously reported, VUI-202012/01 proved to be about 70% more transmissible. Hence, the usefulness and effectiveness of the newly U.S. Food and Drug Administration (FDA)-approved COVID-19 vaccines against these new variants are doubtfully questioned. As a result of these unexpected mutants from COVID-19 and due to lack of time, much research interest is directed toward assessing secondary metabolites as potential candidates for developing lead pharmaceuticals. In this study, a marine-derived fungus Aspergillus terreus was investigated, affording two butenolide derivatives, butyrolactones I (1) and III (2), a meroterpenoid, terretonin (3), and 4-hydroxy-3-(3-methylbut-2-enyl)benzaldehyde (4). Chemical structures were unambiguously determined based on mass spectrometry and extensive 1D/2D NMR analyses experiments. Compounds (1-4) were assessed for their in vitro anti-inflammatory, antiallergic, and in silico COVID-19 main protease (Mpro) and elastase inhibitory activities. Among the tested compounds, only 1 revealed significant activities comparable to or even more potent than respective standard drugs, which makes butyrolactone I (1) a potential lead entity for developing a new remedy to treat and/or control the currently devastating and deadly effects of COVID-19 pandemic and elastase-related inflammatory complications.

Cytotoxic saponins and other natural products from flowering tops of Narthecium ossifragum L

For more than four centuries, the intake of Narthecium ossifragum has been associated with poisoning in domesticated animals. Saponins occurring in flowering tops of the plant are considered to cause kidney damage in calves. At present, there are more than 30 papers on the saponins of N. ossifragum in the literature, although the structures of these compounds have hitherto not been determined. Here, we identify the saponins of N. ossifragum as sarsasapogenin, sarsasapogenin-3-O-β-galactopyranoside, sarsasapogenin-3-O-(2'-O-β-glucopyranosyl-β-galactopyranoside) and sarsasapogenin-3-O-(2'-O-β-glucopyranosyl-3'-O-α-arabinopyranosyl-β-galactopyranoside). Moreover, six aromatic natural products were isolated and characterized from the methanolic extract from flowers of N. ossifragum. Five of these aromatic compounds, chrysoeriol 6-C-β-arabinofuranoside-8-C-β-glucopyranoside, chrysoeriol 6-C-β-arabinopyranosyl-8-C-β-glucopyranoside, chrysoeriol 6-C-β-xylopyranosyl-8-C-β-galactopyranoside, chrysoeriol 6-C-β-galactopyranosyl-8-C-β-glucopyranoside and chrysoeriol 6-C-β-glucopyranosyl-8-C-β-galactopyranoside are undescribed. All compounds were tested for cytotoxicity in mammalian cell lines derived from the heart, kidney, and haematological tissues. The saponins exhibited cytotoxicity in the micromolar range, with proportionally increasing cytotoxicity with increasing number of glycosyl substituents. The most potent compound was the main saponin sarsasapogenin-3-O-(2'-O-β-glucopyranosyl-3'-O-α-arabinopyranosyl-β-galactopyranoside), which produced cell death at concentrations below 3-4 μM in all three cell lines tested. This indicates that the saponins are the toxicants mainly responsible for kidney damage observed in cattle after ingestion of N. ossifragum. Our findings also pave the way for analysis of individual compounds isolated during the biopsies of intoxicated animals.

Polycyclic polyprenylated acylphloroglucinol and phenolic metabolites from the aerial parts of Hypericum elatoides and their neuroprotective and anti-neuroinflammatory activities

A phytochemical study on the aerial parts of Hypericum elatoides led to the isolation of a previously undescribed polycyclic polyprenylated acylphloroglucinol derivative, hyperelatone A, seven previously undescribed phenolic metabolites, hyperelatones B-H, along with ten known analogues. The structures of hyperelatones A-H were elucidated by 1D and 2D NMR spectroscopy, HRESIMS experiment, single-crystal X-ray diffraction and comparison of experimental and calculated ECD spectra, as well as chemical derivatization. All compounds were evaluated for their neuroprotective activity against hydrogen peroxide (H₂O₂)-induced cell injury in rat pheochromocytoma PC-12 cells and inhibitory effects on lipopolysaccharide (LPS)-induced nitric oxide (NO) production in BV-2 microglial cells. Hyperelatones B-D and H, cinchonain Ib, and tenuiside A showed noticeable neuroprotection at concentrations of 1.0-100.0 μM. Hyperelatones D, G, and H, (-)-epicatechin, tenuiside A, and (Z)-3-hexenyl-β-D-glucopyranoside exhibited significant anti-neuroinflammatory activity with IC₅₀ values ranging from 0.75 ± 0.02 to 5.83 ± 0.23 μM.