New guaiane sesquiterpenes from Artemisia rupestris and their inhibitory effects on nitric oxide production

Small molecule α-methylene-γ-butyrolactone, an evolutionarily conserved moiety in sesquiterpene lactones, ameliorates arthritic phenotype via interference DNA binding activity of NF-κB

Rheumatoid arthritis (RA) is an inflammatory disease accompanied by abnormal synovial microenvironment (SM). Sesquiterpene lactones (SLs) are the main anti-inflammatory ingredients of many traditional herbs utilized in RA treatment. α-Methylene-γ-butyrolactone (α-M-γ-B) is a core moiety that widely exists in natural SLs. This study was designed to investigate the anti-arthritic potential of α-M-γ-B as an independent small molecule in vitro and in vivo. α-M-γ-B exhibited stronger electrophilicity and anti-inflammatory effects than the other six analogs. α-M-γ-B inhibited the production of pro-inflammatory mediators via repolarizing M1 macrophages into M2 macrophages. The transcriptome sequencing suggested that α-M-γ-B regulated the immune system pathway. Consistently, α-M-γ-B attenuated collagen type II-induced arthritic (CIA) phenotype, restored the balance of Tregs-macrophages and remodeled SM via repolarizing the synovial-associated macrophages in CIA mice. Mechanistically, although α-M-γ-B did not prevent the trans-nucleus of NF-κB it interfered with the DNA binding activity of NF-κB via direct interaction with the sulfhydryl in cysteine residue of NF-κB p65, which blocked the activation of NF-κB. Inhibition of NF-κB reduced the M1 polarization of macrophage and suppressed the synovial hyperplasia and angiogenesis. α-M-γ-B failed to ameliorate CIA in the presence of N-acetylcysteine or when the mice were subjected to the macrophage-specific deficiency of Rela. In conclusion, α-M-γ-B significantly attenuated the CIA phenotype by directly targeting NF-κB p65 and inhibiting its DNA binding ability. These results suggest that α-M-γ-B has the potential to serve as an alternative candidate for treating RA. The greater electrophilicity of α-M-γ-B, the basis for triggering strong anti-inflammatory activity, accounts for the reason why α-M-γ-B is evolutionarily conserved in the SLs by medical plants.

Acetylenic spiroketal enol ethers from Artemisia rupestris and their synergistic antibacterial effects on methicillin-resistant Staphylococcus aureus

Synergistic bioassay-guided isolation of the extracts of Artemisia rupestris L, which belongs to the family Asteraceae, afforded two acetylenic spiroketal enol ethers, namely rupesdiynes A (1) and B (2). Their structures were determined based on spectroscopic analysis and experimental and calculated ECD investigations. The two compounds exhibited synergistic activity and were able to reduce the minimum inhibitory concentration (MIC) of oxacillin four-fold, with a fractional inhibitory concentration index (FICI) of 0.5 in combination with oxacillin against the oxacillin-resistant EMRSA-16. Biofilm formation inhibitory and Ethidium bromide (EtBr) efflux assay were further employed to verify the possible mechanism of the synergistic antibacterial effect. Additionally, molecular docking studies were conducted to investigate the binding affinities of the two compounds with penicillin-binding protein 2a (PBP2a) of EMRSA-16. Taken together, rupesdiynes A (1) and rupesdiyne B (2) showed moderate synergistic activity against EMRSA-16 with oxacillin via inhibiting biofilm formation and efflux pump activity, respectively.

Anti-inflammatory activity of caffeic acid derivatives from Ilex rotunda

Ilex rotunda Thunb. has been used in traditional medicine for treating rheumatoid arthritis, relieving pain and indigestion. In the present study, we isolated three new caffeic acid benzyl ester (CABE) analogs (1-3) along with eight known compounds (4-11) from the extract of I. rotunda. The absolute configuration of α-hydoxycarboxylic acid in 1 was assigned with the phenylglycine methyl ester (PGME) method. We further investigated their anti-inflammatory activities in lipopolysaccharide (LPS)-induced macrophages (RAW 264.7) cells. Among them, compounds 2-4, 7, 8, 10, and 11 suppressed the production of nitric oxide (NO), pro-inflammatory mediators. It was additionally confirmed that the anti-inflammatory effect of active compound 2 was through significant suppression of cytokines, including interleukin (IL)-6, IL-1β, tumor necrosis factor (TNF)-α, and IL-8 in LPS-stimulated RAW 264.7 cells and colon epithelial (HT-29) cells. Western blot analysis revealed that compound 2 decreased the LPS-induced expression of inducible nitric oxide synthase (iNOS), cyclooxygenase (COX-2), and phosphorylated extracellular regulated kinase (pERK)1/2. The following molecular docking simulations showed the significant interactions of compound 2 with the iNOS protein. These results suggested that the compound 2 can be used as potential candidate for treating inflammatory diseases such as inflammatory bowel disease (IBD).

New meroterpenoids and C-methylated flavonoid isolated from Baeckea frutescens

Phytochemical investigation of the aerial parts of Baeckea frutescens resulted in the isolation of three new mono- or sesquiterpene-based meroterpenoids, frutescones S-U (1-3), and one pair of new (±)-5,7-dihydroxy-8-isobutyryl-6-methyldihydroflavonol (4). Their structures and absolute configurations were established by HR-ESI-MS, 1D and 2D NMR, and quantum chemical ECD calculation. Compound 1 exhibited inhibitory effect on NO production in LPS-activated RAW 264.7 macrophages with an IC₅₀ value being 0.81 μmol·L^-1.

Chemical Components and Hepatoprotective Mechanism of Xwak Granule in Mice Treated with Acute Alcohol

Objective

To evaluate the hepatoprotective mechanism of Xwak granule (Xwak) in treatment of mice with alcoholic liver injury via activating ERK/NF-κB and Nrf/HO-1 signaling pathways.

Methods

The chemical composition of Xwak was tested by liquid chromatography coupled with mass spectrometry (LC-MS). Herein, 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging assay and 2,2-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid (ABTS) radical tests were performed in vitro. The hepatoprotective effect of Xwak was assessed at different concentrations (1.5, 3, and 6 g/kg) in a mouse model of alcoholic liver injury.

Results

Totally, 48 compounds, including 16 flavonoids, 8 tannins, 9 chlorogenic acids, and 15 other compounds, were identified from Xwak. Xwak showed to have a satisfactory antioxidant activity in vitro. In a group of Xwak-treated mice, the serum levels of alanine transaminase (ALT), aspartate transaminase (AST), and alkaline phosphatase (ALP) were decreased compared with a group of the mouse model of alcoholic liver injury. In addition, the levels of antioxidant enzymes, such as glutathione peroxidase (GSH-PX), total superoxide dismutase (T-SOD), and catalase (CAT), were noticeably increased and the levels of malondialdehyde (MDA), tumor necrosis factor-α (TNF-α), transforming growth factor-β (TGF-β), and interleukin-6 (IL-6) were markedly reduced in the liver of mice. The state of oxidative stress in the mouse model of alcoholic liver injury was improved after treatment with Xwak. The improvement of inflammation-mediated disruption may conducive to the Xwak activity in the control of liver injury. The signals of p-ERK1/2, p-NF-κB, COX-2, iNOS, CYP2E1, Nrf, and HO-1 were significantly induced in the liver of mice after treatment with Xwak.

Conclusions

The abovementioned findings indicated that the hepatoprotective mechanism of Xwak could be achieved by activating ERK/NF-κB and Nrf/HO-1 signaling pathways to alleviate oxidative stress and inflammatory.

Chemical constituents from Artemisia rupestris and their neuraminidase inhibitory activity

Two new thiophene derivatives (1 and 2), a new sesquiterpene (3), and 15 known compounds (4-18) were isolated from the whole plants of Artemisia rupestris. The new compounds (1-3) were elucidated by extensive spectroscopic techniques including 1 D (¹H and ¹³C) and 2 D NMR experiments (COSY, HSQC, HMBC and NOESY), and HR-ESI-MS. Most of the isolates (1-6, 8, 10-18) exhibited the neuraminidase inhibitory activity with IC₅₀ values ranging from 74.07-986.54 μM by a fluorescence-based assay. Two known flavonoids (chrysosplenetin B and luteolin) showed a comparable activity to oseltamivir acid on neuraminidase inhibition.

Flavonoids from Artemisia rupestris and their synergistic antibacterial effects on drug-resistant Staphylococcus aureus

This study seeks to discover flavonoids from a traditional Chinese herb, Artemisia rupestris L., with synergistic antibacterial effects against multidrug-resistant Staphylococcus aureus. Five flavonoids, artemetin (1), chrysosplenetin (2), pachypodol (3), penduletin (4) and chrysoeriol (5) were obtained by various column chromatographic methods. Their chemical structures were determined on the basis of comprehensive spectroscopic analysis and comparison with literature data. Three of the compounds (2, 4 and 5) exhibited synergistic activity when combined with norfloxacin against SA1199B, an effluxing fluoroquinolone-resistant strain. The fractional inhibitory concentration indices (FICIs) of 2, 4 and 5 in combination with norfloxacin were 0.375, 0.079 and 0.266 respectively, suggesting synergy. Compound 5 also showed synergistic effects against EMRSA-15 and EMRSA-16 when combined with ciprofloxacin and oxacillin exhibiting FICIs of 0.024 and 0.375 respectively. Real time ethidium bromide (EtBr) efflux assay, qRT-PCR and molecular docking were employed to explore the mechanisms of the synergistic effects.

Two new chromene derivatives from Artemisia songarica

Two new chromene derivatives, songaricachromenes A (1) and B (2), were isolated from Artemisia songarica, along with 10 known compounds (3-12). The structures and stereochemistry of the new compounds were elucidated by analyses of the NMR, MS, and electronic circular dichroism (ECD) data. All the isolates (1-12) were evaluated for their NO inhibitory effects on LPS-stimulated BV-2 microglial cells.

Nitric Oxide Inhibitory Dimeric Sesquiterpenoids from Artemisia rupestris

Twelve new dimeric sesquiterpenoids (1-12) were isolated from the dried whole plants of Artemisia rupestris. Their structures were determined using MS and NMR data, and the absolute configurations were elucidated on the basis of experimental and calculated ECD spectra. Compounds 1-9 are presumably formed via biocatalyzed [2+2] or [4+2] cycloaddition reactions. Stereoselectivity of the [4+2] Diels-Alder reaction dictated the formation of endo-products. The dimeric sesquiterpenoids exhibited moderate inhibition on NO production stimulated by lipopolysaccharide in BV-2 microglial cells, with IC50 values in the range 17.0-71.8 μM.

New sesquiterpene and thiophene derivatives from Artemisia rupestris

A new sesquiterpene, rupestrisin A (1), and three new thiophene derivatives, rupestrienes A-C (2-4), were isolated from Artemisia rupestris. Their structures were determined by analyses of MS and NMR spectroscopic data, and the absolute configuration of 1 was established by calculated ECD spectra using time-dependent density functional theory. In in vitro bioassays, compounds 1-4 showed inhibitory effects on LPS-stimulated NO production in BV-2 microglial cells with IC50 values of 24.3, 20.3, 8.5, and 5.3 μM, respectively.