Nitric oxide inhibitory daphnane diterpenoids as potential anti-neuroinflammatory agents for AD from the twigs of Trigonostemon thyrsoideus

The extensive pathology studies revealed that Alzheimer’s disease (AD) is closely related to neuroinflammation and anti-neuroinflammatory agents may be potentially useful for the treatment of AD. A continuous search for new nitric oxide (NO) inhibitory compounds as anti-neuroinflammatory agents for AD resulted in the isolation of four new (1−4) and eight known (5−12) daphnane diterpenoids from the twigs of Trigonostemon thyrsoideus. Their structures were elucidated on the basis of extensive nuclear magnetic resonance (NMR) spectroscopic data analysis and the time-dependent density functional theory (TDDFT) electronic circular dichroism (ECD) calculations. Compounds 1–4 represent new examples of daphnane diterpenoid orthoesters and 4 features a rare and complex macroring diterpenoid structure. The anti-neuroinflammatory effects were examined by inhibiting NO release in lipopolysaccharide (LPS)-induced murine microglial BV-2 cells. The possible mechanism of NO inhibition of some bioactive compounds was also investigated using molecular docking, which revealed the interactions of bioactive compounds with the inducible nitric oxide synthase (iNOS) protein.     

NO inhibitors function as potential anti-neuroinflammatory agents for AD from the flowers of Inula japonica

The extensive pathology studies revealed that Alzheimer’s disease (AD) is closely related to neuroinflammation and anti-neuroinflammatory agents may be potentially useful for the treatment of AD. Inula japonica is a member of the Asteraceae plant family and its flowers have been used as a healthy tea and a traditional Chinese medicine. Our continuous search for new nitric oxide (NO) inhibitory substances as anti-neuroinflammatory agents for AD resulted in the isolation of two new sesquiterpenes and ten known terpenes from the flowers of I. japonica. Their structures were established on the basis of extensive analysis of NMR and MS spectroscopic data, as well as calculated and experimental electronic circular dichroism (ECD) spectra. Among these isolates, compound 1 is a new sesquiterpene with a rare tricyclic fused skeleton, and 2 processes a 1,10-seco-eudesmane skeleton. The anti-neuroinflammatory effects were examined by inhibiting NO release in LPS-induced murine microglial BV-2 cells. The possible mechanism of NO inhibition was also investigated using molecular docking, which revealed the interactions of bioactive compounds with the iNOS protein. The present study disclosed that the flowers of I. japonica as a healthy tea are potentially useful for AD and related neuroinflammatory diseases.     

Nitric oxide inhibitory limonoids as potential anti-neuroinflammatory agents from Swietenia mahagoni

Recent studies have revealed that there is a close relationship between neuroinflammation and Alzheimer's disease (AD) and compounds with anti-neuroinflammatory effects are potentially useful for the treatment of AD. A phytochemical investigation to obtain new neuroinflammatory inhibitors resulted in the isolation of four new and three known limonoids from Swietenia mahagoni. The structures of these limonoids were established by NMR, MS, and electronic circular dichroism (ECD) data analysis. Compounds 1–3 feature complicated polycyclic caged structures of limonoid orthoester and represent new examples of phragmalin-type limonoids. All of the isolates showed anti-neuroinflammatory activities by inhibiting nitric oxide (NO) release in LPS-induced murine microglial BV-2 cells with compounds 1 and 3–6 having IC₅₀ values of 26.8, 26.1, 26.0, 37.1, and 16.5 μM, respectively. The possible mechanism of NO inhibition of some bioactive compounds was also investigated using molecular docking, which revealed the interactions of bioactive compounds with the inducible nitric oxide synthase (iNOS) protein.     

New bis-thioglycosyl-1,1′-disulfides from Nasturtium officinale R. Br. and their anti-neuroinflammatory effect

As a part of our continuing search for bioactive constituents from Brassicaceae family, three new bis-thioglycosides (1–3) were isolated from the 80% MeOH extract of Nasturtium officinale, together with 13 known compounds (4–16). The chemical structures of three new bis-thioglycosides (1–3) were elucidated using NMR techniques (¹H and ¹³C NMR, ¹H–¹H COSY, HSQC, and HMBC), HRESIMS, and a chemical method. All the compounds were evaluated for their inhibitory effects on nitric oxide (NO) levels in lipopolysaccharide (LPS)-stimulated murine microglia BV-2 cells. Among the isolates, compound 5 exhibited a strong inhibitory effect on NO production, and compounds 4 and 15 showed moderate inhibitory activities, suggesting the neuroprotective and anti-neuroinflammatory effects of bis-thioglycosides from N. officinale.     

Withanolides from Physalis peruviana showing nitric oxide inhibitory effects and affinities with iNOS

A phytochemical study to obtain new nitric oxide (NO) inhibitors resulted in the isolation of five new withanolides from the whole plants of Physalis peruviana. The structures were determined on the basis of extensive NMR spectroscopic data analysis as well as the time-dependent density functional theory (TDDFT) electronic circular dichroism (ECD) calculations. The NO inhibitory effects were examined by inhibiting NO release in lipopolysaccharide-stimulated murine microglial BV-2 cells. Molecular docking studies showed the strong interactions of bioactive compounds with the inducible nitric oxide synthase (iNOS) protein, revealing the potential mechanism of NO inhibition of bioactive compounds.     

Anti-neuroinflammatory constituents from Sinomenium acutum rhizomes

In our continuing search for bioactive constituents from Korean medicinal sources, an investigation of the Sinomenium acutum Rehder et Wilson rhizome afforded three new lignan derivatives (1⿿3) together with nine known compounds (4⿿12). The identification and structural elucidation of these new compounds were based on 1D and 2D-NMR (COSY, HMQC, HMBC and NOESY) and MS data. The absolute configurations were established based on the CD data. Nitric oxide production was evaluated in the BV-2 lipopolysaccharide-activated microglia cell line to investigate the anti-neuroinflammatory effects of the isolated compounds (1⿿12).     

Bioactive terpenoids from Euonymus verrucosus var. pauciflorus showing NO inhibitory activities

In our continuous search for new nitric oxide (NO) inhibitory compounds as potential anti-inflammatory agents or lead compounds for inflammatory diseases, the chemical constituents of Euonymus verrucosus var. pauciflorus were investigated, leading to the isolation of eleven terpenoids including six new diterpenoids, designated as euonymupenes A–F. The structures were elucidated on the basis of NMR and ECD data analysis. Euonymupenes A, C, and F feature rare labdane-type norditerpenoid skeletons. The NO inhibitory effects were evaluated and all of the isolates were found to inhibit lipopolysaccharide (LPS)-induced NO production in murine microglial BV-2 cells. Western blotting analysis indicated that the most active compound (5) can regulate iNOS (inducible nitric oxide synthase) expression. The further molecular docking studies exhibited the affinities of bioactive compounds with iNOS.     

Bioactive terpenoids from Silybum marianum and their suppression on NO release in LPS-induced BV-2 cells and interaction with iNOS

Three new (1–3) and one known (4) bioactive terpenoids were isolated from the seeds of Silybum marianum based on the investigation to get new NO inhibitors. Their structures were determined by extensive NMR (1D and 2D NMR) and MS spectroscopic data, and the absolute configurations were identified by experimental and calculated ECD spectra. The NO inhibitory activities in murine microglial BV-2 cells and interactions with iNOS protein by molecular docking were evaluated for all compounds. The results showed that these compounds had potent NO inhibitory effects.     

Phytochemicals with NO inhibitory effects and interactions with iNOS protein from Trigonostemon howii

A phytochemical investigation to obtain new NO inhibitors led to the isolation of nine compounds including one new guaiane-type sesquiterpenoid (1) and two new cleistanthane diterpenoids (2 and 3) from the stems of Trigonostemon howii. Their structures were elucidated on the basis of extensive 1D and 2D NMR spectroscopic data analysis, and the absolute configurations of new compounds 1–3 were established via comparison of experimental and calculated electronic circular dichroism (ECD) spectra. Compounds 2 and 3 possess a rare 3,4-seco-cleistanthane diterpenoid skeleton. All of the compounds showed inhibitory effects on lipopolysaccharide-induced NO production in murine microglial BV-2 cells. The further molecular docking studies indicated the strong interactions between some bioactive compounds with the iNOS protein, which revealed the possible and potential mechanism of NO inhibition of bioactive compounds.     

Two new phenolic compounds from the white flower of Impatiens balsamina

During the course of our continuing search for biologically active compounds from Korean medicinal sources, we investigated the white flower of Impatiens balsamina. From the MeOH extract, two new phenolic compounds (1–2) containing a nitrile group and eleven known phenolic compounds (3–13) were isolated. The chemical structures of new compounds (1–2) were determined through NMR, HRMS, and CD data. We tested the isolated compounds (1–13) for their cytotoxic activities by determining their inhibitory effects on human tumor cell lines (A549, SK-OV-3, SK-MEL-2, and HCT15) in vitro using the sulforhodamine B (SRB) assay. We also investigated their neuroprotective activity by determining their effects on nerve growth factor (NGF) secretion in C6 cells, and anti-neuroinflammatory activity by measuring nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated BV-2 cells.     

Neolignans from Piper kadsura and their anti-neuroinflammatory activity

Bioassay-guided column chromatographic separation of the methanolic extract of dried aerial parts of Piper kadsura (Piperaceae) led to the isolation of a new neolignan, piperkadsin C (1), together with eight known neolignans (2–9). The structures of the isolated compounds were elucidated by combined spectroscopic methods. The anti-neuroinflammatory activities of these compounds were evaluated by assessing nitric oxide (NO) production in LPS-activated BV-2 cells, a microglia cell line. Piperkadsin C (1) and futoquinol (2) potently inhibited NO production with an IC₅₀ value of 14.6 and 16.8 μM in microglia cells, respectively. Compounds 3, 4, 5, 8, and 9 also exhibited moderate inhibition of NO production in BV-2 cells.     

Anti-neuroinflammatory oleanane-type triterpenoids from the seeds of Quercus serrata Thunb.

Chinese oak (Quercus serrata Thunb.) is widely distributed throughout China and plays an important role as a building material. Its seeds (acorns) have served as a traditional herbal medicine in East Asia. Eighteen oleanane-type triterpenoids, including seven previously undescribed (1, 2, and 4–8) and eleven known triterpenoids, were isolated and identified from acorns. Their structures were elucidated using various spectroscopic and chemical methods. All isolated triterpenoids were screened for anti-neuroinflammatory effects by measuring their abilities to inhibit nitric oxide (NO) production in lipopolysaccharide (LPS)-induced BV-2 microglial cells, and most of the triterpenoids exhibited obvious anti-neuroinflammatory activity. Among them, Compounds 1 and 5 exhibited the strongest NO inhibitory activity, reduced the expression of inflammatory cytokines (iNOS, COX-2, and TNF-α), and blocked the nuclear translocation of NF-κB.     

Anti-neuroinflammatory effects of sesquiterpenoids isolated from Nardostachys jatamansi

Two new nardosinone-type sesquiterpenoids, namely kanshone J (1) and kanshone K (2) along with seven known terpenoids (3–9) were isolated from the rhizomes and roots of Nardostachys jatamansi DC (Valerianaceae). The structures of these compounds were determined mainly by analysis of 1D-, 2D-NMR and MS data. In addition, the absolute configuration of compound 1 was assigned by application of the modified Mosher’s method. In an initial assay to evaluate their anti-neuroinflammatory effects, compounds 1–5 and 9 exhibited dose-dependent inhibitory effects on lipopolysaccharide (LPS)-induced nitric oxide (NO) production in BV2 cells, with IC₅₀ values ranging from 2.43 to 46.54?μM. Particularly, desoxo-narchinol A (3) and narchinol B (4) significantly inhibited LPS-induced NO overproduction in BV2 cells with IC₅₀ values of 3.48?±?0.47 and 2.43?±?0.23?μM, respectively. Furthermore, compounds 3 and 4 exhibited anti-neuroinflammatory effects by inhibiting the production of pro-inflammatory mediators, including prostaglandin E₂ (PGE₂), inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) proteins, and pro-inflammatory cytokines, such as interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF)-α, in LPS-stimulated BV2 and primary microglial cells.     

Anti-neuroinflammatory of Chloroform Extract of Panax ginseng Root Culture on Lipopolysaccharide-stimulated BV2 Microglia Cells

Background:It is believed that activation of microglia in the central nervous system upon detection of stimulus like lipopolysaccharides provokes neuroinflammation via the production of pro-inflammatory mediators and cytokines. The cytoprotective and anti-inflammatory properties of various folk medicine has been gaining attention as a strategy to combat various disease. This study aimed to assess the anti-neuroinflammatory properties of chloroform extract of in vitro Panax ginseng root culture based on nitric oxide and cytokines production.Methods:The study was initiated with the determination of maximum non-toxic dose (MNTD) of P. ginseng root culture chloroform extract using the MTT assay. The lipopolysaccharides-stimulated BV2 microglia cells were treated with MNTD and ½MNTD of the extract and its anti-neuroinflammatory properties were assessed by measuring the production of nitric oxide (NO) via Griess assay, as well as TNF-α, IL-6 and IL-10 using Quantikine ELISA.Results:It was found that the MNTD and ½MNTD of the extract did not play a significant role in the production of pro-inflammatory cytokines such as NO, TNF-α and IL-6. However, the MNTD and ½MNTD of chloroform extract significantly increased the anti-inflammatory IL-10 compared to the untreated cells.Conclusion:With this, the chloroform extract of P. ginseng root culture potentially exerts anti-neuroinflammatory properties.Key Words: Anti-inflammatory cytokines, Ginsenosides, Microglia cells, Neuroinflammation, Pro-inflammatory cytokines     

Anti-neuroinflammatory Effect of Emodin in LPS-Stimulated Microglia: Involvement of AMPK/Nrf2 Activation

AMPK/Nrf2 signaling regulates multiple antioxidative factors and exerts neuroprotective effects. Emodin is one of the main bioactive components extracted from Polygonum multiflorum, a plant possessing important activities for human health and for treating a variety of diseases. This study examined whether emodin can activate AMPK/Nrf2 signaling and induce the expression of genes targeted by this pathway. In addition, the anti-neuroinflammatory properties of emodin in lipopolysaccharide (LPS)-stimulated microglia were examined. In microglia, the emodin treatment increased the levels of LKB1, CaMKII, and AMPK phosphorylation. Emodin increased the translocation and transactivity of Nrf2 and enhanced the levels of HO-1 and NQO1. In addition, the emodin-mediated expression of HO-1 and NQO1 was attenuated completely by an AMPK inhibitor (compound C). Moreover, emodin decreased dramatically the LPS-induced production of NO and PGE₂ as well as the protein expression and promoter activity of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). In addition, emodin effectively inhibited the production of pro-inflammatory cytokines, TNF-α and IL-6, and reduced the level of IκBα phosphorylation, leading to the suppression of the nuclear translocation, phosphorylation, and transactivity of NF-κB. Emodin also suppressed the LPS-stimulated activation of STATs, JNK, and p38 MAPK. The anti-inflammatory effects of emodin were reversed by transfection with Nrf-2 and HO-1 siRNA and by a co-treatment with an AMPK inhibitor. These results suggest that emodin isolated from P. multiflorum can be used as a natural anti-neuroinflammatory agent that exerts its effects by inducing HO-1 and NQO1 via AMPK/Nrf2 signaling in microglia.     

Natural NO inhibitors from the leaves of Callicarpa kwangtungensis: Structures,activities, and interactions with iNOS

A phytochemical investigation to obtain new NO inhibitors resulted in the isolation of a new diterpenoid with a rare 9,10-seco-abietane skeleton (1) and twelve known terpenoids (2–13) from Callicarpa kwangtungensis. Their structures were elucidated on the basis of extensive 1D and 2D NMR spectroscopic data analyses, and the absolute configuration of compound 1 was established by comparison of the calculated and experimental electronic circular dichroism (ECD) spectra. The inhibitory activities on lipopolysaccharide-induced NO production in murine microglial BV-2 cells of these terpenoids were evaluated, and all of the compounds showed inhibitory effects. The following molecular docking studies showed interactions of the bioactive compounds with the iNOS protein.     

Steroidal constituents from the leaves of Hosta longipes and their inhibitory effects on nitric oxide production

Hosta longipes (FR. et SAV.) MATSUMURA (Liliaceae) is an edible vegetable in Korea. This study was conducted with the aim of evaluating the potential of H. longipes as a functional food for the treatment of neurodegenerative diseases such as Alzheimer’s disease and Parkinson’s disease. In this respect, the study resulted in the identification of three new steroidal compounds, longipenane (1), longipenane 26-O-β-d-glucopyranoside (2) and neogitogenin 3-O-α-l-rhamnopyranosyl-(1→2)-O-[β-d-glucopyranosyl-(1→4)]-β-d-galactopyranoside (3), along with two known steroidal saponins (4 and 5). The identification and structural elucidation of these compounds were based on 1D and 2D NMR measurements, high-resolution FAB mass spectroscopy (HR-FAB-MS), and chemical methods. A proinflammatory mediator, nitric oxide (NO), in murine microglial BV-2 cells was used to assess the anti-neuroinflammatory effect of the isolated compounds from H. longipes. Among them, compounds 4 and 5 showed strong inhibitory effects on NO production without high cell toxicity in lipopolysaccharide-activated BV-2 cells (IC₅₀ = 17.66 and 13.16 μM, respectively).     

Chemical constituents of the root bark of Ulmus davidiana var. japonica and their potential biological activities

The root bark of Ulmus davidiana var. japonica (Ulmaceae), commonly known as yugeunpi, has been used as a traditional Korean medicine for the treatment of gastroenteric and inflammatory disorders. As part of continuing projects to discover bioactive natural products from traditional medicinal plants with pharmacological potential, phytochemical investigation of the root bark of this plant was carried out. This led to the successful isolation of a new chromane derivative (1) and 22 known compounds: catechin derivatives (2–5), megastigmane glycoside (6), dihydrochalcone glycosides (7 and 8), flavanone glycosides (9 and 10), coumarins (11 and 12), lignan derivatives (13–17), and phenolic compounds (18–23). The structure of the new compound (1) was determined with 1D and 2D NMR spectroscopy and HR-ESIMS, and its absolute configurations were achieved by chemical reactions and the gauge-including atomic orbital (GIAO) NMR chemical shifts calculations. All the isolated compounds were evaluated for their potential biological activities including neuro-protective, anti-neuroinflammatory, and anti-Helicobacter pylori activities. Among the isolates, compounds 1, 8, and 20 displayed stronger potency by causing a greater increase in the production and the activity of nerve growth factor (NGF) in C6 glioma cells (147.04 ± 4.87, 206.27 ± 6.70, and 143.70 ± 0.88%, respectively), whereas compounds 11, 14, and 19 inhibited nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated murine microglial cells (IC₅₀ of 18.72, 12.31, and, 21.40 µM, respectively). In addition, compounds 1, 11, 18, and 20 showed anti-H. pylori activity with MIC values of 25 or 50 µM against two strains of H. pylori 51 and 43504. These findings provide scientific evidence that supports the traditional usage of U. davidiana var. japonica root bark in the treatment of gastroenteric and inflammatory disorders.     

Acutissimalignan B from traditional herbal medicine Daphne kiusiana var. atrocaulis (Rehd.) F. Maekawa inhibits neuroinflammation via NF-κB Signaling pathway

Background: Emerging evidence indicates the important role of herbal medicine for neuroinflammation, which is closely associated with neurodegenerative diseases.Objective: To clarify the characteristics and primary mechanisms of action of the traditional herbal medicine Daphne kiusiana var. atrocaulis (Rehd.) F. Maekawa in neuroinflammation by phytochemistry and bioassays using both in vitro and in vivo assays.Methods: The chemical composition of D. kiusiana var. atrocaulis was clarified using multiple chromatography technologies and spectroscopic analysis. The anti-neuroinflammatory effects of the identified components were evaluated in LPS-induced BV-2 cells by monitoring the production of nitric oxide. C57BL/6 mice were used to construct a neuroinflammatory model by injecting LPS into the lateral ventricle of the brain. The most promising component was evaluated in vivo by measuring the number of Iba-1 cells and expression of inflammatory factors. Furthermore, the anti-neuroinflammatory mechanism involved in the activation of the NF-κB pathway was investigated using western blot and immunofluorescence.Results: Thirty-two constituents (1–32), including five new compounds, were successfully identified from D. kiusiana var. atrocaulis. Compounds 3, 5, 12–15, and 20 (IC₅₀ values from 5.41 to 57.27 μM) could considerably inhibit the LPS-induced production of NO in BV-2 cells, displaying stronger anti-neuroinflammatory activities than that of minocycline (IC₅₀ = 67.08 μM). The concentration of the most potential compound 13 (IC₅₀ 5.41 μM) was 5.4% of the ethyl acetate fraction. Acutissimalignan B (13) could reduce the mRNA expression of iNOs, TNF-α, IL-1β, and IL-6, inhibit the phosphorylation of IκBα, and inhibit the nuclear translocation of NK-κB p65 in BV-2 cells induced by LPS. Moreover, in the LPS-induced mouse model, compound 13 was found to exert anti-neuroinflammatory activity by attenuating the activation of microglia in the cortex and hippocampus, repressing the phosphorylation of IκBα, inhibiting the nuclear translocation of NK-κB p65, and decreasing the mRNA expression of iNOs, TNF-α, IL-1β, and IL-6 in the cortex.Conclusion: We found that D. kiusiana var. atrocaulis had an inhibitory activity on neuroinflammation. In addition, the main active component (-)-acutissimalignan B (13) showed anti-neuroinflammatory effects in both in vivo and in vitro assays. Its mechanism of action may be associated with the inhibition of the NF-κB signaling pathway. Our current findings provide new information on D. kiusiana var. atrocaulis in the treatment of neuroinflammation.     

Anti-neuroinflammatory diarylheptanoids from the rhizomes of Dioscorea nipponica

In a continuing search for bioactive constituents from Dioscoreaceae medicinal plants, two new cyclic diarylheptanoids, diosniponol A (1) and B (2), together with 10 known compounds (3–12) were isolated from the rhizomes of Dioscorea nipponica. The structures of these new compounds were determined by spectroscopic analyses, including extensive two-dimensional nuclear magnetic resonance, high-resolution mass spectrometry, and optical rotation. All isolated compounds 1–12 were evaluated for their effects on nitric oxide (NO) production in murine microglia cell line BV-2. Compounds 8 and 11 showed potent inhibitory activities on NO production (IC₅₀ 13.36 and 14.36 μM, respectively) without cell toxicity in lipopolysaccharide-activated BV-2 cells.