ent-Strobane and ent-Pimarane Diterpenoids from Siegesbeckia pubescens

Development of a Synthetic Platform for Ent-Pimaranes Reveals their Potential as Novel Non-Redox Active Ferroptosis Inhibitors

We present a comprehensive account on the evolution of a synthetic platform for a subfamily of ent-pimaranes. For the most complex member, norflickinflimiod C, five distinct strategies relying on either cationic or radical polyene cyclizations to construct the requisite tricyclic carbon scaffold were explored. Insights from early and late stage oxidative and reductive dearomatization studies ultimately led to a mild, rhodium-catalyzed arene hydrogenation for the final synthetic route. A Sharpless asymmetric dihydroxylation was found to be suitable to render the platform enantioselective and diversification of a late-stage key intermediate culminated in the total synthesis of eight ent-pimaranes in 11-16 steps. These compounds were found to inhibit the formation of pro-inflammatory leukotrienes and other 5-lipoxygenase products. Notably, three ent-pimaranes exhibited low micromolar, non-redox active ferroptosis inhibition with remarkable structural specificity.

A review on medical plants Siegesbeckia based on diterpenoids and sesquiterpenoids: phytochemistry, pharmacology and clinical applications

Natural products, owing to their chemical diversity, biological activity, and historical success, continue to be a precious source of lead compounds and potential candidates for drug discovery. Siegesbeckia, in particular, presents a promising avenue for drug discovery due to its long history of usage in traditional Chinese medicine and its well-established clinical applications. Diterpenoids and sesquiterpenoids, the characteristic metabolites of Siegesbeckia, have consistently attracted considerable attention in related scientific research because of their diverse structures and extensive range of bioactivities, including anti-inflammatory and anti-cancer properties. Herein, we provide an overview of the phytochemistry, biosynthesis, pharmacological action, as well as clinical applications of Siegesbeckia. This paper will provide a valuable reference for advancing further research and development of Siegesbeckia.

Pimarane diterpenoids: sources, structures and biological activities

The pimarane diterpenoids, a widespread class of secondary metabolites, have been found in several dozens of plant species from various families and in organisms from other taxonomic groups. According to the different chiral centres, pimarane diterpenes can be divided into four types, including pimarane, isopimarane, ent-pimarane, and ent-isopimarane. Meanwhile, these compounds possessed many pharmacological activities, such as cytotoxic, anti-inflammatory, and antibacterial activities. Due to their notable structure and biological activities these substances have attracted interest in recent years. A comprehensive account of the structural diversity (368 structures, 117 references) and biological activities of pimarane diterpenes discovered from 2000 until 2023 is given in this review.

Three new diterpenoids from the roots of Euphorbia fischeriana and their cytotoxicity

Euphorbiabietane F (1), a novel abietane diterpenoid with the unprecedented 6/6/5/6/5 carbon skeleton, one new strobane diterpenoid (2), together with one new pimarane diterpenoid (3) were isolated from the roots of Euphorbia fischeriana. The structures were elucidated by the extensive spectroscopic data, gauge-independent atomic orbital (GIAO) NMR calculations, the comparison of experimental and calculated ECD spectra, as well as single crystal X-ray diffraction. The cytotoxicity result suggested the moderate inhibition rate of 1 on the cell lines of HepG2 and A549.

Three new diterpenoids isolated from Euphorbia nematocypha Hand.-Mazz and their anti-fungal activity

Three new diterpenoids, named nematocynine A-C (1-3), together with twelve known compounds (4-15) were isolated from the aerial part of Euphorbia nematocypha Hand.-Mazz (Hereinafter referred to E. nematocypha). Their structures were elucidated by detailed spectroscopic analysis and comparison with literature data. In addition, all the compounds were tested for their anti-candida albicans activities used alone or in combination with fluconazole against sensitive strain and resistant strain in vitro. Wherein only compound 11 shows weak activity against candida albicans resistant strain (MIC50 = 128.15 μg/mL) when used alone. Compounds 1, 4, 7, 8, 9, 10, 12, 13 and 15 in combination with fluconazole showed potent anti-fungal activities (MIC50 = 15 ± 5 μg/mL, FICI = 0.05 ± 0.04) against the Candida albicans resistant strain SC5314-FR. The synergistic effects were weaker against the Candida albicans resistant strain SC5314-FR when the compounds 2, 3, 5 and 14 were combined with fluconazole (FICI = 0.16 ± 0.06).

Ent-16β,17-dihydroxy-kauran-19-oic acid (DKA), a kaurane diterpenoid from Sigesbeckia pubescens(Makino) Makino, inhibits the migration of MDA-MB-231 breast cancer

Ent-kaurane diterpenoids were studied as a biologically active ingredient group of Sigesbeckia pubescens (Makino) Makino. Here, five known ent-kaurane diterpenoids were isolated and identified, named ent-16β,17-dihydroxy-kauran-19-oic acid (1), ent-16β,17-dihydroxy-kauran-19-oate (2), ent-18-acetoxy-17-hydroxykauran-19-oic acid (3), ent-16β,17,18-trihydroxy-kauran-19 -oic acid (4), and ent-17-hydroxy-kauran-16βH-19-oic acid (5). Their inhibitory effects of these compounds on MDA-MB-231 breast cancer migration were firstly tested in a chemotaxis invasion assay. Among them, compound 1 (DKA) showed superior inhibitory activities with IC50 value of 1.96 µM. Then, a wound healing assay and BALB/c nude mice were used for further studying the inhibitory activity of DKA on MDA-MB-231 breast cancer migration in vitro and in vivo, respectively. The wound healing assay showed that DKA (1, 5, and 25 μM) can significantly inhibit cell migration and the mouse model of lung metastasis showed that DKA (2.5, 5, and 10 mg/kg) could strongly suppress the lung metastasis of MDA-MB-231 breast cancer cells.

Asymmetric syntheses of ent-pimarane diterpenoids

Aromatic ent-pimaranes are a group of aromatized tricyclic diterpenoids that exhibit diverse bioactivities. In this work, the first total syntheses of two aromatic ent-pimaranes were achieved via a C-ABC construction sequence enabled by chiral auxiliary controlled asymmetric radical polyene cyclization, and the subsequent substrate-controlled stereo-/regio-specific hydroboration of alkene allowed for access to both natural products with C19 oxidation modifications.

Sustainable biosynthesis of valuable diterpenes in microbes

Diterpenes, or diterpenoids, are the most abundant and diverse subgroup of terpenoids, the largest family of secondary metabolites. Most diterpenes possess broad biological activities including anti-inflammatory, antiviral, anti-tumoral, antimicrobial, anticancer, antifungal, antidiabetic, cardiovascular protective, and phytohormone activities. As such, diterpenes have wide applications in medicine (e.g., the anticancer drug Taxol and the antibiotic pleuromutilin), agriculture (especially as phytohormones such as gibberellins), personal care (e.g., the fragrance sclareol) and food (e.g., steviol glucosides as low-calorie sweeteners) industries. Diterpenes are biosynthesized in a common route with various diterpene synthases and decoration enzymes like cytochrome P450 oxidases, glycosidases, and acyltransferases. Recent advances in DNA sequencing and synthesis, omics analysis, synthetic biology, and metabolic engineering have enabled efficient production of diterpenes in several chassis hosts like Escherichia coli, Saccharomyces cerevisiae, Yarrowia lipolytica, Rhodosporidium toruloides, and Fusarium fujikuroi. This review summarizes the recently discovered diterpenes, their related enzymes and biosynthetic pathways, particularly highlighting the microbial synthesis of high-value diterpenes directly from inexpensive carbon sources (e.g., sugars). The high titers (>4 g/L) achieved mean that some of these endeavors are reaching or close to commercialization. As such, we envisage a bright future in translating microbial synthesis of diterpenes into commercialization.

ent-Pimarane Diterpenes from the Aerial Parts of Siegesbeckia pubescens

Five new ent-pimarane diterpenes (1-5) and five known analogs (6-10) were isolated from the aerial parts of Siegesbeckia pubescens. Their structures, including absolute configurations, were determined by comprehensive spectroscopic methods especially 1D and 2D NMR and quantum chemical electronic circular dichroism calculations. All the isolated compounds were evaluated for their cytotoxicity against human BT549, A549 and H157 cancer cell lines. Among them, compounds 1 and 2 showed mild cytotoxicity against lung cancer cell lines H157 with IC₅₀ values of 16.35±2.59 and 18.86±4.83 μM, respectively.

Short, Divergent, and Enantioselective Total Synthesis of Bioactive ent-Pimaranes

We present the first total synthesis of eight ent-pimaranes via a short and enantioselective route (11-16 steps). Key features of the divergent synthesis are a Sharpless asymmetric dihydroxylation, a Brønsted acid catalyzed cationic bicyclization, and a mild Rh-catalyzed arene hydrogenation for rapid access to a late synthetic branching point. From there on, selective functional group manipulations enable the synthesis of ent-pimaranes bearing different modifications in the A- and C-rings.

A novel ent-pimarane-type diterpenoid from Sigesbeckia glabrescens with anti-inflammatory activity

A novel ent-pimarane-type diterpenoid, sigesbeckia J (1), along with two known diterpenoids, siegesbeckia acid (2) and ent-18-acetoxy-16R,17-dihydroxykauran-19-oic acid (3), were isolated from the aerial parts of Sigesbeckia glabrescens Makino. Their chemical structures were elucidated based on extensive spectroscopic interpretation. The absolute configuration of ent-pimarane-type diterpenoid (1) was determined by comparing experimental and calculated ECD spectra. Compared with the positive control minocycline (IC₅₀ 32.84 μM), compound 1 exhibited moderate cell growth anti-inflammatory activities in vitro by testing their inhibition of LPS-induced NO production in BV2 microglial cells, with IC₅₀ value of 58.74 μM.

Kirenol: A promising bioactive metabolite from siegesbeckia species: A detailed review

ETHNOPHARMACOLOGICAL RELEVANCE

Kirenol (Kr) is an ent-pimarane type diterpenoid that has been reported from Siegesbeckiaorientalis, S. pubescens, and S. glabrescens (family Asteraceae). These plants have been used traditionally for treating various ailments such as hypertension, neurasthenia, rheumatoid arthritis, asthma, snakebites, allergic disorders, paralysis, soreness, cutaneous disorders, rubella, menstrual disorders, numbness of limbs, dizziness, headache, and malaria. Importantly, in recent years, Kr has received great attention due to its diversified pharmacological activities.

AIM OF THE STUDY

The current work aims to give an overview on the reported pharmacological activities of Kr. Furthermore, the findings regarding its methods for extraction, quantitative analysis, purification, pharmacokinetics, pharmaceutical and food preparations, biosynthesis, identification, semisynthetic analogues, and toxicity are highlighted to provide a reference and perspective for its further investigation.

METHODS

Electronic databases including ScienceDirect, Web of Knowledge, SCOPUS, Wiley Online Library, Taylor & Francis, PubMed, Springer, JACS, and Google Scholar were searched up to the beginning of 2021 to identify the reported studies.

RESULTS

A total of 93 articles have been reviewed. The reported data suggested that Kr possessed various bioactivities including cytotoxic, apoptotic, anticancer, anti-inflammatory, cardio-protective, anti-photo-aging, anti-adipogenic, antimicrobial, muscle function improvement, fracture and wound healing, and anti-arthritic. In addition, studies revealed that the antioxidative and anti-inflammatory activities of Kr may mediate many of its therapeutic potentials as confirmed by several in-vitro and in-vivo studies.

CONCLUSION

This review provides an updated summary of the recent studies on Kr, including methods for extraction, quantitative analysis, purification, pharmacokinetics, pharmaceutical and food preparations, biosynthesis, and identification, as well as semisynthetic analogues, pharmacological activities, and toxicity. Thus, this work can provide useful considerations for planning and design future research on Kr.

Diterpenoids and Diacetylenes from the Roots of Aralia cordata with Inhibitory Effects on Nitric Oxide Production

Bioactivity-guided isolation of a MeOH extract of Aralia cordata led to the isolation of four new ent-pimarane diterpenoids (1-4) and a diacetylene (5) together with 21 known compounds (6-26). Their structures were established based on the interpretation of one- and two-dimensional NMR and HRESIMS data. The absolute configurations of the new isolates were determined by electronic circular dichroism data analysis, single crystal X-ray diffraction, and Mosher's esterification method. All compounds exhibited inhibitory effects on lipopolysaccharide-induced nitric oxide production in RAW 264.7 macrophages with IC₅₀ values ranging from 1.1 to 69.4 μM.

Sigesbeckia K and L, two new diterpenoids from Sigesbeckia glabrescens with anti-inflammatory activity

A chemical investigation of Sigesbeckia glabrescens Makino identified four compounds. On the basis of spectroscopic data, they were determined to be ent-pimarane-type diterpenoids and their analogues, among which were two previously undescribed compounds, Sigesbeckia K (1) and Sigesbeckia L (2). The anti-inflammatory effects of these compounds were evaluated by testing their inhibition of LPS-induced NO production in BV2 microglial cells, which revealed potential inhibitory effects with IC₅₀ value at 62.56 μM and compared with the positive control minocycline (IC₅₀ 32.84 μM).

Diverse diterpenoids and sesquiterpenoids from Siegesbeckia pubescens and their activity against RANKL-induced osteoclastogenesis

Phytochemical investigation of the aerial parts of Siegesbeckia pubescens led to seventeen diterpenoids (1-17) and twelve sesquiterpenoids (18-29). Their structures were varied including twelve ent-pimarane (1-12), three ent-kaurane (13-15), two acyclic diterpenoids (16-17), ten germacrene (18-27), one guaiane (28), and one caryolane (29) sesquiterpenoids. Eight of twenty-nine were new ones (1, 3, 4, 16-18, 23, and 28). Their structures were elucidated by extensive spectroscopic analysis. The absolute configurations of compounds 1 and 2 were identified using X-ray diffraction analysis, and of compounds 18, 23, and 28 were elucidated by the experimental and calculated electronic circular dichroism (ECD) spectra. All the isolated compounds (1-29) were assayed for their inhibition of RANKL-induced osteoclastogenesis in bone marrow macrophages (BMMs). Four sesquiterpenoids 18, 25, 26, and 27 exhibited potent inhibition of osteoclastogenesis with IC₅₀ value of 0.51, 0.80, 0.50, and 0.83 μM, respectively. Here we demonstrated that S. pubescens may be a resource for discovery of anti-osteoporosis agents.

A New Diterpene and Anti-inflammatory Sesquiterpene Lactones from Sigesbeckia orientalis

Sigesbeckia orientalis, more commonly referred to as Herba Sigesbeckiae or Xi Xian Cao in traditional Chinese medicine and hy thiêm in traditional Vietnamese medicine, is used in China and Vietnam to treat inflammatory diseases such as arthritis, rheumatism, and joint pain. In initial investigations, the dichloromethane extract from the aerial parts of S. orientalis showed distinct inhibitory effects on the release of interleukin-8 in human neutrophils. Therefore, the purpose of the present study was the phytochemical investigation of the bioactive dichloromethane extract and the in vitro analysis of the effects of the isolated compounds on interleukin-8, interleukin-1β, tumor necrosis factor-α, and monocyte chemoattractant protein 1 release, and surface expression of adhesion molecules (CD11a, CD11b, and CD62L) in lipopolysaccharide-stimulated human neutrophils to identify the active principle(s). The separation of the bioactive dichloromethane extract using various chromatographic techniques led to the isolation of nine compounds. Their chemical structures were elucidated from nuclear magnetic resonance and mass spectrometry data. One diterpene, 17(13 → 14)-abeo-ent-3S*,13S*,16-trihydroxystrob-8(15)-ene, was identified as a new natural product. Three germacranolide sesquiterpene lactones inhibited interleukin-8 production with IC₅₀ values between 1.6 and 6.3 µM, respectively, and tumor necrosis factor-α production with IC₅₀ values between 0.9 and 3.3 µM, respectively. Furthermore, they significantly inhibited interleukin-1β and monocyte chemoattractant protein 1 production and diminished the effects of lipopolysaccharide on the surface expression of the adhesion molecules CD11a, CD11b, and CD62L. These findings support the traditional use of S. orientalis in the treatment of inflammatory diseases.

xOPBE: A Specialized Functional for Accurate Prediction of 13C Chemical Shifts

In this study, we present a new hybrid functional denoted as xOPBE, which is optimized at the 6-311+G(2d,p) basis set and designed with a specific aim of providing accurate ¹³C chemical shifts. By mixing the Hartree-Fock exchange into the OPBE functional, xOPBE provides a significantly improved overall performance as compared to its parent OPBE functional, while OPBE was shown previously as an excellent functional for ¹³C chemical shifts. Even in the case of the 1-adamantyl cation, for which OPBE completely fails in reproducing the experimental results, xOPBE still performs very well with similar accuracy as the standard CCSD(T) method with a large basis set. Our results also demonstrate that xOPBE not only can improve quantitatively the description of the correct assignments given by OPBE but also can revert OPBE's incorrect assignments qualitatively. Thus, we would like to recommend the use of xOPBE for routine evaluations of ¹³C chemical shifts.

New oxylipins from Siegesbeckia glabrescens as potential antibacterial agents

Seven rare oxylipins, siegesbeckins A-G (1-7) representing further bioactive constituents different from the general terpenyl compounds found in Siegesbeckia species, have been obtained from the aerial parts of Siegesbeckia glabrescens. These isolates were identified to be a series of methyl 4-methylpentanoates incorporating fatty acid moieties of different chain lengths, based on spectroscopic techniques, and their absolute configurations were determined via chemical degradation and comparison of experimental and theoretically calculated ECD spectra. With respect to bioactivity, antibacterial, anti-inflammatory and cytotoxic properties of selected compounds were evaluated. Compounds 1 and 5 showed moderate antibacterial activity against two Gram-positive bacteria with MIC values of 4.3 μg/mL, while 3 showed no pronounced activity in these assays.

Unraveling Plant Natural Chemical Diversity for Drug Discovery Purposes

The screening and testing of extracts against a variety of pharmacological targets in order to benefit from the immense natural chemical diversity is a concern in many laboratories worldwide. And several successes have been recorded in finding new actives in natural products, some of which have become new drugs or new sources of inspiration for drugs. But in view of the vast amount of research on the subject, it is surprising that not more drug candidates were found. In our view, it is fundamental to reflect upon the approaches of such drug discovery programs and the technical processes that are used, along with their inherent difficulties and biases. Based on an extensive survey of recent publications, we discuss the origin and the variety of natural chemical diversity as well as the strategies to having the potential to embrace this diversity. It seemed to us that some of the difficulties of the area could be related with the technical approaches that are used, so the present review begins with synthetizing some of the more used discovery strategies, exemplifying some key points, in order to address some of their limitations. It appears that one of the challenges of natural product-based drug discovery programs should be an easier access to renewable sources of plant-derived products. Maximizing the use of the data together with the exploration of chemical diversity while working on reasonable supply of natural product-based entities could be a way to answer this challenge. We suggested alternative ways to access and explore part of this chemical diversity with in vitro cultures. We also reinforced how important it was organizing and making available this worldwide knowledge in an "inventory" of natural products and their sources. And finally, we focused on strategies based on synthetic biology and syntheses that allow reaching industrial scale supply. Approaches based on the opportunities lying in untapped natural plant chemical diversity are also considered.

Isolation and characterization of ent-pimarane diterpenoids from Sigesbeckia pubescens

Five new ent-pimarane diterpenoids ent-16-nor-2-oxopimar-8(14)-ene-15,19-dial (1), ent-16-nor-2α,19-dihydroxypimar-8-en-15-al (2), 3-O-acetyldarutigenol (3), 19-O-acetylkirenol (4), ent-16-nor-3β,15-dihydroxypimar-8(14)-ene (5) were isolated and characterized from the ethanol extract of Sigesbeckia pubescens. Their structures were elucidated on the basis of spectroscopic analysis. The absolute configuration of C-15 in compounds 3 and 4 was assigned using Snatzke's method. All these compounds were assessed for their anti-inflammatory potential by measuring the inhibitory effects on NO production in LPS-induced RAW 264.7 macrophage cells and compound 4 showed significantly inhibitory activity with IC₅₀ value of 5.9 μM.

Diterpenoids of terrestrial origin

This review covers the isolation and chemistry of diterpenoids from terrestrial sources from 2017.

Semisynthesis of ent-norstrobane diterpenoids as potential inhibitor for factor Xa

A semisynthesis of two ent-strobane diterpenoids strobols C (7) and D (14) was accomplished via a Wagnar-Meerwein rearrangement. Compounds 7, 14, and the intermediate products were evaluated for their inhibition on factor Xa (FXa). Among all the compounds screened for FXa inhibitory activity, three compounds 6, 7, and 9 showed significant inhibitory activities with IC₅₀ values of 1067 ± 164, 81 ± 11, 1023 ± 89 nM, respectively. The inhibitory activity on FXa described in this study highlight the importance of structural modification based on natural products in the development of FXa inhibitors.

Comparative Analysis of Chemical Composition, Anti-Inflammatory Activity and Antitumor Activity in Essential Oils from Siegesbeckiaorientalis, S. glabrescens and S. pubescens with an ITS Sequence Analysis

Herba Siegesbeckiae (HS), derived from the aerial parts of three plants, Siegesbeckia orientalis (SO), S. glabrescens (SG), and S. pubescens (SP), has been used for the treatment of inflammatory diseases in China for centuries. In the present study, hydrodistillation was applied to extract essential oils from dried SO, SG, and SP aerial parts, and chemical composition analysis by gas chromatography⁻mass spectrometry (GC-MS) led to the identification of a total of 148 compounds (56 in SO, 62 in SG, and 59 in SP). The main components in the essential oils of SO, SG, and SP differed significantly. In vitro anti-inflammatory activity assays showed that SP essential oils (IC₅₀, 0.97 μg/mL) significantly reduced the ability of lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages to release NO, and the SO essential oil (IC₅₀, 14.99 μg/mL) was better than the others at inhibiting the LPS-induced release of cytokine IL-6. Furthermore, the essential oils exhibited antitumor activities (IC₅₀, 37.72⁻123.16 μg/mL) against Hep3B (liver) and Hela (cervical) cells. Linear regression analysis showed that, caryophyllene oxide peak area percentages showed remarkably high negative correlation coefficients with IC₅₀ values of Hep3B and Hela cytotoxicity, which suggested the contribution of this compound on the cancer cell cytotoxicity of three essential oils. Finally, the ITS1-5.8S-ITS2 region was amplified and sequenced in order to generate genomic reference sequences for each plant. These can be used to identify the origins of the plants, and will assist other research studies related to these three plants.

Libertellenones O-S and Eutypellenones A and B, Pimarane Diterpene Derivatives from the Arctic Fungus Eutypella sp. D-1

Seven new pimarane-type diterpene derivatives, libertellenones O-S (1-5) and eutypellenones A and B (6 and 7), together with two known compounds (8 and 9), were isolated from the culture of Eutypella sp. D-1 obtained from high-latitude soil of the Arctic. Their structures were elucidated from spectroscopic data, as well as experimental and calculated electronic circular dichroism (ECD) analysis. Structurally, compounds 1-5 possess a cyclopropyl-fused pimarane diterpene moiety, whereas compounds 6 and 7 share an unusual cyclobutyl-fused pimarane diterpene skeleton. Compounds 1-9 exhibited cytotoxicities against HeLa, MCF-7, HCT-116, PANC-1, and SW1990 cells, with IC₅₀ values in the range of 0.3 to 29.4 μM. Compounds 6 and 7 could dose-dependently inhibit the activity of NF-κB and exhibited significantly inhibitory effects on nitric oxide production induced by lipopolysaccharide.

Siegesbeckia pubescens Makino inhibits Pam3CSK4-induced inflammation in RAW 264.7 macrophages through suppressing TLR1/TLR2-mediated NF-κB activation

Background

Siegesbeckia pubescens Makino (SP) is one of the important plant origins for the anti-inflammatory Chinese herbal medicine of Siegesbeckiae Herba. The current investigations indicated that the anti-inflammatory effects of SP were associated with the toll-like receptors (TLRs)-mediated nuclear factor-κB (NF-κB) and the mitogen-activated protein kinase (MAPK) signaling pathways.

Methods

Raw 264.7 macrophages were pretreated with the 50% ethanol extract of SP (SPE, 50–200 µg/mL) and then co-treated with Pam₃CSK₄ (200 ng/mL) for another 12 h. The inhibitory effect of SPE on Pam₃CSK₄-stimulated NO release and post-inflammatory cytokines secretions were determined using Griess reagent and Elisa kits, respectively. The influence of SPE on NF-κB and MAPKs signaling relevant proteins was measured by Western blotting analysis, while the intracellular nitric oxide (NO) generation and NF-κB/p65 nuclear translocation were determined using Leica TCS SP8 laser scanning confocal microscope. Moreover, the effect of SPE on luciferase reporter gene in NF-κB-luc DNA transfected raw 264.7 cells was determined using the Dual-Glo luciferase assay system kit.

Results

SPE dose-dependently (50–200 µg/mL) attenuated Pam₃CSK₄-induced NO release, post-inflammatory cytokines (IL-6, TNF-α and MCP-1) secretions and intracellular NO generation in raw 264.7 cells. Biologically, SPE suppressed Pam₃CSK₄-induced expressions of cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), phosphorylation of NF-κB/p65 and IκBα, but did not significantly show effect on the proteins involved in MAPKs signaling (p38, ERK and JNK). The results were further confirmed by NF-κB-luc reporter gene assay and p65 nuclear translocation assay.

Conclusions

In conclusion, SPE ameliorated Pam₃CSK₄-induced inflammation in raw 264.7 cells through suppressing TLR 1/2-mediated NF-κB activation.

Electronic supplementary material

The online version of this article (10.1186/s13020-018-0193-x) contains supplementary material, which is available to authorized users.