Antiviral benzofurans from Eupatorium chinense

Chemical Constituents and Their Bioactivities of Plants from the Genus Eupatorium (2015-Present)

The genus Eupatorium belongs to the Asteraceae (Compositae) family and has multiple properties, such as invasiveness and toxicity, and is used in folk medicine. The last review on the chemical constituents of this genus and their biological activities was published in 2015. The present review provides an overview of 192 natural products discovered from 2015 to the present. These products include 63 sesquiterpenoids, 53 benzofuran derivatives, 39 thymol derivatives, 15 fatty acids, 7 diterpenoids, 5 monoterpenoids, 4 acetophenones, and 6 other compounds. We also characterized their respective chemical structures and cytotoxic, antifungal, insecticidal, antibacterial, anti-inflammatory, and antinociceptive activities.

Synthesis and inhibitory activity of euparin derivatives as potential dual inhibitors against α-glucosidase and protein tyrosine phosphatase 1B (PTP1B)

Diabetes mellitus is a serious threat to human life and health. The α-glucosidase and protein tyrosine phosphatase 1B (PTP1B) were important targets for the treatment of type 2 diabetes mellitus. In this paper, euparin, a natural product from Eupatorium chinense possessed extensive pharmacological activities, was selected as the lead compound. It was derived into chalcone compounds with high efficiency, and the inhibitory activities of these 30 products on α-glucosidase and PTP1B were tested. The results showed that compounds 12 and 15 had good inhibitory activities against both enzymes. The IC50 value of 12 to inhibit α-glucosidase and PTP1B was 39.77 and 39.31 μM, and the IC50 value of 15 to inhibit α-glucosidase and PTP1B was 9.02 and 3.47 μM, respectively. In addition, molecular docking results showed that compounds 12 and 15 exhibited good binding affinities toward both α -glucosidase and PTP1B with negative binding energies. The results of the present study demonstrate that compounds 12 and 15 might be beneficial in the treatment of type 2 diabetes.

Discovery of New Heterocyclic/Benzofuran Hybrids as Potential Anti-Inflammatory Agents: Design, Synthesis, and Evaluation of the Inhibitory Activity of Their Related Inflammatory Factors Based on NF-κB and MAPK Signaling Pathways

NF-κB and MAPK are classic inflammation signaling pathways which regulate inflammation signal transmission and induce the expression of many inflammatory factors. Based on the potent anti-inflammatory activity of benzofuran and its derivatives, several new heterocyclic/benzofuran hybrids were first designed and synthesized by molecular hybridization. Their structure was confirmed by ¹H NMR, ¹³C NMR, HRMS or X-single crystal diffraction. The anti-inflammatory activity of these new compounds was screened by compounds; compound 5d exhibited an excellent inhibitory effect on the generation of NO (IC₅₀ = 52.23 ± 0.97 μM), and low cytotoxicity (IC₅₀ > 80 μM) against the RAW-264.7 cell lines. To further elucidate the possible anti-inflammatory mechanisms of compound 5d, the hallmark protein expressions of the NF-κB and MAPK pathways were studied in LPS-stimulated RAW264.7 cells. The results indicate that compound 5d not only significantly inhibits the phosphorylation levels of IKKα/IKKβ, IKβα, P65, ERK, JNK and P38 in the classic MAPK/NF-κB signaling pathway in a dose-dependent manner, but also down-regulates the secretion of pro-inflammatory factors such as NO, COX-2, TNF-α and IL-6. Further, the in vivo anti-inflammatory activity of compound 5d indicated that it could regulate the involvement of neutrophils, leukocytes and lymphocytes in inflammation processes, and reduce the expression of IL-1β, TNF-α and IL-6 in serum and tissues. These results strongly suggest that the piperazine/benzofuran hybrid 5d has a good potential for developing an anti-inflammatory lead compound, and the anti-inflammatory mechanism might be related to the NF-κB and MAPK signaling pathways.

New Benzofuran Oligomers from the Roots of Eupatorium heterophyllum Collected in China

The chemical constituents of two root samples of Eupatorium heterophyllum DC. collected in Yunnan Province, China, were investigated. Five new oligomeric benzofurans (1-5), nine new benzofuran/dihydrobenzofuran derivatives, and a new thymol analog were isolated, and their structures were determined using extensive spectroscopic techniques, such as 1D and 2D NMR spectroscopy and DFT calculations of the CD spectra. Most of the new compounds, including oligomeric benzofurans (1-5), were obtained from only one of the root samples. Furthermore, this is the first example that produces oligomeric benzofurans in this plant. These results imply that diversification of secondary metabolites in E. heterophyllum is ongoing. Plausible biosynthetic pathways for 1-5 are also proposed.

Structures and Anti-Inflammatory Evaluation of Phenylpropanoid Derivatives from the Aerial Parts of Dioscorea polystachya

Seven undescribed phenylpropanoid constituents, including three new bibenzyl derivatives (1–3) along with four new benzofuran stilbene derivatives (4–7), were isolated from the aerial parts of Dioscorea polystachya. The structures of these compounds were elucidated using a combination of spectroscopic analyses, including UV, IR, HRESIMS, 1D, and 2D NMR. Further, all the compounds were evaluated on the anti-inflammatory activity for their inhibition of nitric oxide (NO) production by RAW 264.7 macrophages cells, and some of them (1–3 and 6) displayed inhibitory activity with IC₅₀ values in the range of 9.3–32.3 μM. Moreover, compound 3 decreased the expression of iNOS in Western blot analysis, suggesting compound 3 is mediated via the suppression of an LPS-induced NF-κB inflammasome pathway.

Ten undescribed cadinane-type sesquiterpenoids from Eupatorium chinense

Ten undescribed cadinane-type sesquiterpenes (1-10) were isolated from the whole plant of Eupatorium chinense. Their planar structures were mainly elucidated by extensive analysis of spectroscopic data and DFT NMR calculations. The absolute configurations of 1, 2, and 3 were determined by TDDFT ECD calculations while those of compounds 4-7 and 9 were confirmed by single crystal X-ray diffraction experiments. Compounds 2 and 3 are a pair of C-10 epimers, compounds 4 and 5 a pair of C-1 epimers, and compounds 9 and 10 a pair of compounds isomerized at both C-1 and C-10. A possible biosynthetic pathway for these new sesquiterpenes was proposed.

Alkyl-benzofuran dimers from Eupatorium chinense with insulin-sensitizing and anti-inflammatory activities

Five new racemic alkyl-benzofuran dimers, (±)-dieupachinins I-M (1-5), were isolated from the root tubers of Eupatorium chinense, a well-known traditional Chinese medicine for the treatment of diphtheria in Guangdong province. The structures of these compounds, especially the first examples of 12,10'-epoxy dimer dieupachinin I (1), 12-nor-dimer dieupachinin J (2), and 12,12'-dinor-dimer dieupachinin K (3), were elucidated by spectroscopic data analysis. Chiral resolution were further carried out on a cellulose column by HPLC, and compounds 2-5 were successfully separated into two enantiomers, respectively. The absolute configurations of (+)-(2-5) and (-)-(2-5) were established by theoretical ECD calculation. All the compounds were evaluated for insulin-stimulated glucose uptake in C2C12 myotubes and (±)-dieupachinin I (1) exhibited the best activity. Compound 1 enhanced insulin-stimulated glucose uptake via activating the insulin receptor substrate 1/protein kinase B/glycogen synthase kinase-3β signaling pathway. Moreover, all the isolates were tested for their nitric oxygen (NO) inhibitory effects in lipopolysaccharide-treated RAW264.7 macrophages, and compounds (±)-1, (±)-2, and (±)-4 showed promising inhibitory effects with IC₅₀ values of 6.42 ± 1.85, 6.29 ± 1.94, and 16.03 ± 2.07 μM, respectively. (±)-Dieupachinin I (1) again dose-dependently suppressed LPS-induced expression of inducible NO synthase and nuclear translocation of p65.

Recent Achievement in the Synthesis of Benzo[b]furans

BACKGROUND

Benzo[b]furan derivatives are oxygen-containing heterocyclic compounds consisting of fused benzene and furan rings and are present in a large number of natural and non-natural compounds. This class of compounds has a wide spectrum of biological activities, such as antiarrhythmic, anticancer, inflammatory, antioxidant, antimicrobial, and antiviral. Furthermore, benzo[b]furan derivatives have also been applied in various areas, such as organic electroluminescence device materials and organic dyes, photosensitizing material, organic synthesis as building blocks or intermediates. Because of a broad range of applicability, the synthesis of benzo[b]furan derivative has drawn great attention of chemists and many studies on the synthesis of this class of compounds have been reported recently. This review will give an overview of benzo[b]furan preparation based on studies dating back to the year 2012.

OBJECTIVE

In this review, recent development in the synthesis of benzo[b]furans are discussed. There has been increasingly new methodologies for the construction of benzo[b]furans skeleton to improve efficiency or develop environmentally friendly procedures. In some studies, reaction mechanisms were also outlined.

CONCLUSION

Many methods for the synthesis of benzo[b]furans have been reported recently. Most of them involve cyclization or cycloisomerization processes. Unquestionably, more imaginative strategies for the construction of benzo[b]furan skeleton will be established in the near future. Application of known methods to natural products or drug synthesis, on industrial scale for the synthesis of economically or medicinally important benzo[ b]furans will probably be paid attention to.

Natural source, bioactivity and synthesis of benzofuran derivatives

Benzofuran compounds are a class of compounds that are ubiquitous in nature. Numerous studies have shown that most benzofuran compounds have strong biological activities such as anti-tumor, antibacterial, anti-oxidative, and anti-viral activities. Owing to these biological activities and potential applications in many aspects, benzofuran compounds have attracted more and more attention of chemical and pharmaceutical researchers worldwide, making these substances potential natural drug lead compounds. For example, the recently discovered novel macrocyclic benzofuran compound has anti-hepatitis C virus activity and is expected to be an effective therapeutic drug for hepatitis C disease; novel scaffold compounds of benzothiophene and benzofuran have been developed and utilized as anticancer agents. Novel methods for constructing benzofuran rings have been discovered in recent years. A complex benzofuran derivative is constructed by a unique free radical cyclization cascade, which is an excellent method for the synthesis of a series of difficult-to-prepare polycyclic benzofuran compounds. Another benzofuran ring constructed by proton quantum tunneling has not only fewer side reactions, but also high yield, which is conducive to the construction of complex benzofuran ring systems. This review summarizes the recent studies on the various aspects of benzofuran derivatives including their important natural product sources, biological activities and drug prospects, and chemical synthesis, as well as the relationship between the bioactivities and structures.

Cyclopropylmethyl Protection of Phenols: Total Synthesis of the Resveratrol Dimers Anigopreissin A and Resveratrol-Piceatannol Hybrid

We demonstrate the versatile use of the cyclopropylmethyl group to protect phenols through the total synthesis of two benzofuran-based natural products, that is, anigopreissin A and the resveratrol-piceatannol hybrid. This protecting group is a good alternative to the conventional methyl group, owing to the feasibility of introduction, stability under a variety of conditions, and its relative ease of removal under different acidic conditions.

Germacrane-Type Sesquiterpenoids with Antiproliferative Activities from Eupatorium chinense

Ten new germacrane-type sesquiterpenoids (1-10) were isolated from a whole plant extract of Eupatorium chinense. The structures were elucidated by analysis of their NMR and MS data as well as by comparison with literature values. The absolute configuration of eupachinsin A (1) was determined by single-crystal X-ray diffraction analysis. Compounds 3 and 4 exhibited cytotoxicity against a human breast cancer cell line (MDA-MB-231), with IC₅₀ values of 0.8 and 3.4 μM, respectively. In addition, compounds 3-5 showed cytotoxicity against the human hepatocellular carcinoma cell line (HepG₂), with IC₅₀ values ranging from 3.6 to 7.6 μM.

Three new areca alkaloids from the nuts of Areca catechu

Three new areca alkaloids arecatemines A-C (1-3), together with five known ones (4-8), were isolated from the nuts of Areca catechu. The structures of new compounds including absolute configurations were elucidated using comprehensive spectroscopic and electronic circular dichroism (ECD). The known compounds were identified by comparing with data in the literature.

Eupatorium fortunei and Its Components Increase Antiviral Immune Responses against RNA Viruses

Eupatorium fortunei (EF) has long been used as herbal medicine in Korea, China, and Asian countries to treat a variety of diseases. Recent studies have reported that EF has anti-metastatic, anti-angiogenic, anti-bacterial, and anti-oxidant activities, as well as activities against malignant metastatic human cancers. The effect of EF and its components on viruses has not been reported. In the present study, the antiviral activity and mechanism of action of an aqueous extract of EF (WEF) and its components were evaluated in vitro. We found that pretreatment with WEF markedly reduced viral replication, as evaluated using a green fluorescent protein (GFP)-tagged virus (influenza A virus, Newcastle disease virus, and vesicular stomatitis virus) in murine RAW 264.7 macrophage cells. We demonstrated that WEF induces the production of type I IFN including pro-inflammatory cytokines. Additionally, we identified the active anti-viral components of WEF as quercetin, psoralen, and quercitrin. Thus, WEF and its active components are immunomodulators of the innate immune response in murine macrophages, a finding that is potentially useful to developing prophylactic or therapeutic treatments against a range of viruses.

Isocoumarins and benzofurans from the mangrove endophytic fungus Talaromyces amestolkiae possess α-glucosidase inhibitory and antibacterial activities

Six new isocoumarins, compounds1–4and14–15, two new benzofurans,16–17, along with nine known isocoumarin analogues,5–13were obtained from the mangrove endophytic fungusTalaromyces amestolkiaeYX1.