Chromene and chromone derivatives as liver X receptors modulators from a marine-derived Pestalotiopsis neglecta fungus

Chemical profiling and anti-inflammatory effect of phenolic extract of Gentiana rigescens Franch

ETHNOPHARMACOLOGICAL RELEVANCE

Gentiana rigescens Franch. (G. rigescens), known as "Dian Long Dan" in Southern Yunnan Herbal, has a long history in traditional Chinese medicine for treating hepatitis, allergies, postherpetic neuralgia, cholecystitis and rheumatism.

AIM OF THE STUDY

This study aims to comprehensively analyze the phenolic composition of G. rigescens, evaluate its potential anti-inflammatory effects, elucidate underlying mechanisms, and identify its in vivo bioactive phenolic constituents.

MATERIALS AND METHODS

The extraction of G. rigescens phenolic compounds (GRP) was optimized using the Box-Behnken response surface method, with four phenolic compounds (mangiferin, esculetin, ferulic acid and kaempferol) used as quality index markers. GRP's phytochemical composition was subsequently profiled via UPLC-Q-TOF-MS/MS analysis. Anti-inflammatory activity and mechanisms were assessed in LPS-stimulated RAW264.7 cells and murine models, utilizing NO production assays, ELISA, qRT-PCR, Western blotting and histopathological analysis. Bioactive phenolic compounds in blood were identified post-oral administration for in vivo activity prediction.

RESULTS

The optimal extraction conditions for GRP were determined as follows: Soxhlet extraction using acetone with hydrochloric acid 0.06 mol/L, at a liquid-to-solid ratio of 132: l. for 6.6 h. Seventy-one of phenolic compounds were identified in GRP using UPLC-Q-TOF-MS/MS. GRP significantly inhibited LPS-induced NO production in RAW 264.7 macrophages and reduced pro-inflammatory cytokines IL-6, IL-1β, and TNF-α while increasing anti-inflammatory IL-10. In the carrageenan-induced inflammatory model, GRP exhibited a 69.81% inhibition rate of toe swelling at high doses (1 g/kg), along with protective effects against joint injury, as observed in histological assessments. Mechanistically, GRP downregulated mRNA levels of inflammatory cytokines and reduced the expression of inflammatory proteins iNOS, COX-2, p65, p-p65 and P-IκB as shown by Western blotting. Twenty-five of phenolic compounds, including mangiferin, swertianolin, acacetin, umbelliferone and caffeic acid, were identified in vivo in the blood, indicating potential bioactive roles.

CONCLUSIONS

This study provides the first comprehensive profile of the phenolic composition of G. rigescen, alongside a detailed investigation of its anti-inflammatory activity, mechanisms, and in vivo bioactive components. These findings highlight the therapeutic potential of Dian Long Dan's phenolic constituents and support further research on G. rigescens.

Recent advances in the structures and bioactivities of benzopyrans derived from marine fungi: a review

Marine fungi represent a treasure trove of bioactive secondary metabolites, with benzopyran compounds emerging as a significant class of these natural products. This review delves into the structural diversity, biological activities, and sources of benzopyran compounds, highlighting their isolation from marine fungi inhabiting diverse environments such as sponges, marine sediments, algae, mangroves, and corals. Our literature search, conducted from 2000 to 2023, has identified a wealth of benzopyran compounds, showcasing their potential as lead compounds in drug development. The characteristics of benzopyran from marine fungi are explored, encompassing various subclasses such as chromones, isocoumarins, citrinins, and other related compounds. These compounds exhibit a remarkable chemical diversity, which is crucial for their diverse biological activities. The potential of benzopyran compounds in drug development is also discussed, emphasizing their roles in anti-tumor, antibacterial, anti-inflammatory, and enzyme inhibitory activities. In recent years, a remarkable 210 bioactive benzopyran compounds have been isolated from the secondary metabolites of marine fungi. These findings underscore the importance of marine fungi as a source of novel bioactive compounds, offering a plethora of potential lead compounds for the development of marine-derived drugs. This review aims to provide a comprehensive overview of the current state of research on benzopyran compounds, setting the stage for future advancements in the field of marine natural products.

New Sesquiterpenoids from the Mangrove-Derived Fungus Talaromyces sp. as Modulators of Nuclear Receptors

Four new sesquiterpenoids, talaroterpenes A-D (1-4), were isolated from the mangrove-derived fungus Talaromyces sp. SCSIO 41412. The structures of compounds 1-4 were elucidated through comprehensive NMR and MS spectroscopic analyses. The absolute configurations of 1-4 were assigned based on single-crystal X-ray diffraction and calculated electronic circular dichroism analysis. Talaroterpenes A-D (1-4) were evaluated with their regulatory activities on nuclear receptors in HepG2 cells. Under the concentrations of 200 μM, 1, 3 and 4 exhibited varying degrees of activation on ABCA1 and PPARα, while 4 showed the strongest activities. Furthermore, 4 induced significant alterations in the expression of downstream target genes CLOCK and BMAL1 of RORα, and the in silico molecular docking analysis supported the direct binding interactions of 4 with RORα protein. This study revealed that talaroterpene D (4) was a new potential non-toxic modulator of nuclear receptors.

New Bioactive Polyketides from the Mangrove-Derived Fungus Penicillium sp. SCSIO 41411

Three new polyketides, including three ester derivatives (1, 3, and 5) and a new natural product, which was a benzoquinone derivative, embelin A (4), together with nine known ones (2 and 6-13), were isolated from the mangrove-derived fungus Penicillium sp. SCSIO 41411. Their structures were determined by detailed NMR and MS spectroscopic analyses. The X-ray single-crystal diffraction analysis of 4 was described for the first time. Compound 9 displayed obvious inhibition against PDE4 with an inhibitory ratio of 40.78% at 10 μM. Compound 12 showed DPPH radical scavenging activity, with an EC50 of 16.21 µg/mL, compared to the positive control (ascorbic acid, EC50, 11.22 µg/mL). Furthermore, compound 4 exhibited cytotoxicity against PC-3 and LNCaP with IC50 values of 18.69 and 31.62 µM, respectively.

Exserolide J ameliorates lipid accumulation in vitro by regulating liver X receptor alpha and peroxisome proliferator-activated receptor alpha proteins

Exserolides are isocoumarin derivatives containing lactone moiety. Recently, some isocoumarins have been demonstrated to ameliorate hyperlipidemia, a major factor for inducing cardiovascular diseases. However, the effects and mechanisms of action of exserolides on hyperlipidemia are not known. The aim of this study is to investigate whether the marine fungus Setosphaeria sp.-derived exserolides (compounds I, J, E, and F) exert lipid-lowering effects via improving reverse cholesterol transport (RCT) in vitro. RAW264.7 macrophages and HepG2 cells were used to establish lipid-laden models, and the levels of intracellular lipids and RCT-related proteins were determined by assay kits and Western blotting, respectively. We observed that exserolides (at a 5 μM concentration) significantly decreased intracellular cholesterol and triglyceride levels in oxidized low-density lipoprotein-laden RAW264.7 cells and markedly improved [3H]-cholesterol efflux. Among the four tested compounds, exserolide J increased the protein levels of ATP-binding cassette transporter A1, peroxisome proliferator-activated receptor α (PPARα), and liver X receptor α (LXRα). Furthermore, treatment with exserolides significantly decreased oleic acid-laden lipid accumulation in HepG2 hepatocytes. Mechanistically, exserolides enhance PPARα protein levels; furthermore, compound J increases cholesterol 7 alpha-hydroxylase A1 and LXRα protein levels. Molecular docking revealed that exserolides, particularly compound J, can interact with PPARα and LXRα proteins. These data suggest that the terminal carboxyl group of compound J plays a key role in lowering lipid levels by stimulating LXRα and PPARα proteins. In conclusion, compound J exhibits powerful lipid-lowering effects in vitro. However, its hypolipidemic effects in vivo should be investigated in the future.

Discovery of Anti-Hypercholesterolemia Agents Targeting LXRα from Marine Microorganism-Derived Natural Products

A strategy integrating in silico molecular docking with LXRα and phenotypic assays was adopted to discover anti-hypercholesterolemia agents in a small library containing 205 marine microorganism-derived natural products, collected by our group in recent years. Two fumitremorgin derivatives, 12R,13S-dihydroxyfumitremorgin C (1) and tryprostatin A (3), were identified as potential LXRα agonists, by real-time qPCR and Western blot (WB) analysis, together with a surface plasmon resonance (SPR) assay. The anti-hypercholesterolemic effects of 1 and 3, together with their mechanisms, were investigated in depth using different cell and mouse models, among which the study of LXRα is of crucial importance. Compound 1 or 3 exhibited the capacity to effectively reverse excessive lipid accumulation in a hepatic steatosis cell model and significantly reduce liver damage and blood cholesterol levels in high cholesterol diet (HCD)-fed wild-type mice, whereas those beneficial effects were completely nullified in HCD-fed LXRα-knockout mice. Furthermore, 1 and 3 outperformed common LXRα agonists by suppressing the expression of sterol regulatory element-binding protein 1 (SREBP1) in HCD-fed mice, mitigating lipotoxicity. Thus, this study highlights the discovery of two marine microorganism-derived anti-hypercholesterolemia agents targeting LXRα.

Natural compounds targeting nuclear receptors for effective cancer therapy

Human nuclear receptors (NRs) are a family of forty-eight transcription factors that modulate gene expression both spatially and temporally. Numerous biochemical, physiological, and pathological processes including cell survival, proliferation, differentiation, metabolism, immune modulation, development, reproduction, and aging are extensively orchestrated by different NRs. The involvement of dysregulated NRs and NR-mediated signaling pathways in driving cancer cell hallmarks has been thoroughly investigated. Targeting NRs has been one of the major focuses of drug development strategies for cancer interventions. Interestingly, rapid progress in molecular biology and drug screening reveals that the naturally occurring compounds are promising modern oncology drugs which are free of potentially inevitable repercussions that are associated with synthetic compounds. Therefore, the purpose of this review is to draw our attention to the potential therapeutic effects of various classes of natural compounds that target NRs such as phytochemicals, dietary components, venom constituents, royal jelly-derived compounds, and microbial derivatives in the establishment of novel and safe medications for cancer treatment. This review also emphasizes molecular mechanisms and signaling pathways that are leveraged to promote the anti-cancer effects of these natural compounds. We have also critically reviewed and assessed the advantages and limitations of current preclinical and clinical studies on this subject for cancer prophylaxis. This might subsequently pave the way for new paradigms in the discovery of drugs that target specific cancer types.

Caryophyllene sesquiterpenoids with various ring systems from the fungus Pestalotiopsis chamaeropis

Six undescribed caryophyllene sesquiterpenoids named pestalotiopsins O-T, along with eight known analogues, were obtained from the fungus Pestalotiopsis chamaeropis. Their structures and absolute configurations were assigned by NMR spectroscopic analyses, HRESIMS, single-crystal X-ray diffraction, electronic circular dichroism (ECD) calculations, Mo₂(OAc)₄-induced ECD, and chemical derivatization. Pestalotiopsin P represents the first example of a caryophyllene sesquiterpenoid possessing an oxatricyclo [7.2.2.0^3.6]tridecane decorated with a rare bridgehead double bond, while pestalotiopsin Q has an oxatricyclic [6.3.1.0^1,4]dodecane skeleton with an unusual ether bridge between C-1 and C-5. These undescribed caryophyllene sesquiterpenoids were screened for their cytotoxic and anti-inflammatory activities.

Marine natural products

Covering: January to December 2021This review covers the literature published in 2021 for marine natural products (MNPs), with 736 citations (724 for the period January to December 2021) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1425 in 416 papers for 2021), together with the relevant biological activities, source organisms and country of origin. Pertinent reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. An analysis of the number of authors, their affiliations, domestic and international collection locations, focus of MNP studies, citation metrics and journal choices is discussed.

Pestalotiopsis Diversity: Species, Dispositions, Secondary Metabolites, and Bioactivities

Pestalotiopsis species have gained attention thanks to their structurally complex and biologically active secondary metabolites. In past decades, several new secondary metabolites were isolated and identified. Their bioactivities were tested, including anticancer, antifungal, antibacterial, and nematicidal activity. Since the previous review published in 2014, new secondary metabolites were isolated and identified from Pestalotiopsis species and unidentified strains. This review gathered published articles from 2014 to 2021 and focused on 239 new secondary metabolites and their bioactivities. To date, 384 Pestalotiopsis species have been discovered in diverse ecological habitats, with the majority of them unstudied. Some may contain secondary metabolites with unique bioactivities that might benefit pharmacology.

1,4,6-trihydroxy-8-alkylated-9,10-anthraquinones with antibacterial activities from soil-derived Streptomyces sp. WS-13394

Two new 1,4,6-trihydroxy-8-alkylated-9,10-anthraquinones (1-2) were isolated from the culture broth of the soil actinomycete Streptomyces sp. WS-13394. Their structures were elucidated on the basis of extensive spectroscopic analysis, including mass spectrometry (MS), nuclear magnetic resonance (NMR), and electronic circular dichroism (ECD). Compounds 1 and 2, together with eight analogs (3-10), were evaluated for their antibacterial activities against five pathogens. The tested derivatives of alkylated anthraquinone exhibited selective activities to Gram-positive bacteria, while compounds 1 and 5 showed obvious activities against two zoonotic pathogens, Erysipelothrix rhusiopathiae and Streptococcus suis, with MIC values ranging from 3.13 to 12.5 µg ml^-1.

Natural Products Targeting Liver X Receptors or Farnesoid X Receptor

Nuclear receptors (NRs) are a superfamily of transcription factors induced by ligands and also function as integrators of hormonal and nutritional signals. Among NRs, the liver X receptors (LXRs) and farnesoid X receptor (FXR) have been of significance as targets for the treatment of metabolic syndrome-related diseases. In recent years, natural products targeting LXRs and FXR have received remarkable interests as a valuable source of novel ligands encompassing diverse chemical structures and bioactive properties. This review aims to survey natural products, originating from terrestrial plants and microorganisms, marine organisms, and marine-derived microorganisms, which could influence LXRs and FXR. In the recent two decades (2000-2020), 261 natural products were discovered from natural resources such as LXRs/FXR modulators, 109 agonists and 38 antagonists targeting LXRs, and 72 agonists and 55 antagonists targeting FXR. The docking evaluation of desired natural products targeted LXRs/FXR is finally discussed. This comprehensive overview will provide a reference for future study of novel LXRs and FXR agonists and antagonists to target human diseases, and attract an increasing number of professional scholars majoring in pharmacy and biology with more in-depth discussion.

Chromone Derivatives with α-Glucosidase Inhibitory Activity from the Marine Fungus Penicillium thomii Maire

The fungal strain YPGA3 was isolated from the sediments of the Yap Trench and identified as Penicillium thomii. Eight new chromone derivatives, named penithochromones M-T (1-8), along with two known analogues, 9 and 10, were isolated from the strain. The structures were established by detailed analyses of the spectroscopic data. The absolute configuration of the only chiral center in compound 1 was tentatively determined by comparing the experimental and the calculated specific rotations. Compounds 7 and 8 represent the first examples of chromone derivatives featuring a 5,7-dioxygenated chromone moiety with a 9-carbon side chain. Bioassay study revealed that compounds 6-10 exhibited remarkable inhibition against α-glucosidase with IC₅₀ values ranging from 268 to 1017 μM, which are more active than the positive control acarbose (1.3 mmol).