Antiallergic Agents from Natural Sources 9. Inhibition of Nitric Oxide Production by Novel Chalcone Derivatives from Mallotus philippinensis (Euphorbiaceae)

A Promising Drug Candidate as Potent Therapeutic Approach for Neuroinflammation and Its In Silico Justification of Chalcone Congeners: a Comprehensive Review

Multiple genetic, environmental, and immunological variables cause neuropsychiatric disorders (NPDs). The induced inflammatory immune response is also connected to the severity and treatment outcomes of various NPDs. These reactions also significantly impact numerous brain functions such as GABAergic signaling and neurotransmitter synthesis through inflammatory cytokines and chemokines. Chalcones (1,3-diaryl-2-propen-1-ones) and their heterocyclic counterparts are flavonoids with various biological characteristics including anti-inflammatory activity. Several pure chalcones have been clinically authorized or studied in humans. Chalcones are favored for their diagnostic and therapeutic efficacy in neuroinflammation due to their tiny molecular size, easy manufacturing, and flexibility for changes to adjust lipophilicity ideal for BBB penetrability. These compounds reached an acceptable plasma concentration and were well-tolerated in clinical testing. As a result, they are attracting increasing attention from scientists. However, chalcones' therapeutic potential remains largely untapped. This paper is aimed at highlighting the causes of neuroinflammation, more potent chalcone congeners, their mechanisms of action, and relevant structure-activity relationships.

Immunomodulatory Effect of Phytoactive Compounds on Human Health: A Narrative Review Integrated with Bioinformatics Approach

BACKGROUND

Immunomodulation is the modification of immune responses to control disease progression. While the synthetic immunomodulators have proven efficacy, they are coupled with toxicity and other adverse effects, and hence, the efforts were to identify natural phytochemicals with immunomodulatory potential.

OBJECTIVE

To understand the immunomodulatory properties of various phytochemicals and investigate them in Echinacea species extracts using an in silico approach.

METHODOLOGY

Several scientific database repositories were searched using different keywords: "Phytochemicals," "Alkaloids," "Polyphenols," "Flavonoids," "Lectins," "Glycosides," "Tannins," "Terpenoids," "Sterols," "Immunomodulators," and "Human Immune System" without any language restriction. Additionally, the study specifically investigated the immunomodulatory properties of Echinacea species extracts using gene expression analysis of GSE12259 from NCBI-GEO through the Bioconductor package GEOquery and limma.

RESULTS

A total of 182 studies were comprehensively analyzed to understand immunomodulatory phytochemicals. The in silico analysis highlighted key biological processes (positive regulation of cytokine production, response to tumor necrosis factor) and molecular functions (cytokine receptor binding, receptor-ligand activity, and cytokine activity) among Echinacea species extracts contributing to immune responses. Further, it also indicated the association of various metabolic pathways, i.e., pathways in cancer, cytokine-cytokine receptor interaction, NF-kappa B, PI3K-Akt, TNF, MAPK, and NOD-like receptor signaling pathways, with immune responses. The study revealed various hub targets, including CCL20, CCL4, GCH1, SLC7A11, SOD2, EPB41L3, TNFAIP6, GCLM, EGR1, and FOS.

CONCLUSION

The present study presents a cumulative picture of phytochemicals with therapeutic benefits. Additionally, the study also reported a few novel genes and pathways in Echinacea extracts by re-analyzing GSE 12259 indicating its anti-inflammatory, anti-viral, and immunomodulatory properties.

Hydroxy Chalcones and Analogs with Chemopreventive Properties

The aim of this review is to highlight the chemopreventive properties of hydroxy-substituted natural and synthetic chalcones along with a number of their analogs. These products display various biological activities, and have many applications against various diseases. Antioxidant and anti-inflammatory properties of chalcones bearing hydroxy substituents are underlined. The influence of hydroxy substituents located on ring A, B, or both are systematized according to the exhibited biological properties.

Structure-based virtual screening of novel natural products as chalcone derivatives against SARS-CoV-2 Mpro

Coronavirus disease 2019 (COVID-19), which is caused by SARS-CoV-2, has spread quickly around the world, causing a global pandemic. It has infected more than 500 million people as of April 28, 2022. Much research has been reported to stop the virus from spreading, but there are currently no approved medicines to treat COVID-19. In this work, a dataset of 142 natural products collected from various medicinal plants was used to perform structure-based virtual screening (SBVS) through the combined application of molecular docking and molecular dynamics (MD) simulation methods. First, the dataset of compounds was optimized using the density functional theory (DFT) approach. The optimized compounds were then submitted to the first screening, which was done by the pKCM web server to look for drug-likeness and the PyRx to look for binding affinity. Among the 142 natural substances, 10 compounds were selected for docking validation. Compounds that interact with CYS145 and LEU141, the essential catalytic residues, as well as compounds with binding affinities less than -8.0 kcal/mol, are considered promising anti-SARS-CoV-2 drug candidates. The top-ranked compounds were then evaluated by MD simulations and MM-GBSA method. These results could help researchers come up with new natural compounds that could be used to treat SARS-CoV-2.Communicated by Ramaswamy H. Sarma.

Chalcone: A Promising Bioactive Scaffold in Medicinal Chemistry

Chalcones are a class of privileged scaffolds with high medicinal significance due to the presence of an α,β-unsaturated ketone functionality. Numerous functional modifications of chalcones have been reported, along with their pharmacological behavior. The present review aims to summarize the structures from natural sources, synthesis methods, biological characteristics against infectious and non-infectious diseases, and uses of chalcones over the past decade, and their structure–activity relationship studies are detailed in depth. This critical review provides guidelines for the future design and synthesis of various chalcones. In addition, this could be highly supportive for medicinal chemists to develop more promising candidates for various infectious and non-infectious diseases.

Synthesis and NLRP3-Inflammasome Inhibitory Activity of the Naturally Occurring Velutone F and of Its Non-Natural Regioisomeric Chalconoids

Plant-derived remedies rich in chalcone-based compounds have been known for centuries in the treatment of specific diseases, and nowadays, the fascinating chalcone framework is considered a useful and, above all, abundant natural chemotype. Velutone F, a new chalconoid from Millettia velutina, exhibits a potent effect as an NLRP3-inflammasome inhibitor; the search for new natural/non-natural lead compounds as NLRP3 inhibitors is a current topical subject in medicinal chemistry. The details of our work toward the synthesis of velutone F and the unknown non-natural regioisomers are herein reported. We used different synthetic strategies both for the construction of the distinctive benzofuran nucleus (BF) and for the key phenylpropenone system (PhP). Importantly, we have disclosed a facile entry to the velutone F via synthetic routes that can also be useful for preparing non-natural analogs, a prerequisite for extensive SAR studies on the new flavonoid class of NLRP3-inhibitors.

Chalcone Scaffolds, Bioprecursors of Flavonoids: Chemistry, Bioactivities, and Pharmacokinetics

Chalcones are secondary metabolites belonging to the flavonoid (C6-C3-C6 system) family that are ubiquitous in edible and medicinal plants, and they are bioprecursors of plant flavonoids. Chalcones and their natural derivatives are important intermediates of the flavonoid biosynthetic pathway. Plants containing chalcones have been used in traditional medicines since antiquity. Chalcones are basically α,β-unsaturated ketones that exert great diversity in pharmacological activities such as antioxidant, anticancer, antimicrobial, antiviral, antitubercular, antiplasmodial, antileishmanial, immunosuppressive, anti-inflammatory, and so on. This review provides an insight into the chemistry, biosynthesis, and occurrence of chalcones from natural sources, particularly dietary and medicinal plants. Furthermore, the pharmacological, pharmacokinetics, and toxicological aspects of naturally occurring chalcone derivatives are also discussed herein. In view of having tremendous pharmacological potential, chalcone scaffolds/chalcone derivatives and bioflavonoids after subtle chemical modification could serve as a reliable platform for natural products-based drug discovery toward promising drug lead molecules/drug candidates.

Chalcones: Synthetic Chemistry Follows Where Nature Leads

Chalcones belong to the flavonoid class of phenolic compounds. They form one of the largest groups of bioactive natural products. The potential anticancer, anti-inflammatory, antimicrobial, antioxidant, and antiparasitic properties of naturally occurring chalcones, and their unique chemical structural features inspired the synthesis of numerous chalcone derivatives. In fact, structural features of chalcones are easy to construct from simple aromatic compounds, and it is convenient to perform structural modifications to generate functionalized chalcone derivatives. Many of these synthetic analogs were shown to possess similar bioactivities as their natural counterparts, but often with an enhanced potency and reduced toxicity. This review article aims to demonstrate how bioinspired synthesis of chalcone derivatives can potentially introduce a new chemical space for exploitation for new drug discovery, justifying the title of this article. However, the focus remains on critical appraisal of synthesized chalcones and their derivatives for their bioactivities, linking to their interactions at the biomolecular level where appropriate, and revealing their possible mechanisms of action.

Protective Role of Natural Products in Glioblastoma Multiforme: A Focus on Nitric Oxide Pathway

In spite of therapeutic modalities such as surgical resection, chemotherapy, and radiotherapy, Glioblastoma Multiforme (GBM) remains an incurable fatal disease. This necessitates further therapeutic options that could enhance the efficacy of existing modalities. Nitric Oxide (NO), a short-lived small molecule, has been revealed to play a crucial role in the pathophysiology of GBM. Several studies have demonstrated that NO is involved in apoptosis, metastasis, cellular proliferation, angiogenesis, invasion, and many other processes implicated in GBM pathobiology. Herein, we elaborate on the role of NO as a therapeutic target in GBM and discuss some natural products affecting the NO signaling pathway.

Pharmacological Properties of Chalcones: A Review of Preclinical Including Molecular Mechanisms and Clinical Evidence

Chalcones are among the leading bioactive flavonoids with a therapeutic potential implicated to an array of bioactivities investigated by a series of preclinical and clinical studies. In this article, different scientific databases were searched to retrieve studies depicting the biological activities of chalcones and their derivatives. This review comprehensively describes preclinical studies on chalcones and their derivatives describing their immense significance as antidiabetic, anticancer, anti-inflammatory, antimicrobial, antioxidant, antiparasitic, psychoactive, and neuroprotective agents. Besides, clinical trials revealed their use in the treatment of chronic venous insufficiency, skin conditions, and cancer. Bioavailability studies on chalcones and derivatives indicate possible hindrance and improvement in relation to its nutraceutical and pharmaceutical applications. Multifaceted and complex underlying mechanisms of chalcone actions demonstrated their ability to modulate a number of cancer cell lines, to inhibit a number of pathological microorganisms and parasites, and to control a number of signaling molecules and cascades related to disease modification. Clinical studies on chalcones revealed general absence of adverse effects besides reducing the clinical signs and symptoms with decent bioavailability. Further studies are needed to elucidate their structure activity, toxicity concerns, cellular basis of mode of action, and interactions with other molecules.

Design and synthesis of methoxyphenyl- and coumarin-based chalcone derivatives as anti-inflammatory agents by inhibition of NO production and down-regulation of NF-κB in LPS-induced RAW264.7 macrophage cells

Exaggerated inflammatory responses may cause serious and debilitating diseases such as acute lung injury and rheumatoid arthritis. Two series of chalcone derivatives were prepared as anti-inflammatory agents. Methoxylated phenyl-based chalcones 2a-l and coumarin-based chalcones 3a-f were synthesized and compared for their inhibition of COX-2 enzyme and nitric oxide production suppression. Methoxylated phenyl-based chalcones showed better inhibition to COX-2 enzyme and nitric oxide suppression than the coumarin-based chalcones. Among the 18 synthesized chalcone derivatives, compound 2f exhibited the highest anti-inflammatory activity by inhibition of nitric oxide concentration in LPS-induced RAW264.7 macrophages (IC₅₀ = 11.2 μM). The tested compound 2f showed suppression of iNOS and COX-2 enzymes. Moreover, compound 2f decreases in the expression of NF-κB and phosphorylated IκB in LPS-stimulated macrophages. Finally, docking studies suggested the inhibition of IKKβ as a mechanism of action and highlighted the importance of 2f hydrophobic interactions.

Promising anti-inflammatory effects of chalcones via inhibition of cyclooxygenase, prostaglandin E2, inducible NO synthase and nuclear factor κb activities

Chalcones (1, 3-Diphenyl-2-propen-1-one) consist of a three carbon α, β-unsaturated carbonyl system and act as precursors for the biosynthesis of flavonoids in plants. However, laboratory synthesis of various chalcones has also been reported. Both natural and synthetic chalcones are known to exhibit a variety of pharmacological activities such as anti-inflammatory, antitumor, antibacterial, antifungal, antimalarial and antituberculosis. These promising activities, ease of synthesis and simple chemical structure have awarded chalcones considerable attraction. This review focuses on the anti-inflammatory effects of chalcones, caused by their inhibitory action primarily against the activities and expressions of four key inflammatory mediators viz., cyclooxygenase, prostaglandin E₂, inducible NO synthase, and nuclear factor κB. Various methodologies for the synthesis of chalcones have been discussed. The potency of recently synthesized chalcones is given in terms of their IC₅₀ values. Structure-Activity Relationships (SARs) of a variety of chalcone derivatives have been discussed. Computational methods were applied to calculate the ideal orientation of a typical chalcone scaffold against three enzymes, namely, cyclooxygenase-1, cyclooxygenase-2 and inducible NO synthase for the formation of stable complexes. The global market of anti-inflammatory drugs and its expected growth (from 2018 to 2026) have been discussed. SAR analysis, docking studies, and future prospects all together provide useful clues for the synthesis of novel chalcones of improved anti-inflammatory activities.

Chemical Compounds in Natural Medicines That Affect Macropharges and Adipocyte Cells

Macrophages play major roles in inflammation, immunity and host defense mechanisms. Once activated they produce and release cytokines, oxygen and nitrogen species, and eicosanoids. The best characterized stimuli to induce the transcription of genes encoding pro-inflammatory proteins in macrophages in vitro is bacterial lipopolysaccharide (LPS). LPS could be used alone or in combination with recombinant mouse interferon-γ (IFN-γ). Such stimulation results in cytokine release and the synthesis of enzymes such as cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS). The nitric oxide (NO) radical is known to play a central role in inflammatory and immune reactions for self-protection. However, the excessive production of NO may lead to tissue damage. In inflammatory diseases such as rheumatoid arthritis, excessive NO production by activated macrophages has been observed. Adipose tissue is composed of various cell types such as mature adipocytes, preadipocytes, fibroblasts, endothelial cells, vascular cells, and macrophages. Recent studies indicate that obesity is associated with low-grade chronic inflammation of adipose tissues, and that such inflammation is one of the potential mechanisms leading to the insulin resistance. It has been demonstrated that obese adipose tissue is characterized by the increased infiltration of macrophages. Therefore, we attempted to identify natural anti-inflammatory compounds that not only inhibit the secretion of NO from RAW 264.7 cells, but also inhibit triglyceride accumulation in 3T3-L1 adipocytes. This review describes the NO prpduction inhibitory activity or the TG accumulation inhibitory activity of the compounds obtained from 18 plants and a fungi that have been used as traditional medicines.

Isoprenylated Flavonoids with PTP1B Inhibition from Macaranga denticulata

Three new C-methylated and isoprenylated chalcone derivatives, dentichalcones A-C (1-3), together with six known compounds (4-9), were isolated from the twigs and leaves of Macaranga denticulata. Their structures were elucidated by spectroscopic analysis, including 1D, 2D NMR, and MS data. The known compounds, (2E)-1-(5,7-dihydroxy-2,2,6-trimethyl-2H-benzopyran-8-yl)-3-(4-methoxyphenyl)-2-propen-1-one (4), (2E)-1-(5,7-dihydroxy-2,2-dimethyl-2H-benzopyran-8-yl)-3-phenyl-2-propen-1-one (5), laxichalcone (6), macarangin (7), bonanniol A (8), and bonannione A (9), showed inhibitory activities against protein tyrosine phosphatase 1B (PTP1B) in vitro. Three new C-methylated and isoprenylated chalcone derivatives, dentichalcones A-C (1-3), together with six known compounds, were isolated from the twigs and leaves of Macaranga denticulata. Some compounds showed inhibitory activities against PTP1B in vitro.

The Mosaic of Rottlerin

The first total synthesis of rottlerin is described. The methodology allows the development of potential novel protein kinase C δ (PKCδ) analogues for better treatment of various diseases. Kamalachalcone A and dimeric rottlerin were synthesized in a very practical and economical way using FeCl3 as a catalyst.

Plant-derived immunomodulators: an insight on their preclinical evaluation and clinical trials

The phagocyte-microbe interactions in the immune system is a defense mechanism but when excessively or inappropriately deployed can harm host tissues and participate in the development of different non-immune and immune chronic inflammatory diseases such as autoimmune problems, allergies, some rheumatoid disorders, cancers and others. Immunodrugs include organic synthetics, biological agents such as cytokines and antibodies acting on single targets or pathways have been used to treat immune-related diseases but with limited success. Most of immunostimulants and immunosuppressants in clinical use are the cytotoxic drugs which possess serious side effects. There is a growing interest to use herbal medicines as multi-component agents to modulate the complex immune system in the prevention of infections rather than treating the immune-related diseases. Many therapeutic effects of plant extracts have been suggested to be due to their wide array of immunomodulatory effects and influence on the immune system of the human body. Phytochemicals such as flavonoids, polysaccharides, lactones, alkaloids, diterpenoids and glycosides, present in several plants, have been reported to be responsible for the plants immunomodulating properties. Thus the search for natural products of plant origin as new leads for development of potent and safe immunosuppressant and immunostimulant agents is gaining much major research interest. The present review will give an overview of widely investigated plant-derived compounds (curcumin, resveratrol, epigallocatechol-3-gallate, quercetin, colchicine, capsaicin, andrographolide, and genistein) which have exhibited potent effects on cellular and humoral immune functions in pre-clinical investigations and will highlight their clinical potential.

Mallotus philippinensis Muell. Arg (Euphorbiaceae): ethnopharmacology and phytochemistry review

Mallotus philippinensis Muell. Arg (Euphorbiaceae) are widely distributed perennial shrub or small tree in tropical and subtropical region in outer Himalayas regions with an altitude below 1,000 m and are reported to have wide range of pharmacological activities. Mallotus philippinensis species are known to contain different natural compounds, mainly phenols, diterpenoids, steroids, flavonoids, cardenolides, triterpenoids, coumarins, isocoumarins, and many more especially phenols; that is, bergenin, mallotophilippinens, rottlerin, and isorottlerin have been isolated, identified, and reported interesting biological activities such as antimicrobial, antioxidant, antiviral, cytotoxicity, antioxidant, anti-inflammatory, immunoregulatory activity protein inhibition against cancer cell. We have selected all the pharmacological aspects and toxicological and all its biological related studies. The present review reveals that Mallotus philippinensis is a valuable source of medicinally important natural molecules and provides convincing support for its future use in modern medicine. However, the existing knowledge is very limited about Mallotus philippinensis and its different parts like steam, leaf, and fruit. Further, more detailed safety data pertaining to the acute and subacute toxicity and cardio- and immunotoxicity also needs to be generated for crude extracts or its pure isolated compounds. This review underlines the interest to continue the study of this genus of the Euphorbiaceae.

A New Lignan Dimer from Mallotus philippensis

A new lignan dimer, bilariciresinol (1), was isolated from the leaves of Mallotus philippensis, along with platanoside (2), isovitexin (3), dihydromyricetin (4), bergenin (5), 4 -O-galloylbergenin (6), and pachysandiol A (7). Their structures were elucidated by spectroscopic experiments including 1D and 2D NMR and FTICR-MS.

Anti-tuberculosis Compounds from Mallotus philippinensis

Bioassay-directed fractionation of the organic extract of Mallotus philippinensis gave five compounds (1-5), the most active of which against Mycobacterium tuberculosis was a new compound, 8-cinnamoyl-5,7-dihydroxy-2,2-dimethyl-6-geranylchromene (1) for which the name mallotophilippen F is suggested. Compound (2), 8-cinnamoyl-2,2-dimethyl-7-hydroxy-5-methoxychromene, was isolated from a natural source for the first time, while the remaining three compounds, rottlerin (3), isoallorottlerin=isorottlerin (4) and the so-called “red compound,” 8-cinnamoyl-5,7-dihydroxy-2,2,6-trimethylchromene (5), had been isolated previously from this plant. All compounds were identified by analysis of their spectra including 2D-NMR, which was used to correct the literature NMR spectral assignments of compounds 2-4. The C-13 NMR of 5 is reported for the first time.

Prenylflavones from Psoralea corylifolia inhibit nitric oxide synthase expression through the inhibition of I-kappaB-alpha degradation in activated microglial cells

The overproduction of nitric oxide (NO) by inducible nitric oxide synthase (iNOS) switches the function of NO from a physiological neuromodulator to a neurotoxic effector in central nervous system (CNS) after brain injury. From the methanol extracts of Psoralea corylifolia, we purified two inhibitors of NO production in lipopolysaccharide (LPS)-activated microglia by activity guided purification along with two inactive compounds. The active compounds were identified as a chromenoflavanone [7,8-dihydro-8-(4-hydroxyphenyl)-2,2-dimethyl-2H,6H-benzo-(1,2-b:5,4-b')dipyran-6-one] (1) and 4-hydroxylonchocarpin (2). And the inactive two compounds were identified as bavachinin (3) and bavachalcone (4) by spectral analysis. The compound 2 was isolated first time from this plant. Compounds 1 and 2 inhibited the production of NO in LPS-activated microglia in a dose dependent manner (IC(50)'s were 11.4, 10.2 microM, respectively). They also suppressed the expression of protein and mRNA of iNOS in LPS-activated microglial cells at 10 muM as observed in Western blot analysis and RT-PCR experiment. Furthermore they inhibited the degradation of I-kappaB-alpha in activated microglia. These results imply that compounds 1 and 2 can be lead compounds for the development of neuroprotective drug with the inhibitory activity of NO overproduction by activated microglial cells.

Anti-inflammatory Activity of New Guaiane Type Sesquiterpene from Wikstroemia indica

In our investigation of in vitro anti-allergic screening of medicinal herbal extracts, the ethyl acetate extract of the root of Wikstroemia indica was observed to inhibit nitric oxide (NO) production in a lipopolysaccharide (LPS) and recombinant mouse interferon-gamma (IFN-gamma) activated murine macrophage-like cell line, RAW 264.7. Fractionation of the active extract led to the isolation of one new guaiane type sesquiterpene, indicanone (1), and two known biflavonoids, sikokianin B (2) and sikokianin C (3). 1 inhibited NO production with IC50 values at 9.3 microM and also inhibit the inducible nitric oxide synhase (iNOS) gene expression. This is the first report of NO production inhibitory activity of Wikstroemia indica and supports the pharmacological use of it, which has been employed as an herbal medicine for the treatment of inflammation.