Anti-inflammatory activity of Barleria lupulina: Identification of active compounds that activate the Nrf2 cell defense pathway, organize cortical actin, reduce stress fibers, and improve cell junctions in microvascular endothelial cells

Acetyl barlerin from Barleria trispinosa induces chemopreventive NQO1 and attenuates LPS-induced inflammation: in vitro and molecular dynamic studies

Extraction and fractionation of Barleria trispinosa growing in Saudi Arabia yielded four iridoid compounds identified by spectroscopic techniques as acetylbarlerin (1), barlerin (2), shanzhiside methyl ester (3) and 6-⍺-L-rhamnopyranosyl-8-O-acetylshanzihiside methyl ester (4). Preliminary experiments confirmed that compound 1 acts as an inducer of chemopreventive NAD(P)H:Quinone oxidoreductase 1 (NQO1) enzymatic activity in a murine hepatoma (Hepa1c1c7) chemoprevention model. It also demonstrated the ability to inhibit the lipopolysaccharides (LPS)-induced nitric oxide (NO) production in the RAW264.7 macrophage model. Western blotting revealed the ability of compound 1 to up-regulate the protein expression of the NQO1 marker. Furthermore, compound 1 elicited NO suppression in RAW264.7 macrophages by inhibiting iNOS protein expression. Molecular docking and molecular simulation studies of 1 supported its experimental results as an inhibitor of the nuclear factor erythroid 2-Kelch-like ECH-associated protein 1 (Nrf2-KEAP1) complex, resulting in Nrf2-mediated induction of chemopreventive NQO1.Communicated by Ramaswamy H. Sarma.

A critical appraisal on the involvement of plant-based extracts as neuroprotective agents (2012-2022): an effort to ease out decision-making process for researchers

The purpose of this review study is to provide a condensed compilation of 164 medicinal plants that have been investigated for their neuroprotective aspects by researchers between the years 2012 and 2022 which also includes a recent update of 2023-2024. After using certain keywords to retrieve the data from SCOPUS, it was manually sorted to eliminate any instances of duplication. The article is streamlined into three major segments. The first segment takes a dig into the current global trend and attempts to decrypt vital information related to plant names, families, plant parts used, and neurological disorders investigated. The second segment of the article makes an attempt to present a comprehensive insight into the various mechanistic pathways through which phytochemicals can intervene to exert neuroprotection. The final segment of the manuscript is a bibliometric appraisal of all researches conducted. The study is based on 256 handpicked articles based on decided inclusion criteria. Illustrative compilation of various pathways citing their activation and deactivation channels are also presented with possible hitting points of various phytochemicals. The present study employed Microsoft Excel 2019 and VOS viewer as data visualisation tools.

Evaluating birch leaf tea as a functional herbal beverage: Beneficial impact on the urinary tract, and metabolism in human organism

Herbal teas are considered as a potential constituent of novel functional beverages consumed daily. One of the commonly used herbal teas is silver birch (Betula pendula Roth) leaf infusion, traditionally used in urinary tract diseases. In this study, the potential of birch leaf infusion as a functional beverage, emphasizing its active ingredients' bioavailability, anti-inflammatory, and antiadhesive properties concerning urinary tract health, was investigated. A complex approach was proposed, which included phytochemical screening, bioavailability, gut microbiota biotransformation, and an in vivo test for urine metabolomics assessment. The bioassays confirmed significant anti-inflammatory (interleukins IL-6 and IL-8 secretion) and anti-adhesive (Uropathogenic Escherichia coli and T24 bladder cells) activities. The high-resolution mass spectrometry metabolomics studies linked gut microbiota metabolites and the metabolites present in the urine. Several metabolites connected with phenolics' consumption were detected in the urine, e.g., glucuronides and sulfates of caffeic acid and dihydroxyphenyl-γ-valerolactones. Based on the presented results, the birch leaf should be considered useful in designing functional beverages, especially targeted to the groups at high risk of urinary diseases.

Challenges and advances in biotechnological approaches for the synthesis of canolol and other vinylphenols from biobased p-hydroxycinnamic acids: a review

p-Hydroxycinnamic acids, such as sinapic, ferulic, p-coumaric and caffeic acids, are among the most abundant phenolic compounds found in plant biomass and agro-industrial by-products (e.g. cereal brans, sugar-beet and coffee pulps, oilseed meals). These p-hydroxycinnamic acids, and their resulting decarboxylation products named vinylphenols (canolol, 4-vinylguaiacol, 4-vinylphenol, 4-vinylcatechol), are bioactive molecules with many properties including antioxidant, anti-inflammatory and antimicrobial activities, and potential applications in food, cosmetic or pharmaceutical industries. They were also shown to be suitable precursors of new sustainable polymers and biobased substitutes for fine chemicals such as bisphenol A diglycidyl ethers. Non-oxidative microbial decarboxylation of p-hydroxycinnamic acids into vinylphenols involves cofactor-free and metal-independent phenolic acid decarboxylases (EC 4.1.1 carboxyl lyase family). Historically purified from bacteria (Bacillus, Lactobacillus, Pseudomonas, Enterobacter genera) and some yeasts (e.g. Brettanomyces or Candida), these enzymes were described for the decarboxylation of ferulic and p-coumaric acids into 4-vinylguaiacol and 4-vinylphenol, respectively. The catalytic mechanism comprised a first step involving p-hydroxycinnamic acid conversion into a semi-quinone that then decarboxylated spontaneously into the corresponding vinyl compound, in a second step. Bioconversion processes for synthesizing 4-vinylguaiacol and 4-vinylphenol by microbial decarboxylation of ferulic and p-coumaric acids historically attracted the most research using bacterial recombinant phenolic acid decarboxylases (especially Bacillus enzymes) and the processes developed to date included mono- or biphasic systems, and the use of free- or immobilized cells. More recently, filamentous fungi of the Neolentinus lepideus species were shown to natively produce a more versatile phenolic acid decarboxylase with high activity on sinapic acid in addition to the others p-hydroxycinnamic acids, opening the way to the production of canolol by biotechnological processes applied to rapeseed meal. Few studies have described the further microbial/enzymatic bioconversion of these vinylphenols into valuable compounds: (i) synthesis of flavours such as vanillin, 4-ethylguaiacol and 4-ethylphenol from 4-vinylguaiacol and 4-vinylphenol, (ii) laccase-mediated polymer synthesis from canolol, 4-vinylguaiacol and 4-vinylphenol.

Pharmacology-based molecular docking of 4-methylcatechol and its role in RANKL-mediated ROS/Keap1/Nrf2 signalling axis and osteoclastogenesis

4-Methylcatechol (4-MC) is an agonist of various neurotrophic factors, which can upregulate the expression of Heme oxygenase 1 (HO-1) protein by activating nuclear factor erythroid 2-related factor 2 (Nrf2), thereby inhibiting oxidative stress-induced neural stem cell death. During RANKL-stimulated osteoclast differentiation, intracellular reactive oxygen species (ROS) levels were increased. Nonetheless, the effect of 4-MC on osteoclast formation and bone resorption function has not been researched. In this study, we investigated the effect of HO-1 upregulation by 4-MC on RANKL-induced osteoclastogenesis and explored the molecular mechanism of HO-1 upregulation by 4-MC. We found that the small molecule compound 4-MC could bind to Keap1 amino acid residue of glycine GLY 367, isoleucine ILE 559 and valine VAL 606, with a predicted binding energy of -4.99 kcal/mol. 4-MC was found to inhibit osteoclast differentiation in vitro by activating Nrf2 to scavenge ROS, inhibiting NF-κB phosphorylation, and alleviating osteoporosis in ovariectomized (OVX) mice. Taken together, 4-MC reduces ROS by inhibiting Keap1, thereby preventing OVX-induced bone loss.

The Antiplatelet Effect of 4-Methylcatechol in a Real Population Sample and Determination of the Mechanism of Action

A polyphenol-rich diet has beneficial effects on cardiovascular health. However, dietary polyphenols generally have low bioavailability and reach low plasma concentrations. Small phenolic metabolites of these compounds formed by human microbiota are much more easily absorbable and could be responsible for this effect. One of these metabolites, 4-methylcatechol (4-MC), was suggested to be a potent anti-platelet compound. The effect of 4-MC was tested ex vivo in a group of 53 generally healthy donors using impedance blood aggregometry. The mechanism of action of this compound was also investigated by employing various aggregation inducers/inhibitors and a combination of aggregometry and enzyme linked immunosorbent assay (ELISA) methods. 4-MC was confirmed to be more potent than acetylsalicylic acid on both arachidonic acid and collagen-triggered platelet aggregation. Its clinically relevant effect was found even at a concentration of 10 μM. Mechanistic studies showed that 4-MC is able to block platelet aggregation caused by the stimulation of different pathways (receptors for the von Willebrand factor and platelet-activating factor, glycoprotein IIb/IIIa, protein kinase C, intracellular calcium elevation). The major mechanism was defined as interference with cyclooxygenase-thromboxane synthase coupling. This study confirmed the strong antiplatelet potential of 4-MC in a group of healthy donors and defined its mechanism of action.

Recent Advances in KEAP1/NRF2-Targeting Strategies by Phytochemical Antioxidants, Nanoparticles, and Biocompatible Scaffolds for the Treatment of Diabetic Cardiovascular Complications

Significance: Modulation of nuclear factor (erythroid-derived 2)-like 2 (Nrf2)-mediated antioxidant response is a key aspect in the onset of diabetes-related cardiovascular complications. With this review, we provide an overview of the recent advances made in the development of Nrf2-targeting strategies for the treatment of diabetes, with particular attention toward the activation of Nrf2 by natural antioxidant compounds, nanoparticles, and oxidative stress-modulating biocompatible scaffolds. Recent Advances: In the past 30 years, studies addressing the use of antioxidant therapies to treat diabetes have grown exponentially, showing promising but yet inconclusive results. Animal studies and clinical trials on the Nrf2 pathway have shown promising results, suggesting that its activation can delay or reverse some of the cardiovascular impairments in diabetes. Critical Issues: Hyperglycemia- and oscillating glucose levels-induced reactive oxygen species (ROS) accumulation is progressively emerging as a central factor in the onset and progression of diabetes-related cardiovascular complications, including endothelial dysfunction, retinopathy, heart failure, stroke, critical limb ischemia, ulcers, and delayed wound healing. In this context, accumulating evidence suggests a central role for Nrf2-mediated antioxidant response, one of the most studied cellular defensive mechanisms against ROS accumulation. Future Directions: Innovative approaches such as tissue engineering and nanotechnology are converging toward targeting oxidative stress in diabetes. Antioxid. Redox Signal. 36, 707-728.

Phytochemicals and Biological Activities of Barleria (Acanthaceae)

Plant species belonging to the family Acanthaceae are globally known to possess various medicinal properties and have cultural and economic importance in both traditional medicine and horticulture. They are important to both animals and humans and are used as food or for ornamental purposes worldwide. Barleria is the third largest genus in the family Acanthaceae. A few of the highly important and reported species of Barleria include B. prionitis, B. cristata, B. grandiflora, and B. lupulina. The flowers, leaves, stems, roots, and seed extracts of plants belonging to this genus are rich in bioactive compounds and have exhibited significant medicinal potential for the treatment of various ailments and infections. Evidence derived from several studies has demonstrated the antioxidant, antibacterial, antifungal, anti-inflammatory, anticancer, antidiabetic, antiulcer, hepatoprotective, analgesic, antiamoebic, antihelminthic, antiarthritic, antihypertensive, antiviral properties and toxicity of extracts, in addition inhibition of acetylcholinesterase activity and biosynthesis of nanoparticles, of the plant and seed extracts of species belonging to Barleria. Studies have reported that bioactive compounds such as flavonoids, quinones, iridoids, phenylethanoid glycosides, the immunostimulant protein “Sankaranin”, and antibiotics isolated from Barleria species are resposnsible for the above biological activities. Traditionally, the genus Barleria has significant medicinal potential; however, there is a scarcity of information on various species that are yet to be evaluated. This review provides a comprehensive report on existing literature, concerning the phytochemistry and biological activities of the genus Barleria.

Integrin α4β1 is required for IL-1α- and Nrf2-dependent, Cox-2 induction in fibroblasts, supporting a mechanism that suppresses α-SMA expression

Growth and repair processes, both normal and pathological, require reciprocal interactions between cells and their microenvironment. Integrins are bidirectional, cell surface receptors that transduce mechanical and chemical signals to and from the extracellular matrix. We recently reported that keratinocyte α3β1 is required for interleukin (IL)-1α secretion. Importantly, IL-1α regulates fibroblast Cox-2 expression and prostaglandin E2 (PGE₂ ) secretion, thereby linking keratinocyte integrin function to a paracrine signal that suppresses the myofibroblast phenotype. We now report that fibroblast integrin α4β1 is required for this IL-1α-induced, Cox-2 expression. Moreover, Cox-2 induction by IL-1α requires Nuclear factor erythroid 2-related factor 2 (Nrf2), the master regulator of redox homeostasis; and integrin α4β1 is necessary to maintain IL-1α-dependent, Nrf2 levels. Treating fibroblasts with a Nrf-2 activating compound inhibits TGF-β-dependent, alpha smooth muscle actin (α-SMA) expression and stress fibre formation. Our data suggest that fibroblast integrin α4β1 regulates-depending on microenvironmental cues-the differentiated state of fibroblasts through a signalling network in which IL-1α, Cox-2 and Nrf2 participate.

Optimizing Conditions for Microwave-Assisted Extraction of Polyphenolic Content and Antioxidant Activity of Barleria lupulina Lindl

Barleria lupulina Lindl. (Acanthaceae) as an ornamental plant has been widely used in folklore medicine due to its abundancy in polyphenolic compounds. The present study examined conditions for optimal extraction of antioxidants from B. lupulina leaf extracts by using the microwave-assisted extraction (MAE) method. The effects of ethanol concentrations, microwave power, and extraction time on total phenolic content (TPC), total flavonoid content (TFC), 1-diphenyl-2-picrylhydrazyl (DPPH), and 2,20-azino-bis (3-ethylbenzothizoline-6-sulfonic acid) (ABTS) were investigated by single-factor experiments. Response surface methodology (RSM) was applied to observe interactions of three independent variables (ethanol concentrations, microwave power, and extraction time) on the dependent variables (TPC, TFC, DPPH, and ABTS) to establish optimal extraction conditions. Quadratic polynomial equations in all experimental models yielded favorably with fitted models with R2 and R2adj of more than 0.90 and a non-significant lack of fit at p > 0.05. The optimal conditions for the extraction of antioxidant activity were established at 80% (v/v) ethanol, 400 W, and 30 s with TPC (238.71 mg gallic acid equivalent (GAE)/g sample), TFC (58.09 mg QE/g sample), DPPH (87.95%), and ABTS (89.56%). Analysis by ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-QTOF/MS) successfully identified four new phenylethanoid glycoside compounds in the species.

The anti-inflammatory properties of Acanthus Ebracteatus, Barleria Lupulina and Clinacanthus Nutans: a systematic review

This appraisal is comprised of the inflammatory studies that have been conducted on Clinacanthus nutans, Acanthus ebracteatus, and Barleria lupulina. The review aims to provide a comprehensive evaluation of the supporting and contradictory evidence on each plants' anti-inflammatory properties, whilst addressing the gaps in the current literature. The databases used to obtain relevant studies were Google Scholar, ResearchGate, PubMed and Nusearch (University of Nottingham). A total of 13 articles were selected for this review. A. ebracteatus was found to suppress neutrophil migration and weakly inhibits chronic inflammatory cytokines. Furthermore, B. lupulina and C. nutans were shown to possess very similar anti-inflammatory properties. The studies on C. nutans indicated that its anti-inflammatory effect is strongly related to the inhibition of toll-like receptor 4 (TLR4). Moreover, several phytoconstituents isolated from B. lupulina were shown to activate the anti-inflammatory Nrf2 pathway. Overall, all the studies have provided evidence to support the use of these plants as anti-inflammatory herbal remedies. However, their exact mechanism of action and the responsible phytoconstituents are yet to be established.

Protective effects of sulforaphane in experimental vascular cognitive impairment: Contribution of the Nrf2 pathway

The major pathophysiological process of vascular cognitive impairment (VCI) is chronic cerebral ischemia, which causes disintegration of the blood-brain barrier (BBB), neuronal death, and white matter injury. This study aims to test whether sulforaphane (Sfn), a natural activator of nuclear factor erythroid 2-related factor 2 (Nrf2), reduces the chronic ischemic injury and cognitive dysfunction after VCI. Experimental VCI was induced in rats by permanent occlusion of both common carotid arteries for six weeks. This procedure caused notable neuronal death in the cortex and hippocampal CA1, myelin loss in the corpus callosum and hippocampal fimbria, accumulation of myelin debris in the corpus callosum, and remarkable cognitive impairment. Sfn treatment alleviated these ischemic injuries and the cognitive dysfunction. Sfn-mediated neuroprotection was associated with enhanced activation of Nrf2 and upregulation of heme oxygenase 1. Sfn also reduced neuronal and endothelial death and maintained the integrity of BBB after oxygen-glucose deprivation in vitro in an Nrf2 dependent manner. Furthermore, Nrf2 knockdown in endothelial cells decreased claudin-5 protein expression with downregulated claudin-5 promoter activity, suggesting that claudin-5 might be a target gene of Nrf2. Our results demonstrate that Sfn provides robust neuroprotection against chronic brain ischemic injury and may be a promising agent for VCI treatment.

Multicombination Approach Suppresses Listeria monocytogenes-Induced Septicemia-Associated Acute Hepatic Failure: The Role of iRhom2 Signaling

The mortality rate of acute liver failure significantly increases due to fatal septicemia. Inactive rhomboid protein 2 (iRhom2) is an essential regulator of shedding TNF-α by trafficking with TNF-α converting enzyme (TACE). Fisetin, a flavonoid present in various fruits and plants, possesses anti-oxidative stress and anti-inflammatory activities. Here, multi-combination nanoparticles Fe@Au conjugated with fisetin, iRhom2 small interfering RNA (siRNA), and TNF-α inhibitor (FN) are prepared to examine their effects on fatal septicemia-associated hepatic failure induced by Listeria monocytogenes (LM) in mice and to reveal the underlying mechanisms. After LM infection, upregulation of glutamic-oxalacetic transaminease, glutamic-pyruvic transaminase, alkaline phosphatase, TNF-α, malondialdehyde, H₂ O₂ , and O₂^- is observedcompared to FN-treated mice. The iRhom2/TACE/TNF-α signals are enhanced in vivo and in vitro, resulting in oxidative stress, which is especially associated with the activation of kupffer cells and other macrophages. Decrease in Nrf2 activation and increase of inflammation-associated regulators are also noted in vivo and in vitro. Furthermore, overexpression of TNF-α derived from macrophages aggravates hepatic failure. Inversely, the processes above are restored by FN nanoparticles through the regulation of the iRhom2/TACE/TNF-α axis and Nrf2 activation. These findings suggest that FN may be a potential approach to protect against bacterial septicemia-related diseases by targeting iRhom2.

Two flavonoid metabolites, 3,4-dihydroxyphenylacetic acid and 4-methylcatechol, relax arteries ex vivo and decrease blood pressure in vivo

SCOPE

The flavonoid quercetin reduces arterial blood pressure in animals and humans but the mechanisms remains elusive. The aim of this study was to test the activity of flavonoid microbial metabolites, which can participate on the final vasorelaxant effect.

METHODS AND RESULTS

Both ex vivo (isolated rat thoracic aorta and mesenteric artery) and in vivo (normotensive and spontaneously hypertensive rats) approaches were used in this study. 4-methylcatechol and 3,4-dihydroxyphenylacetic acid (DHPA) had greater vasorelaxant effects on mesenteric artery than 3-(3-hydroxyphenyl)propionic acid, the previously reported metabolite with vasorelaxant effect. In vivo testing confirmed their blood pressure decreasing effect given both as bolus and slow infusion. Their mechanism at molecular level was different.

CONCLUSIONS

This study is the first to show that flavonoid metabolites DHPA and 4-methylcatechol decrease arterial blood pressure and hence a mixture of microbial metabolites formed in the gastrointestinal tract may be responsible for or contribute to the effect of orally ingested quercetin.

Conflicting actions of 4-vinylcatechol in rat lymphocytes under oxidative stress induced by hydrogen peroxide

4-Vinylcatechol (4VC) has been identified as an aroma compound in roasted foods, especially coffee. It is also a component in traditional herbal medicines. This compound may be subconsciously ingested through foods and herbs. Recent experimental evidence has shown that 4VC possesses an antioxidative action. However, the antioxidative action of 4VC at cellular levels is not well characterized. The effects of 4VC (0.1-100 µM) were examined on rat thymic lymphocytes without and with oxidative stress induced by 300 µM hydrogen peroxide (H₂O₂). Cell treatment with 100 µM 4VC alone for 4 h significantly increased the population of dead cells. Thus, 4VC at 100 µM or above elicits cytotoxicity. However, 4VC at sublethal concentrations (1-10 µM) significantly attenuated the H₂O₂-induced increase in cell lethality in a concentration-dependent manner. While application of 10 µM 4VC slowed the process of cell death induced by H₂O₂, 4VC did not antagonize the H₂O₂-induced reduction of cellular nonprotein thiols. Although 4VC at 10 µM did not affect intracellular Ca²⁺ and Zn²⁺ levels, the agent potentiated the H₂O₂-induced increases in these levels. These actions of 10 µM 4VC are adverse to the cells under the oxidative stress. However, 10 µM 4VC partly attenuated the cell death induced by 100 nM A23187, a calcium ionophore. There are conflicting actions of 4VC at 1-100 µM on the cells under oxidative stress although the agent is used for an antioxidant. Thus, caution is required when using 4VC as a therapeutic agent.

The Role of Nrf2 in Cardiovascular Function and Disease

Free radicals, reactive oxygen/nitrogen species (ROS/RNS), hydrogen sulphide, and hydrogen peroxide play an important role in both intracellular and intercellular signaling; however, their production and quenching need to be closely regulated to prevent cellular damage. An imbalance, due to exogenous sources of free radicals and chronic upregulation of endogenous production, contributes to many pathological conditions including cardiovascular disease and also more general processes involved in aging. Nuclear factor erythroid 2-like 2 (NFE2L2; commonly known as Nrf2) is a transcription factor that plays a major role in the dynamic regulation of a network of antioxidant and cytoprotective genes, through binding to and activating expression of promoters containing the antioxidant response element (ARE). Nrf2 activity is regulated by many mechanisms, suggesting that tight control is necessary for normal cell function and both hypoactivation and hyperactivation of Nrf2 are indicated in playing a role in different aspects of cardiovascular disease. Targeted activation of Nrf2 or downstream genes may prove to be a useful avenue in developing therapeutics to reduce the impact of cardiovascular disease. We will review the current status of Nrf2 and related signaling in cardiovascular disease and its relevance to current and potential treatment strategies.

Diabetic Wound Healing and Activation of Nrf2 by Herbal Medicine

Nrf2 defense is a very important cellular mechanism to control oxidative stress, which is implicated in wound healing. Nrf2 can induce many cytoprotective genes, including HO-1, NQO1 and G6PD. Among many natural products that have been reported as Nrf2 activators, sulforaphane and curcumin have been studied more widely than any others, and both are in clinical trials for non-cancerous disorders. Recently, we reported 4-ethyl catechol and 4-vinyl catechol as Nrf2 co-factors that can induce Nrf2 as potently as sulforaphane and curcumin. These new Nrf2 co-factors were identified in hot aqueous extract of an herbal medicine Barleria lupulina, and fermented Noni (Morinda citrifolia) juice, which are used traditionally for diabetic wound healing.