In vitro activity of isoimperatorin, alone and in combination, against Mycobacterium tuberculosis

Antibacterial phenolic compounds from the flowering plants of Asia and the Pacific: coming to the light

CONTEXT

The emergence of pan-resistant bacteria requires the development of new antibiotics and antibiotic potentiators.

OBJECTIVE

This review identifies antibacterial phenolic compounds that have been identified in Asian and Pacific Angiosperms from 1945 to 2023 and analyzes their strengths and spectra of activity, distributions, molecular masses, solubilities, modes of action, structures-activities, as well as their synergistic effects with antibiotics, toxicities, and clinical potential.

METHODS

All data in this review was compiled from Google Scholar, PubMed, Science Direct, Web of Science, and library search; other sources were excluded. We used the following combination of keywords: 'Phenolic compound', 'Plants', and 'Antibacterial'. This produced 736 results. Each result was examined and articles that did not contain information relevant to the topic or coming from non-peer-reviewed journals were excluded. Each of the remaining 467 selected articles was read critically for the information that it contained.

RESULTS

Out of ∼350 antibacterial phenolic compounds identified, 44 were very strongly active, mainly targeting the cytoplasmic membrane of Gram-positive bacteria, and with a molecular mass between 200 and 400 g/mol. 2-Methoxy-7-methyljuglone, [6]-gingerol, anacardic acid, baicalin, vitexin, and malabaricone A and B have the potential to be developed as antibacterial leads.

CONCLUSIONS

Angiosperms from Asia and the Pacific provide a rich source of natural products with the potential to be developed as leads for treating bacterial infections.

A review of the ethnomedicinal, phytochemical, and pharmacological properties of the Ferulago genus based on Structure-Activity Relationship (SAR) of coumarins

BACKGROUND

The Ferluago W.D.J. Koch genus includes 48 accepted perennial herbs that are distributed in the Mediterranean region, Southeast Europe, Central and Middle East of Asia. These plants are widely used in folk and conventional medicine due to their biological benefits such as anti-microbial, anti-inflammatory, anti-cancer, and immunomodulatory properties. Conducting a comprehensive review based on the structure activity relationships (SARs) of the coumarins, which has not been previously documented, can lead to a better insight into the genus Ferulago and its beneficial therapeutic activities.

METHODS

This review covers literature from 1969 to 2023, were collected from various scientific electronic databases to review phytochemical, pharmacological, and ethnopharmacological data of Ferulago species, as well as latest information on the SAR of reported coumarins from this genus.

RESULTS

Phytochemical studies showed that the biological actions of this genus are mediated by the reported specialized metabolites, such as coumarins and flavonoids. Simple coumarins, prenylated coumarins, furanocoumarins, and pyranocoumarins are the largest subclasses of coumarins found in diverse Ferulago species, which have discussed the biological effects of them with a focus on the Structure-Activity Relationship (SAR). For example, prenylated coumarins have shown potential leishmanicidal and anti-neuropsychiatric effects when substituted with a prenyl group at the 7-hydroxy, as well as the C6 and C8 positions in their scaffold. Similarly, furanocoumarins exhibit varied biological activities such as anti-inflammatory, anti-proliferative, and anti-convulsant effects. Modifying substitutions at the C5 and C6 positions in furanocoumarins can enhance these activities.

CONCLUSION

This study conducted a comprehensive review of all available information on the phytochemical and pharmacological characteristics of Ferulago species. Given the high occurrence of coumarins in this genus, which exhibit potential anti-Alzheimer and anti-microbial properties, it presents promising new therapeutic avenues for addressing these common issues. Further investigation is needed to understand the molecular-level mechanisms of action and to explore their clinical applications.

Bioactive Chemical Constituents and Pharmacological Activities of Ponciri Fructus

Ponciri Fructus is a crude drug obtained from the dried immature fruits of Poncirus trifoliata (L). Raf. (Syn. Citrus trifoliata L.). This study aims to compile and analyze the ethnomedicinal uses, bioactive constituents, and pharmacological activities of Ponciri Fructus. Various online bibliographic databases namely, SciFinder, PubMed, Google Scholar, and Web of Science were used for collecting information on traditional uses, biological activities, and bioactive constituents. Concerning ethnomedicinal uses, Ponciri Fructus is extensively used in traditional Korean, Chinese, and Kampo medicines to mitigate allergic reactions, inflammation, edema, digestive complications, respiratory problems, spleen-related problems, liver complications, neuronal pain, hyperlipidemia, rheumatoid arthritis, cardiovascular problems, hernia, sinusitis, and insomnia. Several studies have shown that Ponciri Fructus is a major source of diverse classes of bioactive compounds namely flavonoids, terpenoids, coumarins, phytosterols, and alkaloids. Several in vivo and in vitro pharmacological activity evaluations such as antidiabetic, anti-obesity, anti-inflammatory, antiallergic, antimelanogenic, gastroprotective, anticancer, and neuroprotective effects have been conducted from Ponciri Fructus. However, scientific investigations focusing on bioassay-guided isolation and identification of specific bioactive constituents are limited. Therefore, an in-depth scientific investigation of Ponciri Fructus focusing on bioassay-guided isolation, mechanism based pharmacological studies, pharmacokinetic studies, and evaluation of possible toxicities is necessary in the future.

Simultaneous separation and determination of six furanocoumarins in Radix Angelicae dahuricae by CZE with dual CDs system

A novel, simple and efficient capillary electrophoresis method was developed to simultaneous determination of six furanocoumarins (psoralen, isopsoralen, imperatorin, isoimperatorin, phellopterin, and cnidilin). The separation buffer consisted of 30 mM boric acid, 12 mM sulfobutylether-β-cyclodextrin and 1.5 mM 2-hydroxypropyl-β-cyclodextrin (pH 7.8); the voltage was 20 kV, the temperature was 25 °C and the detection wavelength was at 246 nm with a diode array detector (DAD). Under the above conditions, the analytes could be separated with high resolution in less than 7 min. This method was used to simultaneously determine the content of psoralen, imperatorin, isoimperatorin and phellopterin in Angelica Dahurica Radix. And good linearities were obtained with correlation coefficients from 0.9992 to 0.9999. The limits of detection (LOD, S/N = 3) and the limits of quantitation (LOQ, S/N = 10) ranged from 0.6 to 3.0 μg/mL and from 2.1 to 9.9 μg/mL, respectively. The recoveries ranged between 98.8% and 101.8%. The results indicated the method can achieve baseline separation and quantitative analysis of furanocoumarins in Chinese herbal medicines and formulations.

Antibiotic resistance modifying ability of phytoextracts in anthrax biological agent Bacillus anthracis and emerging superbugs: a review of synergistic mechanisms

Background and objectives

The chemotherapeutic management of infections has become challenging due to the global emergence of antibiotic resistant pathogenic bacteria. The recent expansion of studies on plant-derived natural products has lead to the discovery of a plethora of phytochemicals with the potential to combat bacterial drug resistance via various mechanisms of action. This review paper summarizes the primary antibiotic resistance mechanisms of bacteria and also discusses the antibiotic-potentiating ability of phytoextracts and various classes of isolated phytochemicals in reversing antibiotic resistance in anthrax agent Bacillus anthracis and emerging superbug bacteria.

Methods

Growth inhibitory indices and fractional inhibitory concentration index were applied to evaluate the in vitro synergistic activity of phytoextract-antibiotic combinations in general.

Findings

A number of studies have indicated that plant-derived natural compounds are capable of significantly reducing the minimum inhibitory concentration of standard antibiotics by altering drug-resistance mechanisms of B. anthracis and other superbug infection causing bacteria. Phytochemical compounds allicin, oleanolic acid, epigallocatechin gallate and curcumin and Jatropha curcas extracts were exceptional synergistic potentiators of various standard antibiotics.

Conclusion

Considering these facts, phytochemicals represents a valuable and novel source of bioactive compounds with potent antibiotic synergism to modulate bacterial drug-resistance.

An Efficient Ionic Liquid-Mediated Extraction and Enrichment of Isoimperatorin from Ostericum koreanum (Max.) Kitagawa

Ionic liquids (ILs) have attracted significant interest because of their desirable properties. These characteristics have improved their application to overcome the shortcomings of conventional separation techniques for phytochemicals. In this study, several ILs were investigated for their capacity to extract isoimperatorin, a bioactive furanocoumarin, from the roots of Ostericum koreanum. Herein, 1-Butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) was selected as a promising IL for separating isoimperatorin. A central composite design was applied to optimize the extraction conditions. Under the optimal conditions, the yield of isoimperatorin reached 97.17 ± 1.84%. Additionally, the recovery of isoimperatorin from the [Bmim][BF4] solution was successfully achieved (87.73 ± 2.37%) by crystallization using water as an antisolvent. The purity of the isoimperatorin was greatly enhanced, from 0.26 ± 0.28% in the raw material to 26.94 ± 1.26% in the product, in a one-step crystallization process. Namely, an enhancement of approximately 103-folds was reached. The developed approach overcomes the shortcomings of conventional separation methods applied for gaining isoimperatorin by significantly reducing the laboriousness of the process and the consumption of volatile organic solvents. Moreover, the simplicity and effectiveness of the method are assumed to be valuable for producing isoimperatorin-enriched products and for promoting its purification. This work also confirms the efficiency of ILs as a promising material for the separation of phytochemicals.

Antiviral Activity of Isoimperatorin Against Influenza A Virus in vitro and its Inhibition of Neuraminidase

Influenza A virus (IAV) poses a severe threat to human health and is a major public health problem worldwide. As global anti-influenza virus drug resistance has increased significantly, there is an urgent need to develop new antiviral drugs, especially drugs from natural products. Isoimperatorin, an active natural furanocoumarin, exhibits a broad range of pharmacologic activities including anticoagulant, analgesic, anti-inflammatory, antibacterial, anti-tumor, and other pharmacological effects, so it has attracted more and more attention. In this study, the antiviral and mechanistic effects of isoimperatorin on influenza A virus in vitro were studied. Isoimperatorin illustrated a broad-spectrum antiviral effect, especially against the A/FM/1/47 (H1N1), A/WSN/33 (H1N1, S31N, amantadine resistant), A/Puerto Rico/8/34 (H1N1), and A/Chicken/Guangdong/1996 (H9N2) virus strains. The experimental results of different administration modes showed that isoimperatorin had the best antiviral activity under the treatment mode. Further time-of-addition experiment results indicated that when isoimperatorin was added at the later stage of the virus replication cycle (6–8 h, 8–10 h), it exhibited an effective antiviral effect, and the virus yield was reduced by 81.4 and 84.6%, respectively. In addition, isoimperatorin had no effect on the expression of the three viral RNAs (mRNA, vRNA, and cRNA). Both the neuraminidase (NA) inhibition assay and CETSA demonstrated that isoimperatorin exerts an inhibitory effect on NA-mediated progeny virus release. The molecular docking experiment simulated the direct interaction between isoimperatorin and NA protein amino acid residues. In summary, isoimperatorin can be used as a potential agent for the prevention and treatment of influenza A virus.

Gut Metabolism of Furanocoumarins: Proposed Function of Co O-Methyltransferase

Gut metabolism of natural products is of great interest due to the altered biological activity of the metabolites. To study the gut metabolism of the dietary furanocoumarins, the biotransformation of Angelica dahurica was studied with human gut microbiota. The major components of Avenula dahurica, including xanthotoxin (1), bergapten (2), imperatorin (3), isoimperatorin (4), oxypeucedanin (5), and byakangelicol (6), were all metabolized by the human fecal sample, and each furanocoumarin was also biotransformed by Blautia sp. MRG-PMF1 responsible for intestinal O-demethylation. Oxypeucedanin (5) and byakangelicol (6) were converted to oxypeucedanin hydrate (9) and desmethylbyakangelicin (12), respectively. The gut microbial conversion of xanthotoxin (1) and bergapten (2) with the MRG-PMF1 strain resulted in the production of xanthotoxol (7) and bergaptol (8), respectively, due to the methyl aryl ether cleavage by O-methyltransferase. Unexpectedly, the biotransformation of prenylated furanocoumarins, imperatorin (3), and isoimperatorin (4) resulted in the corresponding deprenylated furanocoumarins of xanthotoxol (7) and bergaptol (8), respectively. The cleavage of the prenyl aryl ether group by gut microbiota was unprecedented metabolism. Our data presented the first deprenylation of prenylated natural products, presumably by the anaerobic prenyl aryl ether cleavage reaction catalyzed by Co-corrinoid enzyme.

Coumarins as Modulators of the Keap1/Nrf2/ARE Signaling Pathway

The Keap1/Nrf2/ARE system is a central defensive mechanism against oxidative stress which plays a key role in the pathogenesis and progression of many diseases. Nrf2 is a redox-sensitive transcription factor controlling a variety of downstream antioxidant and cytodefensive genes. Nrf2 has a powerful anti-inflammatory activity mediated via modulating NF-κB. Therefore, pharmacological activation of Nrf2 is a promising therapeutic strategy for the treatment/prevention of several diseases that are underlined by both oxidative stress and inflammation. Coumarins are natural products with promising pharmacological activities, including antioxidant, anticancer, antimicrobial, and anti-inflammatory efficacies. Coumarins are found in many plants, fungi, and bacteria and have been widely used as complementary and alternative medicines. Some coumarins have shown an ability to activate Nrf2 signaling in different cells and animal models. The present review compiles the research findings of seventeen coumarin derivatives of plant origin (imperatorin, visnagin, urolithin B, urolithin A, scopoletin, esculin, esculetin, umbelliferone, fraxetin, fraxin, daphnetin, anomalin, wedelolactone, glycycoumarin, osthole, hydrangenol, and isoimperatorin) as antioxidant and anti-inflammatory agents, emphasizing the role of Nrf2 activation in their pharmacological activities. Additionally, molecular docking simulations were utilized to investigate the potential binding mode of these coumarins with Keap1 as a strategy to disrupt Keap1/Nrf2 protein-protein interaction and activate Nrf2 signaling.

One-step Synthesized Silver Nanoparticles Using Isoimperatorin: Evaluation of Photocatalytic, and Electrochemical Activities

In the current study, isoimperatorin, a natural furanocoumarin, is used as a reducing reagent to synthesize isoimperatorin mediated silver nanoparticles (Iso-AgNPs), and photocatalytic and electrocatalytic activities of Iso-AgNPs are evaluated. Iso-AgNPs consisted of spherically shaped particles with a size range of 79-200 nm and showed catalytic activity for the degradation (in high yields) of New Fuchsine (NF), Methylene Blue (MB), Erythrosine B (ER) and 4-chlorophenol (4-CP) under sunlight irradiation. Based on obtained results, Iso-AgNPs exhibited 96.5%, 96.0%, 92%, and 95% degradation rates for MB, NF, ER, and 4-CP, respectively. The electrochemical performance showed that the as-prepared Iso-AgNPs exhibited excellent electrocatalytic activity toward hydrogen peroxide (H2O2) reduction. It is worth noticing that the Iso-AgNPs were used as electrode materials without any binder. The sensor-based on binder-free Iso-AgNPs showed linearity from 0.1 µM to 4 mM with a detection limit of 0.036 μM for H2O2. This binder-free and straightforward strategy for electrode preparation by silver nanoparticles may provide an alternative technique for the development of other nanomaterials based on isoimperatorin under green conditions. Altogether, the application of isoimpratorin in the synthesis of nano-metallic electro and photocatalysts, especially silver nanoparticles, is a simple, cost-effective and efficient approach.

The potential of plant systems to break the HIV-TB link

Tuberculosis (TB) and human immunodeficiency virus (HIV) can place a major burden on healthcare systems and constitute the main challenges of diagnostic and therapeutic programmes. Infection with HIV is the most common cause of Mycobacterium tuberculosis (Mtb), which can accelerate the risk of latent TB reactivation by 20-fold. Similarly, TB is considered the most relevant factor predisposing individuals to HIV infection. Thus, both pathogens can augment one another in a synergetic manner, accelerating the failure of immunological functions and resulting in subsequent death in the absence of treatment. Synergistic approaches involving the treatment of HIV as a tool to combat TB and vice versa are thus required in regions with a high burden of HIV and TB infection. In this context, plant systems are considered a promising approach for combatting HIV and TB in a resource-limited setting because plant-made drugs can be produced efficiently and inexpensively in developing countries and could be shared by the available agricultural infrastructure without the expensive requirement needed for cold chain storage and transportation. Moreover, the use of natural products from medicinal plants can eliminate the concerns associated with antiretroviral therapy (ART) and anti-TB therapy (ATT), including drug interactions, drug-related toxicity and multidrug resistance. In this review, we highlight the potential of plant system as a promising approach for the production of relevant pharmaceuticals for HIV and TB treatment. However, in the cases of HIV and TB, none of the plant-made pharmaceuticals have been approved for clinical use. Limitations in reaching these goals are discussed.

Indexing Natural Products for their Antifungal Activity by Filters-based Approach: Disclosure of Discriminative Properties

Methods:

A set of 240 FDA-approved antifungal drugs, which represent the active domain, and a set of 2,892 natural products, which represent the inactive domain, were used to construct predictive models and to index natural products for their antifungal bioactivity. The area under the curve for the produced predictive model was 0.89. When applying it to a database that is composed of active/inactive chemicals, we succeeded to detect 42% of the actives (antifungal drugs) in the top one percent of the screened chemicals, compared with one-percent when using a random model.

Results and Conclusion:

Eight natural products, which were highly scored as likely antifungal drugs, are disclosed. Searching PubMed showed only one molecule (Flindersine) out of the eight that have been tested was reported as an antifungal. The other seven phytochemicals await evaluation for their antifungal bioactivity in a wet laboratory.</P>

Pharmacological and Nutritional Effects of Natural Coumarins and Their Structure-Activity Relationships

Coumarins are fused benzene and pyrone ring systems with a wide spectrum of bioactivities, including antitumor, anti-inflammation, antiviral, and antibacterial effects. In this paper, the current development of coumarin-based drugs is introduced, and their structure-activity relationship is discussed by reviewing the relevant literature published in the past 20 years. Coumarin molecules can be customized by the target site to prevent systemic side effects by virtue of structural modification. The ortho-phenolic hydroxyl on the benzene ring has remarkable antioxidant and antitumor activities. Coumarins with aryl groups at the C-4 position have good activities in anti-HIV, antitumor, anti-inflammation, and analgesia. C-3 phenylcoumarins have strong anti-HIV and antioxidant effects. Tetracycline pyranocoumarins can significantly inhibit HIV; osthol structural analogues have antimicrobial activity. Praeruptorin C and its derivatives play an important role in lowering blood pressure and dilating coronary arteries, and khellactone derivatives have significant inhibitory effects on AIDS, cancer, and cardiovascular diseases. It is concluded that the specific site on the core structure of coumarin exhibits one or more activities due to the electronic or steric effects of the substituents. This review is intended to be conducive to rational design and development of more active and less toxic agents with a coumarin scaffold.

Plants in our combating strategies against Mycobacterium tuberculosis: progress made and obstacles met

CONTEXT

Traditionally used plants for treating chest-related problems/tuberculosis (TB) have not been evaluated in detail and hence a thorough study is needed in this regard. This knowledge may find application in developing new anti-TB drugs.

OBJECTIVE

This article elaborates on studying the activity of medicinal plants against different forms of Mycobacterium tuberculosis (Mtb) using different model strains, in vitro and ex vivo assays for studying the tuberculocidal activity and discusses the results from different studies on the activity against different forms of Mtb and human immunodeficiency virus-tuberculosis (HIV-TB) co-infection.

METHODS

Scientific databases such as PubMed, Elsevier, Scopus, Google scholar, were used to retrieve the information from 86 research articles (published from 1994 to 2016) related to the topic of this review.

RESULTS

Twenty-three plant species have been reported to possess active molecules against multi-drug resistant (MDR) isolates of Mtb. Seven plants were found to be active against intracellular Mtb and six against dormant bacilli. Seven plants were synergistically effective when combined with anti-TB drugs. Six studies suggest that the beneficial effects of plant extracts are due to their wide array of immuno-modulatory effects manifested by the higher expression of cytokines. Some studies have also shown the dual activity (anti-HIV and anti-TB) of plants.

CONCLUSION

We emphasize on identifying plants based on traditional uses and testing their extracts/phytomolecules against MDR strains, intracellular Mtb as well as against dormant Mtb. This will help in future to shorten the current therapeutic regimens for TB and also for treating HIV-TB co-infection.

New coumarins from the roots of Angelica dahurica var. formosana cv. Chuanbaizhi and their inhibition on NO production in LPS-activated RAW264.7 cells

A new linear pyranocoumarin named (-)-hydroxydecursinol (1) and a new biscoumarin named (±)-dahuribiscoumarin (2), together with six known compounds isoimperatorin (3), imperatorin (4), phellopterin (5), isodemethylfuropinarine (6), demethylfuropinarine (7), and (+)-decursinol (8) were isolated from the 75% ethanolic extract of the roots of Angelica dahurica var. formosana cv. Chuanbaizhi. Their structures were elucidated by extensive spectroscopic techniques, including 2D NMR spectroscopy and mass spectrometry, and the structure of 2 was confirmed by single-crystal X-ray diffraction. All of the isolated compounds were evaluated for the inhibition against nitric oxide (NO) production in the lipopolysaccharide (LPS)-activated RAW264.7 macrophage cell line, and exhibited the inhibitory activity on NO production in a concentration-dependent manner. Furthermore, real-time PCR analysis revealed that compounds 2, 5-8 could significantly suppress the expression levels of inducible nitric oxide synthase mRNA in a concentration-dependent manner. And their primary structure-activity relationships of NO inhibitory effects were also briefly discussed. These compounds are potential candidates for further bioassay studies to determine their suitability as drug leads.