Studies on the antibacterial and antifungal properties of 1, 4-naphthoquinones

An overview on the antibacterial properties of juglone, naphthazarin, plumbagin and lawsone derivatives and their metal complexes

Bacterial resistance development represents a serious threat to human health across the globe and has become a very serious clinical problem for many classes of antibiotics. Hence, there is a constant and urgent need for the discovery and development of new effective antibacterial agents to stem the emergence of resistant bacteria. 1,4-naphthoquinones are an important class of natural products and have been known for decades as a privileged scaffold in medicinal chemistry regarding their many biological properties. The significant biological properties of specific 1,4-naphthoquinones hydroxyderivatives have drawn the attention of researchers in order to find new derivatives with an optimized activity, mainly as antibacterial agents. Based on juglone, naphthazarin, plumbagin and lawsone moieties, structural optimization was realized with the purpose of improving the antibacterial activity. Thereupon, relevant antibacterial activities have been observed on different panels of bacterial strains including resistant ones. In this review, we highlight the interest of developing new 1,4-naphthoquinones hydroxyderivatives and some metal complexes as promising antibacterial agents alternatives. Here, we thoroughly report for the first time both the antibacterial activity and the chemical synthesis of four different 1,4-naphthoquinones (juglone, naphthazarin, plumbagin and lawsone) from 2002 to 2022 with an emphasis on the structure-activity relationship, when applicable.

Role of the Phytochemical Compounds like Modulators in Gut Microbiota and Oxidative Stress

BACKGROUND

Currently, daily consumption of green herb functional food or medicinal herbs has increased as adopted by many people worldwide as a way of life or even as an alternative to the use of synthetic medicines. Phytochemicals, which are a series of compounds of relatively complex structures and restricted distribution in plants, usually perform the defensive functions for plants against insects, bacteria, fungi or other pathogenic factors. A series of studies have found their effectiveness in the treatment or prevention of systemic diseases such as autoimmune diseases, cancer, neurodegenerative diseases, Crohn's disease and so on.

OBJECTIVE

This review systematizes the literature on the mechanisms of the phytochemicals that react against unique free radicals and prevent the oxidative stress and also summarizes their role in gut microbiota inhibiting bacterial translocation and damage to the intestinal barrier and improving the intestinal membrane condition.

CONCLUSION

The gut microbiota modulation and antioxidant activities of the phytochemicals shall be emphasized on the research of the active principles of the phytochemicals.

New 2-Acetyl-3-aminophenyl-1,4-naphthoquinones: Synthesis and In Vitro Antiproliferative Activities on Breast and Prostate Human Cancer Cells

The reaction of 2-acyl-1,4-naphthoquinones with N,N-dimethylaniline and 2,5-dimethoxyaniline, promoted by catalytic amounts of CeCl₃·7H₂O under “open-flask” conditions, produced a variety of 2-acyl-3-aminophenyl-1,4-naphthoquinones structurally related to the cytotoxic 2-acetyl-3-phenyl-1,4-naphthoquinone, an inhibitor of the heat shock chaperone protein Hsp90. The members of the 2-acyl-3-aminophenyl-1,4-naphthoquinone series were isolated in good yields (63-98%). The cyclic voltammograms of the 2-acyl-3-aminophenyl-1,4-naphthoquinone exhibit two one-electron reduction waves to the corresponding radical-anion and dianion and two quasireversible oxidation peaks. The first and second half-wave potential values (E_1/2) of the members of the series are sensitive to the push-pull electronic effects of the substituents in the naphthoquinone scaffold. Furthermore, the in vitro antiproliferative properties of these new quinones were evaluated on two human cancer cells DU-145 (prostate) and MCF-7 (mammary) and a nontumorigenic HEK-293 (kidney) cell line, using the MTT colorimetric method. Two members, within the series, exhibited interesting cytotoxic activities on human prostate and mammary cancer cells.

Synergistic Antibacterial Activity Between 1,4-Naphthoquinone and β-Lactam Antibiotics Against Methicillin-Resistant Staphylococcus aureus

Aims: Currently, limited antibiotics are available to treat methicillin-resistant Staphylococcus aureus (MRSA) infections. One approach is the use of adjuvants in antibiotic therapy. 1,4-Naphthoquinones are naturally occurring alkaloids shown to have antibacterial properties. The objective of this study is to investigate the synergy between 1,4-naphthoquinone and selected β-lactam antibiotics and to evaluate the potential use of 1,4-naphthoquinone as an adjuvant in antibiotic treatment against MRSA infections. Methods: The antibacterial activity of 1,4-naphthoquinone and plumbagin was tested against nine pathogenic bacterial strains using the microdilution broth method. The interactions between 1,4-naphthoquinone and three antibiotics (cefuroxime, cefotaxime, and imipenem) were estimated by calculating the fractional inhibitory concentration of the combination. Results: The compounds 1,4-naphthoquinone and plumbagin exhibited a broad range of bacteriostatic and bactericidal effects against both Gram-positive and Gram-negative bacteria. The interaction between 1,4-naphthoquinone and imipenem, cefuroxime, and cefotaxime was synergistic against methicillin-sensitive Staphylococcus aureus and MRSA clinical strains. Against ATCC-cultured MRSA, a synergistic effect was observed between 1,4-naphthoquinone and cefotaxime. However, combination with imipenem only produced an additive effect, and an antagonistic action was observed between 1,4-naphthoquinone and cefuroxime. Conclusions: Although individually less potent than common antibiotics, 1,4-naphthoquinone acts synergistically with imipenem, cefuroxime, and cefotaxime against MRSA clinical strains and could potentially be used in adjuvant-antibiotic therapy against multidrug resistant bacteria.

Aspartate semialdehyde dehydrogenase inhibition suppresses the growth of the pathogenic fungus Candida albicans

Potent inhibitors of an essential microbial enzyme have been shown to be effective growth inhibitors of Candida albicans, a pathogenic fungus. C. albicans is the main cause of oropharyngeal candidiasis, and also causes invasive fungal infections, including systemic sepsis, leading to serious complications in immunocompromised patients. As the rates of drug-resistant fungal infections continue to rise novel antifungal treatments are desperately needed. The enzyme aspartate semialdehyde dehydrogenase (ASADH) is critical for the functioning of the aspartate biosynthetic pathway in microbes and plants. Because the aspartate pathway is absent in humans, ASADH has the potential to be a promising new target for antifungal research. Deleting the asd gene encoding for ASADH significantly decreases the survival of C. albicans, establishing this enzyme as essential for this organism. Previously developed ASADH inhibitors were tested against several strains of C. albicans to measure their possible therapeutic impact. The more potent inhibitors show a good correlation between enzyme inhibitor potency and fungal growth inhibition. Growth curves generated by incubating different C. albicans strains with varying enzyme inhibitor levels show significant slowing of fungal growth by these inhibitors against each of these strains, similar to the effect observed with a clinical antifungal drug. The most effective inhibitors also demonstrated relatively low cytotoxicity against a human epithelial cell line. Taken together, these results establish that the ASADH enzyme is a promising new target for further development as a novel antifungal treatment against C. albicans and related fungal species.

Inhibitory effects of leaf extract of Lawsonia inermis on Curvularia lunata and characterization of novel inhibitory compounds by GC-MS analysis

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Isolation of active principle compound was found maximum in acetone extract of L. inermis leaf.

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Phytochemical tests suggest that carbohydrate, steroids, volatile oils, flavonoids, and tannins were found to be present in acetone extract of L. inermis leaf.

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In vitro assay of antifungal activity of all column fractions fraction no. F1 which exhibited most significant antifungal activity against the test fungus.

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GC–MS analysis of column fraction showed the occurrence of total 6 constituents.

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The obtained constituents are hexacosane, octadecane, docosane, heptacosane methyl, octacosane, and tetracosane.

Plants produce a high diversity of natural products with a prominent function in the protection against microbial pathogens on the basis of their toxic effect on growth and reproduction. In the present study, effect of partially purified acetone fraction of L. inermis leaves on various cytomorphological parameters i.e. mycelium width, conidial size, etc. of test fungi and fraction was subjected to confirming the presence of primary and secondary metabolites by rapid qualitative phytochemical tests, chromatographic methods such as TLC, column chromatography, GC–MS, etc. which were responsible for the inhibition of growth of test pathogen conidial size of Curvularia lunata decreased up to 64.76% at 0.039 μg/ml concentration of the extract. Mycelial width of C. lunata increased up to 55.91% at 0.312 μg/ml concentration of the extract. Carbohydrate, steroids, volatile oils, flavonoids, and tannins were found to be present in acetone extract of L. inermis leaf. Total of 7 bands were observed in TLC fingerprinting of L. inermis acetone fraction. Total of 10 fractions were collected from the column chromatography. Fractions which show the most significant antifungal activity against the test fungus was subjected to further GC–MS analysis for the separation and identification of active principle. GC–MS analyses show the presence of total 6 constituents i.e. hexacosane, octadecane, docosane, heptacosane methyl, octacosane, and tetracosane.

Target identification and intervention strategies against amebiasis

Entamoeba histolytica is the etiological agent of amebiasis, which is an endemic parasitic disease in developing countries and is the cause of approximately 70,000 deaths annually. E. histolytica trophozoites usually reside in the colon as a non-pathogenic commensal in most infected individuals (90% of infected individuals are asymptomatic). For unknown reasons, these trophozoites can become virulent and invasive, cause amebic dysentery, and migrate to the liver where they cause hepatocellular damage. Amebiasis is usually treated either by amebicides which are classified as (a) luminal and are active against the luminal forms of the parasite, (b) tissue and are effective against those parasites that have invaded tissues, and (c) mixed and are effective against the luminal forms of the parasite and those forms which invaded the host's tissues. Of the amebicides, the luminal amebicide, metronidazole (MTZ), is the most widely used drug to treat amebiasis. Although well tolerated, concerns about its adverse effects and the possible emergence of MTZ-resistant strains of E. histolytica have led to the development of new therapeutic strategies against amebiasis. These strategies include improving the potency of existing amebicides, discovering new uses for approved drugs (repurposing of existing drugs), drug rediscovery, vaccination, drug targeting of essential E. histolytica components, and the use of probiotics and bioactive natural products. This review examines each of these strategies in the light of the current knowledge on the gut microbiota of patients with amebiasis.

Synthesis and bioactivity investigation of quinone-based dimeric cationic triazolium amphiphiles selective against resistant fungal and bacterial pathogens

A series of synthetic dimeric cationic anthraquinone analogs (CAAs) with potent antimicrobial activities against a broad range of fungi and bacteria were developed. These compounds were prepared in 2-3 steps with high overall yield and possess alkyl chain, azole, quinone, and quaternary ammonium complexes (QACs). In vitro biological evaluations reveal prominent inhibitory activities of lead compounds against several drug-susceptible and drug-resistant fungal and bacterial strains, including MRSA, VRE, Candida albicans and Aspergillus flavus. Mode of action investigation reveals that the synthesized dimeric CAA's can disrupt the membrane integrity of fungi. Computational studies reveal possible designs that can revive the activity of QACs against drug-resistant bacteria. Cytotoxicity assays in SKOV-3, a cancer cell line, show that the lead compounds are selectively toxic to fungi and bacteria over human cells.

Synthesis and SAR study of novel anticancer and antimicrobial naphthoquinone amide derivatives

A series of novel naphthoquinone amide derivatives of the bioactive quinones, plumbagin, juglone, menadione and lawsone, with various amino acids were synthesized. The compounds were characterized by (1)H NMR, (13)C NMR, Mass, IR and elemental analysis. All the compounds were evaluated for their anticancer activity against HeLa and SAS cancer cell lines and 3D-QSAR indicated the presence of electron donating group near sulphur enhanced the activity against HeLa cells. Among the derivatives synthesized, compounds 11f, 10a, 10b and 10g were the most active with IC50 values of 16, 12, 14 and 24.5 μM, respectively. The analogues were also screened for antimicrobial activity against two human bacterial pathogens, the Gram-positive Methicillin resistant Staphylococcus aureus (MRSA) and the Gram-negative Pseudomonas aeruginosa and a human yeast pathogen, Fluconazole resistant Candida albicans (FRCA). Among the synthesized compounds, 8g, 10g and 11g exhibited maximum antibacterial activity towards MRSA and antifungal activity against FRCA in well diffusion method.

Assessment of antistaphylococcal activity of partially purified fractions and pure compounds from Eleutherine americana

Ready-to-eat foods were investigated for contamination with methicillin-resistant Staphylococcus aureus (MRSA), and the partially purified fractions from the bulb of Eleutherine americana were evaluated for their anti-MRSA activity. Partially purified fractions Ea6.3 and Ea9 demonstrated good antibacterial activity with a MIC of 125 to 500 microg/ml and MBC of 250 to > or =1000 microg/ml against all the food isolates. Fraction Ea6.3 produced a MIC and MBC of 250 and 500 microg/ml, respectively, whereas fraction Ea9 yielded MIC and MBC of 125 and > or =1000 microg/ml, respectively, against the enterotoxin-producing reference strains. Growth curves in the presence of fraction Ea6.3 at 4 x MIC resulted in total elimination of all the test strains between 20 and 24 h, while fraction Ea9 reduced bacterial population by at least 6 log relative to the control. The partially purified fractions were further purified to obtain pure compounds identified as eleutherol, eleutherin, isoeleutherin, hongconin, two anthraquinones, and elecanacin. The antibacterial activities of these compounds were also investigated; they produced MICs ranging from 31.25 to > or =1000 microg/ml. This study suggests that E. americana crude extract or its partially purified fractions have potentials for application as natural food preservatives.

Chlorochimaphilin: a new antibiotic from Moneses uniflora

A study of the antimicrobial compounds from Moneses uniflora resulted in the isolation of a novel compound, 8-chloro-2,7-dimethyl-1,4-naphthoquinone (8-chlorochimaphilin) (1), together with chimaphilin (2) and 3-hydroxychimaphilin (3) as the antimicrobial components. 2,7-Dimethyl-1,3-dihydroxynaphthyl 4-O-alpha-L-rhamnopyranoside (4) and 2,7-dimethoxy-1,4,8-trihydroxynaphthalene (6) were also isolated and identified.

Synthesis of novel naphtho[2,1-b]-1,4,5-oxa- or thiadiazepines as potential antimicrobial and anticancer agents

Two novel series of quinone derivatives have been synthesized. Thus, condensation of 2-ethoxycarbonylmethylthio-; 3-ethoxycarbonylmethylthio-2-methyl- and 3-ethoxycarbonylmethoxy-2-methyl derivatives of 1,4-naphthoquinone with substituted phenylhydrazines afforded the corresponding hydrazones, while cyclization of the same quinones with the same substituted hydrazines in glacial acetic acid gave the corresponding naphtho[2,1-b]-1,4,5-oxa- or thiadiazepine derivatives. The antimicrobial and anticancer activities of the synthesized compounds were studied.

The sensitizing capacity of chimaphilin, a naturally-occurring quinone

Chimaphilin is a yellow naphthoquinone which occurs naturally in various chimaphila and Pyrola species. In Chimaphila umbellata (winter green) and C. maculata, it is a major constituent. Folk medicine recommends the leaves of Chimaphila species as a topical application to treat skin diseases. Since 1887, winter green is claimed to have caused dermatitis and to have been responsible for "idiosyncrasy". Experimental sensitization using the open epicutaneous as well as Freund's complete adjuvant technique has now revealed that chimaphilin is a moderate contact sensitizer.

The immunoinhibitory and immunostimulatory effects of hydroxyanthra- and hydroxynaphthoquinone derivatives

The immunostimulatory and immunoinhibitory effects of 44 hydroxyanthra- and hydroxynaphthoquinone derivatives in tissue culture were investigated. In the test system used, the final effect, i.e. production of antibodies against sheep red blood cells is a result of cooperation between macrophages, T lymphocytes and B lymphocytes. It was found when testing selected 20 derivatives that methylation, acetylation or substitution of the hydroxy group by the amino group led to the loss of the inhibitory activity and, on the contrary, pronounced immunostimulatory effects could be observed in other derivatives. Naphthoquinones (juglone, lawsone) were more effective as immunoinhibitors than anthraquinones (alizarin, quinizarin) and their derivatives. In both groups of compounds glucosidation results in a substantial increase of the immunoinhibitory effect. The present work is a part of a more extensive study concerning modification of the molecules of various compounds and its relationship with the effect on immunological reactions.