Quinones as an Efficient Molecular Scaffold in the Antibacterial/Antifungal or Antitumoral Arsenal

Antibiofilm activity of Plumbagin against Staphylococcus aureus

In chronic infections caused by Staphylococcus aureus, biofilm is a major virulence factor. In Staphylococcus aureus biofilms, bacteria are embedded in a matrix of extracellular polymeric substances and are highly tolerant to antimicrobial drugs. However, the lack of effective solutions to inhibit biofilm formation remains a challenge, and the mechanism of inhibition of biofilm formation targeting extracellular polymeric substances is unclear. The aim of the present study was to investigate the inhibitory mechanisms of Plumbagin against Staphylococcus aureus biofilms formation by affecting secretion of extracellular polymeric substances using the high-content screening. Our results showed Plumbagin (16 µg/mL) inhibited biofilm formation, revealing a significant reduction in both biomass and bacterial metabolic activity, and disrupted the biofilm structure, leading to a significant decrease in both biological volume and average thickness (P ≤ 0.01). High-content screening imaging indicated that the Plumbagin treatment induced alterations in the extracellular polymeric substances of Staphylococcus aureus biofilm, significantly reducing the quantities of extracellular polysaccharide, proteins and extracellular DNA. Interestingly, extracellular DNA within the matrix was found to be the most sensitive to Plumbagin treatment. Extracellular DNA formation was significantly inhibited at a concentration of 4 µg/mL, whereas the inhibition of extracellular polysaccharide and proteins required a higher concentration of 8 µg/mL. Overall, these results demonstrated the inhibitory effects of Plumbagin on Staphylococcus aureus biofilm formation and extracellular polymeric substances secretion, suggesting that extracellular DNA may be a potential target for the anti-biofilm activity of Plumbagin. These findings will provide new insights into the mode of action of Plumbagin in treating infections caused by Staphylococcus aureus biofilms.

Advancements in synthetic methodologies and biological applications of lawsone derivatives

2-Hydroxy-1,4-naphthoquinone, widely recognized as lawsone, is a natural dye obtained from the henna plant (Lawsonia inermis), known for its biological activity and diverse applications in biochemistry and analytical chemistry. As a versatile precursor, it plays a crucial role in synthesizing a wide range of structurally diverse and bioactive molecular scaffolds. This review highlights recent progress in the development of lawsone derivatives, emphasizing their extensive biological activities, such as anticancer, antimicrobial, antioxidant, antimalarial, and metabolic enzyme-targeting activities, as well as their structure-activity relationships. Remarkably, this is the first detailed exploration covering both the biological activities and chemical synthesis of significant lawsone derivatives from 2016 to the present.

Exploring natural compounds and synthetic derivatives as potential inhibitors of SARS-CoV-2 PLpro: a computational approach with enzyme inhibition and cytotoxicity assessment

To address coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), there is a pressing need for direct-acting antiviral medications. Papain-like protease (PLpro) domain of Nsp3 from SARS-CoV-2 is central to viral replication and detrimentally affects the host immune response by cleaving ubiquitin and interferon-stimulated gene 15 proteins. Consequently, targeting PLpro with small-molecule therapeutics offers a promising strategy to effectively inhibit the virus and mitigate its impact on the host's immune system. Employing a multifaceted computational approach, we identified three phytochemicals demonstrating substantial molecular interactions and binding affinity [α-lapachone (C1) -37.82 ± 0.08 kcal/mol, Lapachol (C2) -48.56 ± 0.04 kcal/mol and Peshawarquinone (C3) -46.64 ± 0.03 kcal/mol)] with PLpro. Molecular dynamics simulations indicated that these compounds formed stable complexes with the naphthalene-inhibitor binding site, inducing a closed PLpro conformation and altering its normal function. Besides, they are predicted to possess favorable physicochemical, pharmacokinetics and drug-like properties. Among these compounds, C3 exhibited the most potent inhibitory potential (IC50 value: 1.76 ± 0.17 µM), followed by C2 (IC50 value; 2.50 ± 0.12 µM) and C1 (IC50 value: 3.42 ± 0.17 µM). Furthermore, evaluating the cytotoxicity of C1-C3 on human BJ cells revealed minimal harmful effects at a 50 µM dosage. These findings suggest that evaluated compounds hold therapeutic promise and could become potential drug candidates for treating SARS-CoV-2.

Marine Natural Products as Novel Treatments for Parasitic Diseases

Parasitic diseases including malaria, leishmaniasis, and trypanosomiasis have received significant attention due to their severe health implications, especially in developing countries. Marine natural products from a vast and diverse range of marine organisms such as sponges, corals, molluscs, and algae have been found to produce unique bioactive compounds that exhibit promising potent properties, including antiparasitic, anti-Plasmodial, anti-Leishmanial, and anti-Trypanosomal activities, providing hope for the development of effective treatments. Furthermore, various techniques and methodologies have been used to investigate the mechanisms of these antiparasitic compounds. Continued efforts in the discovery and development of marine natural products hold significant promise for the future of novel treatments against parasitic diseases.

A Screen of Traditional Chinese Medicinal Plant Extracts Reveals 17 Species with Antimicrobial Properties

Background/Objectives: Antimicrobial resistance (AMR) is a growing threat that undermines the effectiveness of global healthcare. The Centers for Disease Control and Prevention and the World Health Organization have identified numerous microbial organisms, particularly members of the ESKAPEE pathogens, as critical threats to global health and economic security. Many clinical isolates of these pathogens have become completely resistant to current antibiotics, making treatment nearly impossible. Herbal remedies, such as those found in Traditional Chinese Medicine (TCM), have been practiced for thousands of years and successfully used to treat a wide range of ailments, including infectious diseases. Surprisingly, despite this extensive knowledge of folk medicine, no plant-derived antibacterial drugs are currently approved for clinical use. As such, the objective of this study is to evaluate the antimicrobial properties of extracts derived from TCM plants. Methods: This study explores a comprehensive library comprising 664 extracts from 132 distinct TCM plant species for antimicrobial properties against gram-negative (Escherichia coli) and gram-positive (Micrococcus luteus) bacteria using liquid and solid in vitro assays. Results: Intriguingly, our results reveal 17 plant species with potent antimicrobial properties effective primarily against gram-positive organisms, including Streptococcus aureus and epidermidis. A literature search revealed that nearly 100 purified compounds from the identified TCM plants were previously isolated and confirmed for their antimicrobial properties, collectively inhibiting 45 different bacterial species. Conclusions: Our results indicate that phytobiotics from the identified plants could serve as potential candidates for novel antimicrobials.

Rhodium(III)-Catalyzed Regioselective C-H Alkenylation and Alkylation of Menadione Analogues with β-Trifluoromethyl Enones

Menadione and its structural analogues are important motifs present in various bioactive natural products and drugs with a wide range of biological activities. In addition, β-trifluoromethyl enone has been employed as an efficient fluorinated building block for the synthesis of CF3-containing organic scaffolds. Herein, we report both C-H alkenylation and C-H alkylation reactions using β-CF3 enones as coupling partners with amino-substituted menadiones under Rh(III) catalysis. While β-CF3 enones have been studied in C-H alkylation reactions, we herein for the first time disclose the Rh (III)-catalyzed C-H alkenylation reaction of β-CF3 enones. The presence of an oxidant was crucial for the alkenylation reaction with β-CF3 enone. Meanwhile, the alkylation reaction proceeds via redox-neutral conditions.

A comprehensive review of marine sponge metabolites, with emphasis on Neopetrosia sp

The secondary metabolites that marine sponges create are essential to the advancement of contemporary medicine and are often employed in clinical settings. Over the past five years, microbes associated with sponges have yielded the identification of 140 novel chemicals. Statistics show that most are derived from actinomycetes (bacteria) and ascomycotes (fungi). The aim of this study was to investigate the biological activity of metabolites from marine sponges. Chlocarbazomycins A-D, which are a group of novel chlorinated carbazole alkaloids isolated from the sponge Neopetrosia fennelliae KUFA 0811, exhibit antimicrobial, cytotoxic, and enzyme inhibitory activities. Recently, marine sponges of the genus Neopetrosia have attracted attention due to the unique chemical composition of the compounds they produce, including alkaloids of potential importance in drug discovery. Fridamycin H and fridamycin I are two novel type II polyketides synthesized by sponge-associated bacteria exhibit antitrypanosomal activity. Fintiamin, composed of amino acids and terpenoid moieties, shows affinity for the cannabinoid receptor CB 1. It was found that out of 27 species of Neopetrosia sponges, the chemical composition of only 9 species has been studied. These species mainly produce bioactive substances such as alkaloids, quinones, sterols, and terpenoids. The presence of motuporamines is a marker of the species Neopetrosia exigua. Terpenoids are specific markers of Neopetrosia vanilla species. Although recently discovered, secondary metabolites from marine sponges have been shown to have diverse biological activities, antimicrobial, antiviral, antibacterial, antimicrobial, antioxidant, antimalarial, and anticancer properties, providing many lead compounds for drug development. The data presented in this review on known and future natural products derived from sponges will further clarify the role and importance of microbes in marine sponges and trace the prospects of their applications, especially in medicine, cosmeceuticals, environmental protection, and manufacturing industries.

Profiling sorghum-microbe interactions with a specialized photoaffinity probe identifies key sorgoleone binders in Acinetobacter pittii

Interactions between plants and soil microbial communities that benefit plant growth and enhance nutrient acquisition are driven by the selective release of metabolites from plant roots, or root exudation. To investigate these plant-microbe interactions, we developed a photoaffinity probe based on sorgoleone (sorgoleone diazirine alkyne for photoaffinity labeling, SoDA-PAL), a hydrophobic secondary metabolite and allelochemical produced in Sorghum bicolor root exudates. We applied SoDA-PAL to the identification of sorgoleone-binding proteins in Acinetobacter pittii SO1, a potential plant growth-promoting microbe isolated from sorghum rhizosphere soil. Competitive photoaffinity labeling of A. pittii whole cell lysates with SoDA-PAL identified 137 statistically enriched proteins, including putative transporters, transcriptional regulators, and a subset of proteins with predicted enzymatic functions. We performed computational protein modeling and docking with sorgoleone to prioritize candidates for experimental validation and then confirmed binding of sorgoleone to four of these proteins in vitro: the α/β fold hydrolase SrgB (OH685_09420), a fumarylacetoacetase (OH685_02300), a lysophospholipase (OH685_14215), and an unannotated hypothetical protein (OH685_18625). Our application of this specialized sorgoleone-based probe coupled with structural bioinformatics streamlines the identification of microbial proteins involved in metabolite recognition, metabolism, and toxicity, widening our understanding of the range of cellular pathways that can be affected by a plant secondary metabolite.IMPORTANCEHere, we demonstrate that a photoaffinity-based chemical probe modeled after sorgoleone, an important secondary metabolite released by sorghum roots, can be used to identify microbial proteins that directly interact with sorgoleone. We applied this probe to the sorghum-associated bacterium Acinetobacter pittii and showed that probe labeling is dose-dependent and sensitive to competition with purified sorgoleone. Coupling the probe with proteomics and computational analysis facilitated the identification of putative sorgoleone binders, including a protein implicated in a conserved pathway essential for sorgoleone catabolism. We anticipate that discoveries seeded by this workflow will expand our understanding of the molecular mechanisms by which specific metabolites in root exudates shape the sorghum rhizosphere microbiome.

Exploring naphthoquinone and anthraquinone derivatives as antibiotic adjuvants against Staphylococcus aureus biofilms: Synergistic effects of menadione

Given the ability of Staphylococcus aureus to form biofilms and produce persister cells, making infections difficult to treat with antibiotics alone, there is a pressing need for an effective antibiotic adjuvant to address this public health threat. In this study, a series of quinone derivatives were evaluated for their antimicrobial and antibiofilm activities against methicillin-susceptible and methicillin-resistant S. aureus reference strains. Following analyses using broth microdilution, growth curve analysis, checkerboard assay, time-kill experiments, and confocal laser scanning microscopy, menadione was identified as a hit compound. Menadione exhibited a notable antibacterial profile (minimum inhibitory concentration, MIC = 4-16 μg/ml; minimum bactericidal concentration, MBC = 256 μg/ml) against planktonic S. aureus and its biofilms (minimum biofilm inhibitory concentration, MBIC50 = 0.0625-0.25 μg/ml). When combined with oxacillin, erythromycin, and vancomycin, menadione exhibited a synergistic or additive effect against planktonic cells and biofilms of two S. aureus reference strains and six clinical isolates, highlighting its potential as a suitable adjuvant for further development against S. aureus biofilm-associated infections.

Natural Products from Herbal Medicine Self-Assemble into Advanced Bioactive Materials

Novel biomaterials are becoming more crucial in treating human diseases. However, many materials require complex artificial modifications and synthesis, leading to potential difficulties in preparation, side effects, and clinical translation. Recently, significant progress has been achieved in terms of direct self-assembly of natural products from herbal medicine (NPHM), an important source for novel medications, resulting in a wide range of bioactive supramolecular materials including gels, and nanoparticles. The NPHM-based supramolecular bioactive materials are produced from renewable resources, are simple to prepare, and have demonstrated multi-functionality including slow-release, smart-responsive release, and especially possess powerful biological effects to treat various diseases. In this review, NPHM-based supramolecular bioactive materials have been revealed as an emerging, revolutionary, and promising strategy. The development, advantages, and limitations of NPHM, as well as the advantageous position of NPHM-based materials, are first reviewed. Subsequently, a systematic and comprehensive analysis of the self-assembly strategies specific to seven major classes of NPHM is highlighted. Insights into the influence of NPHM structural features on the formation of supramolecular materials are also provided. Finally, the drivers and preparations are summarized, emphasizing the biomedical applications, future scientific challenges, and opportunities, with the hope of igniting inspiration for future research and applications.

Synthesis of polycyclic aromatic quinones by continuous flow electrochemical oxidation: anodic methoxylation of polycyclic aromatic phenols (PAPs)

The electrochemical oxidation of polycyclic aromatic phenols (PAPs) has been developed in a microfluidic cell to synthesize polycyclic aromatic quinones (PAQs). Methanol was used as nucleophile to trap the phenoxonium cation formed in the oxidation as an acetal, that later were hydrolysed to the quinone. Formation of hydrogen gas as the cathode reaction caused challenges in the flow cell and were overcome by recycling the reaction mixture through the cell at increased flow rate several times. The specific quinones formed were guided by the position of an initial hydroxy group on the polycyclic aromatic hydrocarbon. An available para-position in the PAPs gave p-quinones, while hydroxy groups in the 2- or 3-position led to o-quinones. The substrates were analysed by cyclic voltammetry for estitmation of the HOMO/LUMO energies to shed more light on this transformation. The easy separation of the supporting electrolyte from the product will allow recycling and makes this a green transformation.

Antimicrobial Metabolites of Caucasian Medicinal Plants as Alternatives to Antibiotics

This review explores the potential of antimicrobial metabolites derived from Caucasian medicinal plants as alternatives to conventional antibiotics. With the rise of antibiotic resistance posing a global health threat, there is a pressing need to investigate alternative sources of antimicrobial agents. Caucasian medicinal plants have traditionally been used for their therapeutic properties, and recent research has highlighted their potential as sources of antimicrobial compounds. Representatives of 15 families of Caucasian medicinal plant extracts (24 species) have been explored for their efficacy against these pathogens. The effect of these plants on Gram-positive and Gram-negative bacteria and fungi is discussed in this paper. By harnessing the bioactive metabolites present in these plants, this study aims to contribute to the development of new antimicrobial treatments that can effectively combat bacterial infections while minimizing the risk of resistance emergence. Herein we discuss the following classes of bioactive compounds exhibiting antimicrobial activity: phenolic compounds, flavonoids, tannins, terpenes, saponins, alkaloids, and sulfur-containing compounds of Allium species. The review discusses the pharmacological properties of selected Caucasian medicinal plants, the extraction and characterization of these antimicrobial metabolites, the mechanisms of action of antibacterial and antifungal plant compounds, and their potential applications in clinical settings. Additionally, challenges and future directions in the research of antimicrobial metabolites from Caucasian medicinal plants are addressed.

A Review on the Natural Products in Treatment of Diabetic Cardiomyopathy (DCM)

Diabetic cardiomyopathy is an insidious and fatal disease, imposing major financial and social burdens on affected individuals. Among the various methods proposed for the treatment of diabetic cardiomyopathy (DCM), treatments with natural products have achieved promising results due to their high efficiency and minimal side-effects. Literature was searched, analyzed, and collected using databases, including PubMed, Web of Science, Excerpt Medica, Science Direct, and Springer. In this study, we reviewed the DCM-related studies on 72 representative natural products. These natural products have been confirmed to be applicable in the therapeutic intervention of DCM, acting through various mechanisms such as the amelioration of metabolic abnormalities, protecting the mitochondrial structure and function, anti-oxidant stress, anti-inflammatory, anti-fibrosis, regulation of Ca 2 + homeostasis and regulation of programmed cell death. The nuclear factor kappa B (NF- κ B), nuclear factor erythroid 2-related factor 2 (Nrf-2), and transforming growth factor- β (TGF- β ) have been extensively studied as high frequency signaling pathways for natural product intervention in DCM. The effectiveness of natural products in treating DCM has been revealed and studied, which provides a reference for DCM-specific drug discovery.

Increasing the polarity of β-lapachone does not affect its binding capacity with bovine plasma protein

Despite ortho-quinones showing several biological and pharmacological activities, there is still a lack of biophysical characterization of their interaction with albumin - the main carrier of different endogenous and exogenous compounds in the bloodstream. Thus, the interactive profile between bovine serum albumin (BSA) with β-lapachone (1) and its corresponding synthetic 3-sulfonic acid (2, under physiological pH in the sulphonate form) was performed. There is one main binding site of albumin for both β-lapachones (n ≈ 1) and a static fluorescence quenching mechanism was proposed. The Stern-Volmer constant (KSV) values are 104 M-1, indicating a moderate binding affinity. The enthalpy (-3.41 ± 0.45 and - 8.47 ± 0.37 kJ mol-1, for BSA:1 and BSA:2, respectively) and the corresponding entropy (0.0707 ± 0.0015 and 0.0542 ± 0.0012 kJ mol-1 K-1) values indicate an enthalpically and entropically binding driven. Hydrophobic interactions and hydrogen bonding are the main binding forces. The differences in the polarity of 1 and 2 did not change significantly the affinity to albumin. In addition, the 1,2-naphthoquinones showed a similar binding trend compared with 1,4-naphthoquinones.

In vitro and In vivo Biological Activity of Two Aryloxy-naphthoquinones in Mice Infected with Trypanosoma cruzi Strains

BACKGROUND

Chagas disease, a condition caused by Trypanosoma cruzi, is an endemic disease in Latin American countries that affects approximately eight million people worldwide. It is a continuing public health problem. As nifurtimox and benznidazole are the two pharmacological treatments currently used to treat it, the present research proposes new therapeutic alternatives. Previous studies conducted on naphthoquinone derivatives have found interesting trypanocidal effects on epimastigotes, with the molecules 2-phenoxy-1,4-naphthoquinone (IC50= 50 nM and SI < 250) and 2-(3-nitrophenoxy)-naphthalene-1,4-dione (IC50= 20 nM and SI=625) presenting the best biological activity..

METHODS

The present study evaluated the efficacy of in vitro, ex vivo and in vivo models of two aryloxyquinones, 2-phenoxy-1,4-naphthoquinone (1) and 2-(3-nitrophenoxy)-naphthalene-1,4- dione (2), against two Mexican T. cruzi strains in both their epimastigote and blood Trypomastigote stage. Both compounds were evaluated against T. cruzi using a mouse model (CD1) infected with Mexican isolates of T. cruzi, nifurtimox and benznidazole used as control drugs. Finally, the cytotoxicity of the two compounds against the J774.2 mouse macrophage cell line was also determined.

RESULTS

The in vitro and in vivo results obtained indicated that both quinones were more active than the reference drugs. Compound 1 presents in vivo activity, showing up to 40% parasite reduction after 8 h of administration, a finding which is 1.25 times more effective than the results obtained using nifurtimox.

CONCLUSION

These are encouraging results for proposing new naphthoquinone derivatives with potential anti-T. cruzi activity.

Quinones from Cordia species from 1972 to 2023: isolation, structural diversity and pharmacological activities

Plants of the genus Cordia (Boraginaceae family) are widely distributed in the tropical regions of America, Africa, and Asia. They are extensively used in folk medicine due to their rich medicinal properties. This review presents a comprehensive analysis of the isolation, structure, biogenesis, and biological properties of quinones from Cordia species reported from 1972 to 2023. Meroterpenoids were identified as the major quinones in most Cordia species and are reported as a chemotaxonomic markers of the Cordia. In addition to this property, quinones are reported to display a wider and broader spectrum of activities, are efficient scaffold in biological activity, compared to other classes of compounds reported in Cordia, hence our focus on the study of quinones reported from Cordia species. About 70 types of quinones have been isolated, while others have been identified by phytochemical screening or gas chromatography. Although the biosynthesis of quinones from Cordia species is not yet fully understood, previous reports suggest that they may be derived from geranyl pyrophosphate and an aromatic precursor unit, followed by oxidative cyclization of the allylic methyl group. Studies have demonstrated that quinones from this genus exhibit antifungal, larvicidal, antileishmanial, anti-inflammatory, antibiofilm, antimycobacterial, antioxidant, antimalarial, neuroinhibitory, and hemolytic activities. In addition, they have been shown to exhibit remarkable cytotoxic effects against several cancer cell lines which is likely related to their ability to inhibit electron transport as well as oxidative phosphorylation, and generate reactive oxygen species (ROS). Their biological activities indicate potential utility in the development of new drugs, especially as active components in drug-carrier systems, against a broad spectrum of pathogens and ailments.

Cytotoxic activity of quinolinequinones in cancer: In vitro studies, molecular docking, and ADME/PK profiling

Lead molecules containing 1,4-quinone moiety are intriguing novel compounds that can be utilized to treat cancer owing to their antiproliferative activities. Nine previously reported quinolinequinones (AQQ1-9) were studied to better understand their inhibitory profile to produce potent and possibly safe lead molecules. The National Cancer Institute (NCI) of Bethesda chose all quinolinequinones (AQQ1-9) based on the NCI Developmental Therapeutics Program and tested them against a panel of 60 cancer cell lines. At a single dose and five further doses, AQQ7 significantly inhibited the proliferation of all leukemia cell lines and some breast cancer cell lines. We investigated the in vitro cytotoxic activities of the most promising compounds, AQQ2 and AQQ7, in MCF7 and T-47D breast cancer cells, DU-145 prostate cancer cells, HCT-116 and COLO 205 colon cancer cell lines, and HaCaT human keratinocytes using the MTT assay. AQQ7 showed particularly high cytotoxicity against MCF7 cells. Further analysis showed that AQQ7 exhibits anticancer activity through the induction of apoptosis without causing cell cycle arrest or oxidative stress. Molecular docking simulations for AQQ2 and AQQ7 were conducted against the COX, PTEN, and EGFR proteins, which are commonly overexpressed in breast, cervical, and prostate cancers. The in vitro ADME and in vivo PK profiling of these compounds have also been reported.

Natural products in non-alcoholic fatty liver disease (NAFLD): Novel lead discovery for drug development

With changing lifestyles, non-alcoholic fatty liver disease (NAFLD) has become the most prevalent liver disease worldwide. A substantial increase in the incidence, mortality, and associated burden of NAFLD-related advanced liver disease is expected. Currently, the initial diagnosis of NAFLD is still based on ultrasound and there is no approved treatment method. Lipid-lowering drugs, vitamin supplementation, and lifestyle improvement treatments are commonly used in clinical practice. However, most lipid-lowering drugs can produce poor patient compliance and specific adverse effects. Therefore, the exploration of bio-diagnostic markers and active lead compounds for the development of innovative drugs is urgently needed. More and more studies have reported the anti-NAFLD effects and mechanisms of natural products (NPs), which have become an important source for new drug development to treat NAFLD due to their high activity and low side effects. At present, berberine and silymarin have been approved by the US FDA to enter clinical phase IV studies, demonstrating the potential of NPs against NAFLD. Studies have found that the regulation of lipid metabolism, insulin resistance, oxidative stress, and inflammation-related pathways may play important roles in the process. With the continuous updating of technical means and scientific theories, in-depth research on the targets and mechanisms of NPs against NAFLD can provide new possibilities to find bio-diagnostic markers and innovative drugs. As we know, FXR agonists, PPARα agonists, and dual CCR2/5 inhibitors are gradually coming on stage for the treatment of NAFLD. Whether NPs can exert anti-NAFLD effects by regulating these targets or some unknown targets remains to be further studied. Therefore, the study reviewed the potential anti-NAFLD NPs and their targets. Some works on the discovery of new targets and the docking of active lead compounds were also discussed. It is hoped that this review can provide some reference values for the development of non-invasive diagnostic markers and new drugs against NAFLD in the clinic.

Furanonaphthoquinones, Diterpenes, and Flavonoids from Sweet Marjoram and Investigation of Antimicrobial, Bacterial Efflux, and Biofilm Formation Inhibitory Activities

The chloroform extract of Origanum majorana exhibited high antibacterial and antifungal activities against 12 bacterial and 4 fungal strains; therefore, it was subjected to bioassay-guided isolation to afford six compounds (1-6). The structures were determined via one- and two-dimensional nuclear magnetic spectroscopy and high-resolution electrospray ionization mass spectrometry experiments. The compounds were identified as furanonaphthoquinones [majoranaquinone (1), 2,3-dimethylnaphtho[2,3-b]furan-4,9-dione (2)], diterpenes [19-hydroxyabieta-8,11,13-trien-7-one (3), 13,14-seco-13-oxo-19-hydroxyabieta-8-en-14-al (4)], and flavonoids [sterubin (5) and majoranin (6)]. Compounds 1 and 2 were first obtained from a natural source and compounds 3 and 4 were previously undescribed. Majoranaquinone (1) exhibited a high antibacterial effect against 4 Staphylococcus, 1 Moraxella, and 1 Enterococcus strains (MIC values between 7.8 μM and 1 mM). In the efflux pump inhibition assay, majoranaquinone (1) showed substantial activity in Escherichia coli ATCC 25922 strain. Furthermore, 1 was found to be an effective biofilm formation inhibitor on E. coli ATCC 25922 and E. coli K-12 AG100 bacteria. Our findings proved that bioactivities of majoranaquinone (1) significantly exceed those of the essential oil constituents; therefore, it should also be considered when assessing the antimicrobial effects of O. majorana.

Antimicrobial Peptides: The Production of Novel Peptide-Based Therapeutics in Plant Systems

The increased prevalence of antibiotic resistance is alarming and has a significant impact on the economies of emerging and underdeveloped nations. The redundancy of antibiotic discovery platforms (ADPs) and injudicious use of conventional antibiotics has severely impacted millions, across the globe. Potent antimicrobials from biological sources have been extensively explored as a ray of hope to counter the growing menace of antibiotic resistance in the population. Antimicrobial peptides (AMPs) are gaining momentum as powerful antimicrobial therapies to combat drug-resistant bacterial strains. The tremendous therapeutic potential of natural and synthesized AMPs as novel and potent antimicrobials is highlighted by their unique mode of action, as exemplified by multiple research initiatives. Recent advances and developments in antimicrobial discovery and research have increased our understanding of the structure, characteristics, and function of AMPs; nevertheless, knowledge gaps still need to be addressed before these therapeutic options can be fully exploited. This thematic article provides a comprehensive insight into the potential of AMPs as potent arsenals to counter drug-resistant pathogens, a historical overview and recent advances, and their efficient production in plants, defining novel upcoming trends in drug discovery and research. The advances in synthetic biology and plant-based expression systems for AMP production have defined new paradigms in the efficient production of potent antimicrobials in plant systems, a prospective approach to countering drug-resistant pathogens.

Analysis of Quinolinequinone Analogs with Promising Cytotoxic Activity against Breast Cancer

It is quite challenging to find out bioactive molecules in the vast chemical universe. Quinone moiety is a unique structure with a variety of biological properties, particularly in the treatment of cancer. In an effort to develop potent and secure antiproliferative lead compounds, five quinolinequinones (AQQ1-5) described previously have been selected and submitted to the National Cancer Institute (NCI) of Bethesda to envisage their antiproliferative profile based on the NCI Developmental Therapeutics Program. According to the preliminary in vitro single-dose anticancer screening, four of five quinolinequinones (AQQ2-5) were selected for five-dose screening and they displayed promising antiproliferative effects against several cancer types. All AQQs showed a excellent anticancer profile with low micromolar GI50 and TGI values against all leukemia cell lines, some non-small cell lung and ovarian cancer, most colon, melanoma, and renal cancer, and in addition to some breast cancer cell lines. AQQ2-5 reduced the proliferation of all leukemia cell lines at a single dose and five additional doses, as well as some non-small cell lung and ovarian cancer, the majority of colon cancer, melanoma and renal cancer, and some breast cancer cell lines. This motivated us to use in vitro, in silico, and in vivo technologies to further investigate their mode of action. We investigated the in vitro cytotoxic activities of the most promising compounds, AQQ2 and AQQ3, in HCT-116 colon cancer, MCF7 and T-47D breast cancer, and DU-145 prostate cancer cell lines, and HaCaT human keratinocytes. Concomitantly, IC50 values of AQQ2 and AAQ3 against MCF7 and T-47D cell lines of breast cancer, DU-145 cell lines of prostate cancer, HCT-116 cell lines of colon cancer, and HaCaT human keratinocytes were determined. AQQ2 exhibited anticancer activity through the induction of apoptosis and caused alterations in the cell cycle. In silico pharmacokinetic studies of all analogs have been carried out against ATR, CHK1, WEE1, CDK1, and CDK2. In addition to this, in vitro ADME and in vivo pharmacokinetic profiling for the most effective AAQ (AAQ2) have been studied.

Quinones as Neuroprotective Agents

Quinones can in principle be viewed as a double-edged sword in the treatment of neurodegenerative diseases, since they are often cytoprotective but can also be cytotoxic due to covalent and redox modification of biomolecules. Nevertheless, low doses of moderately electrophilic quinones are generally cytoprotective, mainly due to their ability to activate the Keap1/Nrf2 pathway and thus induce the expression of detoxifying enzymes. Some natural quinones have relevant roles in important physiological processes. One of them is coenzyme Q₁₀, which takes part in the oxidative phosphorylation processes involved in cell energy production, as a proton and electron carrier in the mitochondrial respiratory chain, and shows neuroprotective effects relevant to Alzheimer's and Parkinson's diseases. Additional neuroprotective quinones that can be regarded as coenzyme Q₁₀ analogues are idobenone, mitoquinone and plastoquinone. Other endogenous quinones with neuroprotective activities include tocopherol-derived quinones, most notably vatiquinone, and vitamin K. A final group of non-endogenous quinones with neuroprotective activity is discussed, comprising embelin, APX-3330, cannabinoid-derived quinones, asterriquinones and other indolylquinones, pyrroloquinolinequinone and its analogues, geldanamycin and its analogues, rifampicin quinone, memoquin and a number of hybrid structures combining quinones with amino acids, cholinesterase inhibitors and non-steroidal anti-inflammatory drugs.

Chemistry, Biosynthesis and Pharmacology of Streptonigrin: An Old Molecule with Future Prospects for New Drug Design, Development and Therapy

Streptonigrin is an aminoquinone alkaloid isolated from Streptomyces flocculus and is gaining attention as a drug molecule owing to its potential antitumor and antibiotic effects. It was previously used as an anticancer drug but has been discontinued because of its toxic effects. However, according to the most recent studies, the toxicity of streptonigrin and its structurally modified derivatives has been reduced while maintaining their potential pharmacological action at lower concentrations. To date, many investigations have been conducted on this molecule and its derivatives to determine the most effective molecule with low toxicity to enable new drug discovery. Therefore, the main objective of this study is to provide a comprehensive review and to discuss the prospects for streptonigrin and its derived compounds, which may boost the molecule as a highly interesting target molecule for new drug design, development and therapy. To complete this review, relevant literature was collected from several scientific databases, including Google Scholar, PubMed, Scopus and ScienceDirect. Following a complete screening, the obtained information is summarized in the present review to provide a good reference and accelerate the development and utilization of streptonigrin and its derivatives as pharmaceuticals.