Cinnamomum: The New Therapeutic Agents for Inhibition of Bacterial and Fungal Biofilm-Associated Infection

In silico approaches for developing sesquiterpene derivatives as antagonists of human nicotinic acetylcholine receptors (nAChRs) for nicotine addiction treatment

Cinnamomum, a genus within the Lauraceae family, has gained global recognition due to its wide-ranging utility. Extensive research has been dedicated to exploring its phytochemical composition and pharmacological effects. Notably, the uniqueness of Cinnamomum lies in its terpenoid content, characterized by distinctive structures and significant biological implications. An intriguing discovery is that sesquiterpene compounds originating from Cinnamomum possess the capacity to function as antagonists for human nicotinic acetylcholine receptors (nAChRs), specifically the nAChRÿ3 subtype, rendering them potential candidates for nicotine replacement therapy (NRT) to aid active smokers. This investigation employed molecular docking and molecular dynamics simulations to assess the inhibitory effects of these compounds on nAChRÿ3. Among the 55 compounds examined, Dihydroxyeudesmene, Gibberodione, and Germacrene-E exhibited the highest binding affinities. These compounds demonstrated robust interactions with the nAChRÿ3 receptor, as evidenced by elevated molecular mechanics general surface area (MM/GBSA) values (ΔG Bind = Dihydroxyeudesmene: -36.45 kcal/mol, Gibberodione: -36.51 kcal/mol, and Germacrene-E: -36.51 kcal/mol). Molecular dynamics simulations further confirmed the stability of these three compounds, indicating their potential to effectively compete with native ligands. However, comprehensive in vitro, in vivo, and clinical investigations are imperative to ascertain the efficacy of these promising therapeutic candidates.

Antibacterial and antibiofilm efficacy of eugenol, carvacrol, and cinnamaldehyde against colistin-resistant Klebsiella pneumoniae

BACKGROUND

Colistin-resistant Klebsiella pneumoniae (CR K. pneumoniae) is considered one of the bacteria with the highest levels of antibiotic resistance, necessitating the discovery of alternative therapeutic strategies. This study aimed to evaluate the ability of eugenol, carvacrol, and cinnamaldehyde to inhibit CR K. pneumoniae and the biofilm community of this bacterium.

METHOD

The minimum inhibitory concentration (MIC) and antibiofilm effects of compounds were assessed using broth macrodilution and microtiter plate assays, respectively. Time-kill assays determined the bactericidal effects of natural compounds on CR K. pneumoniae isolates. Protein and nucleic acid leakage were examined to assess metabolic disruption and cell membrane integrity. Real-time PCR was used to evaluate the effect of natural compounds on the expression of biofilm-related genes (mrkA, treC, and luxS).

RESULTS

In the disk diffusion test, the inhibition zones of eugenol, carvacrol, and cinnamaldehyde were 15 ± 1, 29 ± 2, and 30 ± 1 mm, respectively. The MIC of eugenol, carvacrol, and cinnamaldehyde were 260, 119, and 128 µg/mL, respectively. The time-kill assay demonstrated the rapid bactericidal effects of eugenol, carvacrol, and cinnamaldehyde at 2× MIC, with kill times of 6, 2, and 3 h, respectively. At the MIC, the kill times were 12, 10, and 12 h, respectively. These compounds significantly released proteins and nucleic acids from the treated bacteria. They also inhibited biofilm formation and disrupted mature biofilms. Furthermore, mrkA and treC expression levels were significantly reduced in the presence of eugenol and cinnamaldehyde.

CONCLUSION

These natural compounds demonstrated significant antibacterial and antibiofilm activity against CR K. pneumoniae, emerging as a promising natural alternative for treatment.

Exploring daidzein dimethyl ether from Albizzia lebbeck as a novel quorum sensing inhibitor against Pseudomonas aeruginosa: Insights from in vitro and in vivo studies

Infections of multidrug-resistant pathogens including Pseudomonas aeruginosa, cause a high risk of mortality in immunocompromised patients and underscore the need for novel natural antibacterial drugs. In this study, common phytochemicals prevalent in fruits and vegetables have been demonstrated for their ability to inhibit quorum sensing (QS) in Pseudomonas aeruginosa PAO1 (PA). Ten compounds were screened virtually by molecular docking, among which, daidzein dimethyl ether originally from Albizzia lebbeck showed the most significant inhibitory effect on the formation of biofilm and the accumulation of virulence factors, including elastase, pyocyanin and rhamnolipid in PA. Further, both qRT-PCR analysis of key QS components including LasR in PA and luminescence detection of LasR as a reporter in a heterologous system revealed that daidzein dimethyl ether at 10 µM significantly inhibited the transcription of lasR and its downstream targeting genes. At the same time, MD simulations also showed that daidzein dimethyl ether could reduce the stability of LasR. Furthermore, the protective effect of daidzein dimethyl ether against PA infection was demonstrated using zebrafish infection model. It was found to reduce significantly the inflammation in the PA-infected zebrafish and increase their survival rate by inhibiting prominently the accumulation of reactive oxygen species (ROS) and reducing fish mortality in PA-infected zebrafish larvae. Additionally, open field tests suggested that PA-infected zebrafish were observed with impaired swimming behaviour, but daidzein dimethyl ether-treatment rescued zebrafish from such swimming abnormalities. Histopathological analysis revealed that zebrafish treated with both PA and daidzein dimethyl ether showed obvious integrity in intestine tissues, compared to those with only PA treatment. This study firstly demonstrated the preventive advantages of daidzein dimethyl ether in an animal model against PA infection. It is worthwhile to explore further its potential therapeutic intervention as an antimicrobial agent.

Antifungal activity of Cinnamaldehyde derivatives against fluconazole-resistant Candida albicans

BACKGROUND

Candida albicans is an opportunistic pathogen commonly found in human mucous membranes. In light of the escalating challenge posed by antibiotic resistance of C. albicans strains worldwide, it is an urgently necessary to explore alternative therapeutic options.

OBJECTIVE

This study aims to assess the efficacy of two Cinnamaldehyde derivatives, 2-Cl Cinnamaldehyde (2-Cl CA) and 4-Cl Cinnamaldehyde (4-Cl CA), against C. albicans through both in vitro experiments and in vivo murine models and to evaluate their potential as new drug candidates for treating C. albicans.

METHODS AND RESULTS

The minimum inhibitory concentrations (MICs) of Cinnamaldehyde 2-Cl and 4-Cl benzene ring derivatives against C. albicans were 25 μg/mL. Time-killing experiments revealed that both Cinnamaldehyde derivatives exhibited fungicidal activity against C. albicans at concentrations of 5 MIC and 10 MIC. In the checkerboard experiment, 4-Cl CA did not show any antagonistic effect when combined with first-line antifungal drugs. Instead, it exhibited additive effects in combination with nystatin. Both 2-Cl and 4-Cl CA demonstrated inhibitory activity against C. albicans biofilm formation, especially at 8 MIC and 16 MIC concentrations. In C. albicans biofilm eradication experiments, although high drug concentrations of 2-Cl and 4-Cl CA were unable to eradicate the biofilm completely, they were still effective in killing C. albicans cells within the biofilm. Moreover, sub-inhibitory concentrations of 4-Cl CA (ranging from 5 to 20 μg/mL) significantly inhibited cell aggregation and hyphal formation. Furthermore, 4-Cl CA effectively inhibited intracellular C. albicans infection in macrophages. Lastly, the effectiveness of 4-Cl CA was evaluated in a mouse model of hematogenous disseminated candidiasis caused by C. albicans, which revealed that 4-Cl CA significantly reduced fungal burden and improved mouse survival compared to the untreated controls.

CONCLUSION

The 4-Cl CA exhibited inhibitory effects against C. albicans through both in vivo and in vitro models, demonstrating its therapeutic potential as a promising new drug candidate for treating drug-resistant candidiasis albicans.

Antifungal effects of natural extracts on Candida albicans

Fungal infections caused by Candida albicans present significant challenges in clinical settings owing to rising resistance to conventional antifungal treatments. Natural products derived from medicinal plants, including tulsi (Ocimum sanctum), garlic (Allium sativum), cinnamon (Cinnamomum verum) and lemongrass (Cymbopogon citratus), are increasingly recognized for their potential antimicrobial properties and as alternative sources of antifungal therapies. This study evaluated the antifungal efficacy of Tulsi, Garlic, Cinnamon and Lemongrass extracts against Candida albicans using disk diffusion and broth microdilution methods. Natural extracts from Tulsi, Garlic, Cinnamon and Lemongrass demonstrated varying degrees of antifungal activity against Candida albicans. Tulsi emerged as the most effective, followed by garlic and cinnamon, whereas lemongrass showed comparatively lower efficacy. These findings underscore Tulsi's potential as a potent natural antifungal agent and warrant further exploration of its therapeutic applications in fungal infections.

Hyaluronic acid-based multifunctional bio-active coating integrated with cinnamaldehyde/hydroxypropyl-β-cyclodextrin inclusion complex for fruit preservation

Natural preservatives such as cinnamaldehyde (CIN) are garnering increasing interest to replace their synthetic counterparts in maintaining fruit freshness and safety. However, their long-term effectiveness and widespread application have been greatly limited due to high volatility and potent aroma. To address these challenges, we developed a viable and simple strategy to prepare a multifunctional active coating for fruit preservation by incorporating host-guest inclusion complex of CIN and 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) CIN@HP-β-CD into hyaluronic acid (HA), a natural polysaccharide with exceptional film-forming properties. The as-prepared HA/CIN@HP-β-CD coatings exhibited universal surface affinity, excellent antimicrobial performance, and satisfactory antioxidant properties with no potential toxicity. Release kinetic studies have demonstrated that CIN in the coating is continuously and slowly released. Furthermore, freshness preservation experiments on bananas and fresh-cut apples demonstrated that the developed coating is effective in preserving the color of fruit, decreasing the weight loss rate, preventing the microorganism's growth, and significantly extending the period of freshness, exhibiting the potential for application in fruit preservation.

Enhancing Therapeutic Efficacy of Cinnamon Essential Oil by Nanoemulsification for Intravaginal Treatment of Candida Vaginitis

Background

Due to its prevalence, recurrence, and the emergence of drug-resistance, Candida vaginitis significantly impacts the well-being of women. Although cinnamon essential oil (CEO) possesses antifungal activity, its hydrophobic properties limit its clinical application.

Purpose

To overcome this challenge, a nanoemulsification technology was employed to prepare cinnamon essential oil-nanoemulsion (CEO@NE), and its therapeutic efficacy and action mechanism for Candida vaginitis was investigated in vivo and in vitro.

Materials and Methods

CEO@NE, composed of 4% CEO, 78% distilled water, and 18% Tween 80, was prepared by ultrasonic nanoemulsification. The physical properties, anti-Candida activity, cytotoxicity, immunomodulatory potential and storage stability of CEO@NE were explored. Subsequently, the effect of intravaginal CEO@NE treatment on Candida vaginitis was investigated in mice. To comprehend the possible mechanism of CEO@NE, an analysis was conducted to ascertain the production of intracellular reactive oxygen species (ROS) in C. albicans.

Results

CEO@NE, with the droplet size less than 100 nm and robust storage stability for up to 8 weeks, exhibited comparable anti-Candida activity with CEO. CEO@NE at the concentration lower than 400 μg/mL had no cytotoxic and immunomodulatory effects on murine splenocytes. Intravaginal treatment of CEO@NE (400 μg/mL, 20 μL/day/mouse for 5 consecutive days) curbed Candida colonization, ameliorated histopathological changes, and suppressed inflammatory cytokine production in mice intravaginally challenged with C. albicans. Notably, this treatment preserved the density of vaginal lactic acid bacteria (LAB) crucial for vaginal health. Co-culturing C. albicans with CEO@NE revealed concentration-dependent augmentation of intracellular ROS generation and ensuing cell death. In addition, co-culturing LPS-stimulated murine splenocytes with CEO@NE yielded a decrease in the generation of cytokines.

Conclusion

This discovery provides insight into the conceivable antifungal and anti-inflammatory mechanisms of CEO@NE to tackle Candida vaginitis. CEO@NE offers a promising avenue to address the limitations of current treatments, providing novel strategy for treating Candida vaginitis.

In vitro efficacy of essential oils against various Candida species

Candida species are responsible for the most common fungal infections worldwide. We studied the in vitro antifungal activity of a large panel of essential oils (EOs) against various Candida species. The EOs activity against Candida spp. was tested using a gradient microdilution assay ranging from 4% to 0.008% (v/v). After a preliminary screening including 31 EOs, seven selected EOs were tested against 13 clinical isolates and four reference strains belonging to six Candida species. Cinnamomum zeylanicum and Cymbopogon giganteus EOs exhibited the best antifungal activity against all clinical and reference strains, with MIC ranges of 0.015%-0.25% (v/v). EOs from Litsea citrata, Backhousia citriodora and Ocimum sanctum presented MIC ranges of 0.03%-0.5% (v/v). The antifungal efficacy of EOs was independent of the susceptibility of Candida strains to usual antifungal agents. These EOs could have a promising antifungal action.

Enhancing Commercial Antibiotics with Trans-Cinnamaldehyde in Gram-Positive and Gram-Negative Bacteria: An In Vitro Approach

One strategy to mitigate the emergence of bacterial resistance involves reducing antibiotic doses by combining them with natural products, such as trans-cinnamaldehyde (CIN). The objective of this research was to identify in vitro combinations (CIN + commercial antibiotic (ABX)) that decrease the minimum inhibitory concentration (MIC) of seven antibiotics against 14 different Gram-positive and Gram-negative pathogenic bacteria, most of them classified as ESKAPE. MIC values were measured for all compounds using the broth microdilution method. The effect of the combinations on these microorganisms was analyzed through the checkboard assay to determine the type of activity (synergy, antagonism, or addition). This analysis was complemented with a kinetic study of the synergistic combinations. Fifteen synergistic combinations were characterized for nine of the tested bacteria. CIN demonstrated effectiveness in reducing the MIC of chloramphenicol, streptomycin, amoxicillin, and erythromycin (94-98%) when tested on Serratia marcescens, Staphylococcus aureus, Pasteurella aerogenes, and Salmonella enterica, respectively. The kinetic study revealed that when the substances were tested alone at the MIC concentration observed in the synergistic combination, bacterial growth was not inhibited. However, when CIN and the ABX, for which synergy was observed, were tested simultaneously in combination at these same concentrations, the bacterial growth inhibition was complete. This demonstrates the highly potent in vitro synergistic activity of CIN when combined with commercial ABXs. This finding could be particularly beneficial in livestock farming, as this sector witnesses the highest quantities of antimicrobial usage, contributing significantly to antimicrobial resistance issues. Further research focused on this natural compound is thus warranted for this reason.

Multi-Omics Profiling of Candida albicans Grown on Solid Versus Liquid Media

Candida albicans is a common pathogenic fungus that presents a challenge to healthcare facilities. It can switch between a yeast cell form that diffuses through the bloodstream to colonize internal organs and a filamentous form that penetrates host mucosa. Understanding the pathogen's strategies for environmental adaptation and, ultimately, survival, is crucial. As a complementary study, herein, a multi-omics analysis was performed using high-resolution timsTOF MS to compare the proteomes and metabolomes of Wild Type (WT) Candida albicans (strain DK318) grown on agar plates versus liquid media. Proteomic analysis revealed a total of 1793 proteins and 15,013 peptides. Out of the 1403 identified proteins, 313 proteins were significantly differentially abundant with a p-value < 0.05. Of these, 156 and 157 proteins were significantly increased in liquid and solid media, respectively. Metabolomics analysis identified 192 metabolites in total. The majority (42/48) of the significantly altered metabolites (p-value 0.05 FDR, FC 1.5), mainly amino acids, were significantly higher in solid media, while only 2 metabolites were significantly higher in liquid media. The combined multi-omics analysis provides insight into adaptative morphological changes supporting Candida albicans' life cycle and identifies crucial virulence factors during biofilm formation and bloodstream infection.

In vitro antimicrobial activity of extracts and essential oils of Cinnamomum, Salvia, and Mentha spp. against foodborne pathogens: A meta-analysis study

Essential oils (EOs) are a class of natural products that exhibit potent antimicrobial properties against a broad spectrum of bacteria. Inhibition diameters (IDs) and minimum inhibitory concentrations (MICs) are the typical measures of antimicrobial activity for extracts and EOs obtained from Cinnamomum, Salvia, and Mentha species. This study used a meta-analytical regression analysis to investigate the correlation between ID and MIC measurements and the variability in antimicrobial susceptibility tests. By utilizing pooled ID models, this study revealed significant differences in foodborne pathogens' susceptibility to extracts, which were dependent on both the plant species and the methodology employed (p < .05). Cassia showed the highest efficacy against Salmonella spp., exhibiting a pooled ID of 26.24 mm, while cinnamon demonstrated the highest efficacy against Bacillus cereus, with a pooled ID of 23.35 mm. Mint extract showed the greatest efficacy against Escherichia coli and Staphylococcus aureus. Interestingly, cinnamon extract demonstrated the lowest effect against Shiga toxin-producing E. coli, with a pooled ID of only 8.07 mm, whereas its EOs were the most effective against this bacterial strain. The study found that plant species influenced the MIC, while the methodology did not affect MIC measurements (p > .05). An inverse correlation between ID and MIC measurements was identified (p < .0001). These findings suggest that extracts and EOs obtained from Cinnamomum, Salvia, and Mentha spp. have the potential to inhibit bacterial growth. The study highlights the importance of considering various factors that may influence ID and MIC measurements when assessing the effectiveness of antimicrobial agents.

trans-Cinnamaldehyde as a Novel Candidate to Overcome Bacterial Resistance: An Overview of In Vitro Studies

The increasing of drug-resistant bacteria and the scanty availability of novel effective antibacterial agents represent alarming problems of the modern society, which stimulated researchers to investigate novel strategies to replace or assist synthetic antibiotics. A great deal of attention has been devoted over the years to essential oils that contain mixtures of volatile compounds and have been traditionally exploited as antimicrobial remedies. Among the essential oil phytochemicals, remarkable antimicrobial and antibiotic-potentiating activities have been highlighted for cinnamaldehyde, an α,β-unsaturated aldehyde, particularly abundant in the essential oils of Cinnamomum spp., and widely used as a food additive in industrial products. In line with this evidence, in the present study, an overview of the available literature has been carried out in order to define the bacterial sensitizing profile of cinnamaldehyde. In vitro studies displayed the ability of the substance to resensitize microbial strains to drugs and increase the efficacy of different antibiotics, especially cefotaxime, ciprofloxacin, and gentamicin; however, in vivo, and clinical trials are lacking. Based on the collected findings, cinnamaldehyde appears to be of interest as an adjuvant agent to overcome superbug infections and antibiotic resistance; however, future more in-dept studies and clinical investigations should be encouraged to clarify its efficacy and the mechanisms involved.

Cinnamomum sp. and Pelargonium odoratissimum as the Main Contributors to the Antibacterial Activity of the Medicinal Drink Horchata: A Study Based on the Antibacterial and Chemical Analysis of 21 Plants

Horchata, a herbal infusion drink from Ecuador containing a mixture of medicinal plants, has been reported to exhibit anti-inflammatory, analgesic, diuretic, and antioxidant activity. The antibacterial activity of each of the plants contained in the horchata mixture has not been fully evaluated. Thus, in this study, we analysed the antibacterial activity of 21 plants used in horchata, collected from the Ecuadorian Andes region, against bacterial strains of clinical importance. The methanolic extract of Cinnamomum sp. showed minimal inhibitory concentration (MIC) values of 250 µg/mL against Staphylococcus aureus ATCC25923 and Methicillin-resistant S. aureus (MRSA), while Pelargonium odoratissimum exhibited a MIC value of 500 µg/mL towards S. aureus ATCC25923. The high-performance liquid chromatography-diode array detector-tandem mass spectrometry (HPLC-DAD-MS/MS) analyses identified in Cinnamomum sp. epicatechin tannins, cinnamaldehyde, and prehelminthosporol molecules, whereas in P. odoratissimum, gallocatechin and epigallocatechin tannins, some flavonoids, and gallic acid and derivatives were identified. Finally, Cinnamomum sp. and P. odoratissimum showed partial inhibition of biofilm formation of S. aureus ATCC25923 and MRSA. Overall, our findings revealed which of the plants used in horchata are responsible for the antibacterial activity attributed to this herbal drink and exhibit the potential for Cinnamomum sp. and P. odoratissimum secondary metabolites to be explored as scaffolds in drug development.