Anti-Inflammatory Activity of the Essential Oil Citral in Experimental Infection with Staphylococcus aureus in a Model Air Pouch

Preparation of Citral Oleogel and Antimicrobial Properties

The objective of this study was to analyze a natural and safe oleogel with antimicrobial properties that can replace animal fats while lengthening the product's shelf life. The oleogel was created using direct dispersion (MG-SO), and its material characterization exhibited the exceptional performance of the hybrid gelant. Additionally, citral was integrated into the oil gel to prepare the citral oleogel (MG-SO). The antimicrobial nature of the material was examined and the findings revealed that it inhibited the growth of various experimental model bacteria, including Escherichia coli, Staphylococcus aureus, Aspergillus niger, Botrytis cinerea, and Rhizopus stolonifer. In addition, the material had a comparable inhibitory impact on airborne microorganisms. Lastly, MG-SON was utilized in plant-based meat patties and demonstrated an ability to significantly reduce the growth rate of microorganisms.

Mechanisms and Applications of Citral's Antimicrobial Properties in Food Preservation and Pharmaceuticals Formulations

Citral is a monoterpene constituted by two isomers known as neral and geranial. It is present in different plant sources and recognized as safe (GRAS) by the Food and Drug Administration (FDA). In recent years, investigations have demonstrated that this compound exhibited several biological activities, such as antibacterial, antifungal, antibiofilm, antiparasitic, antiproliferative, anti-inflammatory, and antioxidant properties, by in vitro and in vivo assays. Additionally, when incorporated into different food matrices, citral can reduce the microbial load of pathogenic microorganisms and extend the shelf life. This compound has acceptable drug-likeness properties and does not present any violations of Lipinski's rules, which could be used for drug development. The above shows that citral could be a compound of interest for developing food additives to extend the shelf life of animal and vegetable origin foods and develop pharmaceutical products.

Mesosphaerum suaveolens Essential Oil Attenuates Inflammatory Response and Oxidative Stress in LPS-Stimulated RAW 264.7 Macrophages by Regulating NF-κB Signaling Pathway

Mesosphaerum suaveolens (L.) Kuntze (Syn. Hyptis suaveolens (L.) Poit.) is a wild essential-oil-bearing plant having multiple uses in traditional medicine, perfumery, food, agriculture, and pharmaceutical industries. The present paper is the first report on the in vitro anti-inflammatory effects of the leaf essential oil of M. suaveolens (MSLEO) and unravels its molecular mechanism in LPS-stimulated RAW 264.7 macrophage cells. GC-MS analysis of the essential oil (EO) isolated from the leaves by hydro-distillation led to the identification of 48 constituents, accounting for 90.55% of the total oil, and β-caryophyllene (16.17%), phyllocladene (11.85%), abietatriene (11.46%), and spathulenol (7.89%) were found to be the major components. MSLEO treatment had no effect on the viability of RAW 264.7 cells up to a concentration of 100 μg/mL, and the EO was responsible for a reduction in proinflammatory cytokines like IL-6, IL-1β, and TNF-α, a decrease in intracellular ROS production, and the restoration of oxidative damage by elevating the levels of endogenous antioxidative enzymes like CAT, SOD, GPx, and GSH. RT-qPCR analysis indicated that MSLEO reduced the mRNA expression levels of iNOS and COX-2 as compared to the LPS-induced group. In addition, a confocal microscopy analysis showed that MSLEO inhibited the translocation of NF-κB from the cytosol to the nucleus. The results of this experiment demonstrate that MSLEO possesses significant anti-inflammatory potential by preventing the activation of NF-κB, which, in turn, inhibits the downstream expression of other inflammatory mediators associated with the activation of the NF-κB pathway in LPS-induced RAW 264.7 cells. Thus, the leaf essential oil of M. suaveolens may prove to be a promising therapeutic agent for the treatment of inflammation, and targeting the NF-κB signaling pathway may be considered as an attractive approach for anti-inflammatory therapies.

Transcriptomic analyses reveal the potential antibacterial mechanism of citral against Staphylococcus aureus

Background

The emergence of multi-drug resistant Staphylococcus aureus (S. aureus) has posed a challenging clinical problem for treating its infection. The development of novel or new antibacterial agents becomes one of the useful methods to solve this problem, and has received more attention over the past decade. Citral is reported to have antibacterial activity against S. aureus, but its mechanism is yet entirely clear.

Methods

To reveal the antibacterial mechanism of citral against S. aureus, comparative transcriptomic analysis was carried out to analyze the gene expression differences between the citral-treated and untreated groups. The changes of protein, adenosine triphosphate (ATP) and reactive oxygen species (ROS) content in S. aureus caused by citral were also examined.

Results

Six hundred and fifty-nine differentially expressed genes were obtained according to the comparative transcriptomic analysis, including 287 up-regulated genes and 372 down-regulated genes. The oxidoreductase activity and fatty acid degradation pathway were enriched in up-regulated genes, and ribosome and S. aureus infection pathway were enriched in down-regulated genes. Meanwhile, physiological trials revealed a decline in ATP and protein levels, but an increase in ROS content within the citral-treated group. Thus, it can be inferred that the antibacterial effects of citral against S. aureus were likely due to its ability to decrease ATP content by down-regulating ATP synthase genes (atpD and atpG), reduce protein content, induce cell membrane and cell wall damages, accumulate ROS, and down-regulate virulence factor genes to reduce pathogenicity.

Conclusion

These findings revealed the antibacterial mechanism of citral was likely a type of multi-target mode that affected multiple molecular processes in S. aureus, which lays the groundwork for further exploitation of citral as a therapeutic candidate against S. aureus infections.

Immunomodulatory effects of trans-anethole-treated Staphylococcus aureus Newman strain

In our former studies based on a human whole-blood model infected with trans-anethole (TA)-treated Staphylococcus aureus Newman strain, we have observed that selected parameters/mechanisms of innate and acquired immune response were more enhanced in comparison to samples infected with non-treated bacteria. Due to this observation, the current study aimed to evaluate the concentration of selected proteins involved in both types of responses (IL-1α, IL-1β, IL-2, IL-6, IL-12, IL-17, TNF-α, IFN-γ, G-CSF, C5a, CCL1-CCL5, CXCL1, CXCL2, CXCL9-CXCL11, MMP-8, TLR2, and PGLYRP1) in healthy participants' plasma after blood stimulation of TA-treated S. aureus Newman strain. Determination of analyzed protein concentration was conducted using Luminex and ELISA assays. Based on the results, it has been proven that the immunomodulatory potential of TA-treated S. aureus Newman strain on increasing IL-1β, IL-6, TNF-α, IL-12, G-CSF, C5a, CCL2-CCL4, CXCL1, CXCL2, MMP-8 and PGLYRP1 levels in plasma. Moreover, it has been also demonstrated an association between TNF-α and CCL4 in a blood model infected with TA-treated cells. More research is warranted to find more underlying mechanisms involved in the effects of TA-treated S. aureus Newman in human blood, mainly whether the observed "immunity boost" can be regulated after bacteria elimination. Therefore, the potential of TA should be further explored to understand under which conditions it might help treat or prevent infections caused by S. aureus.

Anti-inflammatory properties of an aldehydes-enriched fraction of grapefruit essential oil

Chronic inflammation is linked to the development of numerous diseases and is accompanied by increased cytokine secretion. Macrophages provide a first line of defense against pathogens that under inflammatory stimuli release pro-inflammatory cytokines. The essential oil (EO) fractions obtained from Citrus spp. rich in different compounds have gained the attention of both researchers and users during the last decades. In particular, grapefruit (Citrus paradisi) peel is rich in phenolics and flavonoids with several health benefits, including anti-inflammatory actions. Additionally, its EO consists of a large number of compounds such as monoterpenes, sesquiterpenes, alcohols, aldehydes, esters, and oxides. Among the methods for encapsulating EOs, spray-drying is the main one. In the present study, we aimed to determine the in vitro anti-inflammatory activity of EO from C. paradisi (grapefruit essential oil [GEO]) (whole and fractions) in a lipopolysaccharide (LPS)-induced inflammation model. Results indicate that Fr-GEO and Fr-GEO_SD exert protective effects against LPS-induced inflammation by decreasing gene expression and levels of pro-inflammatory cytokines as IL-6 and TNF-α. Monoterpenes as the most common components, as well as aldehydes and sesquiterpenes, might be responsible for such effects, although a synergistic action is not excluded. Furthermore, a higher percent of aldehydes is linked to improved olfactory properties. Our findings support the anti-inflammatory effects of selected Fr-GEO with a great potential for the development of new nutraceuticals and/or functional food for the treatment of inflammatory-associated diseases. PRACTICAL APPLICATION: The findings of this study support the anti-inflammatory effects of selected Fr-GEO with a great potential for the development of new nutraceuticals and/or functional food for the treatment of inflammatory-associated diseases.

Molecular mechanism of the anti-inflammatory effects of plant essential oils: A systematic review

ETHNOPHARMACOLOGICAL RELEVANCE

Plant essential oils (PEOs) extracted from aromatic compounds of the plant contain complex mixtures of volatile and lipophilic bioactive compounds. In ancient Egypt, Arabia, Greece, and China, PEOs were traditional used in aromatherapy for various health disorders, including pain and inflammation.

AIM OF THE STUDY

In this review, we provide an overview of the anti-inflammatory effects of PEOs and the underlying mechanisms associated with anti-inflammatory effects using in vitro and in vivo models. Further, clinical trials associated with PEOs were explored.

MATERIALS AND METHODS

The literature search was performed using various web-based tools and databases like Google Scholar, Web of Science, PubMed, CNKI and SCOPUS. The keywords used for conducting the literature review were general terms like "essential oils" followed by (AND) the subject of interest like "in vitro and/or in vivo anti-inflammatory models," "inflammatory response," "inflammatory indicators," "pro-inflammatory cytokines," "signaling pathway," "anti-inflammatory mechanism," "toxicology and side effects" and "clinical trials." The articles selected were published between 2017 and 2022. The articles prior to 2017 were only considered if they were associated with molecular mechanisms or signaling pathways involved in the inflammatory responses.

RESULTS

In vitro and in vivo inflammation models have been used to study the anti-inflammatory effects of 48 PEOs. Studies have reported that PEOs targets and inhibit multiple dysregulated signaling pathways associated with inflammation, including Toll-like receptors, nuclear transcription factor-κ B, mitogen-activated protein kinases, Nod-like receptor family pyrin domain containing 3, and auxiliary pathways like the nuclear factor erythroid 2-related factor 2/antioxidant response element and Janus kinase/signal transducers and activators of transcription) signaling pathways.

CONCLUSION

PEOs extracted from different plant materials had varied qualitative and quantitative compositions of biologically active compounds. Different anti-inflammatory potentials and different molecular signal transduction have been attributed to PEOs-derived bioactive compounds with different chemical structures. The data on therapeutic efficacy and the long-term side effects of PEOs as an anti-inflammatory drug are still unknown due to the lack of clinical trials on PEOs. There is still insufficient evidence to draw conclusions on anti-inflammatory properties of PEOs without promising outcomes from clinical trials.

Anti-Diabetes, Anti-Gout, and Anti-Leukemia Properties of Essential Oils from Natural Spices Clausena indica, Zanthoxylum rhetsa, and Michelia tonkinensis

Essential oils (EOs) of Clausena indica fruits, Zanthoxylum rhetsa fruits, and Michelia tonkinensis seeds were analyzed for their phytochemical profiles and biological activities, including anti-diabetes, anti-gout, and anti-leukemia properties. Sixty-six volatile compounds were identified by gas chromatography–mass spectrometry (GC–MS), in which, myristicin (68.3%), limonene (44.2%), and linalool (49.3%) were the most prominent components of EOs extracted from C. indica, Z. rhetsa, and M. tonkinensis, respectively. In addition, only EOs from C. indica inhibited the activities of all tested enzymes comprising α-amylase (IC₅₀ = 7.73 mg/mL), α-glucosidase (IC₅₀ = 0.84 mg/mL), and xanthine oxidase (IC₅₀ = 0.88 mg/mL), which are related to type 2 diabetes and gout. Remarkably, all EOs from C. indica, Z. rhetsa (IC₅₀ = 0.73 mg/mL), and M. tonkinensis (IC₅₀ = 1.46 mg/mL) showed a stronger anti-α-glucosidase ability than acarbose (IC₅₀ = 2.69 mg/mL), a known anti-diabetic agent. Moreover, the growth of leukemia cell Meg-01 was significantly suppressed by all EOs, of which, the IC₅₀ values were recorded as 0.32, 0.64, and 0.31 mg/mL for EOs from C. indica, Z. rhetsa, and M. tonkinensis, respectively. As it stands, this is the first report about the inhibitory effects of EOs from C. indica and Z. rhetsa fruits, and M. tonkinensis seeds on the human leukemia cell line Meg-01 and key enzymes linked to diabetes and gout. In conclusion, the present study suggests that EOs from these natural spices may be promising candidates for pharmaceutical industries to develop nature-based drugs to treat diabetes mellitus or gout, as well as malignant hematological diseases such as leukemia.

Citral modulates human monocyte responses to Staphylococcus aureus infection

Staphylococcus aureus is a Gram-positive bacterium that is considered an important human pathogen. Due to its virulence and ability to acquire mechanisms of resistance to antibiotics, the clinical severity of S. aureus infection is driven by inflammatory responses to the bacteria. Thus, the present study aimed to investigate the modulating role of citral in inflammation caused by S. aureus infection. For this, we used an isolate obtained from a nasal swab sample of a healthy child attending a day-care centre in Vitória da Conquista, Bahia, Brazil. The role of citral in modulating immunological factors against S. aureus infection was evaluated by isolating and cultivating human peripheral blood mononuclear cells. The monocytes were treated with 4%, 2%, and 1% citral before and after inoculation with S. aureus. The cells were analysed by immunophenotyping of monocyte cell surface molecules (CD54, CD282, CD80, HLA-DR, and CD86) and cytokine dosage (IL-1β, IL-6, IL-10, IL-12p70, IL-23, IFN-γ, TGF-β, and TNF-α), and evaluated for the expression of 84 genes related to innate and adaptive immune system responses. GraphPad Prism software and variables with P values < 0.05, were used for statistical analysis. Our data demonstrated citral’s action on the expression of surface markers involved in recognition, presentation, and migration, such as CD14, CD54, and CD80, in global negative regulation of inflammation with inhibitory effects on NF-κB, JNK/p38, and IFN pathways. Consequently, IL-1β, IL-6, IL-12p70, IL-23, IFN-γ, and TNF-α cytokine expression was reduced in groups treated with citral and groups treated with citral at 4%, 2%, and 1% and infected, and levels of anti-inflammatory cytokines such as IL-10 were increased. Furthermore, citral could be used as a supporting anti-inflammatory agent against infections caused by S. aureus. There are no data correlating citral, S. aureus, and the markers analysed here; thus, our study addresses this gap in the literature.

Citral modulates virulence factors in methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is responsible for high morbidity and mortality rates. Citral has been studied in the pharmaceutical industry and has shown antimicrobial activity. This study aimed to analyze the antimicrobial activity of citral in inhibiting biofilm formation and modulating virulence genes, with the ultimate goal of finding a strategy for treating infections caused by MRSA strains. Citral showed antimicrobial activity against MRSA isolates with minimum inhibitory concentration (MIC) values between 5 mg/mL (0.5%) and 40 mg/mL (4%), and minimum bactericidal concentration (MBC) values between 10 mg/mL (1%) and 40 mg/mL (4%). The sub-inhibitory dose was 2.5 mg/mL (0.25%). Citral, in an antibiogram, modulated synergistically, antagonistically, or indifferent to the different antibiotics tested. Prior to evaluating the antibiofilm effects of citral, we classified the bacteria according to their biofilm production capacity. Citral showed greater efficacy in the initial stage, and there was a significant reduction in biofilm formation compared to the mature biofilm. qPCR was used to assess the modulation of virulence factor genes, and icaA underexpression was observed in isolates 20 and 48. For icaD, seg, and sei, an increase was observed in the expression of ATCC 33,591. No significant differences were found for eta and etb. Citral could be used as a supplement to conventional antibiotics for MRSA infections.

Lactobacillus plantarum Lp62 exerts probiotic effects against Gardnerella vaginalis ATCC 49154 in bacterial vaginosis

The severe side-effects elicited by conventional antibiotic therapy and the recurrence of Bacterial vaginosis-associated bacteria and bacterial resistance have led to the development of novel alternative therapies, among which genital probiotics are widely used. In this study, we aimed to evaluate the antimicrobial activities of Lactobacillus plantarum Lp62 and its supernatant against Gardnerella vaginalis, using both in vitro and in vivo approaches. In vitro assays were used to evaluate the viability of the strain and the antimicrobial activities of the supernatant in different pH ranges. An in vivo assay was performed on female BALB/c mice, wherein the animals were divided into eight groups: four control groups and four treated groups (for curative and preventive therapies). After infecting and treating the mice, the animals were killed to quantify the bacterial load using qPCR, evaluate leucocyte cellular response, determine vaginal cytokine levels and perform cytokine tissue gene expression. Our analyses revealed significant activity of the strain and its supernatant against G. vaginalis. Preliminary in vitro tests showed that the strain grew with equal efficiency in different pH ranges. Meanwhile, the presence of halo and inhibition of pathogen growth established the significant activity of the supernatant against G. vaginalis. We observed that both micro-organisms are resident bacteria of mouse microbiota and that the lactobacilli population growth was affected by G. vaginalis and vice versa. We also observed that the treated groups, with their low bacterial load, absence of leucocyte recruitment, reduced cytokine levels in the vaginal lavage and normalized cytokine gene expression, successfully controlled the infection.

Ureaplasma parvum alters the immune tolerogenic state in placental tissue and could cause miscarriage

OBJECTIVE

To study the inflammatory profile and genes involved in the response to bacterial infections in women who developed spontaneous abortion in the presence of Ureaplasma parvum.

DESIGN

Cross-sectional study.

SETTING

A maternal and child referral center.

PATIENT(S)

Eighty-nine women with spontaneous abortion and 20 women with normal vaginal delivery (control group) were studied.

INTERVENTION(S)

Samples of biopsied placental tissue were collected for Mollicutes detection.

MAIN OUTCOME MEASURE(S)

The samples were subjected to histologic analysis, immunohistochemical evaluation for macrophages and lymphocytes, cytokine quantification, and quantitative polymerase chain reaction array to evaluate the expression of 84 genes related to the innate and adaptive immune responses.

RESULT(S)

The presence of U. parvum in the abortion group was positively associated with the influx of polymorphonuclear cells in the placental tissue and increased concentrations of interleukin-6 and interleukin-12p70. U. parvum caused downregulation of genes involved in the immune response, such as attraction of immune cells, activation of an inflammatory response, T-helper cell 17 response activation, and activation of the complement system at the beginning and end of pregnancy.

CONCLUSION

The direct action of U. parvum on placental tissue altered the gestational tolerogenic state, reducing the immune response against pathogens and activating the extrinsic apoptotic pathway, causing spontaneous abortion.

p53 Rather Than β-Catenin Mediated the Combined Hypoglycemic Effect of Cinnamomum cassia (L.) and Zingiber officinale Roscoe in the Streptozotocin-Induced Diabetic Model

Background: The antioxidant, hypoglycemic, and insulin-enhancing effects of ginger and cinnamon were previously confirmed in experimental and human studies, while the combined effect of ginger and cinnamon was not thoroughly investigated until now.

Objectives: This study was designed to assess the antidiabetic effect of combined administration of ginger (Zingiber officinale Roscoe) and cinnamon (Cinnamomum cassia L.) in streptozotocin (STZ)-induced diabetic rats compared to metformin and to explain the mechanism behind this effect.

Materials and methods: STZ was utilized to induce diabetes mellitus in male Sprague–Dawley rats. Assessments of fasting blood glucose level (BGL), the total antioxidant capacity (TAC), serum insulin, HOMA-IR, and HOMA–β cells were performed. Pancreatic gene expression of β-catenin and p53 was assessed using RT-PCR. Assessment of histopathological alterations of pancreatic islet cells was performed using routine and immunohistochemical techniques.

Results: BGL significantly decreased (p = 0.01), while serum insulin and TAC significantly increased (p < 0.001) in both metformin- and ginger plus cinnamon–treated groups compared to the untreated diabetic group. HOMA–β cell index significantly increased (p = 0.001) in ginger plus cinnamon, indicating their enhancing effect on insulin secretion in diabetic conditions. p53 gene expression was significantly upregulated (p < 0.001), while β-catenin was insignificantly downregulated (p = 0.32) in ginger plus cinnamon–treated groups. Insulin immunoexpression in β cells significantly increased (p = 0.001, p = 0.004) in metformin- and ginger plus cinnamon–treated groups, respectively.

Conclusions: The combined administration of ginger and cinnamon has a significant hypoglycemic and antioxidant effect in STZ-induced diabetes mostly through enhancing repair of islet cells mediated via upregulation of pancreatic p53 expression. Therefore, testing this effect in diabetic patients is recommended.

Features, Pharmacological Chemistry, Molecular Mechanism and Health Benefits of Lemon

Background:

Citrus limon, a Mediterranean-grown citrus species of plants belonging to the Rutaceae family, occupies a place of an impressive range of food and medicinal uses with considerable value in the economy of the fruit of the country. Citrus fruits are economically important with large-scale production of both the fresh fruits and industrially processed products. The extracts and phytochemicals obtained from all parts of C. limon have shown immense therapeutic potential because of their anticancer, anti-tumor and anti-inflammatory nature, and also serve as an important ingredient in the formulation of several ethnic herbal medicines. These properties are mediated by the presence of different phytochemicals, vitamins and nutrients in the citrus fruits.

Material and Methods:

The methods involved in the preparation of the present article included the collection of information from various scientific databases, indexed periodicals, and search engines such as Medline Scopus google scholar PubMed, PubMed central web of science, and science direct.

Results:

This communication presents an updated account of different pharmacological aspects of C. limon associated with its anti-oxidative, antiulcer, antihelmintic, insecticidal, anticancer, cytotoxic, and estrogenic activities. In addition, C. limon extracts possess hepatoprotective, anti-hyperglycemic, and antimicrobial properties. The present article includes the structure and function of different key chemical constituents from different parts of C. limon. Also, the possible molecular mechanisms of actions of bioactive compounds from C. limon are displayed.

Conclusion:

The traditional and ethno-medicinal literature revealed that C. limon is very effective in different pathologies. Most of these compounds possessing antioxidant properties would be implicated in offering health benefits by acting as potential nutraceuticals to humans with special reference to disease management of health and disease.

In vitro effects of citral on the human myometrium: Potential adjunct therapy to prevent preterm births

BACKGROUND

Premature infants contribute to infant morbidity and mortality especially in low resource settings. Information on tocolytic and/or anti-inflammatory effects of several plant extracts, such as citral, could help prevent preterm birth cases and reduce the number of preterm infants. The aim of this study was to evaluate the in vitro tocolytic and anti-inflammatory effect of citral on myometrial tissues of the human uterus.

METHODS

Myometrial samples from uteri obtained after hysterectomy were used in functional tests to evaluate the inhibitory effect of citral on PGF-2α induced contractions. The intracellular cyclic adenosine monophosphate (cAMP) levels generated in response to citral in human myometrial homogenates were measured by ELISAs. Forskolin was used as a positive control. The anti-inflammatory effect of citral was determined through the measurement of two pro-inflammatory cytokines, tumor necrosis factor-α (TNFα) and interleukin (IL)-1β, and the anti-inflammatory cytokine IL-10, in human myometrial explants stimulated with lipopolysaccharide (LPS).

RESULTS

Citral was able to induce a significant inhibition of PGF-2α induced contractions at the highest concentration level (p < .05). Citral caused a concentration-dependent increase in myometrial cAMP levels (p < .05) and a concentration-dependent decrease in LPS-induced TNFα and IL-1β production, while IL-10 production increased significantly (p < .05). The anti-inflammatory and tocolytic effects induced by citral could be associated with an increase in cAMP levels in human myometrial samples.

CONCLUSION

These properties place citral as a potentially safe and effective adjuvant agent in preterm birth cases, an obstetric and gynecological problem that requires urgent attention.

Proteomic and Systematic Functional Profiling Unveils Citral Targeting Antibiotic Resistance, Antioxidant Defense, and Biofilm-Associated Two-Component Systems of Acinetobacter baumannii To Encumber Biofilm and Virulence Traits

Acinetobacter baumannii is a nosocomial-infection-causing bacterium and also possesses multidrug resistance to a wide range of conventional antibiotics. The biofilm-forming ability of A. baumannii plays a major role in its resistance and persistence. There is an alarming need for novel treatment strategies to control A. baumannii biofilm-associated issues. The present study demonstrated the strong antibiofilm and antivirulence efficacy of citral against A. baumannii. In addition, proteomic analysis revealed the multitarget potential of citral against A. baumannii. Furthermore, citral treatment enhances the susceptibility of A. baumannii to the host innate immune system and reactive oxygen species (ROS). Cytotoxicity analysis revealed the nonfatal effect of citral on human PBMCs. Therefore, citral could be the safest therapeutic compound and can be taken for further clinical evaluation for the treatment of biofilm-associated infections by A. baumannii.

Acinetobacter baumannii has been reported as a multidrug-resistant bacterium due to biofilms and antimicrobial resistance mechanisms. Hence, novel therapeutic strategies are necessary to overcome A. baumannii infections. This study revealed that citral at 200 μg/ml attenuated A. baumannii biofilms by up to 90% without affecting viability. Furthermore, microscopic analyses and in vitro assays confirmed the antibiofilm efficacy of citral. The global effect of citral on A. baumannii was evaluated by proteomic, transcriptional, and in silico approaches. Two-dimensional (2D) gel electrophoresis and matrix-assisted laser desorption ionization–time of flight/time of flight (MALDI-TOF/TOF) analyses were used to assess the effect of citral on the A. baumannii cellular proteome. Quantitative real-time PCR (qPCR) analysis was done to validate the proteomic data and identify the differentially expressed A. baumannii genes. Protein-protein interactions, gene enrichment, and comparative gene network analyses were performed to explore the interactions and functional attributes of differentially expressed proteins of A. baumannii. Global omics-based analyses revealed that citral targeted various mechanisms such as biofilm formation, antibiotic resistance, antioxidant defense, iron acquisition, and type II and type IV secretion systems. The results of antioxidant analyses and antibiotic sensitivity, blood survival, lipase, and hemolysis assays validated the proteomic results. Cytotoxicity analysis showed a nontoxic effect of citral on peripheral blood mononuclear cells (PBMCs). Overall, the current study unveiled that citral has multitarget efficacy to inhibit the biofilm formation and virulence of A. baumannii.

IMPORTANCEAcinetobacter baumannii is a nosocomial-infection-causing bacterium and also possesses multidrug resistance to a wide range of conventional antibiotics. The biofilm-forming ability of A. baumannii plays a major role in its resistance and persistence. There is an alarming need for novel treatment strategies to control A. baumannii biofilm-associated issues. The present study demonstrated the strong antibiofilm and antivirulence efficacy of citral against A. baumannii. In addition, proteomic analysis revealed the multitarget potential of citral against A. baumannii. Furthermore, citral treatment enhances the susceptibility of A. baumannii to the host innate immune system and reactive oxygen species (ROS). Cytotoxicity analysis revealed the nonfatal effect of citral on human PBMCs. Therefore, citral could be the safest therapeutic compound and can be taken for further clinical evaluation for the treatment of biofilm-associated infections by A. baumannii.

Citral Inhibits the Inflammatory Response and Hyperalgesia in Mice: The Role of TLR4, TLR2/Dectin-1, and CB2 Cannabinoid Receptor/ATP-Sensitive K+ Channel Pathways

Citral ((2E)-3,7-dimethylocta-2,6-dienal), a bioactive component of lemongrass, inhibits oxidant activity, nuclear factor kappa B (NF-κB) activation, and cyclooxygenase-2 (COX-2) expression, even as it activates peroxisome proliferator-activated receptor (PPAR)-α and γ. Additionally, citral produces long-lasting inhibition of transient receptor potential (TRP) channels that are found in sensory neurons, such as TRPV1-3 and TRPM8, while it transiently blocks TRPV4 and TRPA1. Here, the effect of citral in experimental models of acute inflammation and hyperalgesia in mice, and the underlying citral mechanisms of action were investigated. ADMET properties and molecular targets were predicted using the online server. The immunomodulatory and antihyperalgesic effects of citral were evaluated, using mechanical and thermal stimuli, at different time-points on carrageenan, lipopolysaccharides (LPS), and zymosan-induced paw edema and hyperalgesia in mice. ADMET analysis ensures that the citral has not violated Lipinski's rule of five, indicating its safety consumption, and molecular target prediction software identified that citral is a potential fatty acid amide hydrolase (FAAH) inhibitor. Oral treatment with citral (50-300 mg/kg) significantly inhibited carrageenan-induced paw edema and thermal allodynia. Furthermore, citral modulated the inflammation induced by LPS and zymosan, toll-like receptor (TLR) 4, and TLR2/dectin-1 ligands, respectively. Moreover, pretreatment with cannabinoid receptor type 2 (CB2R) antagonists and ATP-sensitive K⁺ channel inhibitor, but not with a cannabinoid receptor type 1 (CB1R) antagonist, significantly reversed the anti-inflammatory effect of citral. Intriguingly, citral did not cause any relevant action in the central nervous system, and it was safe when assessed in a 14 day toxicity assay in male mice. Therefore, citral constitutes a promising, innovative, and safe molecule for the management of immunoinflammatory conditions and pain states.

Shift of Volatile Organic Compounds (VOCs) in Gluten-Free Hemp-Enriched Sourdough Bread: A Metabolomic Approach

Hemp seed flour represents a potential ingredient for protein enrichment of gluten-free bakery products, the nutritional value of which could be further increased by fermentation with sourdough or with beneficial lactic acid bacteria strains. In this study, a metabolomic approach was used to evaluate the effect of hemp seed flour addition and sourdough fermentation on the production of flavoring and health-related volatile organic compounds (VOCs) in a gluten-free bread. Multivariate analysis of VOCs provided an in-depth description of the effects of hemp seed flour addition and sourdough fermentation on flavoring and bioactive compounds. In particular, an increased concentration of antimicrobial compounds, a larger spectrum of bioactive VOCs and a typical flavoring profile was evidenced in comparison to standard products. Furthermore, an increase of fermentation metabolites was observed in comparison to a standard dough, relating to abundances of 2-butanone-3-hydroxy, acetic acid, ethanol, and 1,4-butanediol. This study provides new insights on the evolution of flavoring and bioactive hemp seed flour constituents during sourdough fermentation, evidencing their retention in baked goods, and describes a new approach that could guide the formulation of innovative, fermented food with enhanced nutritional value.

Citral Inhibition of Human Salivary Aldehyde Dehydrogenase

Human salivary aldehyde dehydrogenase (hsALDH) protects us from the toxic effect of aldehydes. It has both diagnostic and therapeutic importance. Citral possesses many biological and pharmacological properties. The aim of this work was to investigate the inhibitory effect and the mechanism of inhibition of citral on hsALDH. Citral inhibits the dehydrogenase activity of hsALDH. It decreased the substrate affinity and to a lesser extent, the catalytic efficiency of hsALDH. Citral showed linear mixed-type inhibition with a higher tendency of competitive behavior with little, but significant, non-competitive inhibition. The nucleophilicity of active site Cys residue is not a significant contributing factor in the inhibition process. Citral shows uncompetitive inhibition towards the co-enzyme (NAD⁺). α-helix and β-sheet content of the enzyme were changed in presence of citral. Biophysical studies showed that citral quenches the intrinsic fluorescence of hsALDH in a static manner by forming complex with the enzyme. Molecular docking study showed that both the isomers of citral bind to the catalytic site of hsALDH interacting with few evolutionary preserved amino acid residues through multiple non-covalent interactions. Ligand efficiency metrics values indicate that citral is an efficient ligand for the enzyme in terms of its physicochemical and pharmacokinetic properties.

Preparation and Characterization of Self Nano-Emulsifying Drug Delivery System Loaded with Citraland Its Antiproliferative Effect on Colorectal Cells In Vitro

Citral is an active compound naturally found in lemongrass, lemon, and lime. Although this pale-yellow liquid confers low water solubility, the compound has been reported to possess good therapeutic features including antiproliferative and anticancer modalities. The self nano-emulsifying drug delivery system (SNEDDS) is a type of liquid-lipid nanocarrier that is suitable for the loading of insolubilized oil-based compound such as Citral. This study reports the design and optimization of a SNEDDS formulation, synthesis and characterization as well as loading with Citral (CIT-SNEDDS). Further assessment of theantiproliferative effects of CIT-SNEDDS towards colorectal cancer cells was also conducted. SNEDDS composed of coconut oil, dimethyl sulfoxide (DMSO) and Tween 80. CIT-SNEDDS was prepared via gentle agitation of SNEDDS with 0.5% Citral for 72 h at room temperature. Physicochemical characterization was performed using several physicochemical analyses. The average particle size of CIT-SNEDDS was16.86 ± 0.15 nm, zeta potential of 0.58 ± 0.19 mV, and polydispersity index (PDI) of 0.23 ± 0.01. In vitro drug release of Citral from CIT-SNEDDS was 79.25% of release, and for Citral the release percentage was 93.56% over 72 h. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was done to determine the cytotoxicity effect of CIT-SNEDDS in human colorectal cancer cell lines HT29 and SW620. The half maximal inhibitory concentrations (IC₅₀) for 72 hof CIT-SNEDDS and Citral on SW620 were 16.50 ± 0.87 µg/mL and 22.50 ± 2.50 µg/mL, respectively. The IC₅₀ values of CIT-SNEDDS and Citral after 72 h of treatment on HT29 were 34.10 ± 0.30 µg/mL and 21.77 ± 0.23 µg/mL, respectively. This study strongly suggests that CIT-SNEDDS has permitted the sustained release of Citral and that CIT-SNEDDS constitutes a potential soluble drug nanocarrier that is effective against colorectal cancer cells.

Effect and mechanism of citral against methicillin-resistant Staphylococcus aureus in vivo

BACKGROUND

Citral is an active component of many plant extracts, and it is a safe additive used in food and cosmetics. A previous study showed that citral has a good antibacterial effect against methicillin-resistant Staphylococcus aureus (MRSA) in vitro, but its in vivo anti-infective activity has not been studied. Anti-MRSA activity and the preliminary mechanism of citral against MRSA were investigated in MRSA-infected KM mice. The ED₅₀ was calculated using Karber's method. Groups were selected for inflammatory and oxidative stress level tests, and lung and liver tissues were counterstained with HE for detection of pathological changes. Cytokines and oxidative factors were evaluated using the ELISA method (one-way ANOVA computed using SPSS 19.0.).

RESULTS

With the increase in the concentration of citral, the survival rate of MRSA-infected mice increased accordingly. The ED₅₀ values of citral for intramuscular injection and intragastric administration were 0.09 and 0.26 g kg^-1 respectively. Citral significantly reduced cytokines (IL-1β, IL-6, TNF-α) and oxidative factors (malondialdehyde and hydroxyl radicals) of MRSA-infected mice, whereas it increased gluthtione and superoxide dismutase levels. Citral can reduce the lung inflammatory infiltrates infected by MRSA.

CONCLUSIONS

Citral exerted a dose-dependent anti-MRSA effect and ameliorated MRSA-induced abnormal changes in inflammation and oxidative stress. This indicates that citral has the potential for development as a new anti-MRSA drug. © 2019 Society of Chemical Industry.

Endotoxin Contributes to Artificial Loosening of Prostheses Induced by Titanium Particles

Background

Aseptic loosening of orthopedic implants caused by wear particles is a major cause of joint replacement failure. However, the mechanism of aseptic loosening has not yet been defined. The present study explored whether endotoxin adherent on the titanium (Ti) particles contributes to aseptic loosening.

Material/Methods

Limulus amebocyte lysate detection was conducted to detect the levels of endotoxin adhered to the Ti particles. A mouse air pouches model was established and mice were divided into 4 groups and injected with phosphate-buffered saline (PBS) or Ti particles suspensions (0.1, 1, 10 mg/mL), following detection of the number of macrophages and the level of endotoxin. Scanning electron microscopy (SEM) was used to characterize the microstructures of Ti particles adhered with endotoxin.

Results

In vitro experiments showed that the level of endotoxin adhered to the Ti particles was significantly increased after adding LPS back to these “endotoxin-free” particles. In vivo experiments showed that Ti particles injection significantly increased the number of macrophages and the level of endotoxin.

Conclusions

In conclusion, these results suggest that adherent endotoxin may play an important role in aseptic loosening induced by Ti particles.

Investigation of molecular mechanism of recognition between citral and MARK4: A newer therapeutic approach to attenuate cancer cell progression

Microtubule affinity regulating kinase 4 (MARK4) is a member of AMP-activated protein kinase, found to be involved in apoptosis, inflammation and many other regulatory pathways. Since, its aberrant expression is directly associated with the cell cycle and thus cancer. Therefore, MARK4 is being considered as a potential drug target for cancer therapy. Here, we investigated the mechanism of inhibition of MARK4 activity by citral. Docking studies suggested that citral effectively binds to the active site cavity, and complex is stabilized by several interactions. We further performed molecular dynamics simulation of MARK4-citral complex under explicit water condition for 100ns and observed that binding of citral to MARK4 was quite stable. Fluorescence binding studies suggested that citral strongly binds to MARK4 and thereby inhibits its enzyme activity which was measured by the kinase inhibition assay. We further performed MTT assay and observed that citral inhibits proliferation of breast cancer cell line MCF-7. This work provides a newer insight into the use of citral as novel cancer therapeutics through the MARK4 inhibition. Results may be employed to design novel therapeutic molecule using citral as a scaffold for MARK4 inhibition to fight related diseases.