Identification of key genes controlling monoterpene biosynthesis of Citral-type Cinnamomum bodinieri Levl. Based on transcriptome and metabolite profiling.

The citral-type is the most common chemotype in Cinnamomum bodinieri Levl (C. bodinieri), which has been widely used in the daily necessities, cosmetics, biomedicine, and aromatic areas due to their high citral content. Despite of this economic prospect, the possible gene-regulatory roles of citral biosynthesis in the same geographic environment remains unknown. In this study, the essential oils (EOs) of three citral type (B1, B2, B3) and one non-citral type (B0) varieties of C. bodinieri were identified by GC-MS after hydrodistillation extraction in July. 43 components more than 0.10% were identified in the EOs, mainly composed of monoterpenes (75.8-91.84%), and high content citral (80.63-86.33%) were identified in citral-type. Combined transcriptome and metabolite profiling analysis, plant-pathogen interaction(ko04626), MAPK signaling pathway-plant(ko04016), starch and sucrose metabolism(ko00500), plant hormone signal transduction(ko04075), terpenoid backbone biosynthesis (ko00900) and monoterpenoid biosynthesis (ko00902) pathways were enriched significantly. The gene expression of differential genes were linked to the monoterpene content, and the geraniol synthase (CbGES), alcohol dehydrogenase (CbADH), geraniol 8-hydroxylase-like (CbCYP76B6-like) and 8-hydroxygeraniol dehydrogenase (Cb10HGO) were upregulated in the citral-type, indicating that they were associated with high content of geraniol and citral. The activities of CbGES and CbADH in citral type were higher than in non-citral type, which was corroborated by enzyme-linked immunosorbent assay (ELISA). This study on the accumulation mechanism of citral provides a theoretical basis for the development of essential oil of C. bodinieri.

Development of Corynebacterium glutamicum as a monoterpene production platform.

Monoterpenes are commonly known for their role in the flavors and fragrances industry and are also gaining attention for other uses like insect repellant and as potential renewable fuels for aviation. Corynebacterium glutamicum, a Generally Recognized as Safe microbe, has been a choice organism in industry for the annual million ton-scale bioproduction of amino acids for more than 50 years; however, efforts to produce monoterpenes in C. glutamicum have remained relatively limited. In this study, we report a further expansion of the C. glutamicum biosynthetic repertoire through the development and optimization of a mevalonate-based monoterpene platform. In the course of our plasmid design iterations, we increased flux through the mevalonate-based bypass pathway, measuring isoprenol production as a proxy for monoterpene precursor abundance and demonstrating the highest reported titers in C. glutamicum to date at 1504.6 mg/L. Our designs also evaluated the effects of backbone, promoter, and GPP synthase homolog origin on monoterpene product titers. Monoterpene production was further improved by disrupting competing pathways for isoprenoid precursor supply and by implementing a biphasic production system to prevent volatilization. With this platform, we achieved 321.1 mg/L of geranoids, 723.6 mg/L of 1,8-cineole, and 227.8 mg/L of linalool. Furthermore, we determined that C. glutamicum first oxidizes geraniol through an aldehyde intermediate before it is asymmetrically reduced to citronellol. Additionally, we demonstrate that the aldehyde reductase, AdhC, possesses additional substrate promiscuity for acyclic monoterpene aldehydes.

Evaluation of antifungal and apoptotic effects of linalool, citral, and carvacrol separately and in combination with nystatin against clinical isolates of Pichia kudriavzevii.

Pichia kudriavzevii (formerly Candida krusei) poses a significant threat to immunocompromised patients due to its inherent resistance to various antifungal drugs. This study explored the anticandidal potential of citral, linalool, and carvacrol in combination with nystatin against P. kudriavzevii strains.Using the microdilution method following CLSI guidelines, Minimum Inhibitory Concentrations (MICs) and fungicidal concentrations (MFCs) were determined. Citral exhibited MIC values ranging from 50 to 100 µg/ml, averaging 70.24 ± 16.99 µg/ml, while carvacrol had MIC values of 50 to 100 µg/ml, averaging 86.90 ± 16.99 µg/ml. Linalool demonstrated weaker antifungal activity, with MIC values between 100 and 200 µg/ml, averaging 150 ± 38.73 µg/ml. The study assessed the synergistic effectsof these phenols with nystatin through fractional inhibitory concentration indices (FICIS). In addition, flow cytometry was employed to assess apoptosis induction in P. kudriavzevii cells.Carvacrol displayed a remarkable synergistic effect in combination with nystatin against all 21 isolates tested. Conversely, linalool showed synergy in 17 isolates, while citral exhibited synergy in only 2 isolates. These findings highlight distinct patterns of synergy between the different compounds and nystatin against P. kudriavzevii. Also, Carvacrol emerged as the most potent inducer of apoptosis across all P. kudriavzevii strains, followed by citral and linalool. This suggests that carvacrol not only possesses a stronger antifungal effect but also has a more pronounced ability to trigger programmed cell death in P. kudriavzevii. In conclusion, the study supports the potential of carvacrol, citral and linalool, as anticandidal agents, suggesting their supplementation with nystatin for treating P. kudriavzevii infections.

Citral and triclosan synergistically silence quorum sensing and potentiate antivirulence response in Pseudomonas aeruginosa.

Among the ESKAPE pathogens, Pseudomonas aeruginosa is an extensively notorious superbug that causes difficult-to-treat infections. Since quorum sensing (QS) directly promotes pseudomonal virulence, targeting QS circuits is a promising approach for disarming phenotypic virulence. Hence, this study scrutinizes the anti-QS, antivirulence, and anti-biofilm potential of citral (CiT; phytochemical) and triclosan (TcN; disinfectant), alone and in combination, against P. aeruginosa PAO1/PA14. The findings confirmed synergism between CiT and TcN and revealed their quorum quenching (QQ) potential. At sub-inhibitory levels, CiT-TcN combination significantly impeded pyocyanin, total bacterial protease, hemolysin, and pyochelin production alongside inhibiting biofilm formation in P. aeruginosa. Moreover, the QQ and antivirulence potential of CiT and TcN was positively correlated by molecular docking studies that predicted strong associations of the drugs with QS receptors of P. aeruginosa. Collectively, the study identifies CiT-TcN as an effective drug combination that harbors QQ, antivirulence, and anti-biofilm prospects against P. aeruginosa.

Inhibitory activity and antioomycete mechanism of citral against Phytophthora capsici.

The natural terpenoid citral has antifungal activity against multiple fungi, but its bioactivity against oomycetes is unclear. Therefore, this study investigated the antioomycete activity and mechanism of citral against Phytophthora capsici, a highly destructive invasive oomycete. Results showed that citral not only had a great inhibition on the mycelial growth of P. capsici (EC50 = 94.15 mg/L), but also had a significant inhibition on multiple spores, such as sporangia formation, zoospore discharge and zoospore germination. Citral at 4000 mg/L exhibited favorable protective (73.33%) and curative efficacy (55.11%) against pepper Phytophthora blight. Citral significantly damaged the hyphal morphology, disrupted the cell membrane integrity, increased the permeability of cell membrane, and increased the glycerol content in P. capsici. A total of 250 upregulated and 288 downregulated proteins were identified in iTRAQ-based quantitative proteomic analysis. Downregulated proteins were mostly enriched in pathways of ABC transporters, cyanoamino acid metabolism and starch and sucrose metabolism, suggesting an inhibition of citral on transmembrane transporter (e.g., ABC transporters) and pathogenicity (e.g., ß-glucosidases) proteins. Upregulated proteins were enriched in biosynthesis of unsaturated fatty acids, pyruvate metabolism and glycolysis/gluconeogenesis, suggesting an activation of citral on energy generation proteins, including acyl-CoA oxidase, D-lactate dehydrogenase, pyruvate kinase, acetyl-CoA synthetase and phosphoenolpyruvate carboxykinase. Biochemical and iTRAQ analysis suggested that cell membrane may be the target of citral in P. capsici.

Influence of essential oil composition on antioxidant and antibacterial activities of three cultivars of Cymbopogon flexuosus: in vitro and in silico study.

The present study investigates and compares the chemical composition, antioxidant, and antibacterial properties of lemongrass essential oils (LEOs) extracted from fresh leaves of three cultivars of C. flexuosus: Krishna (CF-KA), Cauvery (CF-CA), and Nima (CF-NI), grown in Chhattisgarh plains. Analysis through gas chromatography techniques revealed that citral content was highest in CF-CA (79.82 ± 1.00%), followed by CF-KA (69.75 ± 2.70%) and CF-CA (54.75 ± 1.22%). In vitro antioxidant experiments demonstrated that CF-CA had better scavenging capacity in DPPH (SC50 = 164.55 ± 9.35 µg/mL) and ABTS (SC50 = 4.76 ± 0.57 GEAC/g) free radical scavenging assays. The in vitro antibacterial experiments against Staphylococcus aureus (MTCC3160) and Escherichia coli (MTCC2412) demonstrated CF-NI's enhanced antibacterial efficacy with significant inhibition zones and low MIC values. In silico molecular docking results revealed that LEO compounds like caryophyllene oxide, humulene epoxide, ß-caryophyllene etc. have better binding affinities towards targeted protein molecules responsible for bacterial cell mechanisms and production of reactive oxygen species (ROS) compared to their native ligands. Variations in biological activities among cultivars were potentially linked to the proportion of phytoconstituents in their chemical composition.

Inhibition and Mechanism of Citral on Bacillus cereus Vegetative Cells, Spores, and Biofilms.

Bacillus cereus causes food poisoning by producing toxins that cause diarrhea and vomiting and, in severe cases, endocarditis, meningitis, and other diseases. It also tends to form biofilms and spores that lead to contamination of the food production environment. Citral is a potent natural antibacterial agent, but its antibacterial activity against B. cereus has not been extensively studied. In this study, we first determined the minimum inhibitory concentrations and minimum bactericidal concentrations, growth curves, killing effect in different media, membrane potential, intracellular adenosine triphosphate (ATP), reactive oxygen species levels, and morphology of vegetative cells, followed by germination rate, morphology, germination state of spores, and finally biofilm clearance effect. The results showed that the minimum inhibitory concentrations and minimum bactericidal concentrations of citral against bacteria ranged from 100 to 800 µg/mL. The lag phase of bacteria was effectively prolonged by citral, and the growth rate of bacteria was slowed down. Bacteria in Luria-Bertani broth were reduced to below the detection limit by citral at 800 µg/mL within 0.5 h. Bacteria in rice were reduced to 3 log CFU/g by citral at 4000 µg/mL within 0.5 h. After treatment with citral, intracellular ATP concentration was reduced, membrane potential was altered, intracellular reactive oxygen species concentration was increased, and normal cell morphology was altered. After treatment with citral at 400 µg/mL, spore germination rate was reduced to 16.71%, spore morphology was affected, and spore germination state was altered. It also had a good effect on biofilm removal. The present study showed that citral had good bacteriostatic activity against B. cereus vegetative cells and its spores and also had a good clearance effect on its biofilm. Citral has the potential to be used as a bacteriostatic substance for the control of B. cereus in food industry production.

Enhancing Selectivity and Inhibitory Effects of Chemotherapy Drugs Against Myelogenous Leukemia Cells with Lippia alba Essential Oil Enriched in Citral.

Acute myelogenous leukemia (AML) is one of the most lethal cancers, lacking a definitive curative therapy due to essential constraints related to the toxicity and efficacy of conventional treatments. This study explores the co-adjuvant potential of Lippia alba essential oils (EO) for enhancing the effectiveness and selectivity of two chemotherapy agents (cytarabine and clofarabine) against AML cells. EO derived from L. alba citral chemotype were produced using optimized and standardized environmental and extraction protocols. Rational fractionation techniques were employed to yield bioactive terpene-enriched fractions, guided by relative chemical composition and cytotoxic analysis. Pharmacological interactions were established between these fractions and cytarabine and clofarabine. The study comprehensively evaluated the cytotoxic, genotoxic, oxidative stress, and cell death phenotypes induced by therapies across AML (DA-3ER/GM/EVI1+) cells. The fraction rich in citral (F2) exhibited synergistic pharmacological interactions with the studied chemotherapies, intensifying their selective cytotoxic, genotoxic, and pro-oxidant effects. This shift favored transitioning from necrosis to a programmed cell death phenotype (apoptotic). The F2-clofarabine combination demonstrated remarkable synergistic anti-leukemic performance while preserving cell integrity in healthy cells. The observed selective antiproliferative effects may be attributed to the potential dual prooxidant/antioxidant behavior of citral in L. alba EO.

Expanding Knowledge about the Influence of Citral on Cognitive Functions-In Vitro, In Vivo and Ex Vivo Studies.

Citral, a common monoterpene found in numerous plants, is an interesting compound that has been shown to have various biological activities. Although it is widely distributed in nature and there are many studies presenting its biological activities, its anti-neurodegenerative activity, especially under in vivo conditions, is very poorly understood. Thus, this paper aimed to deepen knowledge about citral activity towards factors and symptoms of neurodegeneration. To accomplish this, several comprehensive tests were conducted, including the estimation of butyrylcholinesterase inhibition, the evaluation of hepatotoxicity and the detection of oxidative stress and lipid peroxidation in vitro, as well as an in vivo behavioral assessment using mice models. Additionally, ex vivo determination of level of the compound in the brain and blood of a tested animal was undertaken. The results obtained revealed that citral is able to inhibit butyrylcholinesterase activity and protect hepatic cells against oxidative stress and lipid peroxidation in vitro. Moreover, behavioral tests in vivo indicated that citral (50 mg/kg) improves memory processes associated with acquisition (passive avoidance test), both in acute and subchronic administration. Additionally, we found that the administration of citral at 25 mg/kg and 50 mg/kg did not significantly affect the locomotor activity. Beyond the aforementioned, gas chromatography-mass spectrometry analysis revealed the presence of the compound in the blood and brain after subchronic administration of citral. Taken together, the results obtained in vitro, in vivo and ex vivo clearly indicate that citral is a promising monoterpene that can potentially be used towards cognition improvement.

Ability of Selected Monoterpenes to Reduce Fe(III) Ions Being Pro-Neurodegenerative Factors: Tests Based on a FRAP Reaction Extended to 48 Hours.

Monoterpenes are secondary plant metabolites, and such volatile compounds have antioxidant, antibacterial, antiviral, and enzyme inhibitory properties. These compounds are also able to reduce the potentially pro-neurodegenerative trace metal ions that can be sources of free radicals. One basic method used to evaluate the ability of chemical compounds to reduce Fe(III) is FRAP. To date, most studies based on a FRAP assay were performed within several dozen minutes. However, taking into account the diversity of compounds, it is justified to observe their activity over a much longer period of time. The present study aimed to observe the activity of isopulegol, γ-terpinene, α-terpinene, linalool, carvone, citral, and α-phellandrene over a 48 h period. Our study indicates that the lengthened reaction period enhanced activity from several dozen to several hundred percent. The obtained results also revealed an explicit high correlation of the increase in the activity of compounds with the increase in monoterpene concentration. Due to the hydrophobic character of monoterpenes, the FRAP method was modified by the addition of Tween 20. The highest activity was obtained for α-terpinene and γ-terpinene.

Acyclic monoterpenoid-rich essential oil of Cymbopogon distans mitigates skin inflammation: a chemico-pharmacological study.

The topical application of essential oils is considered an effective treatment for skin diseases. Cymbopogon distans (Nees ex Steud.) Wats (Poaceae) is a promising aromatic grass widespread in the Himalayan temperate zone. Therefore, using in-vitro and in-vivo bioassays, we examined the chemical and pharmacological characteristics of essential oil hydro-distilled from C. distans coded as CDA-01, specifically concerning skin inflammation. Characterization using GC-FID and GC-MS provided a chemical fingerprint for CDA-01, enabling the identification of 54 compounds; amongst them, citral (34.3%), geranyl acetate (21.2%), and geraniol (16.4%) were the most abundant. To examine the anti-inflammatory potential, CDA-01 treatment on LPS-stimulated macrophage cells in addition to 12-O-tetradecanoylphorbol-13-acetate (TPA) generated cutaneous inflammatory reaction in the mouse ear was assessed through quantification of the inflammatory markers. Consequently, CDA-01 demonstrated protection against inflammation caused by LPS by lowering the pro-inflammatory cytokines (IL-6 and TNF-α) level in HaCaT cells with negligible cytotoxicity. Consistent with the in-vitro findings, CDA-01 treatment reduced pro-inflammatory mediators (TNF-, IL-6, and NO) and lipid peroxidation in an in-vivo investigation. Subcutaneous inflammation in TPA-treated mice ears was similarly decreased, as evidenced by the histological and morphological studies. As a result of our findings, it is possible that CDA-01 could be an effective treatment for skin inflammation disorders.

Identification and functional analysis of a deduced geraniol synthase from Camphora officinarum.

The market demand for essential oil containing citral is increasing. Our research group identified a rare chemotype of Camphora officinarum whose leaves are high in citral content by examining over 1000 wild trees across the entire native distribution area of C. officinarum in China. Because C. officinarum is suitable for large-scale cultivation, it is therefore seen as a promising source of natural citral. However, the molecular mechanism of citral biosynthesis in C. officinarum is poorly understood. In this study, transcriptomic analyses of C. officinarum with different citral contents revealed a strong positive correlation between the expression of a putative geraniol synthase gene (CoGES) and citral content. The CoGES cDNA was cloned, and the CoGES protein shared high similarity with other monoterpene synthases. Enzymatic assays of CoGES with geranyl diphosphate (GPP) as substrate yielded geraniol as the single product, which is the precursor of citral. Further transient expression of CoGES in Nicotiana benthamiana resulted in a higher relative content of geranial and the appearance of a new substance, neral. These findings indicate that CoGES is a geraniol synthase-encoding gene, and the encoded protein can catalyze the transformation of GPP into geraniol, which is further converted into geranial and neral through an unknown mechanism in vivo. These findings expand our understanding of citral biosynthesis in Lauraceae plants. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-024-01463-4.

[Study on mechanism of inhibiting proliferation of head and neck cancer cells by citral, active ingredient of lemon essential oil].

To explore the active substances exerting anti-tumour effect in lemon essential oil and the molecular mechanism inhibiting the proliferation of head and neck cancer cells SCC15 and CAL33, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay(MTT) was utilized to identify the active component inhibiting the proliferation of head and neck cancer cells, namely citral. The IC_(50) of citral inhibiting the proliferation of head and neck cancer cells and normal cells were also determined. In addition, a 5-ethynyl-2'-deoxyuridine(EdU) staining assay was used to detect the effect of citral on the proliferation rate of head and neck cancer cells, and a colony formation assay was used to detect the effect of citral on tumor sphere formation of head and neck cancer cells in vitro. The cell cycle arrest and apoptosis induction of head and neck cancer cells by citral were evaluated by flow cytometry, and Western blot was used to detect the effect of citral on the expression levels of cell cycle-and apoptosis-related proteins in head and neck cancer cells. The findings indicated that citral could effectively inhibit the proliferation and growth of head and neck cancer cells, with anti-tumor activity, and its half inhibitory concentrations for CAL33 and SCC15 were 54.78 and 25.23 µg·mL~(-1), respectively. Furthermore, citral arrested cell cycle at G_2/M phase by down-regulating cell cycle-related proteins such as S-phase kinase associated protein 2(SKP2), C-MYC, cyclin dependent kinase 1(CDK1), and cyclin B. Moreover, citral increased the cysteinyl aspartate-specific proteinase-3(caspase-3), cysteinyl aspartate-specific proteinase-9(caspase-9), and cleaved poly ADP-ribose polymerase(PARP). It up-regulated the level of autophagy-related proteins including microtubule associated protein 1 light chain 3B(LC3B), sequestosome 1(P62/SQSTM1), autophagy effector protein Beclin1(Beclin1), and lysosome-associate membrane protein 1(LAMP1), suggesting that citral could effectively trigger cell apoptosis and cell autophagy in head and neck cancer cells. Furthermore, the dual-tagged plasmid system mCherry-GFP-LC3 was used, and it was found that citral impeded the fusion of autophagosomes and lysosomes, leading to autophagic flux blockage. Collectively, our findings reveal that the main active anti-proliferation component of lemon essential oil is citral, and this component has a significant inhibitory effect on head and neck cancer cells. Its underlying molecular mechanism is that citral induces apoptosis and autophagy by cell cycle arrest and ultimately inhibits cell proliferation.

Transcriptomics reveal the antibiofilm mechanism of NaCl combined with citral against Vibrio parahaemolyticus.

Vibrio parahaemolyticus (VP) as a prominent foodborne pathogen in seafood generally adheres to various surfaces and forms biofilms in the processing of aquatic products. The study aimed to elucidate the inhibitory efficacy and potential mechanism of salinity (NaCl) or it combined with citral against the biofilm formation of VP. Three VP strains formed the most biofilm at 1.0% NaCl, and their biofilms gradually declined with the increase of NaCl concentration. Compared with 1% NaCl, applying 3% and 5% NaCl or NaCl in combination with citral at 10-40 µg/mL significantly reduced biofilm biomass, cellular activity, and viable cells, as well as extracellular polymeric substances (EPS) and cell surface hydrophobicity. Sparser and thinner VP biofilm with large dead cells were observed under the combined treatment, in contrast to the dense architectures of biofilm formed at 1% NaCl. Although VP exhibited the strongest swimming and swarming ability at 3% NaCl, the two motilities were both significantly reduced by citral for all three salinities. Transcriptomic profiling revealed that, compared with 1% NaCl (Con), the two treatments consisting of 3% NaCl (Sal3) and it combined with 40 µg/mL citral (Com) drastically altered gene expression patterns in VP biofilm cells, resulting in 1196 and 1304 differentially expressed genes, respectively. The treatment of Com group altered the transcription of various genes related to chemotaxis, flagellar assembly, EPS synthesis, LuxS and CqsA-mediated quorum sensing, and c-di-GMP, which might interfere with biofilm development of VP. Our findings provided novel insights into the combined regulatory mechanism of high salinity and citral for antibiofilm formation in VP. KEY POINTS: • High salinity enhanced the antibiofilm efficacy of citral against Vibrio parahaemolyticus. • Combined treatment downregulated the expression of exopolysaccharide synthesis genes. • A total of 3% NaCl and combined treatments interfered with signaling pathways of QS and c-di-GMP.

In vitro anthelmintic activity of Lippia alba essential oil chemotypes against Haemonchus contortus.

The aim of the present study was to evaluate the effects of the essential oils of Lippia alba chemotypes carvone and citral on H. contortus. Chemical characterization was performed by means of gas chromatography coupled to mass spectrometry (GC/MS). The anthelmintic effects of the essential oils were assessed through the egg hatch test (EHT) and the adult worm motility test (AWMT) using a multidrug-resistant H. contortus Kokstad isolate. Confocal laser scanning microscopy (CLSM) of eggs and adults of H. contortus and scanning electron microscopy (SEM) of adults were performed after treatment with oils for qualitative observations of their effects. The carvone chemotype of L. alba (LaCV) presented 70% carvone, and the citral chemotype of L. alba (LaCT) presented 29.4% geranial and 20.4% neral, respectively. In the EHT, the EC50 values of LaCV and LaCT were 0.2 and 0.3 mg/mL, respectively. In AWMT, after 12 h of exposure to 2 mg/mL LaCV and 2 mg/mL LaCT, 100% of adult nematodes were immobile. CLSM showed changes in larval motility inside the egg caused by LaCV, while LaCT promoted changes in larval formation. In adults exposed to both chemotypes, alterations in the anterior portion of the oesophagus were observed. In SEM, morphological changes were observed in the buccal capsule and in the medial portion of H. contortus adults. It is concluded that the two essential oils of L. alba, the chemotypes carvone and citral, caused morphological changes and inhibited the hatching of eggs and the motility of adult H. contortus nematodes.

Citral and trans-cinnamaldehyde, two plant-derived antimicrobial agents can induce Staphylococcus aureus into VBNC state with different characteristics.

Viable but nonculturable (VBNC) state bacteria are difficult to detect in the food industry due to their nonculturable nature and their recovery characteristics pose a potential threat to human health. The results of this study indicated that S. aureus was found to enter the VBNC state completely after induced by citral (1 and 2 mg/mL) for 2 h, and after induced by trans-cinnamaldehyde (0.5 and 1 mg/mL) for 1 h and 3 h, respectively. Except for VBNC state cells induced by 2 mg/mL citral, the VBNC state cells induced by the other three conditions (1 mg/mL citral, 0.5 and 1 mg/mL trans-cinnamaldehyde) were able to be resuscitated in TSB media. In the VBNC state cells induced by citral and trans-cinnamaldehyde, the ATP concentration was reduced, the hemolysin-producing ability was significantly decreased, but the intracellular ROS level was elevated. The results of heat and simulated gastric fluid experiments showed different environment resistance on VBNC state cells induced by citral and trans-cinnamaldehyde. In addition, by observing the VBNC state cells showed that irregular folds on the surface, increased electron density inside and vacuoles in the nuclear region. What's more, S. aureus was found to enter the VBNC state completely after induced by meat-based broth containing citral (1 and 2 mg/mL) for 7 h and 5 h, after induced by meat-based broth containing trans-cinnamaldehyde (0.5 and 1 mg/mL) for 8 h and 7 h. In summary, citral and trans-cinnamaldehyde can induce S. aureus into VBNC state and food industry needs to comprehensively evaluate the antibacterial capacity of these two plant-derived antimicrobial agents.

Phytochemical and Biological Profile of Essential Oils of Elionurus muticus (Spreng.) Growing in Northeastern Argentina.

The purpose of this study was to investigate essential oils (EOs) from leaves of Elionurus muticus growing in Northeastern Argentina regarding their physicochemical profiles as well as their biological potential. Roots of a selected E. muticus population were investigated too. For this purpose, EOs of fresh materials were obtained by steam distillation and the chemical composition was characterized by gas chromatography GC/MS-FID. Antibacterial, antioxidant and eco-toxicity activities of the essential oils (EOs) were tested by in vitro assays. The EOs showed three E. muticus chemotypes: citral (neral+geranial), acorenone+bisabolone, acorenone+geranial. EO of roots of citral population contains mainly acorenone derivatives. EOs have high antibacterial effect against Staphylococcus aureus, being found minor antibacterial effect against Gram-negative bacteria. The half-maximal inhibitory concentration of EOs against DPPH⋅ were 7.1-30.0 mg/mL and the eco-toxicity was high with LD50 <39 µg/mL. Based on the findings, given the high variability in their chemical composition and biological activity of E. muticus EO and the promising yields, it could be potentially chosen for industrial applications.

Citral Modulates MMP-2 and MMP-9 Activities on Healing of Gastric Ulcers Associated with High-Fat Diet-Induced Obesity.

Obesity causes low-grade inflammation that results in the development of comorbidities. In people with obesity, exacerbation of gastric lesion severity and delayed healing may aggravate gastric mucosal lesions. Accordingly, we aimed to evaluate the citral effects on gastric lesion healing in eutrophic and obese animals. C57Bl/6 male mice were divided into two groups: animals fed a standard diet (SD) or high-fat diet (HFD) for 12 weeks. Gastric ulcers were induced using acetic acid (80%) in both groups. Citral (25, 100, or 300 mg/kg) was administered orally for 3 or 10 days. A vehicle-treated negative control (1% Tween 80, 10 mL/kg) and lansoprazole-treated (30 mg/kg) were also established. Lesions were macroscopically examined by quantifying regenerated tissue and ulcer areas. Matrix metalloproteinases (MMP-2 and -9) were analyzed by zymography. The ulcer base area between the two examined periods was significantly reduced in HFD 100 and 300 mg/kg citral-treated animals. In the 100 mg/kg citral-treated group, healing progression was accompanied by reduced MMP-9 activity. Accordingly, HFD could alter MMP-9 activity, delaying the initial healing phase. Although macroscopic changes were undetectable, 10-day treatment with 100 mg/kg citral exhibited improved scar tissue progression in obese animals, with reduced MMP-9 activity and modulation of MMP-2 activation.

Citral protects against LPS-induced endometritis by inhibiting ferroptosis through activating Nrf2 signaling pathway.

INTRODUCTION: Endometritis is the inflammatory condition of the uterus. Citral, a component of lemongrass oil, is known to exhibit anti-inflammatory activity. AIM: The effects of citral on LPS-induced endometritis were tested and the mechanisms were investigated. METHODS: LPS-induced endometritis mice model was established and the effects of citral were detected using this model. Inflammatory cytokines were tested by ELISA. Ferroptosis was assessed by detecting GSH, ATP, MDA, and Fe2+ levels. Signaling pathway was tested by western blot analysis. RESULTS: Citral prevented LPS-induced endometritis through attenuating uterine pathological changes and inflammatory cytokine release. Meanwhile, citral prevents LPS-induced ferroptosis through attenuating MDA and Fe2+ levels, as well as increasing ATP and GSH levels. Furthermore, citral up-regulated Nrf2 and HO-1 expression and attenuated NF-κB activation. In addition, in Nrf2 knockdown mice, the inhibitory roles of citral on ferroptosis and endometritis were largely reversed. CONCLUSION: Taken together, citral inhibited LPS-induced endometritis through preventing ferroptosis, which were regulated by Nrf2 signaling pathway.

Essential Oil Composition Analysis of Cymbopogon Species from Eastern Nepal by GC-MS and Chiral GC-MS, and Antimicrobial Activity of Some Major Compounds.

Cymbopogon species essential oil (EO) carries significant importance in pharmaceuticals, aromatherapy, food, etc. The chemical compositions of Cymbopogon spp. Viz. Cymbopogon winterianus (citronella) Cymbopogon citratus (lemongrass), and Cymbopogon martini (palmarosa) were analyzed by gas chromatography−mass spectrometry (GC-MS), enantiomeric distribution by chiral GC-MS, and antimicrobial activities of some selected pure major compound and root and leaves EOs of citronella. The EO of leaves of Cymbopogon spp. showed comparatively higher yield than roots or other parts. Contrary to citral (neral and geranial) being a predominant compound of Cymbopogon spp., α-elemol (53.1%), α-elemol (29.5%), geraniol (37.1%), and citral (90.4%) were detected as major compounds of the root, root hair with stalk, leaf, and root stalk with shoot of citronella EO, respectively. Palmarosa leaves' EO contains neral (36.1%) and geranial (53.1) as the major compounds. In the roots of palmarosa EO, the prime components were α-elemol (31.5%), geranial (25.0%), and neral (16.6%). Similarly, lemongrass leaves' EO contains geraniol (76.6%) and geranyl acetate (15.2%) as major compounds, while the root EO contains a higher amount of geraniol (87.9%) and lower amount of geranyl acetate (4.4%). This study reports for the first time chiral terpenoids from Cymbopogon spp. EOs. Chiral GC-MS gave specific enantiomeric distributions of nine, six, and five chiral terpenoids in the root, root stalk with a shoot, and leaves of citronella EOs, respectively. Likewise, four and three chiral terpenoids in the root and leaves of lemongrass oil followed by two chiral terpenoids in the leaves and root of palmarosa EOs each. Additionally, the root and leaves' EOs of citronella exhibit noticeable activity on bacteria such as Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus pyogenes and fungus such as Candida albicans, Microsporum canis, and Trichophyton mentagrophytes. So, geranial-, neral-, geraniol-, and citronellal-rich EOs can be used as an alternative antimicrobial agent.