Our research addresses the challenge of low concentrations of viridiflorol, a unique and highly valuable sesquiterpene found in various Mentha species. We employed biotechnological strategies to enhance viridiflorol production, which could significantly boost export revenue. Mentha piperita L. sesquiterpene synthase (MpTPS4) was the focus of our study because it is a key enzyme in the biosynthesis of viridiflorol. Through biochemical characterization, we confirmed that MpTPS4 exclusively synthesizes viridiflorol. By overexpressing MpTPS4 in M. ×piperita L. using a glandular trichome-specific promoter, we achieved a notable increase (9-25 %) in viridiflorol content. Additionally, we explored the practical application of viridiflorol as a deterrent against the herbivore Helicoverpa armigera. The RNAi-mediated knockdown of MpTPS4 resulted in a significant reduction in viridiflorol levels in the essential oil. More importantly, these results show how relevant MpTPS4 is for making viridiflorol and how biotechnology could be used to increase biosynthesis. Our research provides valuable insights into enhancing the production of this commercially important sesquiterpene, offering promising opportunities for the mentha industry.

Essential oils (EOs) extracted from aromatic and medicinal plants have the potential to inhibit the growth of various pathogens and, thus, be useful in the control of dangerous diseases. The application of environmentally friendly approaches to protect agricultural and forestry ecosystems from invasive and hazardous species has become more significant in last decades. Therefore, the identification and characterization of essential oils with a strong inhibitory activity against aggressive and widespread pathogens are of key importance in plant protection research. The main purpose of our study is to evaluate the impact of essential oils originating from different genotypes of bee balm, mint, and marigold on Botrytis cinerea, Fusarium solani, and Phytophthora pseudocryptogea. Twelve essential oils, including five EOs originating from Monarda fistulosa, one oil each from Monarda russeliana, Mentha longifolia, Mentha piperita, Tagetes patula, and Tagetes erecta, and two EOs from Tagetes tenuifolia were derived by steam or water distillation. The chemical composition of the tested EOs was determined by GS-MS analyses and their corresponding chemotypes were identified. The most effective against all three pathogens were determined to be the EOs originating from M. fistulosa and M. russeliana. B. cinerea, and P. pseudocryptogea were also significantly affected by the M. piperita essential oil. The most efficient EOs involved in this investigation and their potential to control plant pathogens are discussed.

Mentha haplocalyx essential oil (MEO) has demonstrated inhibitory effects on Fusarium oxysporum. Despite its environmentally friendly properties as a natural product, the limited water solubility of MEO restricts its practical application in the field. The use of nanoemulsion can improve bioavailability and provide an eco-friendly approach to prevent and control Panax notoginseng root rot. In this study, Tween 80 and anhydrous ethanol (at a mass ratio of 3) were selected as carriers, and the ultrasonic method was utilized to produce a nanoemulsion of MEO (MNEO) with an average particle size of 26.07 nm. Compared to MTEO (MEO dissolved in an aqueous solution of 2% DMSO and 0.1% Tween 80), MNEO exhibited superior inhibition against F. oxysporum in terms of spore germination and hyphal growth. Transcriptomics and metabolomics results revealed that after MNEO treatment, the expression levels of certain genes related to glycolysis/gluconeogenesis, starch and sucrose metabolism were significantly suppressed along with the accumulation of metabolites, leading to energy metabolism disorder and growth stagnation in F. oxysporum. In contrast, the inhibitory effect from MTEO treatment was less pronounced. Furthermore, MNEO also demonstrated inhibition on meiosis, ribosome function, and ribosome biogenesis in F. oxysporum growth process. These findings suggest that MNEO possesses enhanced stability and antifungal activity, which effectively hinders F. oxysporum through inducing energy metabolism disorder, meiotic stagnation, as well as ribosome dysfunction, thus indicating its potential for development as a green pesticide for prevention and control P. notoginseng root rot caused by F.oxyosporum.

Microbes maneuver strategies to become incessant and biofilms perfectly play a role in scaling up virulence to cause long-lasting infections. The present study was designed to assess the use of an eco-friendly formulation of functionalized silver nanoparticles generated from Mentha longifolia leaf extract (MℓE) for the treatment of biofilm-producing microbes. Nanoparticles synthesized using MℓE as a reducing agent were optimized at different strengths of AgNO3 (1 mM, 2 mM, 3 mM, and 4 mM). Synthesis of M. longifolia silver nanoparticles (MℓAgNPs) was observed spectrophotometrically (450 nm) showing that MℓAgNPs (4 mM) had the highest absorbance. Various techniques e.g., Fourier transforms Infrared spectroscopy (FTIR), Dynamic light scattering (DLS), zeta potential (ZP), X-ray Diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM) were used to characterize MℓAgNPs. In the present study, the Kirby-Bauer method revealed 4mM was the most detrimental conc. of MℓAgNPs with MIC and MBC values of 0.62 μg/mL and 1.25 μg/mL, 0.03 μg/mL and 0.078 μg/mL, and 0.07 μg/mL and 0.15 μg/mL against previously isolated and identified clinical strains of Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Staphylococcus aureus, respectively. Moreover, the MℓAgNP antibiofilm activity was examined via tissue culture plate (TCP) assay that revealed biofilm inhibition of up to 87.09%, 85.6%, 83.11%, and 75.09% against E. coli, P. aeruginosa, K. pneumonia, and S. aureus, respectively. Herbal synthesized silver nanoparticles (MℓAgNPs) tend to have excellent antibacterial and antibiofilm properties and are promising for other biomedical applications involving the extrication of irksome biofilms. For our best knowledge, it is the first study on the use of the green-synthesized silver nanoparticle MℓAgNP as an antibiofilm agent, suggesting that this material has antibiotic, therapeutic, and industrial applications.

Extraction is the first and most important step in obtaining the effective ingredients of medicinal plants. Mentha longifolia (L.) L. is of considerable economic importance as a natural raw material for the food and pharmaceutical industries. Since the effect of different extraction methods (traditional and modern methods) on the quantity, quality and antimicrobial activity of the essential oil of this plant has not been done simultaneously; the present study was designed for the first time with the aim of identifying the best extraction method in terms of these features. For this purpose, extracting the essential oil of M. longifolia with the methods of hydrodistillation with Clevenger device (HDC), steam distillation with Kaiser device (SDK), simultaneous distillation with a solvent (SDE), hydrodistillation with microwave device (HDM), pretreatment of ultrasonic waves and Clevenger (U+HDC) and supercritical fluid (SF) were performed. Chemical compounds were identified by gas chromatography coupled with mass spectrometer (GC-MS). Antimicrobial activity of essential oils against various clinical microbial strains was evaluated by agar diffusion method and determination of the minimum inhibitory concentration and minimum bactericidal concentration (MIC and MBC). The results showed that the highest and lowest yields of M. longifolia leaf essential oil belonged to HDC (1.6083%) and HDM (0.3416%). The highest number of compounds belonged to SDK essential oil and was equal to 72 compounds (with a relative percentage of 87.13%) and the lowest number of compounds was related to the SF essential oil sample (7 compounds with a relative percentage of 100%). Piperitenone (25.2-41.38%), piperitenone oxide (22.02-0%), pulegone (10.81-0%) and 1,8-cineole (5-35.0%) are the dominant and main components of M. longifolia essential oil were subjected to different extraction methods. Antimicrobial activity results showed that the lowest MIC value belonged to essential oils extracted by HDM, SDK, SDE and U+HDC methods with a value of 1000 μg/mL was observed against Gram-negative bacteria Shigella dysenteriae, which was 5 times weaker than rifampin and 7 times weaker than gentamicin. Therefore, it can be concluded that in terms of efficiency of the HDC method, in terms of the percentage of compounds of the HDM method, and in terms of microbial activity, the SDK, HDM and U+HDC methods performed better.

This study investigates using magnesium foliar spray to enhance mint plants\' growth and physiological performance under cadmium toxicity. It examines the effects of foliar application of magnesium oxide (40 mg L-1), in both nano and bulk forms, on mint plants exposed to cadmium stress (60 mg kg-1 soil). Cadmium stress reduced root growth and activity, plant biomass (32%), leaf hydration (19%), chlorophyll levels (27%), magnesium content (51%), and essential oil yield (35%), while increasing oxidative and osmotic stress in leaf tissues. Foliar application of magnesium increased root growth (32%), plant biomass, essential oil production (17%), leaf area (24%), chlorophyll content (10%), soluble sugar synthesis (33%), and antioxidant enzyme activity, and reduced lipid peroxidation and osmotic stress. Although the nano form of magnesium enhanced magnesium absorption, its impact on growth and physiological performance was not significantly different from the bulk form. Therefore, foliar application of both forms improves plants\' ability to withstand cadmium toxicity. However, the study is limited by its focus on a single plant species and specific environmental conditions, which may affect the generalizability of the results. The long-term sustainability of such treatments could provide a more comprehensive understanding of magnesium\'s role in mitigating heavy metal stress in plants.

BACKGROUND: Mentha longifolia L. is a perennial plant belonging to the Lamiaceae family that has a wide distribution in the world. M. longifolia has many applications in the food and pharmaceutical industries due to its terpenoid and phenolic compounds. The phytochemical profile and biological activity of plants are affected by their genetics and habitat conditions. In the present study, the content, constituents and antifungal activity of the essential oil extracted from 20 accessions of M. longifolia collected from different regions of Iran and Iraq countries were evaluated.
RESULTS: The essential oil content of the accessions varied between 1.54 ± 0.09% (in the Divandarreh accession) to 5.49 ± 0.12% (in the Khabat accession). Twenty-seven compounds were identified in the essential oils of the studied accessions, which accounted for 85.5-99.61% of the essential oil. The type and amount of dominant compounds in the essential oil were different depending on the accession. Cluster analysis of accessions based on essential oil compounds grouped them into three clusters. The first cluster included Baziyan, Boukan, Sarouchavah, Taghtagh, Darbandikhan, Isiveh and Harir. The second cluster included Khabat, Kounamasi, Soni and Mahabad, and other accessions were included in the third cluster. Significant correlations were observed between the essential oil content and components with the climatic and soil conditions of the habitats. The M. longifolia essential oil indicated antifungal activity against Fusarium solani in both methods used. In all studied accessions, the fumigation method compared to the contact method was more able to control mycelia growth. In both methods, the inhibition percentage of essential oil on mycelia growth increased with an increase in essential oil concentration. Significant correlations were found between the essential oil components and the inhibition percentage of mycelium growth.
CONCLUSIONS: The studied M. longifolia accessions showed significant differences in terms of the essential oil content and components. Differences in phytochemical profile of accessions can be due to their genetic or habitat conditions. The distance of the accessions in the cluster was not in accordance with their geographical distance, which indicates the more important role of genetic factors compared to habitat conditions in separating accessions. The antifungal activity of essential oils was strongly influenced by the essential oil quality and concentration, as well as the application method. Determining and introducing the elite accession in this study can be different depending on the breeder\'s aims, such as essential oil content, desired chemical composition, or antifungal activity.

Multidrug-resistant bacterial pathogens, such as E. coli, represent a major human health threat. Due to the critical need to overcome this dilemma, since the drug efflux pump has a vital function in the evolution of antimicrobial resistance in bacteria, we have investigated the potential of Mentha essential oil major constituents (1-19) as antimicrobial agents via their ability to inhibit pathogenic DNA gyrase and, in addition, their potential inhibition of the E. coli AcrB-TolC efflux pump, a potential target to inhibit MDR pathogens. The ligand docking approach was conducted to analyze the binding interactions of Mentha EO constituents with the target receptors. The obtained results proved their antimicrobial activity through the inhibition of DNA gyrase (1kzn) with binding affinity ΔG values between -4.94 and -6.49 kcal/mol. Moreover, Mentha EO constituents demonstrated their activity against MDR E. coli by their ability to inhibit AcrB-TolC (4dx7) with ΔG values ranging between -4.69 and -6.39 kcal/mol. The antimicrobial and MDR activity of Mentha EOs was supported via hydrogen bonding and hydrophobic interactions with the key amino acid residues at the binding site of the active pocket of the targeted receptors.

CONCLUSIONS: Transcription factors MhMYB1 and MhMYB2 correlate with monoterpenoid biosynthesis pathway in l-menthol chemotype of Mentha haplocalyx Briq, which could affect the contents of ( -)-menthol and ( -)-menthone. Mentha haplocalyx Briq., a plant with traditional medicinal and edible uses, is renowned for its rich essential oil content. The distinct functional activities and aromatic flavors of mint essential oils arise from various chemotypes. While the biosynthetic pathways of the main monoterpenes in mint are well understood, the regulatory mechanisms governing different chemotypes remain inadequately explored. In this investigation, we identified and cloned two transcription factor genes from the M. haplocalyx MYB family, namely MhMYB1 (PP236792) and MhMYB2 (PP236793), previously identified by our research group. Bioinformatics analysis revealed that MhMYB1 possesses two conserved MYB domains, while MhMYB2 contains a conserved SANT domain. Yeast one-hybrid (Y1H) analysis results demonstrated that both MhMYB1 and MhMYB2 interacted with the promoter regions of MhMD and MhPR, critical enzymes in the monoterpenoid biosynthesis pathway of M. haplocalyx. Subsequent virus-induced gene silencing (VIGS) of MhMYB1 and MhMYB2 led to a significant reduction (P < 0.01) in the relative expression levels of MhMD and MhPR genes in the VIGS groups of M. haplocalyx. In addition, there was a noteworthy decrease (P < 0.05) in the contents of ( -)-menthol and ( -)-menthone in the essential oil of M. haplocalyx. These findings suggest that MhMYB1 and MhMYB2 transcription factors play a positive regulatory role in ( -)-menthol biosynthesis, consequently influencing the essential oil composition in the l-menthol chemotype of M. haplocalyx. This study serves as a pivotal foundation for unraveling the regulatory mechanisms governing monoterpenoid biosynthesis in different chemotypes of M. haplocalyx.

This present study aims to characterize the essential oil compositions of the aerial parts of M. spicata L. and endemic M. longifolia ssp. cyprica (Heinr. Braun) Harley by using GC-FID and GC/MS analyses simultaneously. In addition, it aims to perform multivariate statistical analysis by comparing with the existing literature, emphasizing the literature published within the last two decades, conducted on both species growing within the Mediterranean Basin. The major essential oil components of M. spicata were determined as carvone (67.8%) and limonene (10.6%), while the major compounds of M. longifolia ssp. cyprica essential oil were pulegone (64.8%) and 1,8-cineole (10.0%). As a result of statistical analysis, three clades were determined for M. spicata: a carvone-rich chemotype, a carvone/trans-carveol chemotype, and a pulegone/menthone chemotype, with the present study result belonging to the carvone-rich chemotype. Carvone was a primary determinant of chemotype, along with menthone, pulegone, and trans-carveol. In M. longifolia, the primary determinants of chemotype were identified as pulegone and menthone, with three chemotype clades being pulegone-rich, combined menthone/pulegone, and combined menthone/pulegone with caryophyllene enrichment. The primary determinants of chemotype were menthone, pulegone, and caryophyllene. The present study result belongs to pulegone-rich chemotype.