Identification of Potential Therapeutics of Mentha Essential Oil Content as Antibacterial MDR Agents against AcrAB-TolC Multidrug Efflux Pump from Escherichia coli: An In Silico Exploration

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.

Fabrication and characterization of a Bi2O3-modified chitosan@ZIF-8 nanocomposite for enhanced drug loading-releasing efficacy

In this study, a simple novel hybrid mesoporous nanomaterial derived from a metal-organic framework (ZIF-8) and chitosan, which were coated on green bismuth oxide, has been successfully synthesized, characterized, and applied to investigate its dapsone loading-releasing capability in the aqueous media. This suggested nanocomposite showed promise for drug loading from water b using hydrogen bonds, pi-pi, and electrostatic interactions. Structural and morphological analyses were performed on the proposed green synthesized nanocomposite through scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, Brunauer-Emmett-Teller analysis, and thermogravimetric analysis. Various influencing parameters, including pH, nanocomposite dose, and contact time, were investigated to optimize the dapsone loading process. Utilizing the non-linear optimization methodology, the results show that dapsone-loading efficiency was >85 % for 50 mg.L-1 of dapsone drug. The optimum parameters for achieving maximal loading of dapsone drug were pH = 6.8, hybrid mesosphere dose = 2.6 mg.mL-1, and time = 53 min. Based on the release investigations, the dapsone-loaded nanocomposite was put into phosphate buffer saline, at pH = 7.4 and T = 37 °C, with a maximum efficiency of 93.9 after 24 h.

Mentha piperita silver nanoparticle-loaded hydrocolloid film for enhanced diabetic wound healing in rats

OBJECTIVE

To investigate the role of Mentha piperita silver nanoparticle-loaded carbopol gel for enhanced wound healing in a diabetic rat model. This research further aims to explore bioactive compounds derived from Mentha piperita obtained from high altitude.

METHOD

Methanolic extracts of Mentha piperita (MP), Mentha spicata (MS) and Mentha longifolia (ML) were used to synthesise silver nanoparticles (AgNP). AgNP synthesis was confirmed by ultraviolet-visible (UV-Vis) spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The antioxidant activity was assessed by 2, 2-diphenyl-1-picrylhydrazyl (DDPH) assay. Antiglycation potential was determined by measuring the fluorescent advanced glycation end products. The bioactive compound identified in the Mentha piperita methanolic (MPM) fraction through electrospray ionisation tandem mass spectrometric analysis (ESI-MS) was responsible for the highest antiglycation. The effects of MPM and MPM.AgNP-loaded Carbopol (Sanare Lab, India) on wound healing were compared in male, alloxan-induced, diabetic albino rats (200-250g), divided into control and treated groups. Effects on wound healing were assessed via histopathology.

RESULTS

UV-Vis and FTIR confirmed NP synthesis with peaks for flavonoids and polyphenols. SEM and XRD explored the cubical, 30-63nm crystalline NP. The maximum antioxidant and antiglycation potential was observed in order of; MP.AgNP>MS.AgNP>ML.AgNP. The highest antioxidant activity was observed by methanolic and aqueous MP.AgNPs (88.55% and 83.63%, respectively) at 2mg.ml-1, and (75.16% and 69.73%, respectively) at 1mg.ml-1, compared to ascorbic acid (acting as a positive control, 90.01%). MPM.AgNPs demonstrated the best antiglycation potential of 75.2% and 83.3% at 1mg.ml-1 and 2mg.ml-1, respectively, comparable to positive control (rutin: 88.1%) at 14 days post-incubation. A similar trend was observed for antimicrobial activity against Bacillus subtilis, Micrococcus luteus and Escherichia coli with an inhibition zone of 21mm, 21.6mm and 24.6mm. Rosmarinic acid was the active compound present in Mentha piperita, as identified by ESI-MS. MPM.AgNP-loaded Carbopol resulted in 100% wound closure compared with control at 20 days post-wounding. In the treatment group, re-epithelialisation was achieved by day 18, compared with 25 days for the positive control group.

CONCLUSION

MPM.AgNP-loaded Carbopol demonstrated safer and more effective biological properties, hence accelerating the diabetic excision wound healing process in alloxan-induced diabetic rats.

Morphological and genetic evidence suggest gene flow among native and naturalized mint species

PREMISE

Cultivation and naturalization of plants beyond their natural range can bring previously geographically isolated taxa together, increasing the opportunity for hybridization, the outcomes of which are not predictable. Here, we explored the phenotypic and genomic effects of interspecific gene flow following the widespread cultivation of Mentha spicata (spearmint), M. longifolia, and M. suaveolens.

METHODS

We morphologically evaluated 155 herbarium specimens of three Mentha species and sequenced the genomes of a subset of 93 specimens. We analyzed the whole genomes in a population and the phylogenetic framework and associated genomic classifications in conjunction with the morphological assessments.

RESULTS

The allopolyploid M. spicata, which likely evolved in cultivation, had altered trichome characters, that is possibly a product of human selection for a more palatable plant or a byproduct of selection for essential oils. There were signs of genetic admixture between mints, including allopolyploids, indicating that the reproductive barriers between Mentha species with differences in ploidy are likely incomplete. Still, despite gene flow between species, we found that genetic variants associated with the cultivated trichome morphology continue to segregate.

CONCLUSIONS

Although hybridization, allopolyploidization, and human selection during cultivation can increase species richness (e.g., by forming hybrid taxa), we showed that unless reproductive barriers are strong, these processes can also result in mixing of genes between species and the potential loss of natural biodiversity.

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

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

Growth, oil and physiological parameters of three mint species grown under saline stress levels

Salinity stress is known to have a detrimental effect on mint plants. The aim of the present work was to investigate the possible effects of salinity stress on Mentha spicata, Mentha piperita and Mentha arvensis. Plants were exposed to salinity stress using different concentrations of NaCl (0, 50, 100, 150 mM). Under salinity stress, plant growth, oil yield, content and composition, as well as physiological parameters were adversely affected. Among the studied species, M. arvensis experienced the maximum loss in terms of oil percentage. Physiological characteristics and oil composition were significantly affected with intensification of salt stress. For instance, in M. spicata, with increasing salinity stress, piperitone oxide was decreased from 78.4% in control to 38.0% in 150 mM NaCl, whereas menthol was increased from 1.0 to 37.1%. Moreover, in M. piperita, menthone, isomenthone and limonene were all increased in low stress and then were decreased in high stress conditions. In M. arvensis, the major compound; menthol was not affected but the content of menthone increased. It could be concluded that the salinity stress is detrimental but might be useful and may be recommended as an appropriate approach in improving the oil quality or to producing specific compounds under mild or moderate stress.

Physicochemical Characterization and Antioxidant Properties of Essential Oils of M. pulegium (L.), M. suaveolens (Ehrh.) and M. spicata (L.) from Moroccan Middle-Atlas

The cosmetics and food fields are based on the use of synthetic substances to protect their products against oxidation. However, synthetic antioxidants were reported to have negative effects on human health. The interest to develop natural antioxidants from plants has been growing in recent decades. The aim of this study was to determine the antioxidant properties of three essential oils (EOs) of M. pulegium (L.), M. suaveolens (Ehrh.) and M. spicata (L.) from the Azrou and Ifrane regions. The organoleptic characteristics, yields and physical properties were determined for the selected EOs. Their chemical compositions were identified using GC-MS; then, their antioxidant activities were evaluated using the DPPH^• free radical scavenging activity and were compared with the ascorbic acid standard. The determined physicochemical parameters of dry matter and EOs demonstrated their good quality. The analysis of the EOs showed the dominance of pulegone (68.86-70.92%) and piperitenone (24.81%), piperitenone oxide (74.69-60.3%), and carvone (71.56-54.79%) and limonene (10.5-9.69%) for M. pulegium, M. suaveolens and M. spicata, respectively, from Azrou and Ifrane. Additionally, the antiradical tests demonstrated the remarkable power of these EOs, especially M. pulegium EO (IC₅₀ = 15.93 mg/mL), which recorded the best activity compared with ascorbic acid (IC₅₀ = 8.849 mg/mL). The obtained results indicated that these EOs could be applied as natural antioxidants in the food industry.

Histological and molecular evaluation of Mentha arvensis extract on a polycystic ovary syndrome rat model

OBJECTIVE

This study aimed to investigate the impact of Mentha arvensis on a rat model of polycystic ovary syndrome (PCOS).

METHODS

The PCOS rat model was made by the daily subcutaneous injection of testosterone enanthate (250mg/kg) for 21 days. Thirty rats were divided into five groups, including a healthy control group and four PCOS groups treated with various concentrations of hydroalcoholic extract of Mentha arvensis (0, 50, 100 and 200mg/kg). LH and FSH were measured in the blood. The ovaries were used for histological investigation, Cyp17 and Ptgs2 genes expression and total antioxidant capacity.

RESULTS

Our results indicated that the level of LH and FSH hormones in treated PCOS rats with various concentrations of M. arvensis were reduced in comparison with the untreated PCOS group (p>0.01). Mentha arvensis in the highest concentration (200mg/kg) decreased the number of cysts in this group in comparison with the untreated PCOS group (p<0.01). The expression of Cyp17 and Ptgs2 genes in the treated group with the highest concentration of hydroalcoholic extract were decreased in comparison with the untreated PCOS group (p<0.05). Moreover, the antioxidant capacity in the rats receiving Mentha arvensis hydroalcoholic extract was significantly increased in comparison with that from the untreated PCOS rats (p<0.05).

CONCLUSIONS

For the first time, Mentha arvensis hydroalcoholic extract proved to reduce some polycystic ovary syndrome symptoms. In the present experiment, a dose of 200mg/kg of Mentha arvensis hydroalcoholic extract was regarded as the most efficient dose.

Biochemical basis for the formation of organ-specific volatile blends in mint

Above-ground material of members of the mint family is commercially distilled to extract essential oils, which are then formulated into a myriad of consumer products. Most of the research aimed at characterizing the processes involved in the formation of terpenoid oil constituents has focused on leaves. We now demonstrate, by investigating three mint species, peppermint (Mentha ˣ piperita L.), spearmint (Mentha spicata L.) and horsemint (Mentha longifolia (L.) Huds.; accessions CMEN 585 and CMEN 584), that other organs - namely stems, rhizomes and roots - also emit volatiles and that the terpenoid volatile composition of these organs can vary substantially from that of leaves, supporting the notion that substantial, currently underappreciated, chemical diversity exists. Differences in volatile quantities released by plants whose roots had been dipped in a Verticillium dahliae-spore suspension (experimental) or dipped in water (controls) were evident: increases of some volatiles in the root headspace of mint species that are susceptible to Verticillium wilt disease (peppermint and M. longifolia CMEN 584) were detected, while the quantities of certain volatiles decreased in rhizomes of species that show resistance to the disease (spearmint and M. longifolia CMEN 585). To address the genetic and biochemical basis underlying chemical diversity, we took advantage of the newly sequenced M. longifolia CMEN 585 genome to identify candidate genes putatively coding for monoterpene synthases (MTSs), the enzymes that catalyze the first committed step in the biosynthesis of monoterpenoid volatiles. The functions of these genes were established by heterologous expression in Escherichia coli, purification of the corresponding recombinant proteins, and enzyme assays, thereby establishing the existence of MTSs with activities to convert a common substrate, geranyl diphosphate, to (+)-α-terpineol, 1,8-cineole, γ-terpinene, and (-)-bornyl diphosphate, but were not active with other potential substrates. In conjunction with previously described MTSs that catalyze the formation of (-)-β-pinene and (-)-limonene, the product profiles of the MTSs identified here can explain the generation of all major monoterpene skeletons represented in the volatiles released by different mint organs.

Antimicrobial and Toxic Effects of Boswellia serrata Roxb. and Mentha piperita Linn. Essential Oils on Vaginal Inhabitants

Commercial essential oils (EOs) of incense, Boswellia serrata Roxb, and mint, Mentha piperita L., were investigated against vaginal bacterial and Candida albicans isolates for antimicrobial potential and safety use. The antimicrobial activity of EOs was investigated through a double-dilution micro-plate assay. A brine shrimp assay was used for the determination of toxicity, while the determination of the chemical composition of EOs was carried out using GS-MS. Obtained minimal inhibitory (MIC) and minimal bactericidal concentration (MBC) point to the activity of mint essential oil (EO) against the multi-resistant P. aeruginosa isolate (MIC/MBC at 6.25 µL/mL), while MIC and MBC values for other isolates were reached at higher concentrations (25-50 µL/mL). According to the toxicity assay, the incense EO reached the LC₅₀ value at 3.07 µL/mL, while mint EO showed higher toxicity at lower concentrations (0.5 µL/mL) and the LC₅₀ could not be determined. The highest antimicrobial potential was obtained for incense against P. aeruginosa. Although the toxicity assay showed high toxicity of mint EO to the eggs of aquatic crustaceans Artemia salina, further testing of EO toxicity is proposed, for example on healthy cell-lines. According to the GC/MS spectrometry, the most represented components of mint EO were the oxygenated hydrocarbons L-menthone (20.86%) and menthol (31.86%), and they could be proposed for further antimicrobial and toxicity investigation.

Complete chloroplast genomes of two mint species (Lamiaceae) from Al-Madinah, Saudi Arabia: phylogenetic and genomic comparative analyses

The genus Mentha encompasses mint species cultivated for their essential oils, which are formulated into a vast array of consumer products. However, the systematics of the genus Mentha is very complicated and still uncertain. This is largely because of the presence of frequent interspecific hybridization, variation in chromosome number, cytomixis, polymorphism in morphology and essential oil composition under different environmental conditions, colonial mutant propagation, as well as the occurrence of polyploidy, aneuploidy, and nothomorphs. Here, we present the plastome assemblies for a wilt-resistant Saudi Arabian accession of Mentha longifolia (L.) Huds and an alien hybrid Mentha × verticillata L. which are 152,078 bp and 152,026 bp in length, respectively, and exhibited large single-copy (LSC) and small single-copy (SSC) regions separated by a pair of inverted repeat regions. The chloroplast genome of M. longifolia has 133 annotated genes, including 88 protein-coding genes and 37 tRNAs while M. × verticillata has 133 annotated genes, including 87 protein-coding genes and 38 tRNAs. Both cp genomes have eight rRNA genes. Phylogenetic analysis using a total chloroplast genome DNA sequence of 17 species revealed that M. longifolia sequenced in this study did not form a sister relationship with M. longifolia from another study. This opens a window for further investigations.

Essential Oils from Some Lamiaceae Plants: Antioxidant and Anticancer Potentials besides Thermal Properties

The purpose of this study was to determine the chemical compositions, antioxidant and anticancer activities and thermal behavior of essential oils (EOs) obtained by a microwave assisted Clevenger apparatus from Mentha longifolia subsp. typhoides var. typhoides (ML), Thymus kotschyanus var. glabrescens (TK), Calamintha nepeta subsp. nepeta (CN) and Satureja cuneifolia (SC) in Osmaniye, Turkey. Nepetalactone (34.23 %), thymol (37.40 %), piperitone oxide (27.25 %), and carvacrol (28.34 %) were major compounds in the EOs of ML, TK, CN, and SC. Total phenolic content and antioxidant activity (by FRAP assay) were in the range of 0.27-3.01 mg gallic acid equivalents and 0.62-171.14 μmol trolox equivalent per g EO, respectively. IC50 values of DPPH were mostly greater than ABTS. IC50 levels of the EOs of ML, TK, CN for the cytotoxic activities were 195.7, 265.7, 442.9 μg/ml, and 218.4, 204.2, 133.9 μg/ml for 24 and 48 h, respectively. IC50 of SC-EO could not be calculated in the applied concentration range. The highest fusion enthalpies were in between 58.72 and 81.65 kJ/kg. Both the TK and SC plant EOs had comparable and significant bioactivities. CN-EO reduced cell motility and triggered apoptosis more effectively than the others.

Peppermint essential oil: its phytochemistry, biological activity, pharmacological effect and application

Mentha (also known as peppermint), a genus of plants in the taxonomic family Lamiaceae (mint family), is widely distributed throughout temperate regions of the world. Mentha contains various constituents that are classified as peppermint essential oil (PEO) and non-essential components. PEO, consisting mainly of menthol, menthone, neomenthol and iso-menthone, is a mixture of volatile metabolites with anti-inflammatory, antibacterial, antiviral, scolicidal, immunomodulatory, antitumor, neuroprotective, antifatigue and antioxidant activities. Mounting evidence indicates that PEO may pharmacologically protect gastrointestinal, liver, kidney, skin, respiratory, brain and nervous systems, and exert hypoglycemic and hypolipidemic effects. Clinically, PEO is used for gastrointestinal and dermatological diseases, postoperative adjuvant therapy and other fields. This review aims to address the advances in the extraction and isolation of PEO, its biological activities, pharmacological effects, toxicity and applications, with an emphasis on the efficacy of PEO on burn wounds and psoriasis, providing a comprehensive foundation for research, development and application of PEO in future.

Genetic Manipulation of Biosynthetic Pathways in Mint

In recent years, the study of aromatic plants has seen an increase, with great interest from industrial, academic, and pharmaceutical industries. Among plants attracting increased attention are the Mentha spp. (mint), members of the Lamiaceae family. Mint essential oils comprise a diverse class of molecules known as terpenoids/isoprenoids, organic chemicals that are among the most diverse class of naturally plant derived compounds. The terpenoid profile of several Mentha spp. is dominated by menthol, a cyclic monoterpene with some remarkable biological properties that make it useful in the pharmaceutical, medical, cosmetic, and cleaning product industries. As the global market for Mentha essential oils increases, the desire to improve oil composition and yield follows. The monoterpenoid biosynthesis pathway is well characterised so metabolic engineering attempts have been made to facilitate this improvement. This review focuses on the Mentha spp. and attempts at altering the carbon flux through the biosynthetic pathways to increase the yield and enhance the composition of the essential oil. This includes manipulation of endogenous and heterologous biosynthetic enzymes through overexpression and RNAi suppression. Genes involved in the MEP pathway, the menthol and carvone biosynthetic pathways and transcription factors known to affect secondary metabolism will be discussed along with non-metabolic engineering approaches including environmental factors and the use of plant growth regulators.

Challenges in Medicinal and Aromatic Plants DNA Barcoding-Lessons from the Lamiaceae

The potential value of DNA barcoding for the identification of medicinal plants and authentication of traded plant materials has been widely recognized; however, a number of challenges remain before DNA methods are fully accepted as an essential quality control method by industry and regulatory authorities. The successes and limitations of conventional DNA barcoding are considered in relation to important members of the Lamiaceae. The mint family (Lamiaceae) contains over one thousand species recorded as having a medicinal use, with many more exploited in food and cosmetics for their aromatic properties. The family is characterized by a diversity of secondary products, most notably the essential oils (EOs) produced in external glandular structures on the aerial parts of the plant that typify well-known plants of the basil (Ocimum), lavender (Lavandula), mint (Mentha), thyme (Thymus), sage (Salvia) and related genera. This complex, species-rich family includes widely cultivated commercial hybrids and endangered wild-harvested traditional medicines, and examples of potential toxic adulterants within the family are explored in detail. The opportunities provided by next generation sequencing technologies to whole plastome barcoding and nuclear genome sequencing are also discussed with relevant examples.

Efficient construction of a linkage map and haplotypes for Mentha suaveolens using sequence capture

The sustainability of many crops is hindered by the lack of genomic resources and a poor understanding of natural genetic diversity. Particularly, application of modern breeding requires high-density linkage maps that are integrated into a highly contiguous reference genome. Here, we present a rapid method for deriving haplotypes and developing linkage maps, and its application to Mentha suaveolens, one of the diploid progenitors of cultivated mints. Using sequence-capture via DNA hybridization to target single nucleotide polymorphisms (SNPs), we successfully genotyped ∼5000 SNPs within the genome of >400 individuals derived from a self cross. After stringent quality control, and identification of nonredundant SNPs, 1919 informative SNPs were retained for linkage map construction. The resulting linkage map defined a total genetic space of 942.17 cM divided among 12 linkage groups, ranging from 56.32 to 122.61 cM in length. The linkage map is in good agreement with pseudomolecules from our preliminary genome assembly, proving this resource effective for the correction and validation of the reference genome. We discuss the advantages of this method for the rapid creation of linkage maps.

Essential Oil-Loaded NLC for Potential Intranasal Administration

Complementary and alternative medicines represent an interesting field of research on which worldwide academics are focusing many efforts. In particular, the possibility to exploit pharmaceutical technology strategies, such as the nanoencapsulation, for the delivery of essential oils is emerging as a promising strategy not only in Italy but also all over the world. The aim of this work was the development of nanostructured lipid carriers (NLC) for the delivery of essential oils (Lavandula, Mentha, and Rosmarinus) by intranasal administration, an interesting topic in which Italian contributions have recently increased. Essential oil-loaded NLC, projected as a possible add-on strategy in the treatment of neurodegenerative diseases, were characterized in comparison to control formulations prepared with Tegosoft CT and Neem oil. Homogeneous (polydispersity index, PDI < 0.2) nanoparticles with a small size (<200 nm) and good stability were obtained. Morphological and physical-chemical studies showed the formation of different structures depending on the nature of the liquid oil component. In particular, NLC prepared with Lavandula or Rosmarinus showed the formation of a more ordered structure with higher cytocompatibility on two cell lines, murine and human fibroblasts. Taken together, our preliminary results show that optimized positively charged NLC containing Lavandula or Rosmarinus can be proposed as a potential add-on strategy in the treatment of neurodegenerative diseases through intranasal administration, due to the well-known beneficial effects of essential oils and the mucoadhesive properties of NLC.

Assessment of Lithium, Macro- and Microelements in Water, Soil and Plant Samples from Karst Areas in Romania

Lithium is a critical element for the modern society due to its uses in various industrial sectors. Despite its unequal distribution in the environment, Li occurrence in Romania was scarcely studied. In this study a versatile measurement method using ICP-MS technique was optimized for the determination of Li from various matrixes. Water, soil, and plant samples were collected from two important karst areas in the Dobrogea and Banat regions, Romania. The Li content was analyzed together with other macro- and microelement contents to find the relationship between the concentration of elements and their effect on the plants' Li uptake. In Dobrogea region, half of the studied waters had high Li concentration, ranging between 3.00 and 12.2 μg/L in the case of water and between 0.88 and 11.1 mg/kg DW in the case of plants, while the Li content in the soil samples were slightly comparable (from 9.85 to 11.3 mg/kg DW). In the Banat region, the concentration of Li was lower than in Dobrogea (1.40-1.46 μg/L in water, 6.50-9.12 mg/kg DW in soil, and 0.19-0.45 mg/kg DW in plants). Despite the high Li contents in soil, the Li was mostly unavailable for plants uptake and bioaccumulation.

A high throughput toolbox for comprehensive flavor compound mapping in mint

Essential oils of the genus Mentha are extensively used as flavor ingredients in the industry. To overcome the time consuming and laborious traditional flavor analysis, a new quick, high-throughput toolbox based on a bead-beater homogenization followed by a UHPLC-MS/MS analysis has been developed and validated. While terpenes could be directly detected using atmospheric pressure chemical ionization (APCI), carbonyl compounds and alcohols required derivatization by 3-nitrophenylhydrazine (3-NPH) and glycidyltrimethylammonium chloride (GTMA) to ensure sufficient sensitivity for analysis of a single leaf. Using this approach, in total, 59 flavor-active metabolites representing the characteristic flavor of mint were quantified in leaves as well as in distilled oils using fast and robust UHPLC-MS/MS methods. The application of this toolbox enables a mapping of key pathways of mint flavor biosynthesis and can therefore support extensive breeding studies and the monitoring of chemosensate changes, depending on factors such as growth stages and environmental conditions.

DNA barcoding of some medicinally important plant species of Lamiaceae family in India

Several species of the Lamiaceae family are the primary source of bioactive aromatic oils and secondary metabolites, having broader applications in the cosmetics, pharmaceuticals, food, confectionery and liquor industries. Due to the scarcity of raw materials and high costs of this family's economically vital species, its products often adulterated to cater to the market's high demand. The present study provides a DNA based approach for identifying different species of this family. Henceforth, the performance of three already proposed barcode loci (matK, trnH-psbA and trnL) was examined for their PCR amplification and species recognition efficacy on various Lamiaceae species and cultivars using three different approaches such as pairwise genetic distance method, BLASTn and phylogenetic tree based on maximum likelihood (ML) analysis. Results illustrate that among all the DNA barcoding loci, matK locus can accurately and efficiently distinguish all the studied species followed by trnH-psbA and trnL. Present investigation may help diminish the illegal trade and events of adulteration of medicinally important plants species in genus Mentha, Ocimum and Plectranthus. This investigation will also help fulfil the scarcity of sequences of barcode loci of these species in the NCBI database. Apart from providing a molecular level reference for identifying processed herbal products, this technique also offers a convenient method for species identification and germplasm conservation of the Lamiaceae family.

A Revised Phylogeny of the Mentha spicata Clade Reveals Cryptic Species

The genus Mentha is taxonomically and phylogenetically challenging due to complex genomes, polyploidization and an extensive historical nomenclature, potentially hiding cryptic taxa. A straightforward interpretation of phylogenetic relationships within the section Mentha is further hindered by dominant but outdated concepts on historically identified hybrid taxa. Mentha spicata is traditionally considered to be of hybrid origin, but the evidence for this is weak. Here, we aim to understand the phylogenetic relationships within the section Mentha using large sample sizes and to revisit the hybrid status and identity of M. spicata. We show that two of three traditional species in the subsection Spicatae are polyphyletic, as is the subsection as a whole, while the real number of cryptic species was underestimated. Compared to previous studies we present a fundamentally different phylogeny, with a basal split between M. spicata s.s. and M. longifolia s.s. Cluster analyses of morphological and genotypic data demonstrate that there is a dissociation between morphologically and genotypically defined groups of samples. We did not find any evidence that M. spicata is of hybrid origin, and we conclude its taxonomic status should be revised. The combination of genetic and phenotypic information is essential when evaluating hyperdiverse taxonomic groups.

Verticillium Wilt of Mint in the United States of America

Verticillium wilt, caused by the fungus Verticillium dahliae, is the most important and destructive disease of mint (Mentha spp.) in the United States (U.S.). The disease was first observed in commercial mint fields in the Midwestern U.S. in the 1920s and, by the 1950s, was present in mint producing regions of the U.S. Pacific Northwest. Verticillium wilt continues to be a major limiting factor in commercial peppermint (Mentha x piperita) and Scotch spearmint (Mentha x gracilis) production, two of the most important sources of mint oil in the U.S. The perennial aspect of U.S. mint production, coupled with the soilborne, polyetic nature of V. dahliae, makes controlling Verticillium wilt in mint a challenge. Studies investigating the biology and genetics of the fungus, the molecular mechanisms of virulence and resistance, and the role of soil microbiota in modulating host-pathogen interactions are needed to improve our understanding of Verticillium wilt epidemiology and inform novel disease management strategies. This review will discuss the history and importance of Verticillium wilt in commercial U.S. mint production, as well as provide a format to highlight past and recent research advances in an effort to better understand and manage the disease.

Chemical Diversity of Volatile Compounds of Mints from Southern Part of Pannonian Plain and Balkan Peninsula - New Data

Mints are the most popular economic and traditional herbs. The aim of this article was chemical characterization of volatile compounds from wild populations of Mentha aquatica, M. arvensis, M. longifolia, M. microphylla, M. pulegium, M. spicata, M.×dumetorum, M.×gentillis and M.×verticillata, as well as cultivated samples of M. spicata, M.×piperita 'Alba' and M.×piperita 'Crispa'. Analyses were performed directly from dried aerial parts (herb) of collected samples by headspace gas chromatography-mass spectrometry. In total 54 compounds were detected, representing from 89.99 % to 99.66 % of volatile fractions of all investigated samples. The recorded volatiles were primarily monoterpene hydrocarbons and oxygenated monoterpenes, while oxygenated aromatic monoterpenes, sesquiterpene hydrocarbons and aliphatic compounds were present in lower concentrations in analyzed samples. The major components were linalool, limonene, 1,8-cineol, α-terpinyl acetate, pulegone, β-pinene and menthol. The cluster analysis revealed five main groups or chemotypes according to qualitative and quantitative content of volatiles, as well as similarities among samples. These results contribute to the knowledge on the mints chemistry in Pannonian Plain and Balkan Peninsula.

Hepatoprotection of Mentha aquatica L., Lavandula dentata L. and Leonurus cardiaca L

The phenolic composition of hydroethanolic extracts of Mentha aquatica L., Lavandula dentata L. and Leonurus cardiaca L., obtained from plants grown under organic cultivation, was determined and their hepatoprotective effects were investigated in vitro. L. cardiaca extract was rich in phenylethenoid glycosides, especially lavandolifolioside (254 ± 36 μg/mg), whereas rosmarinic acid and eriodictyol-O-rutinoside were the major phenolic compounds of L. dentata and M. aquatica extracts, accounting for 68 ± 7 μg/mg and 145 ± 22 μg/mg, respectively. These differential phenolic components presumably account for their dissimilar antioxidant properties. While L. cardiaca extract showed moderate biological effects, M. aquatica extract displayed high antioxidant activity in chemical models, and that of L. dentata was effective in counteracting potassium dichromate-induced ROS generation in human hepatocarcinoma cells. Moreover, M. aquatica extract (50 μg/mL) and its mixture (50%/50%) with L. dentata extract displayed an effective cytoprotective effect.

Metabolic Profiling of Nine Mentha Species and Prediction of Their Antioxidant Properties Using Chemometrics

Mentha species are well recognized for their medicinal and aromatic properties. The comprehensive metabolite profiles of nine Mentha species have been determined. The extracts of these Mentha species were also screened for antioxidant and free radical scavenging activities. Forty-seven hydrophilic and seventeen lipophilic compounds were identified and quantified from the selected Mentha species. Also, eleven phenolic compounds, riboflavin and eight carotenoids were present, and their composition and content varied among the various Mentha species. The different Mentha species exhibited a range of antioxidant potencies. Horse mint especially exhibited the strongest antioxidant capacities (1,1-diphenyl-2-picryl-hydrazyl (DPPH), hydrogen peroxide, and reducing power assay) among the nine Mentha species. A difference between different samples from the same species was not observed by multivariate analysis. A high correlation between metabolites involved in closely linked biosynthetic pathways has been indicated. The projection to latent structure method, using the partial least squares (PLS) method, was applied to predict antioxidant capacities based on the metabolite profiles of Mentha leaves. According to the PLS analysis, several carotenoid contents, such as E-β-carotene, 9Z-β-carotene, 13Z-β-carotene and lutein, as well as phenolic compounds, showed a positive relationship in reducing the power of Mentha extracts. Horse mint is a good candidate because of its high antioxidant efficacy among the nine Mentha species included in the study.

Prospective of Essential Oils of the Genus Mentha as Biopesticides: A Review

Mentha is a genus from the family Lamiaceae, whose essential oils has long been used in various forms such as in management of plant pathogens and insect pests, in traditional medicine as well as in culinary and cosmetics. Its major chemical components such as menthol, carvone have now been successfully commercialized in the industry as antimicrobials/insecticidal agents. Current review focuses on chemical composition of essential oils of some Mentha species from different geographical regions with their insecticidal (repellent, antifeedant, and ovicidal) and antimicrobial efficacies against bacterial, fungal plant pathogens and insects of stored products. Reports of the researchers on chemical analysis of essential oils of Mentha species revealed that most of the oils being rich in pulegone, menthon, menthol, carvone, 1, 8-cineole, limonene and β-caryophyllene. Reviewed literature revealed that, essential oils from different Mentha species possess potential antimicrobial activity against plant pathogens and have insecticidal activity against stored product insects. Thus, antimicrobial and insecticidal properties of essential oils of Mentha species offer the prospect of using them as natural pesticides with a commercial value, having social acceptance due to its sustainability and being environment friendly.

Volatile Terpenes and Brain Function: Investigation of the Cognitive and Mood Effects of Mentha × Piperita L. Essential Oil with In Vitro Properties Relevant to Central Nervous System Function

Background: Extracts of several members of the monoterpene-rich Lamiaceae sub-family Nepetoideae, including those from the Salvia (sage), Melissa (Lemon balm) and Rosmarinus (rosemary) genera, evince cognitive and mood effects in humans that are potentially related to their effects on cholinergic and GABAergic neurotransmission. To date, despite promising in vitro properties, the cognitive and mood effects of the closely related Mentha spicata (spearmint) and Mentha piperita (peppermint) remain unexplored. This study therefore assessed the human cognitive/mood effects of the M. spicata/piperita essential oil with the most promising, brain-relevant in vitro properties according to pre-trial in vitro screening. Design: Organic spearmint and peppermint (Mentha spicata/piperita) essential oils were pre-screened for neurotransmitter receptor binding and acetylcholinesterase (AChE) inhibition. In a double-blind, placebo-controlled, balanced cross-over study, 24 participants (mean age 25.2 years) consumed single doses of encapsulated placebo and 50 µL and 100 µL of the most promising essential oil (peppermint with nicotinic/GABAA receptor binding and AChE inhibitory properties, that increased calcium influx in a CAD cell neuronal model). Psychological functioning was assessed with mood scales and a range of standardised, cognitively demanding tasks pre-dose and at 1, 3 and 6 h post-dose. Results: The highest (100 µL) dose of essential oil improved performance on the cognitively demanding Rapid Visual Information Processing task (RVIP) at 1 h and 3 h post-dose and both doses attenuated fatigue and improved performance of the Serial 3 s subtraction task at 3 h post-dose. Conclusion: Peppermint (Mentha piperita) essential oil with high levels of menthol/menthone and characteristic in vitro cholinergic inhibitory, calcium regulatory and GABA_A/nicotinic receptor binding properties, beneficially modulated performance on demanding cognitive tasks and attenuated the increase in mental fatigue associated with extended cognitive task performance in healthy adults. Future investigations should consider investigating higher doses.

Evaluation of Mentha arvensis essential oil and its major constituents for fungitoxicity

Essential oil and major constituents of menthe were evaluated for fungicidal activities. Gas chromatography-mass spectrometry (GC-MS) of essential oil from leaves of Mentha arvensis cv. CIM-Saryu revealed that menthol was found in highest amount (77.94%) followed by isomenthone (5.24%), neomenthyl acetate (5.18%) and menthone (5.00%). Menthol and menthone were extracted from the essential oil by column chromatography. Essential oil, menthol and menthone were screened for their fungicidal activity against Rhizoctonia solani and Fusarium moniliforme. Menthol was highly effective as compared to essential oil as well as menthone. All of them exhibited less activity than standard bavistin at all the tested concentrations.

Pharmacological activity of Mentha longifolia and its phytoconstituents

Current paper reviews the pharmacological activities, therapeutic indications and phytochemicals of M. longifolia. This herb has been consumed traditionally for the treatment of various diseases, including gastrointestinal disorders, respiratory disorders, infectious diseases, inflammatory diseases, as well as menstrual disorders. In the modern era, various pharmacological activities have been confirmed for M. longifolia, such as anti-parasitic, antimicrobial, anti-insect, antimutagenic, antinociceptive, anti-inflammatory, antioxidant, keratoprotective, hepatoprotective, anti-diarrhea, and spasmolytic effects. The plant showed therapeutic benefits in irritable bowel syndrome, amenorrhea and oligomenorrhea, and oxidative stress-associated diseases as well. A vast variety of natural components such as flavonoids, phenolic acids, cinnamates, ceramides, sesquiterpenes, terpenes, and terpenoids have been suggested to be responsible for the pharmacological action of M. longifolia. These natural products can be considered as novel medicinal sources for developing new drugs. Further investigations to explore therapeutic efficacy, tolerability, and pharmaceutical properties of M. longifolia phytochemical agents are recommended.

Composition of volatile compounds and in vitro antimicrobial activity of nine Mentha spp

Background

Mentha plants containing over 25 species are aromatic perennial herbs. These species have been interested and widely used because of various clinical findings. Many volatile compounds facilitate environmental interactions such as protecting themselves from pathogens, parasites, and herbivores. Therefore, this study assessed comparison of volatile composition and antimicrobial activity from nine Mentha species. The composition of volatiles was investigated from the aerial parts of nine different Mentha species using gas chromatography-mass spectrometry (GC/MS). In addition, screened antimicrobial activities against six food borne pathogenic bacteria using extracts obtained these plants.

Results

77 volatile compounds were identified in total and it included 13 monoterpenoids, 19 sesquiterpenoids, and others. In particular, monoterpenoids such as eucalyptol (9.35–62.16 %), (±)camphorquinone (1.50–51.61 %), and menthol (0.83–36.91 %) were mostly detected as major constituents in Mentha species. The ethanol extract of nine Mentha species showed higher activity compared to other solvent extracts (methanol, hexane, di ethyl ether). Among these nine Mentha species chocomint showed higher inhibition activity against all bacteria.

Conclusions

It is concluded that monoterpenoids are mainly rich in Mentha plants. Moreover, most of extracts obtained from Mentha showed strong antimicrobial activity against bacteria. Of these, chocomint indicates the highest inhibition activity.

Analysis of Plant Growth-Promoting Effects of Fluorescent Pseudomonas Strains Isolated from Mentha piperita Rhizosphere and Effects of Their Volatile Organic Compounds on Essential Oil Composition

Many species or strains of the genus Pseudomonas have been characterized as plant growth promoting rhizobacteria (PGPR). We used a combination of phenotypic and genotypic techniques to analyze the community of fluorescent Pseudomonas strains in the rhizosphere of commercially grown Mentha piperita (peppermint). Biochemical techniques, Amplified rDNA Restriction Analysis (ARDRA), and 16S rRNA gene sequence analysis revealed that the majority of the isolated native fluorescent strains were P. putida. Use of two Repetitive Sequence-based PCR (rep-PCR) techniques, BOX-PCR and ERIC-PCR, allowed us to evaluate diversity among the native strains and to more effectively distinguish among them. PGPR activity was tested for the native strains and reference strain P. fluorescens WCS417r. Micropropagated M. piperita plantlets were exposed to microbial volatile organic compounds (mVOCs) emitted by the bacterial strains, and plant biomass parameters and production of essential oils (EOs) were measured. mVOCs from 11 of the native strains caused an increase in shoot fresh weight. mVOCs from three native strains (SJ04, SJ25, SJ48) induced changes in M. pierita EO composition. The mVOCs caused a reduction of metabolites in the monoterpene pathway, for example menthofuran, and an increase in menthol production. Menthol production is the primary indicator of EO quality. The mVOCs produced by native strains SJ04, SJ25, SJ48, and strain WCS417r were analyzed. The obtained mVOC chromatographic profiles were unique for each of the three native strains analyzed, containing varying hydrocarbon, aromatic, and alogenic compounds. The differential effects of the strains were most likely due to the specific mixtures of mVOCs emitted by each strain, suggesting a synergistic effect occurs among the compounds present.

Screening of Repellents against Vespid Wasps

Vespid wasps are ecologically beneficial, but they can be a nuisance and dangerous to people due to their tendency to sting. Here, the aim was to screen samples of volatiles (i.e., essential oils and pure chemicals) for their repellency against wasps. The number of wasps (mainly Vespula vulgaris) present in a glass box with attractant and 5 µL sample was compared to the number of wasps in a similar box with attractant only. Both boxes were connected to a large glass container harboring 18–35 wasps. Among 66 tested samples, some essential oils from Lamiaceae and Asteraceae, as well as some pure natural compounds such as the monoterpenes (−)-terpinen-4-ol and isopulegol showed a significant repellency against vespids. Our results corroborate the potential of (mixtures of) volatiles in repelling these insects.

A Geminivirus-Satellite Complex is Associated with Leaf Deformity of Mentha (Mint) Plants in Punjab

A widespread leaf deformity disease of mentha (mint), accompanied by whiteflies, the vectors of begomoviruses, was observed in Punjab in the last few years. The presence of begomovirus was indicated by DNA dot-blot analysis using the conserved coat protein and replication-associated protein genes of another begomovirus, Sri Lankan cassava mosaic virus (SLCMV). A DNA fragment (2.0 kb), representing a partial genomic DNA of a begomovirus, amplified from the symptomatic mentha leaves was used to design end-primers and further amplify an additional 0.9 kb fragment, representing the remaining portion of the resident viral DNA. The two sequences, assembled together (2.7 kb), showed that they represented the complete sequence of an isolate of Tomato leaf curl Karnataka virus (ToLCKV) DNA. Using universal betasatellite primers, a 1.4 kb fragment was amplified from the same sample. This cloned DNA fragment showed complete sequence identity with the previously reported Cotton leaf curl Multan betasatellite (CLCuMB). Majority of the symptomatic mentha leaf samples, collected from four districts of Punjab, showed cross-hybridization in DNA dot-blot using cloned SLCMV and CLCuMB DNA, indicating the presence of one or more begomoviruses related to SLCMV and the betasatellite, CLCuMB. The begomovirus and betasatellite could be mechanically transmitted to Nicotiana benthamiana. Whitefly transmission of the resident begomovirus could also be demonstrated on mentha. The evidence indicates the association of ToLCKV and CLCuMB, a hitherto new combination of a begomovirus and a betasatellite associated with a leaf deformity disease in mentha in Punjab.