Mint Species Research Articles

Identification of Mint Scents Using a QCM Based E-Nose

Mints emit diverse scents that exert specific biological functions and are relevance for applications. The current work strives to develop electronic noses that can electronically discriminate the scents emitted by different species of Mint as alternative to conventional profiling by gas chromatography. Here, 12 different sensing materials including 4 different metal oxide nanoparticle dispersions (AZO, ZnO, SnO2, ITO), one Metal Organic Frame as Cu(BPDC), and 7 different polymer films, including PVA, PEDOT:PSS, PFO, SB, SW, SG, and PB were used for functionalizing of Quartz Crystal Microbalance (QCM) sensors. The purpose was to discriminate six economically relevant Mint species (Mentha x piperita, Mentha spicata, Mentha spicata ssp. crispa, Mentha longifolia, Agastache rugosa, and Nepeta cataria). The adsorption and desorption datasets obtained from each modified QCM sensor were processed by three different classification models, including Principal Component Analysis (PCA), Linear Discriminant Analysis (LDA), and k-Nearest Neighbor Analysis (k-NN). This allowed discriminating the different Mints with classification accuracies of 97.2% (PCA), 100% (LDA), and 99.9% (k-NN), respectively. Prediction accuracies with a repeating test measurement reached up to 90.6% for LDA, and 85.6% for k-NN. These data demonstrate that this electronic nose can discriminate different Mint scents in a reliable and efficient manner.

Functional characterization of a new terpene synthase from Plectranthus amboinicus

Plectranthus amboinicus (Lour.) Spreng is an aromatic medicinal herb known for its therapeutic and nutritional properties attributed by the presence of monoterpene and sesquiterpene compounds. Up until now, research on terpenoid biosynthesis has focused on a few mint species with economic importance such as thyme and oregano, yet the terpene synthases responsible for monoterpene production in P. amboinicus have not been described. Here we report the isolation, heterologous expression and functional characterization of a terpene synthase involved in P. amboinicus terpenoid biosynthesis. A putative monoterpene synthase gene (PamTps1) from P. amboinicus was isolated with an open reading frame of 1797 bp encoding a predicted protein of 598 amino acids with molecular weight of 69.6 kDa. PamTps1 shares 60–70% amino acid sequence similarity with other known terpene synthases of Lamiaceae. The in vitro enzymatic activity of PamTps1 demonstrated the conversion of geranyl pyrophosphate and farnesyl pyrophosphate exclusively into linalool and nerolidol, respectively, and thus PamTps1 was classified as a linalool/nerolidol synthase. In vivo activity of PamTps1 in a recombinant Escherichia coli strain revealed production of linalool and nerolidol which correlated with its in vitro activity. This outcome validated the multi-substrate usage of this enzyme in producing linalool and nerolidol both in in vivo and in vitro systems. The transcript level of PamTps1 was prominent in the leaf during daytime as compared to the stem. Gas chromatography-mass spectrometry (GC-MS) and quantitative real-time PCR analyses showed that maximal linalool level was released during the daytime and lower at night following a diurnal circadian pattern which correlated with the PamTps1 expression pattern. The PamTps1 cloned herein provides a molecular basis for the terpenoid biosynthesis in this local herb that could be exploited for valuable production using metabolic engineering in both microbial and plant systems.

An essential oil-derived mosquito repellent renewable finish for fabrics

Essential oils derived from aromatic plants like mint species, lemongrass, palmarosa, citronella, vetiver, geranium etc are finding extensive usage in perfumery, flavoring, cosmetics and pharmaceutical industries. Some of these essential oils also possess strong mosquito repellency feature that make them potential candidates for utilization in the huge market of insect repellents and insecticides. In this context, the oils obtained from the hydro-distillation of mint, citronella and lemongrass leaves are in high demand for making herbal formulations/products used in house-hold hygiene and for mosquito repellency. Mosquitoe borne diseases such as dengue, malaria, filariasis and chikungunya have plagued the public health scenario, especially for the homeless people who live on roadsides and are under constant threat of mosquito bite. According to 2011 Census data about 449761 families in India are roadside dwellers. In the present study we have prepared an organic mosquito repellent renewable fabric finish using citronella oil as the base. Application of this product on fabrics has been found very effective in repelling the mosquitoes. Our study suggests that mixed or intercropping of mint species with citronella can be a profitable venture for farmers because of extra income that citronella oil can fetch for preparing above product.

Chiral differentiation of terpenoids in bergamot mint (Mentha citrata) cultivar Kiran: A non-menthol mint essential oil

Mentha citrata, popularly known as bergamot mint,is one of the mint species which does not possess menthol, a terpenoid chemical constituent that gives the name Mentha to the genus. CSIR-CIMAP has developed a cultivar cv. Kiran by induced mutagenesis. Gas chromatographic (GC) analysis of the essential oil of this cultivar shows linalool (44.9 %) and linalyl acetate (28.7%) as the major constituents. Further, the enantioselective GC analysis of the essential oil to determine the enantiomeric ratio of linalool and linalyl acetate indicate that (R)-(-)-linalool is in 78.8% excess over its enantiomer, whereas (R)-(-)-linalyl acetate is present as a single enantiomer. Other chiral terpenoids resolved in the enantioselective GC analysis are (1S)-(-)-ß-pinene as the major exclusive enantiomer with 93.0% enantiomeric excess and (-)-sabinene with 60.2% enantiomeric excess than its enantiomers. The significance of enantiomer separation and enantiomeric excess of chiral terpenoids in the essential oil of M. citrata cv. Kiran is of great importance in ascertaining the authenticity of this essential oil.

Standardised comparison of limonene-derived monoterpenes identifies structural determinants of anti-inflammatory activity

Mint species are widely used in traditional and conventional medicine as topical analgesics for osteoarthritic pain and for disorders of the gastrointestinal and respiratory tracts which are all associated with chronic inflammation. To identify the structural determinants of anti-inflammatory activity and potency which are required for chemical optimization towards development of new anti-inflammatory drugs, a selected group of monoterpenes especially abundant in mint species was screened by measuring bacterial lipopolysacharide (LPS)-induced nitric oxide (NO) production in murine macrophages. Nine compounds significantly decreased LPS-induced NO production by more than 30%. IC50 values were calculated showing that the order of potency is: (S)-(+)-carvone > (R)-(−)-carvone > (+)-dihydrocarveol > (S)-8-hydroxycarvotanacetone > (R)-8-hydroxycarvotanacetone > (+)-dihydrocarvone > (−)-carveol > (−)-dihydrocarveol > (S)-(-)-pulegone. Considering the carbon numbering relative to the common precursor, limonene, the presence of an oxygenated group at C6 conjugated to a double bond at C1 and an isopropenyl group and S configuration at C4 are the major chemical features relevant for activity and potency. The most potent compound, (S)-(+)-carvone, significantly decreased the expression of NOS2 and IL-1β in macrophages and in a cell model of osteoarthritis using primary human chondrocytes. (S)-(+)-carvone may be efficient in halting inflammation-related diseases, like osteoarthritis.

Mentha cervina (Lamiaceae), an emergent aquatic alien species naturalising at South Gare, North-East Yorkshire

There is an increasing interest in recording early colonisation of organisms when studying changes in distribution ranges induced by climate change. Here, I describe one population of Mentha cervina L. (Hart’s pennyroyal), naturalising in the wild at South Gare, v.c.62 North-east Yorkshire. Two other populations have been reported in Britain and none are known from Ireland. Of the three populations ever reported from the wild in Britain, two are still extant. It is unclear what vectors disperse M. cervina in Britain and whether the species is becoming increasingly naturalised or not. Diagnostic characters: digitate bracteoles and four calyx teeth, are provided to facilitate the recording of this mint species by field botanists.

Seed set in inter specific crosses of male sterile Mentha spicata with Mentha longifolia

Mentha is one of the most important genera of the Lamiaceae with a wide geographical distribution and considerable commercial importance. The general aim of this work was to group 34 accessions from four species of mint using ISSR molecular markers to select some accessions to estimate the potential cross-ability of mints valuable in breeding and phytochemical research. The reproductive characteristics including the type of flower, petal color, sepal and petal lengths, length of stamen and pistil as well as the number of free and living pollen grains in the anther were also studied to find out cross-ability patterns and the possible reproductive barriers. Analysis of molecular variance (AMOVA) among and within species showed more intra-specific variation (92.24%) in comparison with inter-species variation (7.76%). Results of cluster analysis based on ISSR data grouped the mint genotypes into five clusters. By this, the greatest genetic similarity was found between Ms12 from M. spicata and Ml29 from M. longifolia. The genotype Ms12 along with Ms22, the other genotype from M. spicata, were found to be male sterile due to stopped stamen development. These two had higher combining ability (seed set) when used as the female parent in intra-specific crosses and when crossed with M. longifolia compared to the other genotypes in diallel crosses. The highest number of hybrid seeds was obtained where Ml29 was crossed as the male parent with male sterile Ms12 as the female one. This high success rate of seed set in interspecific crosses between M. spicata and M. longifolia could be related to their genomic similarity confirmed by ISSR molecular data. Therefore, producing hybrid seeds and subsequent generations from crosses between these species, utilizing male sterility mechanism, can be a source of new genetic variation for mint.

Mint companion plants enhance the attraction of the generalist predator Nesidiocoris tenuis according to its experiences of conspecific mint volatiles

Mint plants enable improvement of pest management by attracting herbivore enemies to constitutively released mint volatiles. The generalist predator Nesidiocoris tenuis is used worldwide to control agricultural pests, but little is known about whether mint can serve as a companion plant that attracts this predator. To examine this, olfactory responses of N. tenuis were assessed using apple mint, candy mint, and spearmint as odor sources. Of the volatiles released by these mint species, candy mint volatiles alone were more attractive than those from undamaged eggplant, and were as attractive as volatiles from eggplant damaged with Spodoptera litura larvae. However, no prominent preference for particular volatile(s) among the mint volatiles was shown by O. strigicollis. When N. tenuis had been previously exposed to candy mint, the predator showed a stronger preference for candy mint volatiles than damaged eggplant volatiles. It was, however, irrelevant whether the predator received benefit or not by predating animal prey during the mint-experience period. In contrast, spearmint-experience increased the preference for spearmint volatiles only when the predator acquired prey during the mint-experience period. These findings suggest that previous exposure of N. tenuis to some particular mint species can increase its preference for volatiles from the conspecific mints.

Estimation of Energy and Emissions Properties of Waste from Various Species of Mint in the Herbal Products Industry

The paper presents the results of research on the physicochemical properties of plant biomass consisting of four mint species, these being Mentha × piperita L. var. citrata Ehrh.—‘Bergamot’, Mentha × rotundifolia L., Mentha spicata L., and Mentha crispa L. The research conducted consisted of the technical analysis of biofuels—determining the heat of combustion and the calorific value of the material under study, and the content of ash, volatile compounds, and humidity. In addition, elemental analysis was carried out for the biomass under study by determining the content of carbon, hydrogen, nitrogen, and sulfur. The research demonstrated that Mentha × piperita L. var. citrata Ehrh.—‘Bergamot’ had the highest energy potential with a gross calorific value of 16.96 MJ·kg−1, and a net calorific value of 15.60 MJ·kg−1. Among the tested materials, Mentha × rotundifolia L. had the lowest content of ash at 7.23%, nitrogen at 0.23%, and sulfur at 0.03%, and at the same time had the highest content of volatile fraction at 70.36%. When compared to hard coal, the estimated emission factors indicated a CO reduction of 29–32%, CO2 reduction of 28–31%, NOx reduction of 40–80%, SO2 reduction of 92–98%, and dust reduction of 45–61%, depending on the type of biomass used.

Evaluation of phenolic bioactive-linked anti-hyperglycemic and Helicobacter pylori inhibitory activities of Asian Basil (Ocimum spp.) varieties

Basil (Ocimum spp.) is an important herb from the Lamiaceae family with a long history of use in traditional medicine and food applications. Thus, targeting basil varieties for developing herbal medicines against non-communicable chronic diseases (NCDs) such as type 2 diabetes has significant merit. The aim of this study was to screen Asian basil varieties with therapeutic potential for type 2 diabetes targeting relevant phenolic bioactive-linked antioxidant, anti-hyperglycemic, and antimicrobial properties and was compared with a high phenolic and high antioxidant mint species (Mentha arvensis). Aqueous and ethanol (12%) extracts of 8 different varieties of Asian basil were analyzed for total soluble phenolic (TSP) content, phenolic acid profiles, total antioxidant activity (TA), α-amylase, and α-glucosidase enzyme inhibitory activities and inhibition of ulcer-causing bacteria, Helicobacter pylori using in vitro assay models. The highest TSP content was observed in mint and all basil varieties were compared to this standard. High TA, and α-glucosidase enzyme inhibitory activity were observed in targeted varieties of Indian basils. Major phenolic acids found were rosmarinic, ellagic, benzoic, and gallic acids, which may potentially contribute to health benefits such as antioxidant and anti-hyperglycemic properties. Inhibitory activity against H. pylori was observed in response to high phenolic mint but not in Asian basil extracts. This in vitro study provides biochemical rationale on phenolic bioactive-linked antioxidant and anti-hyperglycemic potentials of Asian Basil varieties that need to be further validated with in vivo studies for therapeutic and herbal medicine related applications against type 2 diabetes and associated complications.

Polyphenol composition and antioxidant potential of mint leaves

Soluble and insoluble/bound phenolic compounds and an aqueous infusion of two mint species (Medina and Hasawi), were tested for their total phenolic content, 2,2′-azino-bis-3-ethylbenzthiazoline-6-sulphonate (ABTS) and 1,1-diphenyl-2picrylhydrazyl (DPPH) radical scavenging activity, iron (III) reduction, iron (II) chelating and oxygen radical absorbance capacity (ORAC). Furthermore, the potency of the mint extracts in the inhibition of radical-induced DNA scission, human low-density lipoprotein (LDL) cholesterol oxidation, formation of thiobarbituric acid reactive substances (TBARS) in a cooked ground meat system and LPS (lipopolysaccharide)-stimulated cyclooxygenase-2 (COX-2) expression in J774A.1 mouse macrophage cells were monitored. Results showed that the soluble phenolics had a higher phenolic content and antioxidant activity than the insoluble-bound extracts and aqueous infusions in most of the assays. Both varieties exhibited notable antioxidant activities and inhibition of LDL cholesterol oxidation, DNA scission and COX-2 gene expression at transcriptional level. However, Medina mint was a more potent antioxidant than the Hasawi mint. High performance liquid chromatography with online tandem electrospray ionization mass spectrometry (HPLC/ESI-MS/MS) analysis of the extracts revealed that rosmarinic acid was the major phenolic compound present in both mint samples.Graphical abstract

Mint companion plants attract the predatory mite Phytoseiulus persimilis

Mint plants could theoretically serve as companion plants (CPs) that attract enemies of herbivores in tritrophic interactions. In order to explore the traits of mint volatiles as attractant cues for enemies of two-spotted spider mites, we performed Y-tube olfactometer assays of predatory mites, Phytoseiulus persimilis and Neoseiulus californicus, towards three mint species, apple mint, candy mint, and spearmint, as odor source. Clean candy mint and spearmint were attractive to P. persimilis, when compared with clean air and undamaged Phaseolus vulgaris plants serving as the target crop. Moreover, clean candy mint plants were even more attractive than volatiles from P. vulgaris plants damaged by spider mites. These predator responses were induced additively by candy mint volatiles plus volatiles from damaged P. vulgaris plants, as shown using both Y-tube olfactometer and open-space assay systems. However, the number of spider mite eggs consumed by P. persimilis on P. vulgaris plants did not differ in the presence compared to the absence of mint volatiles, indicating that mint volatiles affect the attraction but not the appetite of P. persimilis. Together, these findings suggest that the use of candy mint and spearmint as CPs is an ideal platform for spider mite pest management via the attraction of predatory mites.

Essential oil yield and composition and secondary metabolites in self- and open-pollinated populations of mint (Mentha spp.)

Understanding the reproductive system of mint (Mentha spp.) through self or open pollination is critical for its improvement. In this study, fresh and dry weight, essential oil yield, essential oil composition, flavonoid and phenolic contents of 12 mint populations derived from self and open-pollination, plus their parents belonging to two species, were evaluated. The results showed inbreeding depression in self-pollinated populations compared with the parents, for fresh and dry weights and essential oil yield belonging to Mentha longifolia, but in populations belonging to Mentha spicata, fresh weight, dry weight and essential oil yield increased in self and open-pollinated populations, compared with the parents. The possibility of self-pollination and subsequent improvements in offspring may be considered as an existence of some self-compatibility in mint species. Gas chromatography-mass spectrometry (GC–MS) and GC-FID analyses were also performed to determine the essential oil components. Accordingly, 29 compounds were determined including pulegone (0.87–71%), piperitenone (0.94–76.87%), carvone (0.19–52.01%), and limonene (1.19–26.61%) in the genotypes of M. longifolia and M. spicata. The amount of pulegone, as well as limonene and carvone, significantly decreased in some populations derived from self and open pollination while a significant increase in the amount of piperitenone and menthone was found in this condition. Results also showed that the pollination system had no significant effect on phenolic content while self-pollination significantly increased the flavonoid content of Hamedan and Lorestan populations. Self-pollination in mint may be viewed as a useful way to increase genetic homogenicity for the selection of superior plants in breeding programs for pharmaceutical purposes.

Genetic relationships of Iranian endemic mint species, Mentha mozaffariani Jamzad and some other mint species revealed by ISSR markers

Genetic relationships of Iranian endemic mint species, Mentha mozaffariani Jamzad and some other mint species revealed by ISSR markers

Response of Antioxidant Potential and Essential Oil Components to Irrigation and Fertilization on Three Mint Species (Mentha spp. L.)

Mint (Mentha spp.), one of the most used plants in traditional medicine, is cultivated since antiquity, being mentioned by ancient writings. Besides its use for improving the human health, mint extracts are found in food, cosmetics, detergents, perfumes, biopesticides, etc. Due to its multiple benefits mint consumption has increased continuously in the last years. Besides the interest in mint yield, another interesting trait of this species is the antioxidant activity and the quality of essential oils. According to some research in the field, using water given by irrigation and fertilization leads to an increase of green mass production, but the level of essential oils remains the same. The aims of the present research were to determine the effects of irrigation, fertilization and species over the quality of mint and to identify the best matches of the experimental factors for increasing the antioxidants and essential oils content. Plant material was represented by M. spicata, M. piperita and M. suaveolens. Management followed the growing season of mint plants both in non-irrigated and irrigated conditions, with base fertilization and usage of Lignohumate. The analysis of samples was performed using Photochem where photochemical excitation of free radicals is combined with luminometric detection. The composition of the essential oil was determined by Gas chromatography with flame ionisation detector GC-FID. The research concludes that mint quality increased in conditions of no irrigation. For high phytonutrient content it is recommended to cultivate M. piperita, because it has the highest antioxidants content. M. spicata presented the essential oil with the best content of alcohols, esters and aromatic compounds. M. suaveolens reached the best level of esters, aldehydes and aromatic compounds only in the case of fertilization with Lignohumate.

Ordu Ekolojik Şartlarında Farklı Nane (Mentha sp.) Türlerinin Tarımsal Özelliklerinin Belirlenmesi

Bazı nane türlerinin (Mentha piperita, Menta spicata ve Mentha longifolia) tarımsal özelliklerini belirlemek amacıyla yapılan bu çalışma, 2016-2017 yıllarında Ordu Üniversitesi Ziraat Fakültesi deneme alanında, “Şansa Bağlı Parseller Deneme Planına” göre üç tekrarlamalı olarak yürütülmüştür. Araştırmada bitki boyu, taze herba verimi, drog herba verimi, taze yaprak verimi ve drog yaprak verimi, uçucu yağ verimi ve uçucu yağ oranı gibi özellikler incelenmiştir. Araştırmanın birinci yılında M. piperita ve M. spicata‘da iki, M. longifolia‘ da dört biçim; araştırmanın ikinci yılında M. piperita‘ da bir, M. spicata‘da iki, M. longifolia‘ da dört biçim yapılmıştır. Araştırma sonuçlarına göre, bitki boyu bakımından türler arasında sadece ilk yıl birinci biçimde fark belirlenmiştir. Araştırmanın birinci yılında Mentha piperita‘da toplam taze herba verimi 2.442,73 kg/da, toplam drog herba verimi 585,70 kg/da, toplam taze yaprak verimi 1.120,67 kg/da, toplam drog yaprak verimi 266,87 kg/da, toplam uçucu yağ verimi 6,40 lt/da olarak tespit edilmiştir. İkinci yıl ise Mentha spicata türü toplam taze herba verimi (920,37 kg/da), toplam drog herba verimi (247,93 kg/da), toplam taze yaprak verimi (502,5 kg/da) ve toplam drog yaprak verimi (149,93 kg/da) bakımından öne çıkmıştır. M. longifolia türü toplam uçucu yağ verimi bakımından 2017 araştırma yılında 3,47 lt/da ile diğer türlerin önüne geçmiş, toplam uçucu yağ oranı yönünden ise her iki araştırma yılında da (3,48 lt/da ve 3,19 lt/da) ilk sırada yer almıştır.

Evaluation of Antioxidant, Anti-Inflammatory and Cytoprotective Properties of Ethanolic Mint Extracts from Algeria on 7-Ketocholesterol-Treated Murine RAW 264.7 Macrophages.

The present study consisted in evaluating the antioxidant, anti-inflammatory and cytoprotective properties of ethanolic extracts from three mint species (Mentha spicata L. (MS), Mentha pulegium L. (MP) and Mentha rotundifolia (L.) Huds (MR)) with biochemical methods on murine RAW 264.7 macrophages (a transformed macrophage cell line isolated from ascites of BALB/c mice infected by the Abelson leukemia virus). The total phenolic, flavonoid and carotenoid contents were determined with spectrophotometric methods. The antioxidant activities were quantified with the Kit Radicaux Libres (KRLTM), the ferric reducing antioxidant power (FRAP) and the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays. The MS extract showed the highest total phenolic content, and the highest antioxidant capacity, while the MR extract showed the lowest total phenolic content and the lowest antioxidant capacity. The cytoprotective and anti-inflammatory activities of the extracts were quantified on murine RAW 264.7 macrophages treated with 7-ketocholesterol (7KC; 20 µg/mL: 50 µM) associated or not for 24 h and 48 h with ethanolic mint extracts used at different concentrations (25, 50, 100, 200 and 400 µg/mL). Under treatment with 7KC, an important inhibition of cell growth was revealed with the crystal violet test. This side effect was strongly attenuated in a dose dependent manner with the different ethanolic mint extracts, mainly at 48 h. The most important cytoprotective effect was observed with the MS extract. In addition, the effects of ethanolic mint extracts on cytokine secretion (Interleukin (IL)-6, IL-10, Monocyte Chemoattractant Protein (MCP)-1, Interferon (IFN)-ϒ, Tumor necrosis factor (TNF)-α) were determined at 24 h on lipopolysaccharide (LPS, 0.2 µg/mL)-, 7KC (20 µg/mL)- and (7KC + LPS)-treated RAW 264.7 cells. Complex effects of mint extracts were observed on cytokine secretion. However, comparatively to LPS-treated cells, all the extracts strongly reduce IL-6 secretion and two of them (MP and MR) also decrease MCP-1 and TNF-α secretion. However, no anti-inflammatory effects were observed on 7KC- and (7KC + LPS)-treated cells. Altogether, these data bring new evidences on the potential benefits (especially antioxidant and cytoprotective properties) of Algerian mint on human health.

Organic and Chemical Fertilizer Affected Yield and Essential Oil of Two Mint Species

Two species of mint Mentha piperitha (peppermint) and M. arvensis (Japanese mint) are widely cultivated in Iran but have not been evaluated their response to fertilizer regimes. A field experiment were conducted to investigate the effects of different organic and chemical fertilizer treatments [Control, 100 % urea (95 kg N ha”1), 75% urea (71.25 kg N ha”1) + 25 % Vermicompost (3.3 ton ha-1), 50 % urea (47.5 kg N ha”1) + 50 % Vermicompost (6.75 ton ha-1), 25 % urea (23.75 kg N ha”1) + 75 % vermicompost (10.1 ton ha-1) and 100 % vermicompost (13.5 ton ha-1)] on essential oil contents, yield and morphological parameters of two species of mint (peppermint and Japanese mint) at Tarbiat Modares University during 2015 growing season. Peppermint provided higher plant height, number of internodes, number of leaves and oil percentage than Japanese mint. The results indicated that, irrespective of mint species, plant treated with chemical and organic fertilizers together presented taller plant, higher oil contents and oil yield compared with solo chemical or organic fertilizers. Oil percentage and essential oil yield of mint increased significantly up to 25.75 kg/ha urea + 10.1 t/ha. Plant height and number of leaf increased along the replacement of organic fertilizer with chemical fertilizers. The results showed that there was positive and significant correlation with leaf number and essential oil yield. Application of vermicompost combined with chemical fertilizer increased plant height, oil percentage and essential oil in both species suggesting that organic and chemical fertilizer combination improves performance and environmental sustainability.

Genetic variations among two Egyptian mint species (Mentha spicata and Mentha piperita) using random amplified Polymorphic DNA markers

In the present study, RAPD-PCR was used for identification of two mint species (Mentha spicata and Mentha piperita) collected from Egypt and studying the genetic variations among them. RAPD-PCR was conducted using ten oligonucleotide primers. The ten primers succeeded in amplifying of DNA fragments for the two Mentha species. These primers produced multiple fragments profiles ranging from 3 to 19 fragments. The polymorphism levels differed from primer to another. The number of polymorphic fragments ranged from 0 to 66.29 per primer. The total number of the obtained fragments from the ten primers was 83 fragments with 39 polymorphic fragments (46.98 %) across the two mint species. Forty percent of primers did not exhibit any polymorphism. This study provides evidence that RAPD Markers can be used as an efficient tool for the detection of the genetic variations and identifications of different mint species.

Effect of Heat Stress on Yield, Monoterpene Content and Antibacterial Activity of Essential Oils of Mentha x piperita var. Mitcham and Mentha arvensis var. piperascens.

Heat stress affects the yield of medicinal plants and can reduce biomass and/or metabolite production. In order to evaluate the effect of heat-induced stress on the essential oil production in Mentha x piperita L. var. Mitcham (Mitcham mint) and Mentha arvensis var. piperascens Malinv. ex L. H. Bailey (Japanese mint), we studied the chemical composition of the oils of the two mint species under different heat shock stresses in growth chambers. The antibacterial activity of the essential oils was also evaluated; microscopic observation (fluorescence and electron transmission) was used to assess the effect of the tested samples on bacterial growth. The results obtained shed light on the mint essential oils composition and biological activity in relation to heat stress.