Biochemical Characterization, Antifungal Activity, and Relative Gene Expression of Two Mentha Essential Oils Controlling Fusarium oxysporum, the Causal Agent of Lycopersicon esculentum Root Rot

Tomato (Lycopersicon esculentum Mill.) is important food in daily human diets. Root rot disease by Fusarium oxysporum caused huge losses in tomato quality and yield annually. The extensive use of synthetic and chemical fungicides has environmental risks and health problems. Recent studies have pointed out the use of medicinal plant essential oils (EOs) and extracts for controlling fungal diseases. In the current research, Mentha spicata and Mentha longifolia EOs were used in different concentrations to control F. oxysporum. Many active compounds are present in these two EOs such as: thymol, adapic acid, menthol and menthyl acetate. These compounds possess antifungal effect through malformation and degradation of the fungal cell wall. The relative expression levels of distinctly upregulated defense-related WRKY genes (WRKY1, WRKY4, WRKY33 and WRKY53) in seedling root were evaluated as a plant-specific transcription factor (TF) group in different response pathways of abiotic stress. Results showed significant expression levels of WRKY, WRKY53, WRKY33, WRKY1 and WRKY4 genes. An upregulation was observed in defense-related genes such as chitinase and defensin in roots by application EOs under pathogen condition. In conclusion, M. spicata and M. longifolia EOs can be used effectively to control this plant pathogen as sustainable and eco-friendly botanical fungicides.

Essential Oils from Indigenous Iranian Plants: A Natural Weapon vs. Multidrug-Resistant Escherichia coli

Aim of this study was to investigate the antimicrobial properties of herbal plant essential oils (EOs) from selected Iranian plant species such as Ferulago angulata, Zataria multiflora, Cuminum cyminum, and Mentha longifolia against antibiotic-resistant Escherichia coli (E. coli) strains. For this purpose, the Escherichia coli strains, isolated from raw cow’s milk and local dairy products (yogurt, cream, whey, cheese, and confectionery products) collected from different areas of Hamedan province, Iran, were investigated for their resistance to antibiotics (i.e., streptomycin, tetracycline, gentamicin, chloramphenicol, ciprofloxacin, and cefixime). Thus, the E. coli strains were tested for their susceptibility to the above-mentioned essential oils. Regarding antibiotics, the E. coli strains were highly sensitive to ciprofloxacin. In relation to essential oils, the most effective antibacterial activity was observed with Zataria multiflora; also, the bacteria were semi-sensitive to Cuminum cyminum and Mentha longifolia essential oils. All strains were resistant to Ferulago angulata essential oil. According to the results, the essential oil of Zataria multiflora can be considered as a practical and alternative antibacterial strategy to inhibit the growth of multidrug-resistant E. coli of dairy origin.

Polysaccharide-Based Active Coatings Incorporated with Bioactive Compounds for Reducing Postharvest Losses of Fresh Fruits

This review reports recently published research related to the application of polysaccharide-based biodegradable and edible coatings (BECs) fortified with bioactive compounds obtained from plant essential oils (EOs) and phenolic compounds of plant extracts. Combinations of polysaccharides such as starches, pectin, alginate, cellulose derivatives, and chitosan with active compounds obtained from clove, lemon, cinnamon, lavender, oregano, and peppermint have been documented as potential candidates for biologically active coating materials for retardation of quality changes in fresh fruits. Additionally, polysaccharide-based active coatings supplemented with plant extracts such as cashew leaves, pomegranate peel, red roselle, apple fiber, and green tea extracts rich in phenolic compounds and their derivatives have been reported to be excellent substituents to replace chemically formulated wax coatings. Moreover, EOs and plant polyphenolics including alcohols, aldehydes, ketones phenols, organic acids, terpenes, and esters contain hydroxyl functional groups that contribute bioactivity to BECs against oxidation and reduction of microbial load in fresh fruits. Therefore, BECs enriched with active compounds from EOs and plant extracts minimize physiological and microbial deterioration by reducing moisture loss, softening of flesh, ripening, and decay caused by pathogenic bacterial strains, mold, or yeast rots, respectively. As a result, shelf life of fresh fruits can be extended by employing active polysaccharide coatings supplemented with EOs and plant extracts prior to postharvest storage.

Ovicidal and Repellent Activities of Several Plant Essential Oils Against Periplaneta americana L. and Enhanced Activities from their Combined Formulation

Natural ovicidal and repellent agents against Periplaneta americana are in urgent need, and plant essential oils (EOs) can assume this role quite readily. In this study, ovicidal and repellent activities against Periplaneta americana of EOs from Cymbopogon citratus, Cinnamomum verum, Eucalyptus globulus, Illicium verum, and Zanthoxylum limonella in soybean oil and in ethyl alcohol were determined by topical and dual-choice assays, as well as 10% cypermethrin and a combined formulation of 5% C. verum EO + 5% I. verum EO. Cypermethrin at 10% provided the highest toxicity (100% inhibition rate) against the eggs, but only slightly higher than that (99.3%) provided by the combined EO formulation, while the highest repellent activity against the adults was provided by the combined formulation (89.5% repelled cockroaches at 48 h after treatment). In addition, all EO formulations in soybean oil provided higher ovicidal and repellent activities than in ethyl alcohol. To conclude, the combined EO formulation in soybean oil can replace cypermethrin because their efficacy was nearly equivalent, but the combination should be much safer to use.

Inhibition of the Citrus Bacterial Pathogen Xanthomonas axonopodis pv. citri through Aloysia gratissima Essential Oil and Flourensia spp. Extracts and Prenylflavonoids

Background: Xanthomonas axonopodis pv. citri is a gram-negative bacterium that affects citrus crops, causing a disease known as citrus canker. Although essential oils and other compounds isolated from plants represent a natural alternative to treat this disease, they have the disadvantage of having low solubility in the media in which the bioassays to determine antimicrobial activity are performed. This has led several researchers to evaluate the solubility of plant essential oils in alternative solvents. Objectives: The aim of this study was to evaluate the solubility of the essential oil from Aloysia gratissima as well as that of low-polarity extracts and pure compounds of the genus Flourensia in diluted agar/Tween 80 solutions to test and improve their antimicrobial activity against Xanthomonas axonopodis pv. citri. Methods: Antimicrobial activity against Xanthomonas axonopodis pv. citri was determined by bioautography, agar diffusion, and microdilution methods. Results: The A. gratissima oil showed increased activity in the agar (0.15 % m/v)/Tween80 (0.5 % v/v) 1:1 mixture, with MIC values ranging from 75 to 100 µL/mL, while Flourensia spp. extracts were more soluble in agar solution (0.15 % m/v). The pure compounds tested presented MIC values ranging from 50 to 150 µg/mL. Conclusion: The proven antimicrobial activity of both Aloysia gratissima essential oil and Flourensia spp. extracts and pure compounds allows proposing these natural products as potential antimicrobial agents in the control of citrus canker.

The influence of plant essential oils on in vitro growth of Pectobacterium and Dickeya spp. bacteria

The activity of essential oils from Eucalyptus globulus, Pinus silvestris, Lavandula angustifolia, Juniperus virginiana, Rosmarinus officinalis and Citrus paradise against the soft-rot pathogens Pectobacterium carotovorum subsp. carotovorum, Pectobacterium atrosepticum, Pectobacterium parmentieri and Dickeya solani was determined in vitro. The antibacterial activity of the essential oils will be evaluated using the disk-diffusion method by Kirby-Bauer [Bauer et al. 1966]. It was found that all the presented essential oils varied in antimicrobial activity against the four bacterial strains. No differences in the influence of streptomycin on inhibition of growth of the four bacterial strains were observed. Among six tested plants, essential oils from P. sylvestris had the strongest inhibitory effect on the growth of soft rot bacteria from Pectobacterium genus. This paper constitute the first report on the activity of the essential oils obtained from J. virginiana against soft rot bacteria. They are also the first report on the activity of the essential oils obtained from E. globulus, P. silvestris, L. angustifolia and C. paradisi against P. atrosepticum, P. parmentieri and D. solani as well as on the activity of the R. officinalis essential oils against P. atrosepticum and P. parmentieri.