Chemical composition and antifungal activity of essential oil from the seed of Echinophora platyloba DC. against phytopathogens fungi by two different screening methods

Genus Echinophora-Biological Activity, Chemical Composition, and Future Perspectives

Species belonging to the genus Echinophora (Apiaceae) have been used by humanity since ancient times as flavoring agents, preservatives, and medicines for the treatment of a broad spectrum of conditions, including respiratory, digestive and kidney disorders, fungi infections, wounds, and gastric ulcers. Phytochemical studies on this botanical genus mainly investigate the essential oil composition and reveal the species as a rich source of volatile compounds, including monoterpenes and phenylpropanoids. Among the non-volatile secondary metabolites, flavonoids, coumarins, phenolic acids, phytosterols, and polyacetylenes have been identified. Pharmacological studies revealed Echinophora extracts and essential oils exhibit different biological properties, including antibacterial, antifungal, anticancer, insecticidal, anti-inflammatory, and hepatoprotective activities. However, compared to other genera, the biological activity and chemical diversity of this genus are not well studied. In future decades, it is highly likely that the small genus Echinophora will play an important role in drug discovery and drug development.

Echinophora tenuifolia subsp. sibthorpiana-Study of the Histochemical Localization of Essential Oil

BACKGROUND

Echinophora tenuifolia L. subsp. sibthorpiana is a perennial, aromatic plant used in traditional folk medicine and cuisine of the Mediterranean and the Middle East. However, scholars have not fully studied the pharmacological potential of the herb, and the scientific data on this plant species are limited. This study aimed to evaluate the chemical composition of the essential oil (EO) obtained from the aerial parts of E. tenuifolia subsp. sibthorpiana growing wild in Bulgaria and to perform histochemical analysis.

METHODS

A microscopic histochemical analysis and gas chromatography with mass spectrometry were performed.

RESULTS

The histochemical analysis confirmed the presence of terpenes in the stem and leaf of E. tenuifolia subsp. sibthorpiana. The phenylpropanoid methyleugenol was identified as the main compound in the EO, representing 48.13% of the total oil composition. There were also found considerable amounts of monoterpene hydrocarbons, representing 41.68% of the total EO. Alpha-phellandrene, o-cymene, and β-phellandrene were the most abundant monoterpene hydrocarbons.

CONCLUSION

This is the first histochemical analysis performed on E. tenuifolia subsp. sibthorpiana. This is the first report of the EO composition from Bulgarian E. tenuifolia subsp. sibthorpiana, and our results indicate some future possibilities for evaluating of the biological activity of the EO of E. tenuifolia subsp. sibthorpiana and highlight the potential future use of the EO of this plant species. E. tenuifolia L. subsp. sibthorpiana EO possesses a good potential for use as a biopesticide and repellent an environmentally friendly alternative of synthetic pesticides.

Essential oil from Sabina chinensis leaves: A promising green control agent against Fusarium sp

Sabina chinensis is a woody plant with important ecological functions in different regions of China, but its essential oils (EO) against plant pathogenic fungi remain largely undetermined. The purpose of our study was to assess the chemical composition and antifungal activity of S. chinensis EO based on optimization of the extraction process. In this study, an actionable and effective model with the experimental results and identified optimum conditions (crushing degree of 20 mesh, liquid-solid ratio of 10.1:1, immersion time of 9.1 h) was established successfully to achieve an extraction yield of 0.54%, which was basically consistent with the theoretical value. A total of 26 compounds were identified using headspace gas chromatography-mass spectrometry (GC-MS) and showed that the major constituent was β-phellandrene (26.64-39.26%), followed by terpinen-4-ol (6.53-11.89%), bornyl acetate (6.13-10.53%), etc. For Petri plate assays, our experiments found for the first time that S. chinensis EO revealed high and long-term antifungal activity against the tested strains, including Fusarium oxysporum and Fusarium incarnatum, at EC₅₀ values of 1.42 and 1.15 µL/mL, which especially reached approximately 76% and 90% growth inhibition at a dose of 0.2 µL/mL, respectively. Furthermore, the antifungal activity of EO from different harvest periods showed remarkable variation. The orthogonal partial least-squares discriminant analysis (OPLS-DA) method revealed 11 metabolites with chemical marker components, and 5 of its potential antifungal activities, terpinen-4-ol, α-terpineol, α-elemol, γ-eudesmol, and bornyl acetate, were strongly correlated with the mycelial inhibition rate. In total, this study explored the antifungal activity of EO against root rot fungus as a potential fungicide and provided valuable information into developing potential products from natural agents.

Biological properties of Thymus zygis essential oil with emphasis on antimicrobial activity and food application

The Thymus plants have been used for centuries in traditional medicine and as a food spice, among this genus, Thymus zygis (red thyme) is a widespread plant, vastly used as a culinary flavouring agent. Its essential oil has demonstrated diverse bioactive properties, such as antimicrobial, insecticidal, larvicidal and antiparasitic activities. Numerous studies have characterized this essential oil showing that it possesses a broad antimicrobial spectrum and may even enhance the effect of certain antimicrobial agents. Its potential application as a food preservative has been analysed on different matrixes pointing to its antimicrobial activity against spoilage and pathogenic microorganisms in food. This review provides an insight in the chemical composition, antimicrobial, insecticidal, larvicidal and antiparasitic activities and toxicity of T. zygis essential oil, as well as its potential application in food as a preservative.

Droplet-based microfluidics platform for antifungal analysis against filamentous fungi

Fungicides are extensively used in agriculture to control fungal pathogens which are responsible for significant economic impact on plant yield and quality. The conventional antifungal screening techniques, such as water agar and 96-well plates, are based on laborious protocols and bulk analysis, restricting the analysis at the single spore level and are time consuming. In this study, we present a droplet-based microfluidic platform that enables antifungal analysis of single spores of filamentous fungus Alternaria alternata. A droplet-based viability assay was developed, allowing the germination and hyphal growth of single A. alternata spores within droplets. The viability was demonstrated over a period of 24 h and the antifungal screening was achieved using Kunshi/Tezuma as antifungal agent. The efficacy results of the droplet-based antifungal analysis were compared and validated with the results obtained from conventional protocols. The percentage inhibitions assessed by the droplet-based platform were equivalent with those obtained by the other two methods, and the Pearson correlation analysis showed high correlation between the three assays. Taken together, this droplet-based microfluidic platform provides a wide range of potential applications for the analysis of fungicide resistance development as well as combinatorial screening of other antimicrobial agents and even antagonistic fungi.

Natural Products from Medicinal Plants against Phytopathogenic Fusarium Species: Current Research Endeavours, Challenges and Prospects

Many Fusarium species are pathogenic, causing crop diseases during crop production and spoilage of agricultural products in both commercial and smallholder farming. Fusarium attack often results into food contamination, yield loss and increases in food insecurity and food prices. Synthetic fungicides have been used as a control strategy for the management of crop diseases caused by Fusarium pathogens. The negative effects associated with application of many synthetic pesticides has necessitated the need to search for alternative control strategies that are affordable and environmentally safe. Research on medicinal plants as control agents for Fusarium pathogens has received attention since plants are readily available and they contain wide variety of secondary metabolites that are biodegradable. The activities of solvent extracts, essential oils and compounds from medicinal plants have been tested against Fusarium phytopathogenic species. A summary of recent information on antifungal activity of plants against Fusarium species is valuable for the development of biopesticides. This paper reviews the antifungal research conducted on medicinal plants against Fusarium pathogens, over a 10-year period, from January 2012 to May 2021. We also highlight the challenges and opportunities of using natural products from medicinal plants in crop protection. Several databases (Science Direct and Web of Science) were used to obtain information on botanical products used to control Fusarium diseases on crops. Keywords search used included natural products, antifungal, Fusarium, crops diseases, phytopathogenic, natural compounds and essential oil.

Interaction of human hemoglobin (HHb) and cytochrome c (Cyt c) with biogenic chloroxine-conjugated silver nanoflowers: spectroscopic and molecular docking approaches

In this research, the biological activity of the antibacterial drug Chloroxine-conjugated biogenic AgNPs (COX-AgNPs) was investigated in simulated physiological conditions (pH = 7.40). Different spectroscopic methods such as UV-visible, fluorescence, and circular dichroism spectroscopic and docking simulation were employed to evaluate the structural changes in the most important blood proteins (human hemoglobin (HHb) and Cytochrome c (Cyt c)) in the presence of COX-AgNPs. The results showed that the COX-AgNPs can bind to HHb and Cyt c and the secondary structure of these proteins remains unchanged, which is crucial in providing insights into the side effects of newly synthesized drugs on their carriers.Communicated by Ramaswamy H. Sarma.

Phytotoxicity and antifungal properties of the essential oil from the Juniperus polycarpos var. turcomanica (B. Fedsch.) R.P. Adams leaves

This study was performed to investigate the constituents, in vitro antifungal activity and phytotoxicity potential of the essential oil from Juniperus polycarpos var. turcomanica leaves. The essential oil was analyzed by GC-FID, and GC/MS, which predominantly contains α-pinene (51.21%), germacrene-B (4.80%), and ∆-cadinene (2.56%). The antifungal activity of the essential oil against some phytopathogenic fungi, including Alternaria alternata, Colletotrichum trichellum, Curvularia fallax, Cytospora sacchari, Fusarium oxysporum, and Macrophomina phaseolina was performed through disk diffusion and agar dilution assays. The essential oil of J. polycarpos var. turcomanica had high antifungal activity against tested phytopathogenic fungi. The most susceptible fungi to the essential oil were C. trichellum in agar dilution and M. phaseolina and C. fallax in disk diffusion methods, whereas, the most resistant fungus to the essential oil was obtained from A. alternata in both assays. Screening methods had an influence on antifungal activity of the essential oil as most of the tested fungi in this study were shown to be more resistant in disc diffusion methods. According to the phytotoxic assay results, the essential oil from J. polycarpos var. turcomanica had high phytotoxicity against three species of weeds, including P. oleracea L., A. retroflexus L., and D. stramonium L. The results of this research suggest that the herbicidal and antifungal activities of the essential oil from J. polycarpos var. turcomanica can be attributed to its major group of constituents, monoterpenes hydrocarbons.

Essential Oils as Potential Alternative Biocontrol Products against Plant Pathogens and Weeds: A Review

Naturally produced by aromatic plants, essential oils (EO) contain a wide range of volatile molecules, including mostly secondary metabolites, which possess several biological activities. Essential oils properties such as antioxidant, antimicrobial and anti-inflammatory activities are known for a long time and hence widely used in traditional medicines, cosmetics and food industries. However, despite their effects against many phytopathogenic fungi, oomycetes and bacteria as well as weeds, their use in agriculture remains surprisingly scarce. The purpose of the present review is to gather and discuss up-to-date biological activities of EO against weeds, plant pathogenic fungi, oomycetes and bacteria, reported in the scientific literature. Innovative methods, potentially valuable to improve the efficiency and reliability of EO, have been investigated. In particular, their use towards a more sustainable agriculture has been discussed, aiming at encouraging the use of alternative products to substitute synthetic pesticides to control weeds and plant diseases, without significantly affecting crop yields. An overview of the market and the recent advances on the regulation of these products as well as future challenges to promote their development and wider use in disease management programs is described. Because of several recent reviews on EO insecticidal properties, this topic is not covered in the present review.

TRPA1 Modulating C14 Polyacetylenes from the Iranian Endemic Plant Echinophora platyloba

Phytochemical investigation of the apolar extract obtained from aerial parts of the Iranian endemic plant Echinophora platyloba DC (Apiaceae) resulted in the characterization of the polyacetylene fraction of this plant. This resulted to be composed of the known echinophorins A and B, embedding the very rare α-pyrone terminal, and of the new echinophorin D (3), including also three conjugated triple bonds. The chemical structures of these compounds were secured by detailed inspection of MS and 1D/2D NMR spectra. The isolated polyacteylenes were evaluated for their modulation of six thermo-TRP channels and they revealed a selective activity on TRPA1, an ion channel involved in the mediation of neuropathic and inflammatory pain. This is the first report on the activity of plant polyacetylenes on transient receptor potential (TRP) channels.

In vitro Antifungal Activity of Essential oils and Major Components against Fungi Plant Pathogens

The indiscriminate use of synthetic fungicides has caused several problems to the environment, which place human and animal health at risk. Due to this fact, the search for natural alternatives to control phytopathogenic fungi growth has increased. This study aims to evaluate the antifungal activity of two essential oils (EOs) and three major components of EOs on the radial growth and spore germination of Fusarium verticillioides and Alternaria tenuissima. Minimum and half‐maximal inhibitory concentrations (CMI and CI50) at 96 h for each treatment were calculated. Lemongrass EO and citral caused the highest inhibition for A. tenuissima (CMI of 1000 μl/l and CI50 of 10 μl/l). For F. verticillioides, the most effective component was geraniol (CMI and CI50 of 1000 and 250 μl/l, respectively). Spore germination rate was delayed by the EOs and major components tested. The use of EOs was effective to control these two fungal species in their different grow stages.

Bioactivity of essential oils in phytopathogenic and post-harvest fungi control

Commercial thyme and lavender essential oils were analysed by GC/MS. Sixty-six compounds accounting for 98.6-99.6% of total essential oil were identified. Thymol (52.14 ± 0.21%), followed by p-cymene (32.24 ± 0.16%), carvacrol (3.71 ± 0.01%) and γ-terpinene (3.34 ± 0.02%), were the main compounds in thyme essential oil, while large amounts of oxygenated monoterpenes linalool acetate (37.07 ± 0.24%) and linalool (30.16 ± 0.06%) were found in lavender one. In vitro antifungal activity of the essential oils was evaluated at 200 and 300 μg/mL against 10 phytopathogenic and post-harvest fungi, which significantly affect agriculture. Micelial growth inhibition was calculated for each tested fungus and dose. Thyme essential oil showed satisfactory results with 90-100% growth inhibition in almost all the assayed fungi at 300 μg/mL, while lavender essential oil showed no noteworthy inhibition data at either dose, and its growth was even enhanced. Thyme essential oil represents a natural alternative to control harvest and post-harvest fungi, and to extend the shelf-life of agriculture products.