Exploring the Diverse Biological Properties of Cannabidiol: A Focus on Plant Growth Stimulation

The aim of the current study was to compare some biological activities of edible oils enriched with 10 % of cannabidiol (CBD samples) from the Slovak market. In addition, hemp, coconut, argan, and pumpkin pure oils were also examined. The study evaluated the fatty acids content, as well as antibacterial, antifungal, antioxidant, cytotoxic, and phytotoxic activities. The CBD samples presented antimicrobial activity against the tested bacterial strains at higher concentrations (10000 and 5000 mg/L) and antifungal activity against Alternaria alternata, Penicillium italicum and Aspergillus flavus. DPPH⋅ and FRAP assays showed greater activity in CBD-supplemented samples compared to pure oils and vitamin E. In cell lines (IPEC-J2 and Caco-2), a reduced cell proliferation and viability were observed after 24 hours of incubation with CBD samples. The oils showed pro-germinative effects. The tested activities were linked to the presence of CBD in the oils.

Chemical Profiling, Insecticidal, and Phytotoxic Effect of Essential Oils from Leaves and Inflorescence of Moroccan Chenopodium ambrosioides (L.)

Chenopodium ambrosioides (L.) is a medicinal and aromatic plant widely used in the Moroccan traditional medicine for its important pharmacological properties. In order to contribute to the valorization of this plant, the current study aimed at evaluating, for the first time, the variation in the yield, chemical composition, and insecticidal and phytotoxic activities of C. ambrosioides essential oil (CAEO) isolated from leaves and inflorescences. The results obtained showed that the CAEO yields vary significantly according to the distilled plant part, with 0.75 ± 0.15% for the leaves and 1.2 ± 0.34% for the inflorescences. CAEO profiling showed quantitative more than qualitative differences. Leaf CAEO was rich in δ-3-carene (61.51%), followed by p-cymene (14.67%) and 1,2:3,4-diepoxy-p-menthane (6.19%). However, inflorescence CAEO was dominated by the same compounds but with variable levels (δ-3-Carene: 44.29%; 1,2:3,4-diepoxy-p-menthane: 19.46%; and p-cymene: 17.85%). The CAEOs from the leaves and inflorescences showed a very interesting inhibiting effect on the germination and growth of the three species used, namely Medicago sativa, Linum rusitatissimum, and Raphanus sativus. However, there was no significant difference between these CAEOs. Similarly, for the insecticidal activity, CAEOs exhibited an important and similar toxicity against Tribolium confusum adults with LD50 of 4.30 and 4.46 μL/L of air and LD90 of 6.51 and 9.62 μL/L air for toxicity by fumigation, while values for contact toxicity on filter paper were 0.04 and 0.05 μL/cm2 for LD50 and 0.08 and 0.09 μL/cm2 for LD90.

Origanum heracleoticum Essential Oils: Chemical Composition, Phytotoxic and Alpha-Amylase Inhibitory Activities

Many studies have demonstrated the herbicidal effects of several essential oils and their possible use as substitutes for chemical herbicides. Several enzymes play a very significant role in seed germination: among these, α-amylase could be involved in essential oil phytotoxic processes. The aims of this study were to compare the chemical composition of the essential oils of two ecotypes of O. heracleoticum growing in Cilento (Southern Italy) and to study their possible use as natural herbicide using Raphanus sativus, Sinapis arvensis and Lolium multiflorum seeds. Moreover, a possible inhibitory activity on the α-amylase enzyme extracted from germinating seeds was evaluated as a possible mechanism of action. Both oils, characterized by GC-MS, belonged to a carvacrol chemotype. The alpha-amylase activity was determined using DNSA (dinitrosalicylic acid) assay quantifying the reducing sugar produced. Furthermore, the essential oils demonstrated phytotoxicity at the highest dose tested, and an inhibitory effect on α-amylase, probably correlated with the phytotoxic effects, was registered. The oils showed interesting phytotoxic and alpha-amylase inhibitory activities, which deserve to be further investigated.

Synthetic surfactants in drinking and surface waters in Armenia and apparent non-association with some diseases

The main goal of this study is to compare the concentrations of anionic synthetic surfactants (ASS) in drinking and surface waters in Armenia and to explore possible relationship with diseases of the skin and digestive system. Surfactants are widely employed in numerous field of the economy, are in contact with the entire population throughout life and can be harmful to human health.The samples of drinking and surface waters (n = 144) were collected in Kotayk province to analyze ASS concentrations, physicochemical parameters and phytotoxic activity. The prevalence of diseases was analyzed for different population groups. ASS concentrations in surface waters were significantly higher in summer compared to spring (p = 0.006). In drinking water, concentrations were also higher in summer, but not significantly. In surface waters, ASS levels were 2.4-3 times higher compared to drinking (p = 0.03) and exceeded the permissible limit by 1.4-2.9 times in summer and fall. No phytotoxic activity and differences in both classes of diseases and age groups were revealed. The determination of ASS in both surface and drinking waters with the same trend showed their interrelation to a certain extent. This study provides important information for future research and action which will contribute to the sustainable development of local communities.

Juniperus horizontalis Moench: Chemical Composition, Herbicidal and Insecticidal Activities of Its Essential Oil and of Its Main Component, Sabinene

The composition, herbicidal, larvicidal, and toxic activities of Juniperus horizontalis Moench essential oil and sabinene, its main component, were evaluated. The seed germination percentage and root length of eight different plant species (crops and weeds) were measured for in vitro herbicidal activity tests. Different doses (100, 50, 10, 5, 1, 0.5 µg/mL) of the samples were applied to seeds for 120 h. The same doses were applied to test the toxicity of the samples on Tubifex tubifex (sludge worm) and Chironomus aprilinus (blood worm). Four doses (435, 652.5, 870, and 1740) of samples were in a larvicidal test on Tenebrio molitor L. (mealworm), and bioassays were checked after 24 and 48 h. The analysis of the oil allowed for the identification of dominant components as sabinene (38.7%), α-pinene (10.0%), elemol (8.6%), γ-terpinene (8.3%), limonene (7.8%) and α-thujene (5.3%). The results showed that the effect of oil on root length inhibition was significant in all crop species. The doses which affected root growth were not toxic to Tubifex tubifex and Chironomus aprilinus. Finally, the obtained results in the larvicidal bioassay indicate that the potential of J. horizontalis in yellow mealworm survivorship limitation can be a starting point for future research.

Chemical Composition, Phytotoxic and Antibiofilm Activity of Seven Eucalyptus Species from Tunisia

This study was carried out to characterize the chemical composition of the essential oils from seven Eucalyptus species (E. griffithsii, E. hemiphloia, E. lesouefii, E. longicornis, E. pyriformis, E. viminalis, and E. wandoo), as well as their phytotoxic and antibacterial activities. The essential oils were analyzed by GC/MS and the potential in vitro phytotoxicity was evaluated against germination and radical elongation of Raphanus sativus, Lolium multiflorum, and Sinapis arvensis seeds. The antibiofilm activity was studied against both Gram-negative (Pseudomonas aeruginosa, Escherichia coli and Acinetobacter baumannii) and Gram-positive (Staphylococcus aureus and Listeria monocytogenes) bacteria. The inhibition of biofilm formation and its metabolism was determined at different times. Eucalyptol was the most abundant component in all essential oils studied (ranging from 40.8% for E. lesouefii EO to 73.6% for E. wandoo) except for that of E. pyriformis where it was present but at 15.1%. E. pyriformis was the most active against both germination and radical elongation of S. arvensis. The action of all essential oils proved to be highly effective in inhibiting the bacterial adhesion process of the five strains considered. In light of these results, these essential oils could have potential applications both in the agricultural and health fields.

Phytotoxic Metabolites Isolated from Aspergillus sp., an Endophytic Fungus of Crassula arborescens

Aspergillus sp., an endophytic fungus isolated from Crassula arborescens, displayed potent inhibitory activity against the seed germination of Arabidopsis thaliana. The bioactivity-guided fractionation of the culture extract of Aspergillus sp. MJ01 led to the isolation of nine compounds, including one previously undescribed furanone, namely aspertamarinoic acid (1), and eight known compounds, (-)-dihydrocanadensolide (2), kojic acid (3), citreoisocoumarin (4), astellolide A (5), astellolide B (6), astellolide G (7), cyclo-N-methylphenylalanyltryptophenyl (8) and (-)-ditryptophenaline (9). In the evaluation of the phytotoxic activities of compounds 1-9, the results suggested that 1 and 5 showed significant inhibitory activity on the seed germination of A. thaliana. This is the first report to disclose the phytotoxic activity of these compounds.

Sesquiterpenoids with Phytotoxic and Antifungal Activities from a Pathogenic Fungus Aspergillus alabamensis

Five new carotane sesquiterpenoids (asperalacids A-E (1-5)), one new tricyclic sesquiterpenoid (4-hydroxy-5(6)-dihydroterrecyclic acid A (6)), and two known analogues (7-8) were obtained from a seagrass-derived fungus Aspergillus alabamensis, which was speculated to be a phytopathogenic fungus, isolated from the necrotic leaves of Enhalus acoroides. The structures of 1-6 were established by a combination of spectroscopic methods, including comprehensive NMR analysis, mass spectrometry, conformational analysis, NMR computational methods, and ECD calculations. Compound 4, with higher inhibitory activity on wheat (Triticum aestivum L.) root and shoot elongation than the positive control terbutryn, a broad-spectrum systemic herbicide, is a new natural plant growth inhibitor. Compound 5, belonging to the rare glycosylated sesquiterpenoid class, represents the first example of glycosylated carotane sesquiterpenoid whose sugar moiety was identified as α-d-glucose. Compounds 1-4 and 6 displayed weak to potent antimicrobial activity against the plant pathogenic fungi Fusarium oxysporum, Fusarium graminearum, and Penicillium italicum and the Gram-positive bacteria Bacillus subtilis and Staphylococcus aureus.

Antibacterial, Antioxidant, and Phytotoxic Potential of Phytosynthesized Silver Nanoparticles Using Elaeagnus umbellata Fruit Extract

Due to its eco-friendliness, cost-effectiveness, ability to be handled safely, and a wide variety of biological activities, the green plant-mediated synthesis of nanoparticles has become increasingly popular. The present work deals with the green synthesis and characterization of silver nanoparticles (AgNPs) using Elaeagnus umbellata (fruit) and the evaluation of its antibacterial, antioxidant, and phytotoxic activities. For the synthesis of AgNPs, fruit extract was treated with a 4 mM AgNO₃ solution at room temperature, and a color change was observed. In UV-Visible spectroscopy, an absorption peak formation at 456 nm was the sign that AgNPs were present in the reaction solution. Scanning electron microscopy and physicochemical X-ray diffraction were used to characterize AgNPs, which revealed that they were crystalline, spherical, and had an average size of 11.94 ± 7.325 nm. The synthesized AgNPs showed excellent antibacterial activity against Klebsiella pneumoniae (14 mm), Staphylococcus aureus (13.5 mm), Proteus mirabilis (13 mm), and Pseudomonas aeruginosa (12.5 mm), as well as considerable antioxidant activity against DPPH with 69% inhibition at an IC₅₀ value of 43.38 µg/mL. AgNPs also exhibited a concentration-dependent effect on rice plants. Root and shoot length were found to be positively impacted at all concentrations, i.e., 12.5 µg/mL, 25 µg/mL, 50 µg/mL, and 100 µg/mL. Among these concentrations, the 50 µg/mL concentration of AgNPs was found to be most effective. The plant biomass decreased at higher AgNP exposure levels (i.e., 100 µg/mL), whereas 50 µg/mL caused a significant increase in plant biomass as compared to the control. This study provides an eco-friendly method for the synthesis of AgNPs which can be used for their antibacterial and antioxidant activities and also as growth promoters of crop plants.

Chemical Composition and Phytotoxic, Antibacterial and Antibiofilm Activity of the Essential Oils of Eucalyptus occidentalis, E. striaticalyx and E. stricklandii

The Eucalyptus genus (Myrtaceae) is characterized by a richness in essential oils (EO) with multiple biological activities. This study reports the chemical composition and the phytotoxic and antimicrobial activities of the EOs from Tunisian E.occidentalis, E.striaticalyx and E.stricklandii. The EOs were analyzed using GC/MS and their phytotoxicities were assessed against the germination and seedling growth of Sinapis arvensis, Trifolium campestre and Lolium rigidum. Antimicrobial activity was investigated against both Gram-negative (Pseudomonas aeruginosa, Escherichia coli and Acinetobacter baumannii) and Gram-positive (Staphylococcus aureus and Listeria monocytogenes) bacteria. The inhibition of biofilm formation and its metabolism was determined at different times. All EOs were rich in oxygenated monoterpenes (36.3-84.8%); the EO of E.occidentalis was rich in sesquiterpenes, both oxygenated and hydrocarbon (40.0% and 15.0%, respectively). Eucalyptol was the main constituent in all samples. The EOs showed phytotoxic activity on seed germination and seedling growth, depending both on chemical composition and weed. The EOs show a remarkable antibacterial potential resulting in a significant inhibition of the formation of bacterial biofilm and its metabolism, depending on the EO and the strain, with activity on the mature biofilm as well. Therefore, these Eucalyptus EOs could have potential applications both in the food and health fields.

Solanum linnaeanum Leaves: Chemical Profiling of VOCs and Effects on Seed Germination and Early Growth of Monocots and Dicots

Some Solanaceae plants are a rich source of sesquiterpenoid phytoalexins with allelopathic potential. Powder and aqueous extract obtained from the leaves of Solanum linnaeanum Hepper & P.M.L. Jaeger were used to treat the seeds of three target species (Lolium multiflorum Lam., Sinapis alba L. and Trifolium incarnatum L.). Both matrices were evaluated along with untreated controls to determine their toxicity on germination and seedling growth. The results revealed that the pre-emergence treatments were able to be very effective against all three species in the filter paper test by inhibiting the germination up to 100 %. The effectiveness was reduced by the interaction with soil. Despite this, significant data were obtained, albeit different according to the applied matrix. In general, L. multiflorum was the most sensitive to both the action of the leaf powder and aqueous extract while S. alba was found to be the most resistant to powder activity and T. incarnatum had the strongest response to the extract. For the first time, SPME-GC/MS technique was used to characterize the volatile chemical profile of S. linnaeanum leaves. The analyses highlighted the presence of different classes of compounds including terpenoids and sesquiterpenoids potentially useful in the fight against noxious plants both in natural and cultivated ecosystems.

Synthesis, Fungitoxic Activity against Botrytis cinerea and Phytotoxicity of Alkoxyclovanols and Alkoxyisocaryolanols

Clovane and isocaryolane derivatives have been proven to show several levels of activity against the phytopathogenic fungus Botrytis cinerea. Both classes of sesquiterpenes are reminiscent of biosynthetic intermediates of botrydial, a virulence factor of B. cinerea. Further development of both classes of antifungal agent requires exploration of the structure–activity relationships for the antifungal effects on B. cinerea and phytotoxic effects on a model crop. In this paper, we report on the preparation of a series of alkoxy-clovane and -isocaryolane derivatives, some of them described here for the first time (2b, 2d, 2f–2h, and 4c–4e); the evaluation of their antifungal properties against B. cinerea, and their phytotoxic activites on the germination of seeds and the growth of radicles and shoots of Lactuca sativa (lettuce). Both classes of compound show a correlation of antifungal activity with the nature of side chains, with the best activity against B. cinerea for 2d, 2h, 4c and 4d. In general terms, while 2-alkoxyclovan-9-ols (2a–2e) exert a general phytotoxic effect, this is not the case for 2-arylalkoxyclovan-9-ols (2f–2i) and 8-alkoxyisocaryolan-9-ols (4a–4d), where stimulating effects would make them suitable candidates for application to plants.

Chemical Composition, Antioxidant, Antimicrobial, and Phytotoxic Potential of Eucalyptus grandis × E. urophylla Leaves Essential Oils

Eucalyptus grandis × E. urophylla was a unique hybridization in China. However, the chemical and pharmacological properties were rarely reported. Therefore, in this work, we used a steam distillation method to obtain essential oils from leaves of E. grandis × E. urophylla, and further evaluated the antioxidant, antimicrobial, and phytotoxic potential of the essential oil. Gas chromatography mass spectrometry (GC-MS) was applied to investigate the chemical composition of E. grandis × E. urophylla essential oil (EEO) and the results showed that the main components of EEO were monoterpenes followed by sesquiterpenes. Among them, α-pinene accounted about 17.02%. EEO could also well scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2, 2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) free radicals showing a good free radical clearance ability. In addition, EEO efficiently inhibited the growth of six kinds of bacteria as well as seven kinds of plant pathogens, especially Salmonella typhimurium and Colletotrichum gloeosporioides. Moreover, the seedling germination of Raphanus sativus, Lactuca sativa, Lolium perenne, and Bidens pilosa was significantly suppressed by EEO, thus, indicating essential oils from eucalyptus possessed an excellent phytotoxic activity. This study may give a better understanding on EEO and provide a pharmacological activities analysis contributing to the further research of EEO as a functional drug in agronomic and cosmetic industries.

Laboratory and Field Evaluation of the Phytotoxic Activity of Sapindus mukorossi Gaertn Pulp Extract and Identification of a Phytotoxic Substance

Interest in finding plant-based herbicides to supplement synthesized herbicides is increasing. Although the extract of Sapindus mukorossi Gaertn has been reported to have herbicidal activity, little is known about phytotoxic substances and their efficacy of weed control in the field. To identify phytotoxic substances, the bioassay-guided fractionation by column chromatography and high-speed counter-current chromatography (HSCCC) was carried out. The phytotoxic activity assay, performed by the agar medium method, showed that the 70% ethanol fraction exhibited strong root growth inhibition against Trifolium pratense with an 50% inhibitory concentration (IC₅₀) value of 35.13 mg/L. An active compound was isolated from the 70% ethanol fraction and identified as hederagenin 3-o-β-D-xylopyranosyl-(1→3)-α-l-rhamnopyranosyl-(1→2)-α-l-arabinopyranoside (Compound A). Compound A had an IC₅₀ value of 16.64 mg/L. Finally, a new formulation was prepared based on the 70% ethanol fraction, which exhibited good efficacy against broadleaf weeds in a carrot field. The fresh weight control efficacy was 78.7% by 45 days after treatment at the dose of 1500 g a. i./ha. Hence, the extract of S. mukorossi pulp could be a promising supplement to the synthesized herbicides. Furthermore, compound A from S. mukorossi may be responsible for its phytotoxic activity.

Chemical Profile and Phytotoxic Action of Hibiscus trionum Essential Oil

The chemical profile and phytotoxic action of Hibiscus trionum essential oil (EO) was studied. In total 17 compounds were identified via GC/MS, representing 94.18 % of the entire oil, with phytol (40.37 %) being the dominant constituent. Bioassay revealed that the EO inhibited root elongation of Medicago sativa and Amaranthus retroflexus by 32.66 % and 61.86 % at 5 mg/mL, respectively; meanwhile, the major component phytol also exhibited significant phytotoxic activity, suppressing radical elongation of Pennisetum alopecuroides, M. sativa and A. retroflexus by 26.08 %, 27.55 % and 43.96 % at 1 mg/mL, respectively. The fact that the EO showed weaker activity than phytol implied that some constituents might trigger antagonistic action to decrease the oil's activity. Our study is the first on the chemical profile and phytotoxic effect of H. trionum EO.

Chemical composition and phytotoxic activity of the essential oil of Artemisia sieversiana growing in Xinjiang, China

The chemical profile and phytotoxic activity of the essential oil extracted from Artemisia sieversiana was investigated. In total 17 compounds were identified by GC/MS, representing 99.17% of the entire oil, among which α-thujone (64.46%) and eucalyptol (10.15%) were the most abundant constituents. The major components, their mixture as well as the essential oil exhibited significant phytotoxic activity against Amaranthus retroflexus, Medicago sativa, Poa annua and Pennisetum alopecuroides, with their IC₅₀ values ranged from 1.55 ∼ 6.21 mg/mL (α-thujone), 1.42 ∼ 17.81 mg/mL (eucalyptol), 0.23 ∼ 1.05 mg/mL (the mixture), and 1.89 ∼ 4.69 mg/mL (the essential oil) on the four tested species. The mixture of the major constituents exerted more potent effect compared with each individual compound, indicating the possible involvement of synergistic effect of these two compounds.

Chemical Composition and Biological Activities of the Essential Oils of Leptospermum petersonii and Eucalyptus gunnii

The aim of this study was to characterize the chemical composition and to evaluate the antimicrobial and phytotoxic properties of the essential oils (EOs) obtained from leaves of Leptospermum petersonii chemotype "Variety B" and Eucalyptus gunnii, native to Australia. Geranyl acetate, γ-terpinene, geraniol, terpinolene, α-pinene, p-cimene, and linalool were the main components in L. petersonii EO, confirming also the existence of several chemotypes in such taxa; on the other hand, 1,8-cineole, trans-sabinene hydrate acetate, globulol, longicyclene, terpinolene, and camphene were present in major amounts in the E. gunnii EO. Chemical analysis of L. petersonii revealed that it belongs to the variety "B." E. gunnii EO showed good antibacterial activity, with an MIC of 0.5 and 2 μg/mL against Staphylococcus aureus, and Pectobacterium carotovorum, respectively. The activity of E. gunnii EO was stronger than L. petersonii EO, whose maximum MIC reached 5 μg/mL. E. gunnii and L. petersonii EOs were particularly effective in inhibiting the biofilm formation by S. aureus, already at a concentration of 0.01 μg/mL. The other strains were resistant to both EOs up to a dose of 0.05 μg/mL. The maximum inhibition on biofilm formed by P. carotovorum was recorded for E. gunnii EO, reaching a value of 93.12% at 1.0 μg/mL. This is the first manuscript which studies the biofilm inhibition by EOs and evaluates their effects on biofilm metabolism. Both EOs were more effective against P. carotovorum. In addition, even though L. petersonii EO 0.1 μg/mL was unable to inhibit biofilm formation by Escherichia coli, it decreased the metabolic activity of the biofilm to 78.55% compared to control; furthermore, despite it inducing a relatively low inhibition (66.67%) on biofilm formation, it markedly affected metabolic activity, which decreased to 16.09% with respect to the control. On the contrary, L. petersonii EO 0.5 μg/mL induced a 79.88% inhibition of S. aureus biofilm, maintaining a high metabolic activity (90.89%) compared to the control. Moreover, this EO showed inhibitory activity against radical elongation of Solanum lycopersicum and the germination of radish. On the contrary, E. gunnii EO showed no phytotoxic activity.

Phytochemical profile of fennel essential oils and possible applications for natural antioxidant and controlling Convolvulus arvensis L

The natural compounds such as essential oils are getting more attention due to their potential usage in pharmaceuticals and possibly as natural herbicides. This study was conducted to identify the chemical compositions of essential oils from Foeniculum vulgare Mill. populations collected from different regions of Iran, Turkey, and Germany, and their antioxidant (DPPH·, ABTS·⁺ and reducing power methods) and phytotoxic activity (against Convolvulus arvensis L.). The results exhibited a significant variation in essential oils content (1.74-2.97%). The main compounds in essential oils were trans-anethole (15.23%-90.11%), estragole (4.00-63.72%), fenchone (0.03-12.62%) and limonene (1.05-13.04%). The results revealed that the essential oils have considerable antioxidant (IC₅₀ values in the range of 11.83-36.90 mg mL^-1 in DPPH, 7.65-20.13 mg mL^-1 in ABTS^·+ and EC₅₀ values in the range of 3.65-15.24 mg mL^-1 in reducing power assay) and phytotoxic activity. The results of this study can help in the development of natural antioxidants and herbicides.

Potential Role of Lolium multiflorum Lam. in the Management of Rice Weeds

The phytotoxic relationships between crops and weeds can cover a role in weed management, reducing the use of chemical herbicides. Starting from the organic farmers’ experience, the study aimed to define the inhibitory action of Lolium multiflorum Lam., used as a cover crop before rice sowing, against Echinochloa oryzoides (Ard.) Fritsch, one of the main rice weeds. In vitro 7-day assays were carried out in Petri dishes to compare the effect of different L. multiflorum Lam. parts, in the form of aqueous extract or powder, on the seed germination and seedling growth of Oryza sativa L. and E. oryzoides and to verify the hypothesis of a higher susceptibility of the weed. The total polyphenolic content, as the potential source of allelochemicals, in the L. multiflorum parts was measured. The results showed that both species suffer the phytotoxic action of L. multiflorum, but a more marked effect against E. oryzoides was recorded. In according with the polyphenol quantities, stem and inflorescence extracts showed the more significant species-specific inhibition. In all assays, the weed showed a stronger reduction in the root length and seedling vigor index, and, in some cases, also in the germination percentage and shoot length compared to rice.

Herbicidal Secondary Metabolites from Actinomycetes: Structure Diversity, Modes of Action, and Their Roles in the Development of Herbicides

Weeds had caused significant loss for crop production in the process of agriculture. Herbicides have played an important role in securing crop production. However, the high reliance on herbicides has led to environmental issues as well as the evolution of herbicide resistance. Thus, there is an urgent need for new herbicides with safer toxicological profiles and novel modes of action. Actinomycetes produce very diverse bioactive compounds, of which some show potent biopesticidal activity. The herbicidal secondary metabolites from actinomycetes can be classified into several groups, such as amino acids, peptides, nucleosides, macrolides, lactones, amide, amines, etc., some of which have been successfully developed as commercial herbicides. The structure diversity and evolved biological activity of secondary metabolites from actinomycetes can offer opportunities for the development of both directly used bioherbicides and synthetic herbicides with new target sites, and thus, this review focuses on the structure, herbicidal activity, and modes of action of secondary metabolites from actinomycetes.

Chemical Composition, Phytotoxic, Antimicrobial and Insecticidal Activity of the Essential Oils of Dracocephalum integrifolium

The present investigation studied the chemical composition of the essential oils extracted from Dracocephalum integrifolium Bunge growing in three different localities in northwest China and evaluated the phytotoxic, antimicrobial and insecticidal activities of the essential oils as well as their major constituents, i.e., sabinene and eucalyptol. GC/MS analysis revealed the presence of 21-24 compounds in the essential oils, representing 94.17-97.71% of the entire oils. Monoterpenes were the most abundant substances, accounting for 85.30-93.61% of the oils; among them, sabinene (7.35-14.0%) and eucalyptol (53.56-76.11%) were dominant in all three oils, which occupied 67.56-83.46% of the total oils. In general, phytotoxic bioassays indicated that the IC₅₀ values of the oils and their major constituents were below 2 μL/mL (1.739-1.886 mg/mL) against Amaranthus retroflexus and Poa annua. Disc diffusion method demonstrated that the oils and their major constituents possessed antimicrobial activity against Bacillus subtilis, Pseudomonas aeruginosa, Escherichia coli, Saccharomyces cerevisiae, and Candida albicans, with MIC values ranging from 5-40 μL/mL (4.347-37.712 mg/mL). The oils, sabinene and eucalyptol also exhibited significant pesticidal activity, with the mortality rates of Aphis pomi reaching 100% after exposing to 10 μL oil/petri dish (8.694-9.428 mg/petri dish) for 24 h. To the best of our knowledge, this is the first report on the chemical composition, phytotoxic, antimicrobial and insecticidal activity of the essential oils extracted from D. integrifolium; it is noteworthy to mention that this is also the first report on the phytotoxicity of one of the major constituents, sabinene. Our results imply that D. integrifolium oils and sabinene have the potential value of being further exploited as natural pesticides.

Residues of xenobiotics in the environment and phytotoxic activity in Armenia

The article presents the results of a dynamic study (spring, summer, and fall) of the residues of certain xenobiotics such as organochlorine pesticides (OCPs), synthetic surfactants (SSs) in surface water, soil, sludge, snow and phytotoxic activity in Ararat and Lori marzes of Armenia (2016-2017). A comparative analysis of the environmental status showed that all pollutants studied such as γ-hexachlorocyclohexane (γ-HCH), 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (4,4'-DDT), and p-p'-dichlorodiphenyldichloroethylene (4,4'-DDE) were identified in Ararat marz with the average concentrations and detection rates higher than in Lori marz. The prominent contaminant was γ-HCH. The findings indicated the concentrations of OCPs below of regulatory concern. In Ararat marz an increase in the number of sterile pollen grains of certain wild plants was revealed (14.8-26.0%), compared with Lori marz with the levels within the contingent standard of 5-11%. The phytotoxic activity of soil samples from the Ararat marz studied on Avena sativa seedlings was significantly higher in the summer-fall period. These data correlated with monitoring findings showed an increase in the levels of γ-HCH, 4,4'-DDT, SS in the soil and sludge sampled in summer-fall in Ararat marz. This difference in the environmental status can be considered as the result of active agriculture in Ararat marz, whose share of contribution to a relevant branch of the economy of Armenia is two times higher than in Lori marz, 15.4% and 7.9%, respectively. Mentioned rates of agricultural production may be one of the reasons for the environmental deterioration in Ararat marz. The detection of 4,4-DDT, γ-HCH residues testifies the circulation of these formulations in the environment indicating their use in recent past and confirming their persistence. Although since the 70s of the last century the application of OCPs in the Republic of Armenia has been prohibited. The current situation may be explained by low awareness of farmers on different issues related to the safe management of pesticides. To ensure safe working conditions and raise awareness among the farmers we have developed "Recommendations on Safety requirements when working with pesticides" that are approved by the State Service for Food Safety at the Ministry of Agriculture of RA and included in the reference booklets for farmers as guiding information. Our study shows the understanding of associations between the deterioration of the environmental status and share of agriculture contribution to the economy that provides the evidence for future research programs.

Phytotoxic and nematicide evaluation of Croton ehrenbergii (Euphorbiaceae)

BACKGROUND

Within its natural habitat, Croton ehrenbergii exhibits an innate defense mechanism that is not seen in other plants; it grows unharmed amidst predators and nature, while other species perish. In light of its capacity for defense, C. ehrenbergii was evaluated to better understand the scope of its phytotoxic and nematicide properties. To assess this, fractions obtained by bipartition of a hydro-alcoholic extract, and l-quebrachitol, the main constituent of C. ehrenbergii, were evaluated on Lactuca sativa (dicotyledon) and Lolium perenne (monocotyledon) seeds. Additionally, bipartition fractions and l-quebrachitol were evaluated on a population of Meloidogyne incognita for their nematicide activity.

RESULTS

From this phytochemical research, l-quebrachitol (1), phenylalanine (2), trans-4-hydroxy-N-methylproline (3) and the flavonoids: kaempferol (4), tiliroside (5), nicotiflorine (6) and rutin (7) were identified by spectroscopic analysis. Both methanol and hexane fractions from aerial parts of the plant inhibited the germination and elongation of roots and stems in L. sativa, but not in Lolium perenne, showing that these fractions mostly inhibit the dicotyledon species used in this research. l-Quebrachitol showed slightly higher seed germination inhibition for Lolium perenne in comparison with L. sativa. Three of the fractions evaluated showed nematicide activity against Meloidogyne incognita larvae (J2) at the 48 h benchmark, compared with carbofuran. l-Quebrachitol shows higher mortality after 48 h exposure at a lower concentration than carbofuran.

CONCLUSION

A variety of compounds were isolated from this research, some were common within the Croton genus (4-7), whereas others were not (1-3). This is the first phytochemical, phytotoxic and nematicide report on C. ehrenbergii. Methanol and hexane fractions from the aerial parts of C. ehrenbergii and l-quebrachitol could be used as alternative natural herbicides, predominantly against dicotyledon weed seeds. All fractions had a good mortality percentage against J2 Meloidogyne incognita larvae. © 2019 Society of Chemical Industry.

majorana Essential Oils Growing in Cilento (Southern Italy)

There is a growing interest in a potential use of essential oils (EOs) as a replacement for traditional pesticides and herbicides. The aims of this study were to: (i) Identify the chemical composition of the two EOs derived from Origanum heracleoticum L. and O. majorana L., (ii) evaluate the in vitro antifungal activity of the EOs against some postharvest phytopathogens (Botrytis cinerea, Penicillium expansum, Aspergillus niger and Monilinia fructicola), (iii) evaluate the in vitro antibacterial activity against Bacillus megaterium, Clavibacter michiganensis, Xanthomonas campestris, Pseudomonas fluorescens and P. syringae pv. phaseolicola, (iv) evaluate the effect of both studied EOs on the spore germination percentage and their minimum inhibitory concentration (MIC) against M. fructicola, and (v) study the possible phytotoxicity of the two EOs and their major constituents, carvacrol for O. heracleoticum and terpinen-4-ol for O. majorana, against tha germination and initial radicle growth of radish, lettuce, garden cress and tomato. The two EOs demonstrated promising in vitro antimicrobial and antifungal activities against all tested microorganisms. EOs showed high inhibition of spore germination percentage at the minimal inhibitory concentration of 500 and 2000 µg/mL, respectively. Moreover, both germination and radical elongation of selected plant species were sensitive to the oils.

Sorbicillinoids From the Fungus Ustilaginoidea virens and Their Phytotoxic, Cytotoxic, and Antimicrobial Activities

Ustilaginoidea virens, the causal fungus of rice false smut, was found in previous studies to produce two types of metabolites, ustiloxins and ustilaginoidins. However, genome sequencing of U. virens revealed a plethora of secondary-metabolites-biosynthetic core genes that were capable to biosynthesize unreported metabolites. A large-scale fermentation of U. virens was thus performed, and the fungal extract was chemically re-investigated. After removing the known metabolites, we found a fraction containing unknown phytotoxic substances. Fractionation of this part has led to the isolation of six new sorbicillinoids, namely ustisorbicillinols A~F (1~6), and two new sorbicillinoid-related pyrones, named ustilopyrones A (7) and B (8), together with nine known cogeners (9~17). The structures of the new compounds were elucidated by analysis of their NMR, HRMS, and CD spectra, while ECD, ¹³C NMR and optical rotation calculations were additionally used for configurational assignments. Plausible biosynthetic pathways for the new compounds were proposed. Phytotoxicity assays revealed that the major sorbicillinoids (12~14, and 16) showed strong inhibition against the radicle and germ elongation of rice and lettuce seeds, with compound 12 displaying the strongest inhibition. The isolated compounds were also evaluated for their cytotoxic, antibacterial, and antifungal activities. Compounds 10, and 12~14 showed moderate cytotoxicities against the tested cell lines with IC₅₀s of 8.83~74.7 μM. Compounds 2, and 10~13 were active against the tested bacteria (MICs 4~128 μg/mL), while compounds 11~13 displayed moderate antifungal activities.

New nitrogen-containing metabolites from cultures of rice false smut pathogen Villosiclava virens

Two new nitrogen-containing metabolites methyl N-acetyl-O-(4-acetylphenyl)-L-homoserinate (1), dimethyl (1H-indole-3-carbonyl)-D-glutamate (2), and two new natural products, 1,2-O-isopropylidene-D-mannitol (3), N-acetyl-β-methyl-L-phenylalanine (4), along with five known compounds (5-9) were isolated from the rice false smut pathogen Villosiclava virens UV-8b cultured in the solid rice medium. The structures were elucidated by spectroscopic analysis and by comparison of their physical and spectroscopic data with the literature. These metabolites were evaluated for their antibacterial and phytotoxic activities. Compounds 5-7 showed weak inhibition against the tested bacteria, while compounds 4-6 and 9 displayed inhibitory activity against the radicle elongation of rice seeds.

Chemical Composition and Allelopathic, Phytotoxic and Pesticidal Activities of Atriplex cana Ledeb. (Amaranthaceae) Essential Oil

The chemical composition and allelopathic, phytotoxic and pesticidal activities of Atriplex cana Ledeb. (Amaranthaceae) essential oil were investigated. Nineteen compounds were identified via GC/MS, representing 82.3 % of the total oil, and the most abundant constituents were dibutyl phthalate (21.79 %), eucalyptol (20.14 %) and myrtenyl acetate (15.56 %). The results showed that volatile organic compounds (VOCs) released by A. cana significantly inhibited seedling growth of Amaranthus retroflexus L. and Poa annua L., and 80 g of fresh stems and leaves of A. cana in a 1.5 L airtight container almost completely suppressed the seed germination of both plants. Meanwhile, 5 μg/mL essential oil completely inhibited the seed germination of A. retroflexus, Medicago sativa L., P. annua and Echinochloa crusgalli L. Pesticidal testing revealed that the essential oil had strong behavioral avoidance and lethal effects on Aphis pomi DeGeer. Five microliters of essential oil/Petri dish treatment resulted in an 84.5 % mortality rate after 12 h, and the mortality rate reached nearly 100 % after 48 h. This report is the first one on the chemical composition as well as the biological activity of the essential oil of A. cana, and our results indicate that the oil is valuable in terms of being further exploited as a bioherbicide/insecticide.

Chemical Composition and Phytotoxic Activity of Seriphidium terrae-albae (Krasch.) Poljakov (Compositae) Essential Oil

To evaluate the potential value of Seriphidium terrae-albae (Krasch.) Poljakov essential oil as bioherbicide, its chemical composition as well as phytotoxic activity was investigated. Seventeen compounds were identified via GC/MS, representing 98.1 % of the total oil, and the most abundant constituents were α-thujone (43.18 %), β-thujone (16.92 %), eucalyptol (17.55 %), and camphor (13.88 %). Phytotoxic assay revealed that the essential oil as well as its major constituents exhibited inhibitory activity on root and shoot growth of receiver plants in a dose-dependent manner. When the concentration reached 20 μg/mL, root length of Amaranthus retroflexus was reduced to 31.3 %, 70.6 %, 36.9 %, and 66.6 % of the control, respectively, when treated with α-thujone, eucalyptol, camphor, and the mixture of these compounds; meanwhile, root length of Poa annua was 3.0 %, 24.2 %, 0 %, and 4.4 % of the control when the same chemicals were applied. On the other hand, the essential oil showed a much stronger activity. At 1.5 μL/mL, root and shoot length of A. retroflexus and P. annua were reduced to 0.65 %, 0.5 %, and 1.53 %, 1.51 % of the control, respectively, and seed germination of A. retroflexus and P. annua was completely inhibited when the oil concentration reached 3 μg/mL and 5 μg/mL, respectively. This is the first report on the chemical composition of the essential oil of S. terrae-albae, and our results indicated that it has the potential to be further exploited as a bioherbicide.

Effects of Substituents on the Aromatic Ring of Lignano-9,9'-lactone on Plant Growth Inhibitory Activity

The relationship between the structure of lignano-9,9'-lactone (2,3-dibenzylbutyrolactone) and its activity as a plant growth regulator has been clarified. Derivatives with higher plant growth inhibitory activity than natural dimethylmatairesinol 4 were synthesized. The 2-hydroxy-7- Z-ene derivative 42 displayed growth inhibitory activity against both the shoots (IC50 = 0.65 mM) and roots (IC50 = 0.43 mM) of lettuce seedlings. Regiospecific activity was observed. The 2,3-dihydroxy derivative 24 showed the highest growth inhibitory activity against both the shoots (IC50 = 0.36 mM) and roots (IC50 = 0.13 mM) of Italian ryegrass seedlings. A similar level of activity to 24 against just the roots of Italian ryegrass seedlings was maintained when the hydroxy group at position 3 of the 2,3-dihydroxy derivative 24 was replaced by a fluorine atom. The (2-hydroxy,4-fluoro)-derivative 33 also showed growth inhibitory activity against both the shoots (IC50 = 0.79 mM) and roots (IC50 = 0.14 mM) of Italian ryegrass seedlings. The level of activity was found to depend on the positions of the two hydroxy groups or the hydroxy group and fluorine atom on the aromatic ring. The importance of the lignano-9,9'-lactone structure was also shown.

Phytotoxic and Antifungal Metabolites from Curvularia crepinii QTYC-1 Isolated from the Gut of Pantala flavescens

Four metabolites (1–4), including a new macrolide, O-demethylated-zeaenol (2), and three known compounds, zeaenol (1), adenosine (3), and ergosta-5,7,22-trien-3b-ol (4) were isolated and purified from Curvularia crepinii QTYC-1, a fungus residing in the gut of Pantala flavescens. The structures of isolated compounds were identified on the basis of extensive spectroscopic analysis and by comparison of the corresponding data with those reported in the literature previously. The new compound 2 showed good phytotoxic activity against Echinochloa crusgalli with an IC₅₀ value of less than 5 µg/mL, which was comparable to that of positive 2,4-dichlorophenoxyacetic acid (2,4-D). Compound 1 exhibited moderate herbicidal activity against E. crusgalli with an IC₅₀ value of 28.8 μg/mL. Furthermore, the new metabolite 2 was found to possess moderate antifungal activity against Valsa mali at the concentration of 100 µg/mL, with the inhibition rate of 50%. These results suggest that the new macrolide 2 and the known compound 1 have potential to be used as biocontrol agents in agriculture.

Daurichromenic acid and grifolic acid: Phytotoxic meroterpenoids that induce cell death in cell culture of their producer Rhododendron dauricum

Daurichromenic acid (DCA) is a meroterpenoid with anti-HIV activities that is isolated from Rhododendron dauricum L. We recently reported that DCA is biosynthesized and accumulated in the apoplast of glandular scales attached on the surface of young leaves of R. dauricum. In the present study, we confirmed that a cell suspension culture of R. dauricum could not produce DCA and its precursor grifolic acid even after elicitation with methyl jasmonate and β-cyclodextrin. In addition, exogenous supplementation of DCA and grifolic acid effectively induced cell death in the same culture, with apoptosis-associated phenomena such as cytoplasmic shrinkage, chromatin condensation, and genomic DNA degradation. These findings suggested that DCA and grifolic acid are phytotoxic metabolites that have to be sequestered in the apoplast to avoid self-poisoning.

Cytotoxic, Phytotoxic and Insecticidal Activities of Chrysophthalmum montanum (DC.) Boiss

OBJECTIVES

To investigate the in vitro cytotoxic, phytotoxic, and insecticidal activity of Chrysophthalmum montanum (DC.) Boiss.

MATERIALS AND METHODS

The crude methanol (80%) extract of the aerial parts of C. montanum was fractionated to obtain n-hexane, chloroform, n-butanol, and remaining water fractions. The crude extract and subsequent solvent fractions of the plant were evaluated for their biological activities using screening bioassays such as cytotoxicity on brine shrimp lethality, phytotoxicity against Lemna minor L., and insecticidal activity against Rhyzopertha dominica and Tribolium castaneum.

RESULTS

The cytotoxicity assay revealed that the crude extract, n-hexane, and chloroform fractions of the plant had positive lethality with LD50 values of 71.51, 126.62, and 75.95 µg/mL, respectively. The extract and its fractions, except for the remaining water fraction, showed phytotoxic activity, which was expressed as percentage growth regulation in a concentration-dependent manner. n-hexane and chloroform fractions in particular had 100% growth inhibition (GI) at 1000 μg/mL, followed by the n-butanol fraction (62.6% GI) and crude extract (40.0% GI) of the plant at the same concentration. Otherwise, all samples had no insecticidal activity against R. dominica and T. castaneum.

CONCLUSION

This study demonstrates that C. montanum contains bioactive compounds related to potential biological activities such as cytotoxic and phytotoxic.

Cytotoxic Activity of Origanum Vulgare L. on Hepatocellular Carcinoma cell Line HepG2 and Evaluation of its Biological Activity

The potential of plant essential oils (EOs) in anticancer treatment has recently received many research efforts to overcome the development of multidrug resistance and their negative side effects. The aims of the current research are to study (i) the cytotoxic effect of the crude EO extracted from Origanum vulgare subsp hirtum and its main constituents (carvacrol, thymol, citral and limonene) on hepatocarcinoma HepG2 and healthy human renal cells HEK293; (ii) the antibacterial and phytotoxic activities of the above EO and its main constituents. Results showed that cell viability percentage of treated HepG2 by EO and its main constituents was significantly decreased when compared to untreated cells. The calculated inhibition concentration (IC₅₀) values for HepG2 were lower than healthy renal cells, indicating the sort of selectivity of the studied substances. Citral is not potentially recommended as an anticancer therapeutic agent, since there are no significant differences between IC₅₀ values against both tested cell lines. Results showed also that oregano EO and its main constituents have a significant antibacterial activity and a moderate phytotoxic effect. The current research verified that oregano EO and its main constituents could be potentially utilized as anticancer therapeutic agents.

New Ustilaginoidins from Rice False Smut Balls Caused by Villosiclava virens and Their Phytotoxic and Cytotoxic Activities

Ustilaginoidins are a class of bis-naphtho-γ-pyrones, typically produced by Villosiclava virens, the pathogen of the rice false smut (RFS), which has been one of the most destructive rice fungal diseases. Previously, we found that ustilaginoidins identified from the culture of V. virens on rice medium were less polar than those reported from the RFS balls in general. In this study, we reinvestigated the high-performance liquid chromatography with diode array detection and high-resolution mass spectrometry (HPLC-DAD-HRMS) profile of the ethyl acetate (EtOAc) extract of the RFS balls and found several interesting peaks that correspond to new ustilaginoidins. As a result, eight new and polar congeners, named ustilaginoidins Q-T (1-4), 2,3-dihydroustilaginoidin T (5), and ustilaginoidins U-W (6-8), were isolated. In addition, 17 known ustilaginoidins, including ustilaginoidins K-N (9-12), ustilaginoidin P (13), ustilaginoidin E₁ (14), isochaetochromin B₂ (15), and ustilaginoidins A-J (16-25), were re-isolated. The structures of the new compounds were elucidated by comprehensive analysis of the spectroscopic data. Ustilaginoidins Q (1) and R (2) feature an uncommon 2-hydroxypropyl-substituted skeleton and biogenetically incorporate one more acetate unit than common ustilaginoidins. Ustilaginoidin W (8) is a rare formate-containing bis-naphtho-γ-pyrone. Ustilaginoidins R (2), U (6), B (17), and I (24) showed moderate inhibitory activities toward the radicle or germ elongation of rice seeds. Ustilaginoidins R (2), S (3), V (7), W (8), B (17), C (18), and H-J (23-25) were cytotoxic to the tested human cancer cell lines (HCT116, NCI-H1650, BGC823, Daoy, and HepG2), with IC₅₀ values in the range of 4.06-44.1 μM.

Phytotoxic and antimicrobial activity of volatile and semi-volatile organic compounds from the endophyte Hypoxylon anthochroum strain Blaci isolated from Bursera lancifolia (Burseraceae)

AIMS

To evaluate the phytotoxic, antifungal and antioomycete activity; and, determine the chemical composition of the volatile organic compounds (VOCs) and semi-volatile metabolites produced by the endophyte Hypoxylon anthochroum strain Blaci isolated from Bursera lancifolia.

METHODS AND RESULTS

Based on its macro- and micro-morphological features, the strain Blaci was identified as Nodulisporium sp.; partial analysis of its ITS1-5.8-ITS2 ribosomal gene sequence revealed the identity of the teleomorphic stage of the fungus as H. anthochroum. Phytotoxic and antimicrobial activities of VOCs, and culture medium and mycelium organic extracts from H. anthochroum Blaci were determined by simple and multiple antagonism bioassays, and gas phase and agar dilution bioassays respectively. The volatile and semi-volatile metabolites were identified by gas chromatography-mass spectrometry. VOCs from a 5-day H. anthochroum strain Blaci culture caused the inhibition of seed germination, root elongation and seedling respiration on Amaranthus hypochondriacus, Panicum miliaceum, Trifolium pratense and Medicago sativa. In addition, extracts, phenylethyl alcohol and eucalyptol main compounds present in the VOCs and extract displayed a high phytotoxic activity, inhibiting the three physiological processes on the four test plants in a concentration-dependent manner.

CONCLUSIONS

The results revealed that H. anthochroum strain Blaci produces a mixture of VOCs. These VOCs showed a strong phytotoxic activity on seed germination, root elongation, and seedling respiration of four plants and slightly affected the growth of phytopathogenic fungi and oomycetes. Also, the culture medium and mycelium extracts of H. anthochroum showed a high phytotoxic activity on the four test plants and, generally, the culture medium extract was more phytotoxic than the mycelium extracts.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work firstly reports the phytotoxic activity of volatile and semi-volatile compounds produced by the endophyte H. anthochroum strain Blaci on seed germination, root elongation, and seedling respiration of four different plants; consequently, these compounds could be useful in biocontrol of weeds and plant pathogens.

(Lamiaceae) Exerts Phytotoxic Activity in Vitro against Various Weed Seed

The chemical composition of the essential oil of the flowering aerial parts of Monarda didyma L. cultivated in central Italy was analyzed by Gas Chromatography/Mass Spectrometry (GC/MS). The major compounds of the oil were thymol (59.3%), p-cymene (10.3%), terpinolene (9.2%), δ-3-carene (4.4%), myrcene (3.7%), and camphene (3.4%). The essential oil was tested in vitro for its anti-germination activity against Papaver rhoeas L., Taraxacum officinale F. H. Wigg., Avena fatua L., Raphanus sativus L. and Lepidium sativum L. seeds, demonstrating good inhibitory activity in a dose-dependent way. The exposure of the employed weed seeds to M. didyma essential oil and thymol solution (59.3%) increased the level of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA), markers of oxidative stress, in emerging 5-day-old rootlets.

Chemical Composition, Antibacterial and Phytotoxic Activities of Peganum harmala Seed Essential Oils from Five Different Localities in Northern Africa

Peganum harmala L., also known as Syrian rue or Pègano, is a herbaceous plant belonging to the Zygohpyllaceae family, and is widely used in traditional medicine. The chemical composition of essential oils of P. harmala seeds from five different regions of Northern Africa (Algeria, Egypt, Libya, Morocco and Tunisia) was studied by GC and GC-MS analyses. A total of 105 compounds were identified, the main components being oxygenated monoterpenes and oxygenated sesquiterpenes. Eugenol is the main component in all oils. The antimicrobial activity of the essential oils was assayed against some bacterial strains: Staphylococcus aureus (DSM 25693), Bacillus cereus (DSM 4313), Bacillus cereus (DSM4384), Escherichia coli (DMS 857) and Pseudomonas aeruginosa (ATCC 50071). All the oils showed different inhibitory activity. In the twentieth century this is an important result; we need possible new botanical drugs because the problem of resistance to antimicrobial drugs has become apparent. Moreover, the essential oils were evaluated for their possible in vitro phytotoxic activity against germination and initial radicle growth of Raphanus sativus L., Lepidium sativum L., and Ruta graveolens L. The results showed that both germination and radical elongation were sensitive to the oils.

Nigrosporins A and B, New Phytotoxic and Antibacterial Metabolites Produced by a Fungus Nigrospora oryzae

Nigrosporin A and B, two new phytotoxic and antibacterial metabolites were isolated from a culture filtrate of Nigrospora oryzae. The active principles were absorbed on XAD-2 resin and purified by successive ODS-HPLC. The structures were identified by spectroscopic and derivatization analysis as naphthoquinone derivatives. The substances showed phytotoxic activities, such as root elongation inhibition, necrotic effects, oxygen evolution inhibition, starch synthesis inhibition, and CO2 fixation inhibition at concentrations of 10-100 ppm. They also showed growth inhibition activity against Bacillus subtilis in a disc diffusion assay as well as when compared with streptomycin.

Phytotoxic Terpenoids from Ligularia cymbulifera Roots

Ligularia cymbulifera is one of the predominant species in the Hengduan Mountains, China, and has led to a decrease in the amount of forage grass in this area. However, little is known about the mechanism behind its predominance. In this study, two novel eremophilane sesquiterpenes, ligulacymirin A and B (1 and 2), together with seven other known terpenoids (3-9), were isolated from the roots of L. cymbulifera. The structures of 1 and 2 were determined by spectroscopic methods and single-crystal X-ray diffraction. Each compound showed phytotoxic activities against Arabidopsis thaliana, and each was detected and identified in rhizosphere soil by UHPLC-MS. Compound 3 was the most potent phytotoxin, showing remarkable inhibition against both seedling growth (EC₅₀ = 30.33 ± 0.94 μg/mL) and seed germination (EC₅₀ = 155.13 ± 0.52 μg/mL), with an average content in rhizosphere soil of 3.44 μg/g. These results indicate that terpenoids in L. cymbulifera roots might be released as phytotoxins in rhizosphere soil to interfere with neighboring plants.

Capitate glandular trichomes of Paragutzlaffia henryi harbor new phytotoxic labdane diterpenoids

The morphology and chemical profile of the capitate glandular trichomes (CGTs) of Paragutzlaffia henryi (Acanthaceae) were investigated. Four new labdane diterpenoids named paraguhenryisins A-D (1-4), together with the known physacoztomatin (5), were localized to the CGTs using laser microdissection coupled with cryogenic (1)H NMR and HPLC analyses and were traced and isolated from the CGT extract of inflorescences. Their structures were determined by spectroscopic methods and single-crystal X-ray diffraction. Bioassays indicated significant inhibitory effect for these diterpenoids on Arabidopsis thaliana seed germination and seedling root elongation. The most potent inhibitor, paraguhenryisin C (3), was interestingly detected in both the rhizosphere soil and water rinsed inflorescences extract of P. henryi but not the roots, with average contents in the rhizosphere soil relevant to its phytotoxic EC50 values. These results suggested that phytotoxic labdane diterpenoids in the CGTs might be released into the environment as a defensive measure for P. henryi against other competitive plants.

Phytotoxic and antibacterial metabolites from Fusarium proliferatum ZS07 isolated from the gut of long-horned grasshoppers

In the proceeding of screening new bioactive natural products, the ethyl acetate extract of the fermentation broth of Fusarium proliferatum ZS07, a fungus residing in the gut of long-horned grasshoppers (Tettigonia chinensis), was found possessing selective phytotoxic activity against the radicle growth of Amaranthus retroflexus L. Bioactivity-guided fractionation lead to the isolation of six fungal metabolites 1-6, including a new polyketide derivate O-methylated SMA93 (2) and five known compounds SMA93 (1), rhodolamprometrin (3), radicinin (4), dehydroallogibberic acid (5), and 3-methyl-6,8-dihydroxyisocoumarin (6). Their structures were identified on the basis of spectroscopic analysis and by comparison of the corresponding data to those reported in the literature previously. Phytotoxic effects of the four isolated compounds 1-4 on the radicle growth of A. retroflexus L. seeds were investigated under laboratory conditions, and compounds 2 and 4 showed good phytotoxic activity in the concentration of 100 μg/mL, with the inhibition rates of 83.0 and 65.2%, respectively. Furthermore, the antibacterial activity of compounds 1-5 were evaluated against selected bacteria. Compounds 1-3 were found to possess potent antibacterial activity against Bacillus subtilis (ATCC 6633), with the minimum inhibitory concentration (MIC) values of 3.13-12.50 μg/mL, while Escherichia coli (ATCC 8739) and Salmonella typhimurium [CMCC(B) 50115] were not susceptible. These results suggest that the new polyketide derivate 2 and known compounds 1, 3, and 4 have potential to be used as biocontrol agents in agriculture.

Selective phytotoxic activity of 2,3,11β,13-tetrahydroaromaticin and ilicic acid isolated from Inula graveolens

Inula graveolens is a poisonous annual plant of Mediterranean origin. The invasive nature of the plant suggests that it may possess phytotoxic activity. The aim of this study was to assess the ability of I. graveolens to inhibit the growth of different plants in Petri dish and to identify the main bioactive compounds. Bio-guided fractionation of the plant extracts led to the isolation of 2,3,11β,13-tetrahydroaromaticin (THA) and ilicic acid. Both compounds showed selective and significant phytotoxic activity at 25 ppm. Root length of barley, oat, millet, tuberous canary grass and lentils were significantly reduced by 25 ppm of THA, while the root of cauliflower, cress and radish were similarly reduced by ilicic acid at 25 ppm. The structure of each compound was elucidated by using NMR and HR-MS. X-ray crystallography of THA is reported for the first time to confirm the relative stereochemistry of the compound.

Antifungal, phytotoxic and toxic metabolites produced by Penicillium purpurogenum

Nine known metabolites, 6,8,1'-tri-O-methyl averantin (1), 6,8-di-O-methyl averufnin (2), 6,8-di-O-methyl averufanin (3), aversin (4), 1,3-dihydroxy-6,8-dimethoxy-9,10-anthraquinone (5), 6,8-di-O-methylnidurufin (6), 6,8-di-O-methyl versiconol (7), 5-methyoxysterigmatocystin (8) and (S)-ornidazole (9), were isolated from the extracts of Penicillium purpurogenum, and their structures were elucidated by using spectroscopic methods. The brine shrimp toxicity, anti-phytopathogenic and phytotoxic effects of these compounds were evaluated. Among them, compounds 1 and 8 exhibited the strongest toxicity against brine shrimp (Artemia salina), with lethality rates of 100% at a low concentration of 10 μM, comparable to the positive control toosendanin. Compounds 1, 4 and 7 moderately inhibited the growth of Botrytis cinerea. Moreover, 4 displayed moderate antifungal effects on Gibberella saubinettii. In addition, compounds 6, 7 and 9 produced the phytotoxic effects on radish seedlings at 100 μM. This is the first report on the isolation of these metabolites from this organism.