Contact toxicity and repellent efficacy of Valerianaceae spp. to three stored-product insects and synergistic interactions between two major compounds camphene and bornyl acetate

Mentha spp. essential oils: toxicity to Alphitobius diaperinus, activity against poultry pathogenic bacteria, and Beauveria bassiana compatibility

The botanical insecticide market is growing because of limitations placed on the use of certain synthetic chemical insecticides. In this sense, the lesser mealworm Alphitobius diaperius (Coleoptera: Tenebrionidae) is the main poultry pest. The insect causes weight loss and damage to the digestive system of poultry, and it is a vector and reservoir of pathogens. Consequently, this study explored the following hypotheses: (i) essential oils (EOs) derived from Mentha spp. are toxic to A. diaperius; (ii) these EOs are compatible with Beauveria bassiana, the natural enemy of the poultry pest, that parasite A. diaperinus; (iii) these EOs also exhibit activity against bacteria that are pathogenic to poultry. In topical applications and ingestion tests, EOs from Mentha arvensis, Mentha spicata, and Mentha piperita were toxic to A. diaperinus. Chromatographic analyses revealed that menthol is the predominant compound in M. arvensis and M. piperita, whereas carvone is the major compound in M. spicata. Both (-)- and (+)-menthol, along with (-)- and (+)-carvone, underwent testing with A. diaperinus. Nevertheless, their activity was not as potent as those of the EOs, suggesting a possible synergistic and/or additive effect. The EOs did not have any adverse effects on the conidial germination, vegetative growth, or conidia production per colony of the entomopathogenic fungus B. bassiana. Consequently, these EOs are compatible with this natural enemy. The EO extracted from M. spicata exhibited significant toxicity against Staphylococcus aureus (ATCC 25923), whereas the remaining EOs displayed moderate toxicity against this bacterium. The EOs derived from Mentha spp., as assessed in this study, hold promise for the development of botanical insecticides tailored for the control of A. diaperinus. These insecticides are selective in favor of the natural enemy B. bassiana and can also serve as effective sanitizers, thanks to their antibacterial properties.

A Comparison between Bulgarian Tanacetum parthenium Essential Oil from Two Different Locations

Tanacetum parthenium L. (Asteraceae) is a perennial herbaceous plant with a long-standing historical use in traditional medicine. Recently Tanacetum parthenium L. essential oil has been associated with a promising potential for future applications in the pharmaceutical industry, in the cosmetics industry, and in agriculture. Investigations on the essential oil (EO) have indicated antimicrobial, antioxidant, and repellent activity. The present study aimed to evaluate the chemical composition of Bulgarian T. parthenium essential oil from two different regions, to compare the results to those reported previously in the literature, and to point out some of its future applications. The essential oils of the air-dried flowering aerial parts were obtained by hydrodistillation using a Clevenger-type apparatus. The chemical composition was evaluated using gas chromatography with mass spectrometry (GC-MS). It was established that the oxygenated monoterpenes were the predominant terpene class, followed by the monoterpene hydrocarbons. Significant qualitative and quantitative differences between both samples were revealed. Camphor (50.90%), camphene (16.12%), and bornyl acetate (6.05%) were the major constituents in the feverfew EO from the western Rhodope Mountains, while in the EO from the central Balkan mountains camphor (45.54%), trans-chrysanthenyl acetate (13.87%), and camphene (13.03%) were the most abundant components.

Phytochemical analysis and allelopathic potential of essential oil of yarrow (Achillea spp.) ecotypes against redroot pigweed (Amaranthus retroflexus L.)

This study will contribute to the knowledge of plant allelopathy and its application in weed management, as well as to the valuation of medicinal and neglected plant species. An allelopathy experiment was conducted to introduce Achillea spp. as an effective species on the red root pigweed (Amaranthus retroflexus L.). The allelopathic effect of dry material from the flower, leaf and stem of Tanacetum polycephalum L. and 9 Achillea spp. (Achillea santolina L., A. millefolium L., A. nobilis L., A. conferta DC., A. vermicularis Trin., A. beibersteinii Afan., A. talagonica Boiss., A. tenuifolia Lam., A. aleppica DC.) applied to the soil on the growth of redroot pigweed seedling was tested. Five different ratios of aerial dry material of different species as residues (at 0, 10, 20, 40, and 50 g kg-1 dry weight) were used in the pots. Achillea residual had a significant effect on the growth of redroot pigweed. Achillea vermicolaris and A. aleppica were the most effective species at stopping the growth of redroot pigweed, reducing its dry matter by 90% at 0.07 and 0.02 g kg-1 dry weight, respectively. Based on the results of GC/MS analyses, 152 different compounds were found in the essential oil of Achillea spp. The possible relationship between allelochemicals and seedling investigation by partial least squares regression between effective doses for controlling redroot pigweed and allelochemical compounds of Achillea species. Result showed that cis-Menth-2-en-1-ol, α-Terpinyl, propionate and Bornyl acetate had the most effect on inhibiting the growth of redroot pigweed. Our research revealed that the Achillea genus has a lot of potential as a bioherbicide. This means that its leftovers or mulch could be used as a good cover crop to control redroot pigweed.

The Effect of Botanical Pesticides Azadirachtin, Celangulin, and Veratramine Exposure on an Invertebrate Species Solenopsis invicta (Hymenoptera: Formicidae)

The injudicious and excessive use of synthetic pesticides has deleterious effects on humans, ecosystems, and biodiversity. As an alternative to traditional crop-protection methods, botanical pesticides are gaining importance. In this research endeavor, we examined the contact toxicity, knockdown time, lethal time, and toxicity horizontal transmission of three natural pesticides from plants (azadirachtin, celangulin, and veratramine) on red imported fire ants (RIFA; Solenopsis invicta). Our research findings indicated that azadirachtin and celangulin exhibited relatively high toxicity, with median lethal dose (LD50) values of 0.200 and 0.046 ng/ant, respectively, whereas veratramine exhibited an LD50 value of 544.610 ng/ant for large workers of S. invicta at 24 h post-treatment. Upon treatment with 0.125 mg/L, the (median lethal time) LT50 values of azadirachtin and celangulin were determined to be 60.410 and 9.905 h, respectively. For veratramine, an LT50 value of 46.967 h was achieved after being tested with 200 mg/L. Remarkably, azadirachtin and celangulin were found to exhibit high horizontal transfer among RIFA, with high secondary mortality (100%) and tertiary mortalities (>61%) after 48 h of treatment with 250 mg/L, as well as with their dust formulations for 72 h. However, veratramine did not exhibit significant toxicity or horizontal transfer effects on RIFA, even at high concentrations. These findings suggest that azadirachtin and celangulin are likely to have a highly prominent potential in the management of S. invicta.

A comprehensive overview of breeding strategy to improve phenotypic and quality traits in Valeriana jatamansi Jones

Valeriana jatamansi is a high value perennial herb that grows at an altitude of 1000-3000 MASL in the Indian Himalayan Region and is used in the Ayurvedic, Unani and Chinese systems of medicine. The plant extracts and essential oil (EO) obtained from its roots are used in the pharmaceutical, aromatic and flavouring industries. On account of high global annual demand and lack of organized cultivation of this herb, it is mostly collected from the wild causing depletion of the natural populations and also leading to variable produce making it unsuitable for industrial use. Therefore, to promote its cultivation, it becomes imperative to develop varieties with uniformity. Significant variations have been reported in V. jatamansi populations in terms of underground biomass accumulation, essential oil and valepotriates indicating potential of genotypic variability for effective selection. The review focuses on the diversity and variations at inter- and intra-population levels for phenotypic traits, variations for different active constituents and scope of improvement through selective breeding in V. jatamansi. The species has cross-pollinated breeding behaviour on account of floral dimorphism and presents unique opportunities for development of homozygous progeny lines through controlled self/sib-pollination by applying the breeding methods described in the review for population improvement. The germplasm resources of unique and improved selections can be maintained clonally to ensure their true-to-type identity. This review article was framed in the year 2022 after thoroughly studying the literature from the year 1919-2022. The study focuses on the variations in V. jatamansi which could be used to maximize the production through various breeding techniques for biomass and yield of different active constituents to meet the requirements of pharmaceutical and aroma industries.

Phytochemical Profile, Preliminary Toxicity, and Antioxidant Capacity of the Essential Oils of Myrciaria floribunda (H. West ex Willd.) O. Berg. and Myrcia sylvatica (G. Mey) DC. (Myrtaceae)

The essential oils (EOs) of Myrciaria floribunda (Mflo) and Myrcia sylvatica (Msyl) (Myrtaceae) were obtained by hydrodistillation. The analysis of volatile constituents was performed by GC/MS. Preliminary toxicity was assessed on Artemia salina Leach. The antioxidant capacity was measured by the ABTS•+ and DPPH• radical inhibitory activities. The results indicate that the Mflo EO had the highest yield (1.02%), and its chemical profile was characterized by high levels of hydrocarbon (65.83%) and oxygenated (25.74%) monoterpenes, especially 1,8-cineole (23.30%), terpinolene (22.23%) and α-phellandrene (22.19%). Regarding the Msyl EO, only hydrocarbon (51.60%) and oxygenated (46.52%) sesquiterpenes were identified in the sample, with (Z)-α-trans-bergamotene (24.57%), α-sinensal (13.44%), and (Z)-α-bisabolene (8.33%) at higher levels. The EO of Mflo exhibited moderate toxicity against A. salina (LC50 = 82.96 ± 5.20 µg.mL−1), while the EO of Msyl was classified as highly toxic (LC50 = 2.74 ± 0.50 µg.mL−1). In addition, relative to Trolox, the EOs of Mflo and Msyl showed significant inhibitory effects (p < 0.0001) against the DPPH• radical. This study contributes to the expansion of chemical and biological knowledge on the EOs of Myrtaceae species from the Amazon region.

Sesquiterpenoid-rich Essential Oils from Two Magnolia Plants: Contact and Repellent Activity to Three Stored-product Insects

Stored products have been damaged by insects. Multiple approaches for pest management are employed. Among these approaches, botanical insecticide is an emerging one. This work investigated the pest management potential of Magnolia coriacea and Magnolia macclurei essential oils (EOs) to three major stored-product insects, namely the red flour beetle, cigarette beetle and booklouse. Magnolia coriacea and M. macclurei EOs showed promising contact toxicity to the cigarette beetle, with LD₅₀ values of 11.7 and 12.3 μg/adult. The contact toxicity of M. coriacea EOs to the booklouse (LC₅₀ = 95.5 μg/cm²) was much stronger than that of M. macclurei EOs (LC₅₀ = 245.4 μg/cm²). To explore the contribution of individual compounds to insecticidal activity of EOs, chemical analysis was performed by GC-MS. Results showed that nerolidol (27.84%), agarospirol (18.34%), elixene (15.84%) and helminthogermacrene (12.69%) were major compounds of M. coriacea EOs, β-guaiene (60.31%) and elixene (20.42%) dominated in M. macclurei EOs. Nerolidol and β-guaiene showed contact activity to three insect species. Nerolidol showed stronger contact toxicity to the red flour beetle and cigarette beetle than M. coriacea EOs did, both samples were similar to the booklouse. β-Guaiene was much stronger to the red flour beetle and booklouse, but weaker to the cigarette beetle than M. macclurei EOs did. The repellent effects of EOs and compounds were at various levels. Generally, results suggested that the contact toxic potential of samples could serve as management for the cigarette beetle and booklouse, while repellent effect would be used to control the red flour beetle.

Isolation, screening and identification of key components having intense insect repellent activity against Plodia interpunctella from four different medicinal plant materials

BACKGROUND

Global warming and the indiscriminate use of pesticides have increased the propagation of the stored-product insect pests, leading to enormous losses in the agriculture and food industries. The most used insect repellents are synthetic derivatives; however, these have an adverse effect on human health as well as on the environment. Therefore, we attempted to find materials with insect repellent activity in natural products. The present study aimed to identify the single chemical component with intense insect repellent activity in extracts from four different Oriental medicinal plant materials: (i) Anethum graveolens L. (dill) seeds; (ii) Artemisia capillaris Thunb. (capillary wormwood) leaves; (iii) smoked Prunus mume Siebold & Zucc. (mume) fruits; and (iv) Rhus javanica L. (galls).

RESULTS

As a result of the bioassay-guided fractionation of each extract against the Plodia interpunctella, stored-product insect, the n-hexane fraction of dill seeds extract was confirmed as the optimal fraction between all of the fractions. In total, 32 chemical components were identified from the n-hexane fraction of dill seeds by gas chromatography-mass spectrometry analysis, and the two main components were dillapiole (47.51%) and carvone (26.76%). Of the two components, dillapiole was confirmed as the key component playing an essential role in insect repellent activity.

CONCLUSION

Our study suggests that dillapiole has the potential to be used as a natural insect repellent for the control of P. interpunctella infestation in agricultural and food products during distribution and storage. © 2021 Society of Chemical Industry.

Cloning and Characterization of 1,8-Cineole Synthase (SgCINS) Gene From the Leaves of Salvia guaranitica Plant

Monoterpenes are one of the most common groups belonging to the terpenoid family, with a C10 structure comprising of two isoprene units. Most of monoterpenes are volatile plant compounds, and they act as signaling molecules between plants and the environment, particularly as defensive compounds against herbivores and pathogens. In this study, 1,8-cineole synthase (SgCINS) gene was identified and cloned from the leaves of Salvia guaranitica plant. To examine the role of SgCINS in insect resistance, we transformed and expressed this gene into tobacco leaves. The metabolic analysis revealed that the production of various types and amount of terpenoid was increased and decreased in SgCINS overexpression and control lines, respectively, suggesting that overexpressing SgCINS in transgenic tobacco plants lead to an increase in the production of various types of terpenoids and other phytochemical compounds. These results indicated why transgenic tobacco was highly resistant against cotton worm than the highly susceptible control plants. Our results demonstrate that the SgCINS gene can play an important role in plants against cotton worm insect attack, and pave the way for using terpenoids genes for improving resistance to insect attack in higher plants.

Study on Gas Chromatographic Fingerprint of Essential Oil from Stellera chamaejasme Flowers and Its Repellent Activities against Three Stored Product Insects

The objective of this study was to establish the chromatographic fingerprints of the essential oil (EO) from Stellera chamaejasme flowers collected from various natural sites by gas chromatography (GC) combined with chemometric methods. The EO was obtained by hydrodistillation, and its chemical composition was analyzed by gas chromatography-mass spectrometry (GC-MS). Most components were identified as ketones and the relatively high-content components were fitone (38.973%), n-hentriacontane (5.807%), myristic acid (4.944%) and phytol (3.988%). In addition, the repellent activities of the EO from S. chamaejasme flowers and its four main chemical compounds were evaluated against three stored product pests (Tribolium castaneum, Lasioderma serricorne, Liposcelis bostrychophila) for the first time. In this work, the EO and the four chemical compounds showed a repellent effect against three storage pests after 2 and 4 h exposure. The experimental method and repellent activity of S. chamaejasme flower EO could provide a basis for the development of botanical pesticide and the utilization of the rich plant resources of S. chamaejasme in the future.

Toxicological safety assessment of essential oils used as food supplements to establish safe oral recommended doses

Essential oils (EOs) are increasingly consumed as food supplements. The few published recommended doses available generally lack details both on the methodology used and concentration limits for substances of concern, including genotoxic carcinogens. We propose a tiered approach based on the toxicological evaluation of maximized concentrations of each constituent present in the EO investigated. The genotoxic potential of each constituent is assessed using literature data or QSAR analyses. Genotoxic constituents are evaluated according to the methodology provided in the ICHM7 guideline. A Toxicological Reference Value (TRV) is associated to each non-genotoxic constituent, using one of the following methodologies (decision-tree successive steps): extraction from recognized databases or clinical studies, application of adequate safety factors to NOAELs established in animal studies, read-across analyses and when none was possible, TTC of Cramer classes. An EO recommended dose is considered safe when the safety margin (ratio between TRV and systemic exposure) for all constituents is all at least equal to 1. In conclusion, this methodology has proven to be robust to establish safe recommended doses for EOs used as food supplements, consistent with those publicly available, and avoiding unnecessary dedicated new animal testing.

Chemical Constituents of the Essential Oil Extracted from Elsholtzia densa and Their Insecticidal Activity against Tribolium castaneum and Lasioderma serricorne

Storage pests pose a great threat to global food security. Here, we found that the essential oil (EO) extracted from E. densa possesses obvious effects against the insects that threaten stored-products. In this work, we investigated the chemical constituents of the essential oil extracted from Elsholtzia densa, and their insecticidal (contact and fumigant) toxicity against Tribolium castaneum and Lasioderma serricorne. A total of 45 compounds were identified by GC-MS, accounting for 98.74% of the total EO. Meanwhile, 11 compounds were isolated from the EO, including limonene, β-caryophyllene, ρ-cymene, trans-phytol, α-terpineol, linalool, acetophenone, 1,8-cineole, ρ-cymen-7-ol, 1-O-cerotoylgly-cerol, and palmitic acid. Furthermore, acetophenone, ρ-cymen-7-ol, and 1-O-cerotoylgly-cerol were isolated for the first time from Elsholtzia spp. The results of the bioassays indicated that the EO had the property of insecticidal toxicity against T. castaneum and L. serricorne. All of the compounds showed different levels of insecticidal toxicity against the two species of insects. Among them, 2-ethyl-1H-imidazole had no insecticidal toxicity against T. castaneum, but possessed fumigant and obvious contact toxicity against L. serricorne. ρ-Cymen-7-ol had beneficial insecticidal toxicity against the two species of insects, and fumigant toxicity against L. serricorne. ρ-Cymen-7-ol (LD₅₀ = 13.30 μg/adult), 1-octen-3-ol (LD₅₀ = 13.52 μg/adult), and 3-octanol (LD₅₀ = 17.45 μg/adult) showed significant contact toxicity against T. castaneum. Acetophenone (LD₅₀ = 7.07 μg/adult) and ρ-cymen-7-ol (LD₅₀ = 8.42 μg/adult) showed strong contact toxicity against L. serricorne. ρ-Cymene (LC₅₀ = 10.91 mg/L air) and ρ-cymen-7-ol (LC₅₀ = 10.47 mg/L air) showed powerful fumigant toxicity to T. castaneum. Limonene (LC₅₀ = 5.56 mg/L air), acetophenone (LC₅₀ = 5.47 mg/L air), and 3-octanol (LC₅₀ = 5.05 mg/L air) showed obvious fumigant toxicity against L. serricorne. In addition, the EO and its chemical compounds possessed different levels of repellent activity. This work provides some evidence of the value of exploring these materials for insecticidal activity, for human health purposes. We suggest that the EO extracted from E. densa may have the potential to be developed as an insecticidal agent against stored product insect pests.

Toxicity and action mechanisms of silver nanoparticles against the mycotoxin-producing fungus Fusarium graminearum

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AgNPs possess high activity towards fungicide-resistant strains.

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AgNPs exert great activity against mycotoxin-producing fungus F. graminearum.

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AgNPs induce the expression of two azole resistance-related ABC genes.

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AgNPs lead to accumulation of toxisome and notorious mycotoxin DON by provoking ROS.

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AgNPs combined with DON-reducing fungicides are recommended for FHB control.

Introduction

Fusarium graminearum is a most destructive fungal pathogen that causes Fusarium head blight (FHB) disease in cereal crops, resulting in severe yield loss and mycotoxin contamination in food and feed. Silver nanoparticles (AgNPs) are extensively applied in multiple fields due to their strong antimicrobial activity and are considered alternatives to fungicides. However, the antifungal mechanisms and the effects of AgNPs on mycotoxin production have not been well characterized.

Objectives

This study aimed to investigate the antifungal activity and mechanisms of AgNPs against both fungicide-resistant and fungicide-sensitive F. graminearum strains, determine their effects on mycotoxin deoxynivalenol (DON) production, and evaluate the potential of AgNPs for FHB management in the field.

Methods

Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and fluorescence microscopy were used to examine the fungal morphological changes caused by AgNPs. In addition, RNA-Seq, qRT-PCR, and western blotting were conducted to detect gene transcription and DON levels.

Results

AgNPs with a diameter of 2 nm exhibited effective antifungal activity against both fungicide-sensitive and fungicide-resistant strains of F. graminearum. Further studies showed that AgNP application could impair the development, cell structure, cellular energy utilization, and metabolism pathways of this fungus. RNA-Seq analysis and sensitivity determination revealed that AgNP treatment significantly induced the expression of azole-related ATP-binding cassette (ABC) transporters without compromising the control efficacy of azoles in F. graminearum. AgNP treatment stimulated the generation of reactive oxygen species (ROS), subsequently induced transcription of DON biosynthesis genes, toxisome formation, and mycotoxin production.

Conclusion

This study revealed the underlying mechanisms of AgNPs against F. graminearum, determined their effects on DON production, and evaluated the potential of AgNPs for controlling fungicide-resistant F. graminearum strains. Together, our findings suggest that combinations of AgNPs with DON-reducing fungicides could be used for the management of FHB in the future.

Back to the Roots-An Overview of the Chemical Composition and Bioactivity of Selected Root-Essential Oils

Since ancient times, plant roots have been widely used in traditional medicine for treating various ailments and diseases due to their beneficial effects. A large number of studies have demonstrated that-besides their aromatic properties-their biological activity can often be attributed to volatile constituents. This review provides a comprehensive overview of investigations into the chemical composition of essential oils and volatile components obtained from selected aromatic roots, including Angelica archangelica, Armoracia rusticana, Carlina sp., Chrysopogon zizanioides, Coleus forskohlii, Inula helenium, Sassafras albidum, Saussurea costus, and Valeriana officinalis. Additionally, their most important associated biological impacts are reported, such as anticarcinogenic, antimicrobial, antioxidant, pesticidal, and other miscellaneous properties. Various literature and electronic databases-including PubMed, ScienceDirect, Springer, Scopus, Google Scholar, and Wiley-were screened and data was obtained accordingly. The results indicate the promising properties of root-essential oils and their potential as a source for natural biologically active products for flavor, pharmaceutical, agricultural, and fragrance industries. However, more research is required to further establish the mechanism of action mediating these bioactivities as well as essential oil standardization because the chemical composition often strongly varies depending on external factors.

Profiling Volatile Terpenoids from Calabrian Pine Stands Infested by the Pine Processionary Moth

Terpenoids make up the biggest and most diversified class of chemical substances discovered in plants, encompassing over 40,000 individual compounds. In conifers, the production of terpenoids, either as oleoresin or emitted as volatile compounds, play an important role in the physical and chemical defence responses against pathogens and herbivores. In the present work, we examined, for the first time to the best of our knowledge, the terpenic defensive relations of Calabrian pine (Pinus nigra subsp. laricio (Poiret) Maire), facing the attack of the pine processionary moth (Thaumetopoea pityocampa (Denis and Schiffermüller, 1775)), brought about in the open on adult plant individuals growing at two distinct forest sites. Among the volatile terpenoids emitted from pine needles, bornyl acetate [(4,7,7-trimethyl-3-bicyclo[2.2.1]heptanyl) acetate] was the most frequently and selectively associated with the infestation, increasing during the period of most intense trophic activity of the caterpillars (defoliation), and decreasing thereafter. Although further work is needed to clarify whether the observed response reflects defence reactions and/or they are involved in communication among the infested plants and their biotic environment, the present results boost the currently growing interest in the isolation and characterization of plant secondary metabolites that can be used to control pests, pathogens, and weeds.