Dillapiol: a pyrethrum synergist for control of the Colorado potato beetle

Crithmum maritimum L.-Study on the Histochemical Localization of Essential Oil

Crithmum maritimum L. is a perennial halophyte plant that is a medicinal herb known by people from different cultures since ancient times. However, the therapeutic potential of this halophyte has not been completely investigated, and the scientific data on it are limited. The purpose of the present study was to estimate the chemical composition of the essential oil (EO) obtained from the aerial parts of Crithmum maritimum L. growing wild in Bulgaria, as well as the histolocalization of secretory structures for the synthesis and accumulation of volatile oils. The results obtained on the EO composition of Bulgarian Crithmum maritimum L. provide an opportunity to reveal potential future applications in various fields, such as medicine, pharmacy, agriculture, food, and the cosmetic industry. Gas chromatography with mass spectrometry was performed to assess the chemical profile of the isolated EO. The phenylpropanoid dillapiole was identified as the major compound in the EO, accounting for 34.09% of the total EO. Monoterpene hydrocarbons represented 62.07% of the total oil composition. γ-Terpinene, D-limonene, and β-pinene were the most abundant monoterpene hydrocarbons in the composition of the EO. In addition, histochemical localization of EO in the stem and leaves of Crithmum maritimum L. was carried out. The secretory structures were located in the cortical region of the stem and in the mesophyll tissues of the leaves in the form of secretory ducts. The performed histochemical analysis confirmed the lipophilic nature of the secretion from the duct cells. This is the first report related to the histolocalization and chemical composition of the EO from Bulgarian Crithmum maritimum L. Furthermore, our data indicate some potential possibilities for the evaluation of the therapeutic activity of the EO obtained from this plant species and outline its future applications as a therapeutic agent. Also, the EO from the studied halophyte plant has prominent potential to be used as a biopesticide, which is an environmentally friendly option compared to standard pesticides.

Bioactivity of Deverra tortuosa essential oil, its nanoemulsion, and phenylpropanoids against the cowpea weevil, a stored grain pest with eco-toxicological evaluations

The essential oil (EO) was hydrodistilled from of Deverra tortuosa aerial parts. Fifty-six components amounting 99.3% were identified in EO through using gas chromatography-flame ionization detection (GC-FID) and (GC-MS). Phenylpropanoids, dillapiole (41.6%), elemicin (7.3%) and myristicin (5.1%), and the monoterpene, sabinene (4.2%) were identified as the major terpenes. An oil-in-water nanoemulsion (particle size 70.3 nm) was developed from EO adopting a low-energy method. The EO products showed insecticidal and biochemical effects against the cowpea weevil Callosobruchus maculatus. Based on a 48-h exposure period, the oil nanoemulsion exhibited a superior contact bioactivity (LC₅₀ = 10.3 µg/cm²), followed by EO (LC₅₀ = 23.1 µg/cm²), dillapiole (LC₅₀ = 27.8 µg/cm²), and myristicin (LC₅₀ = 37.1 µg/cm²). Upon fumigation, nanoemulsion and EO were superior as fumigants (LC₅₀ after 48 h were 6.9 and 14.3 µl/l, respectively). Test materials showed a residual bioactivity against C. maculatus, where EO, dillapiole, and myristicin showed the strongest grain protecting activity. EO products significantly inhibited acetylcholinesterase (AChE) activity of C. maculatus adults. Test products were safe toward the non-target earthworms and did not alter the viability of cowpea seeds. There are evidences for the potential of using EO of D. tortuosa and its nanoemulsion and phenylpropanoids as natural grain protectants against C. maculatus.

The use of insecticide mixtures containing neonicotinoids as a strategy to limit insect pests: Efficiency and mode of action

Synthetic insecticides continue to be the main strategy for managing insect pests, which are a major concern for both crop protection and public health. As nicotinic acetylcholine receptors play a central role in insect neurotransmission, they are the molecular target of neurotoxic insecticides such as neonicotinoids. These insecticides are used worldwide and have shown high efficiency in culture protection. However, the emergence of insect resistance mechanisms, and negative side-effects on non-target species have highlighted the need for a new control strategy. In this context, the use of insecticide mixtures with synergistic effects have been used in order to decrease the insecticide dose, and thus delay the selection of resistance-strains, and limit their negative impact. In this review, we summarize the available data concerning the mode of action of neonicotinoid mixtures, as well as their toxicity to various insect pests and non-target species. We found that insecticide mixtures containing neonicotinoids may be an effective strategy for limiting insect pests, and in particular resistant strains, although they could also negatively impact non-target species such as pollinating insects.

Anethum sowa Roxb. ex fleming: A review on traditional uses, phytochemistry, pharmacological and toxicological activities

ETHNOPHARMACOLOGICAL RELEVANCE

Anethum sowa Roxb. ex Fleming (Syn. Peucedanum sowa Roxb. ex Fleming, Family: Apiaceae) is a pharmacologically important as aromatic and medicinal plant. Various parts of this plant are used in traditional medicine systems for carminative, uterine and colic pain, digestion disorder, flatulence in babies, appetite-stimulating agent and used to treat mild flue and cough. The essential oil is used for aromatherapy. It is also used as a spice for food flavouring and culinary preparations in many Asian and European countries.

AIM OF THE REVIEW

This review aims to provide a comprehensive and critical assessment from the reported traditional and pharmaceutical uses and pharmacological activities of the extracts, essential oil and phytoconstituents with emphasis on its therapeutic potential as well as toxicological evaluation of A. sowa.

MATERIALS AND METHODS

Online search engines such as SciFinder®, GoogleScholar®, ResearchGate®, Web of Science®, Scopus®, PubMed and additional data from books, proceedings and local prints were searched using relevant keywords and terminologies related to A. sowa for critical analyses.

RESULTS

The literature studies demonstrated that A. sowa possesses several ethnopharmacological activities, including pharmaceutical prescriptions, traditional applications, and spice in food preparations. The phytochemical investigation conducted on crude extracts has been characterized and identified various classes of compounds, including coumarins, anthraquinone, terpenoids, alkaloid, benzodioxoles, phenolics, polyphenols, phenolic and polyphenols, fatty acids, phthalides and carotenoids. The extracts and compounds from the different parts of A. sowa showed diverse in vitro and in vivo biological activities including antioxidant, antiviral, antibacterial, analgesic and anti-inflammatory, Alzheimer associating neuromodulatory, cytotoxic, anticancer, antidiabetes, insecticidal and larvicidal.

CONCLUSION

A. sowa is a valuable medicinal plant which is especially used in food flavouring and culinary preparations. This review summarized the pertinent information on A. sowa and its traditional and culinary uses, as well as potential pharmacological properties of essential oils, extracts and isolated compounds. The traditional uses of A. sowa are supported by in vitro/vivo pharmacological studies; however, further investigation on A. sowa should be focused on isolation and identification of more active compounds and establish the links between the traditional uses and reported pharmacological activities with active compounds, as well as structure-activity relationship and in vivo mechanistic studies before integrated into the medicine. The toxicological report confirmed its safety. Nonetheless, pharmacokinetic evaluation tests to validate its bioavailability should be encouraged.

High-level field-evolved resistance to spinosad in Colorado potato beetle, Leptinotarsa decemlineata, in organically managed fields

BACKGROUND

Organic pest management eschews synthetic pesticides and insecticide resistance is rarely studied in organically managed systems. Spinosad is a biologically based insecticide used widely by both organic and conventional growers. Colorado potato beetle, Leptinotarsa decemlineata, is infamous for its ability to evolve resistance to insecticides. Spinosad resistance was surveyed in conventionally managed fields in eastern New York in 2006. In response to grower reports of spinosad failure on two organic farms in 2009, resistance to spinosad was assayed in both conventionally and organically managed fields the following year, and growers were surveyed for their prior spinosad use.

RESULTS

In 2006, spinosad resistance measured as median lethal dose (LD₅₀ ) varied 9.8-fold among the eight conventional fields sampled and a laboratory susceptible strain. In 2010, the resistance ratios of LD₅₀ values relative to a laboratory susceptible strain ranged from 17.5 to 40.6 in conventionally managed fields, and from 128.7 to 5750.3 in organically managed fields, a dramatic increase from 2006 with higher resistance ratios in organically managed fields. Organic growers reported much heavier use of spinosad in the years prior to 2010.

CONCLUSION

This is the first report of high-level resistance to spinosad in Coleopterans. Selection strength due to number of years used and number of applications per season appear to have been the primary factors driving the evolution of resistance to spinosad, highlighting the need for resistance management in organic production, where fewer alternative active ingredients for resistance management are available. © 2021 Society of Chemical Industry.

Piper aduncum essential oil: a promising insecticide, acaricide and antiparasitic. A review

Several studies have assessed the potential of essential oils as substitutes for synthetic pesticides, in order to counter insect resistance to commercial pesticides. Piper aduncum L. is a very common shrub in the Amazon Rainforest and in other subtropical areas. The objective of this review was to analyse the existing information on P. aduncum essential oil as a raw material for new bioproducts for sustainable pest disease management. With this review, we collected and critically analysed 59 papers, representing all the studies that aimed to evaluate the essential oil properties of this species as an insecticide, acaricide and antiparasitic. The chemical composition differs depending on the origin, although phenylpropanoid dillapiole is the most cited component, followed by myristicin, 1,8-cineole and β-ocimene. Between the acaricidal, antiparasitic and synergistic activities, the insecticidal effects are highly promising, with optimal results against the malaria vector Aedes aegypti, with an LC50 that ranges between 57 and 200μg/mL. Acaricidal activity has mainly been reported against Tetranychus urticae, showing an LC50 that ranges between 5.83 and 7.17μg/mL. Antiparasitic activity has predominately been found on Leishmania amazonensis, and antipromastigote activity has been found to be between 23.8 and 25.9μg/mL. Concerning the synergistic effect between dillapiole and synthetic insecticides, four studies on Spodoptera frugiperda found promising results with cypermethrin. In this review, we highlighted the potential of P. aduncum essential oil as a biopesticide, also focusing on the lack of information about applied research. We also provide suggestions for future investigations.

Potent CYP3A4 Inhibitors Derived from Dillapiol and Sesamol

Synthesis of 50 analogues of the natural insecticide synergists, dillapiol and sesamol, is reported. These were evaluated as potential insecticide synergists based on their inhibition of human CYP3A4. The most potent inhibitors have a relatively large hydrophobic substituent at either position 5 or 6 of these molecules. For example, 5-(benzyloxy)-6-(3-phenylsulfonyl)propyl)benzo[d][1,3]dioxole (18) and the diphenyl acetate of (6,7-dimethoxybenzo[d][1,3]dioxol-5-yl)propan-1-ol (5n) show inhibitory concentrations for 50% activity IC₅₀ values of 0.086 and 0.2 μM, respectively. These compounds are 106 and 46 times more potent than dillapiol whose IC₅₀ for the inhibition of CYP3A4 is 9.2 μM. The ortho-chloro analogue (8f), whose activity is 86 times the activity of dillapiol, is the most potent of the fourteen 5-(benzyloxy-6-(2 propenyl)benzo[d][1,3]dioxoles prepared for this study.

The effect of insecticide synergist treatment on genome-wide gene expression in a polyphagous pest

Synergists can counteract metabolic insecticide resistance by inhibiting detoxification enzymes or transporters. They are used in commercial formulations of insecticides, but are also frequently used in the elucidation of resistance mechanisms. However, the effect of synergists on genome-wide transcription in arthropods is poorly understood. In this study we used Illumina RNA-sequencing to investigate genome-wide transcriptional responses in an acaricide resistant strain of the spider mite Tetranychus urticae upon exposure to synergists such as S,S,S-tributyl phosphorotrithioate (DEF), diethyl maleate (DEM), piperonyl butoxide (PBO) and cyclosporin A (CsA). Exposure to PBO and DEF resulted in a broad transcriptional response and about one third of the differentially expressed genes (DEGs), including cytochrome P450 monooxygenases and UDP-glycosyltransferases, was shared between both treatments, suggesting common transcriptional regulation. Moreover, both DEF and PBO induced genes that are strongly implicated in acaricide resistance in the respective strain. In contrast, CsA treatment mainly resulted in downregulation of Major Facilitator Superfamily (MFS) genes, while DEGs of the DEM treatment were not significantly enriched for any GO-terms.

Pesticide Interactions: Mechanisms, Benefits, and Risks

Interactions between pesticides at common molecular targets and detoxification systems often determine their effectiveness and safety. Compounds with the same mode of action or target are candidates for cross resistance and restrictions in their recommended uses. Discovery research is therefore focused on new mechanisms and modes of action. Interactions in detoxification systems also provide cross resistance and synergist and safener mechanisms illustrated with serine hydrolases and inhibitors, cytochrome P450 and insecticide synergists, and glutathione S-transferases and herbicide safeners. Secondary targets are also considered for inhibitors of serine hydrolases, aldehyde dehydrogenases, and transporters. Emphasis is given to the mechanistic aspects of interactions, not the incidence, which depends on potency, exposure, ratios, and timing. The benefits of pesticide interactions are the additional levels of chemical control to achieve desired organismal effects. The risks are the unpredictable interactions of complex interconnected biological systems. However, with care, two can be better than one.

Linalool, a Piper aduncum essential oil component, has selective activity against Trypanosoma cruzi trypomastigote forms at 4°C

BACKGROUND

Recent studies showed that essential oils from different pepper species (Piper spp.) have promising leishmanicidal and trypanocidal activities.

OBJECTIVES

In search for natural compounds against Trypanosoma cruzi, different forms of the parasite were incubated for 24 h at 28ºC or 4ºC with Piper aduncum essential oil (PaEO) or its main constituents linalool and nerolidol.

METHODS

PaEO chemical composition was obtained by GC-MS. Drug activity assays were based on cell counting, MTT data or infection index values. The effect of PaEO on the T. cruzi cell cycle and mitochondrial membrane potential was evaluated by flow cytometry.

FINDINGS

PaEO was effective against cell-derived (IC50/24 h: 2.8 μg/mL) and metacyclic (IC50/24 h: 12.1 μg/mL) trypomastigotes, as well as intracellular amastigotes (IC50/24 h: 9 μg/mL). At 4ºC - the temperature of red blood cells (RBCs) storage in blood banks - cell-derived trypomastigotes were more sensitive to PaEO (IC50/24 h = 3.8 μg/mL) than to gentian violet (IC50/24 h = 24.7 mg/mL). Cytotoxicity assays using Vero cells (37ºC) and RBCs (4ºC) showed that PaEO has increased selectivity for cell-derived trypomastigotes. Flow cytometry analysis showed that PaEO does not affect the cell cycle of T. cruzi epimastigotes, but decreases their mitochondrial membrane potential. GC-MS data identified nerolidol and linalool as major components of PaEO, and linalool had trypanocidal effect (IC50/24 h: 306 ng/mL) at 4ºC.

MAIN CONCLUSION

The trypanocidal effect of PaEO is likely due to the presence of linalool, which may represent an interesting candidate for use in the treatment of potentially contaminated RBCs bags at low temperature.

Efficacy of essential oil of Piper aduncum against nymphs and adults of Diaphorina citri

BACKGROUND

Insecticide application is the main way to control Diaphorina citri. However, it causes environmental contamination, has a negative impact on beneficial organisms and leads to psyllid resistance. The essential oil of Piper aduncum has low toxicity towards the environment and contains dillapiol, which has proven to be effective against several crop pests. Here, we studied its efficacy against nymphs and adults of D. citri under laboratory conditions. Oils with three concentrations of dillapiol (69.3, 79.9 and 85.4%) at 0.5, 0.75 and 1.0% dilutions plus 0.025% adjuvant were tested.

RESULTS

All treatments caused 90-100% mortality in nymphs. Topical treatments with oil containing 79.9 and 85.4% dillapiol at 0.75% and 1% dilutions were effective (mortality ≥80%) in adults. However, the essential oil showed no residual activity against adults (mortality ≤30%).

CONCLUSIONS

Dillapiol-rich oil is a promising compound for D. citri control. © 2015 Society of Chemical Industry.

Conifer flavonoid compounds inhibit detoxification enzymes and synergize insecticides

Detoxification by glutathione S-transferases (GSTs) and esterases are important mechanisms associated with insecticide resistance. Discovery of novel GST and esterase inhibitors from phytochemicals could provide potential new insecticide synergists. Conifer tree species contain flavonoids, such as taxifolin, that inhibit in vitro GST activity. The objectives were to test the relative effectiveness of taxifolin as an enzyme inhibitor and as an insecticide synergist in combination with the organophosphorous insecticide, Guthion (50% azinphos-methyl), and the botanical insecticide, pyrethrum, using an insecticide-resistant Colorado potato beetle (CPB) Leptinotarsa decemlineata (Say) strain. Both taxifolin and its isomer, quercetin, increased the mortality of 1(st) instar CPB larvae after 48h when combined with Guthion, but not pyrethrum. Taxifolin had greater in vitro esterase inhibition compared with the commonly used esterase inhibitor, S, S, S-tributyl phosphorotrithioate (DEF). An in vivo esterase and GST inhibition effect after ingestion of taxifolin was measured, however DEF caused a greater suppression of esterase activity. This study demonstrated that flavonoid compounds have both in vitro and in vivo esterase inhibition, which is likely responsible for the insecticide synergism observed in insecticide-resistant CPB.

Plant Essential Oils Synergize and Antagonize Toxicity of Different Conventional Insecticides against Myzus persicae (Hemiptera: Aphididae)

Plant-derived products can play an important role in pest management programs. Essential oils from Lavandula angustifolia (lavender) and Thymus vulgaris (thyme) and their main constituents, linalool and thymol, respectively, were evaluated for insecticidal activity and synergistic action in combination with insecticides against green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae). The essential oils and their main constituents exerted similar insecticidal activity when aphids were exposed by direct sprays, but were non-toxic by exposure to treated leaf discs. In synergism experiments, the toxicity of imidacloprid was synergized 16- to 20-fold by L. angustifolia and T. vulgaris essential oils, but far less synergism occurred with linalool and thymol, indicating that secondary constituents of the oils were probably responsible for the observed synergism. In contrast to results with imidacloprid, the insecticidal activity of spirotetramat was antagonized by L. angustifolia and T. vulgaris essential oils, and linalool and thymol. Our results demonstrate the potential of plant essential oils as synergists of insecticides, but show that antagonistic action against certain insecticides may occur.

Inhibition of insect glutathione S-transferase (GST) by conifer extracts

Insecticide synergists biochemically inhibit insect metabolic enzyme activity and are used both to increase the effectiveness of insecticides and as a diagnostic tool for resistance mechanisms. Considerable attention has been focused on identifying new synergists from phytochemicals with recognized biological activities, specifically enzyme inhibition. Jack pine (Pinus banksiana Lamb.), black spruce (Picea mariana (Mill.) BSP.), balsam fir (Abies balsamea (L.) Mill.), and tamarack larch (Larix laricina (Du Roi) Koch) have been used by native Canadians as traditional medicine, specifically for the anti-inflammatory and antioxidant properties based on enzyme inhibitory activity. To identify the potential allelochemicals with synergistic activity, ethanol crude extracts and methanol/water fractions were separated by Sephadex LH-20 chromatographic column and tested for in vitro glutathione S-transferase (GST) inhibition activity using insecticide-resistant Colorado potato beetle, Leptinotarsa decemlineata (Say) midgut and fat-body homogenate. The fractions showing similar activity were combined and analyzed by ultra pressure liquid chromatography-mass spectrometry. A lignan, (+)-lariciresinol 9'-p-coumarate, was identified from P. mariana cone extracts, and L. laricina and A. balsamea bark extracts. A flavonoid, taxifolin, was identified from P. mariana and P. banksiana cone extracts and L. laricina bark extracts. Both compounds inhibit GST activity with taxifolin showing greater activity compared to (+)-lariciresinol 9'-p-coumarate and the standard GST inhibitor, diethyl maleate. The results suggested that these compounds can be considered as potential new insecticide synergists.