Chemical Composition, Repellent, and Phytotoxic Potentials of the Fractionated Resin Essential Oil from Araucaria heterophylla Growing in Tunisia

The resin essential oil (REO) of the Tunisian Araucaria heterophylla trunk bark was investigated for its chemical composition. Then, it was evaluated for its insecticidal and allelopathic activities. The REO was obtained by hydrodistillation for 9 h (yield of 4.2 % w/w). Moreover, fractional hydrodistillation was carried out at 3-hour intervals, resulting in 3 fractions (R1-R3), to facilitate chemical identification and localization of the aforementioned biological activities. GC/MS analysis of the obtained samples allowed the identification of 25 compounds, representing between 91.2 and 96.3 % of their total constituents, which consisted predominantly of sesquiterpene hydrocarbons, oxygenated sesquiterpenes and diterpene hydrocarbons. α-Copaene (10.8 %), γ-muurolene (5.8 %), α-copaen-11-ol (7.8 %), spathulenol (10.5 %), 15-copaenol (8.2 %), ylangenal (10.3 %), dehydrosaussurea lactone (7.7 %), and sandaracopimaradiene (11.4 %) were identified as major compounds. The second part aimed to assess the impact of the A. heterophylla EO and its three fractions for their insecticidal and repellent activity against Tribolium castaneum (Herbst), a stored grain pest, of which a strong repellent activity was noted. In addition, the studied samples showed high phytotoxic effects against Lactuca sativa. The third fraction (R3) performed a total inhibitory potential on seed germination and seedling growth of the target plant. Furthermore, alongside this discovery, an estimation was conducted through molecular docking analysis. Wherein the main compounds of the studied samples were docked into the active pocket of protoporphyrinogen IX oxidase (PDB: 1SEZ), a key enzyme in chlorophyll biosynthesis. Thus, it is recommended to use the REO of A. heterophylla as a natural herbicide.

Gas Chromatography-Mass Spectrometry Chemical Profiling of Commiphora myrrha Resin Extracts and Evaluation of Larvicidal, Antioxidant, and Cytotoxic Activities

Plant extracts and essential oils can be alternative environmentally friendly agents to combat pathogenic microbes and malaria vectors. Myrrh is an aromatic oligum resin that is extracted from the stem of Commiphora spp. It is used in medicine as an insecticide, cytotoxic, and aromatic. The current study assessed the effect of Commiphora myrrha resin extracts on the biological potency of the third larval stage of Aedes aegypti, as well as its antioxidant and cytotoxic properties against two types of tumor cells (HepG-2 and Hela cell lines). It also used GC-MS to determine the chemical composition of the C. myrrha resin extracts. Fifty components from the extracted plant were tentatively identified using the GC-MS method, with curzerene (33.57%) typically listed as the primary ingredient, but other compounds also make up a significant portion of the mixture, including 1-Methoxy-3,4,5,7-tetramethylnaphthalene (15.50%), β-Elemene (5.80%), 2-Methoxyfuranodiene (5.42%), 2-Isopropyl-4,7-Dimethyl-1-Naphthol (4.71%), and germacrene B (4.35%). The resin extracts obtained from C. myrrha exhibited significant efficacy in DPPH antioxidant activity, as evidenced by an IC50 value of 26.86 mg/L and a radical scavenging activity percentage of 75.06%. The 50% methanol extract derived from C. myrrha resins exhibited heightened potential for anticancer activity. It demonstrated substantial cytotoxicity against HepG-2 and Hela cells, with IC50 values of 39.73 and 29.41 µg mL-1, respectively. Notably, the extract showed non-cytotoxic activity against WI-38 normal cells, with an IC50 value exceeding 100 µg mL-1. Moreover, the selectivity index for HepG-2 cancer cells (2.52) was lower compared to Hela cancer cells (3.40). Additionally, MeOH resin extracts were more efficient against the different growth stages of the mosquito A. aegypti, with lower LC50, LC90, and LC95 values of 251.83, 923.76, and 1293.35 mg/L, respectively. In comparison to untreated groups (1454 eggs/10 females), the average daily number of eggs deposited (424 eggs/L) decreases at higher doses (1000 mg/L). Finally, we advise continued study into the possible use of C. myrrha resins against additional pests that have medical and veterinary value, and novel chemicals from this extract should be isolated and purified for use in medicines.

Insecticidal Activities and Phenological Variations of Characteristic Component from Michelia yunnanensis

Volatile secondary metabolites of plants interact with environments heavily. In this work, characteristic components of Michelia yunnanensis essential oils (EOs) were isolated, purified and identified by column chromatography, GC-MS and NMR. Leaves of M. yunnanensis were collected monthly and extracted for EOs to investigate chemical and insecticidal activity variations as well as potential influencing environments. Different organs were employed to reveal distribution strategies of characteristic components. Results of insecticidal activities showed that all EOs samples exerted stronger contact activity to Lasioderma serricorne, but repellent effect was more efficient on Tribolium castaneum. One oxygenated sesquiterpene was isolated from EOs, basically it could be confirmed as (+)-cyclocolorenone (1). It exerted contact toxicity to L. serricorne (LD 50 = 28.8 μg/adult). Chemical analysis showed that M. yunnanensis leaves in reproductive period would produce and accumulate more 1 than in vegetative period. Moreover, reproductive organs (flowers and fruits) contained more 1 than vegetative organs (leaves and twigs). Partial correlation analysis indicated that temperature-related elements positively correlated with the relative content of 1.

Insights into the Metabolomic Capacity of Podaxis and Isolation of Podaxisterols A-D, Ergosterol Derivatives Carrying Nitrosyl Cyanide-Derived Modifications

Cultures of a termite-associated and a free-living member of the fungal genus Podaxis, revived from spores maintained in century-old herbarium collections, were analyzed for their insecticidal and antimicrobial effects. Their secondary metabolomes were explored to uncover possible adaptive mechanisms of termite association, and dereplication of LC-HRMS/MS data sets led to the isolation of podaxisterols A-D (1-4), modified ergosterol derivatives that result from a Diels-Alder reaction with endogenous nitrosyl cyanide. Chemical structures were determined based on HRMS/MS and NMR analyses as well as X-ray crystallography. The putative origin of the endogenous fungal nitrosyl cyanide and ergosterol derivatives is discussed based on results obtained from stable isotope experiments and in silico analysis. Our "omics"-driven analysis of this underexplored yet worldwide distributed fungal genus builds a foundation for studies on a potential metabolic adaptations to diverse lifestyles.

Bioguided Phytochemical Study of Ipomoea cairica Extracts with Larvicidal Activity against Aedes aegypti

Vector-borne diseases, such as those transmitted by Aedes aegypti, are a constant threat to inhabitants of tropical regions of the planet. Synthetic chemicals are commonly used as a strategy to control them; however, these products are known to persist in ecosystems and drive the appearance of resistance genes in arthropod vectors. Thus, the use of natural products has emerged as an environmentally friendly alternative in integrated vector control strategies. The present bioguided study investigated the larvicidal potential of Ipomoea cairica extracts, fractionated using thin-layer and open-column chromatography, because this species has been shown to exert larvicidal effects on the genus Aedes. The objective of this study was to evaluate the nonvolatile components in ethanolic extract of I. cairica stems as a potential natural larvicidal, and coumarins, such as 7-hydroxy-6-methoxychromen-2-one (scopoletin) and 7-hydroxychromen-2-one (umbelliferone), were identified as major compounds; however, they were not shown to be responsible for the larvicidal activity. Based on the results of the larvicidal action tests, these coumarins are not directly responsible for the larvicidal activity, but this activity might be attributed to a synergistic effect of all the compounds present in the most active secondary fraction, called F.DCM, which had an LC₅₀ value of 30.608 mg/L. This type of study has yet not been conducted in the region; therefore, it is an important contribution to recognizing a natural and easy-to-cultivate source of vector control, such I. cairica.

Evaluation of the Potential of a Lectin Extracted from Polygonum persicaria L. as a Biorational Agent against Sitophilus oryzae L

Rice weevil, Sitophilus oryzae L. (Coleoptera: Curculionidae), is one of the most destructive stored-product pests that is resistant to a wide range of chemical insecticides. In the present study, we investigated whether a lectin extracted from Polygonum persicaria L. (PPA) can be used as a biorational agent to control such insect pests. Along with the lethal digestive assay, the sub-lethal insecticidal activities of PPA, including the effects on digestive, detoxifying, and antioxidant enzyme activities, were evaluated against S. oryzae adults. The effect of feeding a diet containing PPA and carob extract as a food attractant on the mortality of S. oryzae adults was also investigated. Feeding on the diet containing PPA resulted in a significant mortality of S. oryzae adults with a LC₅₀ (Lethal Concentration to kill 50% of insects) of 3.68% (w/w). The activity of digestive enzymes, including α-amylase, α-glucosidase, TAG-lipase, trypsin, chymotrypsin, elastase, and carboxy- and aminopeptidase, were decreased by the sub-lethal concentration of PPA. Detoxifying and antioxidant enzymes, including esterase, superoxide dismutase, catalase, glutathione-S-transferase, ascorbate peroxidase, glucose 6-phosphate dehydrogenase, and malondialdehyde, were activated in adults affected by PPA. These findings indicated that PPA, in addition to causing digestive disorders, leads to oxidative stress in S. oryzae. The presence of carob extract had no effect on the PPA-induced mortality of the insect. According to the results of the present study, PPA has promising insecticidal efficiency against S. oryzae. In addition, the usage of PPA with a food attractant carob extract in bait traps can be recommended as a new biorational formulation in S. oryzae management.

Design, Semisynthesis, Insecticidal and Antibacterial Activities of a Series of Marine-Derived Geodin Derivatives and Their Preliminary Structure–Activity Relationships

To enhance the biological activity of the natural product geodin (1), isolated from the marine-derived fungus Aspergillus sp., a series of new ether derivatives (2–37) was designed and semisynthesized using a high-yielding one-step reaction. In addition, the insecticidal and antibacterial activities of all geodin congeners were evaluated systematically. Most of these derivatives showed better insecticidal activities against Helicoverpa armigera Hübner than 1. In particular, 15 showed potent insecticidal activity with an IC50 value of 89 μM, comparable to the positive control azadirachtin (IC50 = 70 μM). Additionally, 5, 12, 13, 16, 30 and 33 showed strong antibacterial activity against Staphylococcus aureus and Aeromonas salmonicida with MIC values in the range of 1.15–4.93 μM. The preliminary structure–activity relationships indicated that the introduction of halogenated benzyl especially fluorobenzyl, into 1 and substitution of 4-OH could be key factors in increasing the insecticidal and antibacterial activities of geodin.

Discovery of mosquitocides from fungal extracts through a high-throughput cytotoxicity-screening approach

BACKGROUND

Mosquitoes transmit a variety of diseases. Due to widespread insecticide resistance, new effective pesticides are urgently needed. Entomopathogenic fungi are widely utilized to control pest insects in agriculture. We hypothesized that certain fungal metabolites may be effective insecticides against mosquitoes.

METHODS

A high-throughput cytotoxicity-based screening approach was developed to search for insecticidal compounds in our newly established global fungal extract library. We first determined cell survival rates after adding various fungal extracts. Candidate insecticides were further analyzed using traditional larval and adult survival bioassays.

RESULTS

Twelve ethyl acetate extracts from a total of 192 fungal extracts displayed > 85% inhibition of cabbage looper ovary cell proliferation. Ten of these 12 candidates were confirmed to be toxic to Anopheles gambiae Sua5B cell line, and six showed > 85% inhibition of Anopheles mosquito cell growth. Further bioassays determined a LC50, the lethal concentration that kills 50% of larval or adult mosquitoes, of 122 µg/mL and 1.7 µg/mosquito, respectively, after 24 h for extract 76F6 from Penicillium toxicarium.

CONCLUSIONS

We established a high-throughput MTT-based cytotoxicity screening approach for the discovery of new mosquitocides from fungal extracts. We discovered a candidate extract from P. toxicarium that exhibited high toxicity to mosquito larvae and adults, and thus were able to demonstrate the value of our recently developed approach. The active fungal extracts discovered here are ideal candidates for further development as mosquitocides.

The steroidal alkaloids α-tomatine and tomatidine: Panorama of their mode of action and pharmacological properties

The steroidal glycoalkaloid α-tomatine (αTM) and its aglycone tomatidine (TD) are abundant in the skin of unripe green tomato and present in tomato leaves and flowers. They mainly serve as defensive agents to protect the plant against infections by insects, bacteria, parasites, viruses, and fungi. In addition, the two products display a range of pharmacological properties potentially useful to treat various human diseases. We have analyzed all known pharmacological activities of αTM and TD, and the corresponding molecular targets and pathways impacted by these two steroidal alkaloids. In experimental models, αTM displays anticancer effects, particularly strong against androgen-independent prostate cancer, as well as robust antifungal effects. αTM is a potent cholesterol binder, useful as a vaccine adjuvant to improve delivery of protein antigens or therapeutic oligonucleotides. TD is a much less cytotoxic compound, able to restrict the spread of certain viruses (such as dengue, chikungunya and porcine epidemic diarrhea viruses) and to provide cardio and neuro-protective effects toward human cells. Both αTM and TD exhibit marked anti-inflammatory activities. They proceed through multiple signaling pathways and protein targets, including the sterol C24 methyltransferase Erg6 and vitamin D receptor, both directly targeted by TD. αTM is a powerful regulator of the NFkB/ERK signaling pathway implicated in various diseases. Collectively, the analysis shed light on the multitargeted action of αTM/TD and their usefulness as chemo-preventive or chemotherapeutic agents. A novel medicinal application for αTM is proposed.

Analysis of chemical compositions and larvicidal activity of nut extracts from Areca catechu Linn against Aedes (Diptera: Culicidae)

Background

There is a growing need to use green alternative larvicidal control for Aedes larvae compared to chemical insecticides. Substantial reliance on chemical insecticides caused insecticide resistance in mosquito populations. Thus, research for alternate chemical compounds from natural products is necessary to control Aedes larvae. This study explores the analysis of chemical compositions from Areca catechu nut as a potential larvicide for Aedes (Diptera: Culicidae).

Methods

The Areca catechu nut collected from Ipoh, Perak, Malaysia was grounded into powder and used for Soxhlet extraction. The chemical analysis of the extracts and their structures were identified using the GCMS-QP2010 Ultra (Shimadzu) system. National Institute of Standards and Technology (NIST) Chemistry WebBook, Standard Reference Database 69 (https://webbook.nist.gov/chemistry/) and PubChem (https://pubchem.ncbi.nlm.nih.gov/), the two databases used to retrieve the synonyms, molecular formula, molecular weight, and 2-dimensional (2D) structure of chemical compounds. Next, following WHO procedures for larval bioassays, the extracts were used to asses larvicidal activity against early 4^th instar larvae of Aedes aegypti and Aedes albopictus.

Results

The larvicidal activities were observed against early 4^th stage larvae with different concentrations in the range from 200 mg/L to 1600 mg/L. The LC₅₀ and LC₉₅ of Aedes aegypti were 621 mg/L and 2264 mg/L respectively; whereas the LC₅₀ and LC₉₅ of Aedes albopictus were 636 mg/L and 2268 mg/L respectively. Mortality was not observed in the non-target organism test. The analysis using gas chromatography and mass spectrometer recovered several chemical compounds such as Arecaidine, Dodecanoic acid, Methyl tetradecanoate, Tetradecanoic acid <n->, and n-Hexadecanoic acid bioactive components. These chemical constituents were used as additive formulations in pesticides, pest control, insect repellent, and insecticidal agents.

Conclusions

Our study showed significant outcomes from the extract of Areca catechu nut and it deserves further investigation in relation to chemical components and larvicidal actions between different species of Aedes mosquitoes. Even though all these findings are fundamental, it may have some interesting potentials to be developed as natural bio-larvicidal products.

Efficacy of Precocene I from Desmosstachya bipinnata as an Effective Bioactive Molecules against the Spodoptera litura Fab. and Its Impact on Eisenia fetida Savigny

The sustainability of agroecosystems are maintained with agro-chemicals. However, after more than 80 years of intensive use, many pests and pathogens have developed resistance to the currently used chemistries. Thus, we explored the isolation and bioactivity of a chemical compound, Precocene I, isolated from the perennial grass, Desmosstachya bipinnata (L.) Stapf. Fractions produced from chloroform extractions showed suppressive activity on larvae of Spodoptera litura (Lepidoptera: Noctuidae), the Oriental armyworm. Column chromatography analyses identified Precocene I confirmed using FTIR, HPLC and NMR techniques. The bioactivity of the plant-extracted Dp-Precocene I was compared to a commercially produced Precocene I standard. The percentage of mortality observed in insects fed on plant tissue treated with 60 ppm Db-Precocene I was 97, 87 and 81, respectively, for the second, third and fourth instar larvae. The LC50 value of third instars was 23.2 ppm. The percentages of survival, pupation, fecundity and egg hatch were altered at sub-lethal concentrations of Db-Precocene I (2, 4, 6 and 8 ppm, sprays on castor leaves). The observed effects were negatively correlated with concentration, with a decrease in effects as concentrations increased. Distinct changes in feeding activity and damage to gut tissues were observed upon histological examination of S. litura larvae after the ingestion of Db-Precocene I treatments. Comparative analyses of mortality on a non-target organism, the earthworm, Eisenia fetida, at equal concentrations of Precocene I and two chemical pesticides (cypermethrin and monocrotophos) produced mortality only with the chemical pesticide treatments. These results of Db-Precocene I as a highly active bioactive compound support further research to develop production from the grass D. bipinnata as an affordable resource for Precocene-I-based insecticides.

Toxicity of Bioactive Molecule Andrographolide against Spodoptera litura Fab and Its Binding Potential with Detoxifying Enzyme Cytochrome P450

Spodoptera litura Fab. is a polyphagous pest causing damage to many agriculture crops leading to yield loss. Recurrent usage of synthetic pesticides to control this pest has resulted in resistance development. Plant-derived diterpenoid compound andrographolide was isolated from the leaves of Andrographis paniculata. It was analysed by gas chromatography-mass spectroscopy and quantified by HPLC. Nutritional indices and digestive enzymatic profile were evaluated. Third, fourth and fifth instar larvae were treated with different concentrations of andrographolide. At 3, 6 and 9 ppm-treated concentrations the larvae showed decreased RGR, RCR, ECI, ECD values with adverse increase in AD. The digestive enzymes were significantly inhibited when compared with control. Conspicuously, andrographolide showed pronounced mortality of S. litura by inhibition of enzyme secretion and intake of food. The binding ability of andrographolide with CYTP450 showed high affinity with low binding energy. Andrographolide has the potential to be exploited as a biocontrol agent against S. litura as an eco-friendly pesticide.

Austins-Type Meroterpenoids from a Mangrove-Derived Penicillium sp

Three unusual austins-type meroterpenoids penicianstinoids C-E (1-3) were obtained from the mangrove-derived fungus Penicillium sp. TGM112. The structures of 1-3 including absolute configurations were determined by detailed NMR, MS spectroscopic data, X-ray diffraction analysis, and calculated electronic circular dichroism data. Penicianstinoid C (1) was the first austins-type meroterpenoid with a unique 6/6/6/5 rearranged tetracyclic skeleton possessing two unusual spirocyclic moieties (2-oxaspiro[5.5]undeca-4,7-dien-3-one and 6-methylene-2-oxaspiro[4.5]decane-1,4-dione). Penicianstinoid D (2) was an unusual austins-type meroterpenoid with a 6/6/6/6 tetracyclic skeleton containing an octahydro-2H-chromen-2-one unit. Penicianstinoid E (3) possessed a 6/5/6/6/6/5 fused hexacyclic skeleton with an uncommon five-membered ether ring system. The plausible biosynthetic pathway of 1-3 is also proposed. Compounds 1 and 3 inhibited the growth of newly hatched Helicoverpa armigera Hubner larvae with IC₅₀ values of 100 and 200 μg/mL, respectively.

Highly Efficient Removal of Neonicotinoid Insecticides by Thioether-Based (Multivariate) Metal-Organic Frameworks

Circumventing the impact of agrochemicals on aquatic environments has become a necessity for health and ecological reasons. Herein, we report the use of a family of five eco-friendly water-stable isoreticular metal-organic frameworks (MOFs), prepared from amino acids, as adsorbents for the removal of neonicotinoid insecticides (thiamethoxam, clothianidin, imidacloprid, acetamiprid, and thiacloprid) from water. Among them, the three MOFs containing thioether-based residues show remarkable removal efficiency. In particular, the novel multivariate MOF {Sr^IICu^II₆[(S,S)-methox]_1.5[(S,S)-Mecysmox]_1.50(OH)₂(H₂O)}·36H₂O (5), featuring narrow functional channels decorated with both -CH₂SCH₃ and -CH₂CH₂SCH₃ thioalkyl chains-from l-methionine and l-methylcysteine amino acid-derived ligands, respectively-stands out and exhibits the higher removal efficiency, being capable to capture 100% of acetamiprid and thiacloprid in a single capture step under dynamic solid-phase extraction conditions-less than 30 s. Such unusual combination of outstanding efficiency, high stability in environmental conditions, and low-cost straightforward synthesis in 5 places this material among the most attractive adsorbents reported for the removal of this type of contaminants.

The Rapid Evolution of Resistance to Vip3Aa Insecticidal Protein in Mythimna separata (Walker) Is Not Related to Altered Binding to Midgut Receptors

Laboratory selection for resistance of field populations is a well-known and useful tool to understand the potential of insect populations to evolve resistance to insecticides. It provides us with estimates of the frequency of resistance alleles and allows us to study the mechanisms by which insects developed resistance to shed light on the mode of action and optimize resistance management strategies. Here, a field population of Mythimna separata was subjected to laboratory selection with either Vip3Aa, Cry1Ab, or Cry1F insecticidal proteins from Bacillus thuringiensis. The population rapidly evolved resistance to Vip3Aa reaching, after eight generations, a level of >3061-fold resistance, compared with the unselected insects. In contrast, the same population did not respond to selection with Cry1Ab or Cry1F. The Vip3Aa resistant population did not show cross resistance to either Cry1Ab or Cry1F. Radiolabeled Vip3Aa was tested for binding to brush border membrane vesicles from larvae from the susceptible and resistant insects. The results did not show any qualitative or quantitative difference between both insect samples. Our data, along with previous results obtained with other Vip3Aa-resistant populations from other insect species, suggest that altered binding to midgut membrane receptors is not the main mechanism of resistance to Vip3Aa.

Extraction of permethrin from impregnated fabrics for determination by ultra-high performance liquid chromatography with diode array detection

Permethrin is a synthetic pyrethroid insecticide that is largely used in the impregnation of fabrics employed for different purposes. This paper reports a detailed study on the conditions for its extraction from fabrics and for its determination by ultra-high performance liquid chromatography with diode array detection (UHPLC-DAD). Several parameters that could affect the extraction efficiency of permethrin were evaluated, such as the extraction time, agitating mode (mechanical or ultrasound-assisted), solvent type (methanol or acetonitrile), concentration, and volume. Under optimized conditions, the extraction was performed for 10 min using a 2 × 2 cm piece of impregnated fabric and 5 mL of pure methanol. The flask containing the sample and the solvent was shaken mechanically using a horizontal roller mixer. The accuracy of the method was assessed by a recovery test, which presented satisfactory results ranging from 86.8% to 95.2%. The method was employed in the analysis of nine samples of commercial fabrics of different colors and grammages that were impregnated with permethrin. The concentration of permethrin found in these samples varied between 25.6 ± 4.2 and 934 ± 119 mg m^-2.

An Eco-Friendly Approach to the Control of Pathogenic Microbes and Anopheles stephensi Malarial Vector Using Magnesium Oxide Nanoparticles (Mg-NPs) Fabricated by Penicillium chrysogenum

The discovery of eco-friendly, rapid, and cost-effective compounds to control diseases caused by microbes and insects are the main challenges. Herein, the magnesium oxide nanoparticles (MgO-NPs) are successfully fabricated by harnessing the metabolites secreted by Penicillium chrysogenum. The fabricated MgO-NPs were characterized using UV-Vis, XRD, TEM, DLS, EDX, FT-IR, and XPS analyses. Data showed the successful formation of crystallographic, spherical, well-dispersed MgO-NPs with sizes of 7-40 nm at a maximum wavelength of 250 nm. The EDX analysis confirms the presence of Mg and O ions as the main components with weight percentages of 13.62% and 7.76%, respectively. The activity of MgO-NPs as an antimicrobial agent was investigated against pathogens Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, Escherichia coli, and Candida albicans, and exhibited zone of inhibitions of 12.0 ± 0.0, 12.7 ± 0.9, 23.3 ± 0.8, 17.7 ± 1.6, and 14.7 ± 0.6 mm respectively, at 200 µg mL-1. The activity is decreased by decreasing the MgO-NPs concentration. The biogenic MgO-NPs exhibit high efficacy against different larvae instar and pupa of Anopheles stephensi, with LC50 values of 12.5-15.5 ppm for I-IV larvae instar and 16.5 ppm for the pupa. Additionally, 5 mg/cm2 of MgO-NPs showed the highest protection percentages against adults of Anopheles stephensi, with values of 100% for 150 min and 67.6% ± 1.4% for 210 min.

Antifungal and Larvicidal Activities of Phlorotannins from Brown Seaweeds

Phlorotannins are secondary metabolites produced by brown seaweeds with antiviral, antibacterial, antifungal, and larvicidal activities. Phlorotannins' structures are formed by dibenzodioxin, ether and phenyl, ether, or phenyl linkages. The polymerization of phlorotannins is used to classify and characterize. The structural diversity of phlorotannins grows as polymerization increases. They have been characterized extensively with respect to chemical properties and functionality. However, review papers of the biological activities of phlorotannins have focused on their antibacterial and antiviral effects, and reviews of their broad antifungal and larvicidal effects are lacking. Accordingly, evidence for the effectiveness of phlorotannins as antifungal and larvicidal agents is discussed in this review. Online databases (ScienceDirect, PubMed, MEDLINE, and Web of Science) were used to identify relevant articles. In total, 11 articles were retrieved after duplicates were removed and exclusion criteria were applied. Phlorotannins from brown seaweeds show antifungal activity against dermal and plant fungi, and larvicidal activity against mosquitos and marine invertebrate larvae. However, further studies of the biological activity of phlorotannins against fungal and parasitic infections in aquaculture fish, livestock, and companion animals are needed for systematic analyses of their effectiveness. The research described in this review emphasizes the potential applications of phlorotannins as pharmaceutical, functional food, pesticide, and antifouling agents.

Characterization of a New Insecticidal Anthraquinone Derivative from an Endophyte of Acremonium vitellinum against Helicoverpa armigera

Endophytic fungi have proven to be prolific producers of bioactive secondary metabolites with agricultural applications. In this study, bioassay-guided isolation of the endophytic fungus Acremonium vitellinum yielded four anthraquinone derivatives (compounds 1-4), including a previously undescribed dimethylated derivative of bipolarin, 6,8-di-O-methylbipolarin (1). Their structures were determined by 1D and 2D nuclear magnetic resonance analysis as well as high-resolution electrospray ionization mass spectrometry data, and the absolute configuration of 1 was established by comparing the calculated and experimental electronic circular dichroism spectra. The insecticidal activity of the isolated compounds against the cotton bollworm Helicoverpa armigera was evaluated. The new compound 1 showed the strongest larvicidal activity against the 3rd instar larvae of H. armigera with an LC₅₀ value of 0.72 mg/mL. In addition, transcriptome sequencing was performed to evaluate the molecular mechanism of the insecticidal activity. In total, 5732 differentially expressed genes were found, among which 2904 downregulated genes and 2828 upregulated genes were mainly involved in cell autophagy, apoptosis, and DNA mismatch repair and replication. The results presented in this study reveal how 1 exerts its insecticidal effects against H. armigera via genome-wide differential gene expression analyses. Our findings suggest that anthraquinone derivatives are potential biopesticides for cotton bollworm control.

Solanum Nigrum Fruit Extract Increases Toxicity of Fenitrothion-A Synthetic Insecticide, in the Mealworm Beetle Tenebrio Molitor Larvae

Synthetic insecticides are widely used for crop protection both in the fields and in the food stored facilities. Due to their toxicity, and assumptions of Integrated Pest Management, we conducted two independent experiments, where we studied the influence of Solanum nigrum unripe fruit extract on the toxicity of an organophosphorus insecticide fenitrothion. In the first variant of the experiment, Tenebrio molitor larvae were fed with blended fenitrothion (LC50) and the extract in four concentrations (0.01, 0.1, 1 and 10%) in ratio 1:1 for 3 days. In the second variant, a two-day application of fenitrothion (LC40) was preceded by a one-day extract treatment. The first variant did not show any increase in lethality compared to fenitrothion; however, ultrastructure observations exhibited swollen endoplasmic reticulum (ER) membranes in the midgut and nuclear and cellular membranes in the fat body, after application of blended fenitrothion and extract. An increased amount of heterochromatin in the fat body was observed, too. In the second variant, pre-treatment of the extract increased the lethality of larvae, decreased the level of glycogen and lipids in the fat body and disrupted integrity of midgut cellular membranes. S. nigrum extract, applied prior to fenitrothion treatment can be a factor increasing fenitrothion toxicity in T. molitor larvae. Thus, this strategy may lead to decreased emission of synthetic insecticides to the environment.

Residual Larvicidal Activity of Quinones against Aedes aegypti

The number of documented dengue cases has increased dramatically in recent years due to transmission through the Aedes aegypti mosquito bite. Vector control remains the most effective measure to protect against this and other arboviral diseases including Zika, chikungunya and (urban) yellow fever, with an established vaccine only available for yellow fever. Although the quinone class shows potential as leading compounds for larvicide development, limited information restricts the development of optimized structures and/or formulations. Thus, in this contribution we investigated the larvicidal and pupicidal activity of three quinone compounds isolated from a Connarus suberosus root wood ethyl acetate extract together with 28 quinones from other sources. Eight quinones demonstrated larvicidal activity, of which tectoquinone (4) proved to be the most active (LC50 1.1 µg/mL). The essential residual effect parameter of four of these quinones was evaluated in laboratory trials, with tectoquinone (4) and 2-ethylanthraquinone (7) presenting the most prolonged activity. In small-scale field residual tests, tectoquinone (4) caused 100% larvae mortality over 5 days, supporting its selection for formulation trials to develop a prototype larvicide to control Ae. aegypti.

Porous Activated Carbon from Lignocellulosic Agricultural Waste for the Removal of Acetampirid Pesticide from Aqueous Solutions

A facile eco-friendly approach for acetampirid pesticide removal is presented. The method is based on the use of micro- and mesoporous activated carbon (TPAC) as a natural adsorbent. TPAC was synthesized via chemical treatment of tangerine peels with phosphoric acid. The prepared activated carbon was characterized before and after the adsorption process using Fourier- transform infrared (FTIR), X-ray diffraction (XRD), particle size and surface area. The effects of various parameters on the adsorption of acetampirid including adsorbent dose (0.02–0.2 g), pH 2–8, initial adsorbate concentration (10–100 mg/L), contact time (10–300 min) and temperature (25–50 °C) were studied. Batch adsorption features were evaluated using Langmuir and Freundlich isotherms. The adsorption process followed the Langmuir isotherm model with a maximum adsorption capacity of 35.7 mg/g and an equilibration time within 240 min. The adsorption kinetics of acetamiprid was fitted to the pseudo-second-order kinetics model. From the thermodynamics perspective, the adsorption was found to be exothermic and spontaneous in nature. TPAC was successfully regenerated and reused for three consecutive cycles. The results of the presented study show that TPAC may be used as an effective eco-friendly, low cost and highly efficient adsorbent for the removal of acetamiprid pesticides from aqueous solutions.

Spinasterol, 22,23-Dihydrospinasterol and Fernenol from Citrullus Colocynthis L. with Aphicidal Activity against Cabbage Aphid Brevicoryne Brassicae L

Brevicoryne brassicae is a problematic pest in cabbage and other field crops. Synthetic pesticides are used to control this pest, but they are injurious for human health and the environment. The present study aimed to purify and identify the active compounds from Citrullus colocynthis leaves with an appraisal of their efficacy against B. brassicae. Separation and purification were performed via different chromatographic techniques. Molecular analysis and chemical structures were recognized by mass spectrum (MS) and nuclear magnetic resonance (NMR), respectively. Moreover, in vitro and in vivo aphicidal activity was assessed using various concentrations, i.e., 6.25, 12.5, 25 and 50 µg/mL at 12, 24, 48 and 72 h exposure. The outcome shows that mass spectrum analyses of the purified compounds suggested the molecular formulae are C₃₀H₅₀O and C₂₉H₅₀O, C₂₉H₄₈O. The compounds were characterized as fernenol and a mixture of spinasterol, 22,23-dihydrospinasterol by ¹H-NMR and ¹³C-NMR spectrum analysis. The toxicity results showed that the mixture of spinasterol and 22,23-dihydrospinasterol showed LC₅₀ values of 32.36, 44.49 and 37.50 µg/mL by contact, residual and greenhouse assay at 72 h exposure, respectively. In contrast, fernenol recorded LC₅₀ values as 47.99, 57.46 and 58.67 µg/mL, respectively. On the other hand, spinasterol, 22,23-dihydrospinasterol showed the highest mortality, i.e., 66.67%, 53.33% and 60% while, 30%, 23.33% and 25% mortality was recorded by fernenol after 72 h at 50 µg/mL by contact, residual and greenhouse assay, respectively. This study suggests that spinasterol, 22,23-dihydrospinasterol are more effective against B. brassicae which may be introduced as an effective and suitable substitute of synthetic chemical pesticides.

Insecticidal Toxicities of Three Main Constituents Derived from Trachyspermum ammi (L.) Sprague ex Turrill Fruits against the Small Hive Beetles, Aethina tumida Murray

Small hive beetle (Aethina tumida Murray), indigenous to Africa, has spread to other parts of the world where has become a threat to the honeybee industry. In the present study, insecticidal properties (contact, fumigant, and repellent toxicities) of three main constituents derived from Trachyspermum ammi (L.) Sprague ex Turrill fruits essential oil were evaluated against adult small hive beetles under laboratory conditions. The Hydrodistillation of T. ammi fruits, grown in Ethiopia, yielded a pale yellow essential oil (3.5% v/w) with a strong aromatic odor. Analyses by gas chromatography-mass spectrometry identified twenty-two compounds that accounted for 98.68% of the total essential oil. The essential oil was dominated by monoterpenoids, comprising γ-terpinene (32.72%), p-cymene (27.92%), and thymol (24.36%). The essential oil showed strong contact and fumigation toxicities against the small hive beetle adults, with a LD₅₀ value of 66.64 µg/adult and a LC₅₀ value of 89.03 mg/L air, respectively. Among the main constituents, thymol was the most toxic component found in both contact (LD₅₀ = 41.79 µg/adult) and fumigation (LC₅₀ = 52.66 mg/L air) toxicities. The other two components, γ-terpinene and p-cymene, were less effective in both contact and fumigant toxicities testing. The results showed that T. ammi essential oil and thymol could serve as potential alternatives to synthetic insecticides for the control of small hive beetle adults.

Interactions of Destruxin A with Silkworms' Arginine tRNA Synthetase and Lamin-C Proteins

Destruxin A (DA), a cyclodepsipeptidic mycotoxin produced by entomopathogenic fungus Metarhizium anisopliae, has good insecticidal activity and potential to be a new pesticide. However, the mechanism of action is still obscure. Our previous experiments showed that DA was involved in regulation of transcription and protein synthesis and suggested that silkworms’ arginine tRNA synthetase (BmArgRS), Lamin-C Proteins (BmLamin-C) and ATP-dependent RNA helicase PRP1 (BmPRP1) were candidates of DA-binding proteins. In this study, we employed bio-layer interferometry (BLI), circular dichroism (CD), cellular thermal shift assay (CETSA), and other technologies to verify the interaction of DA with above three proteins in vitro and in vivo. The results of BLI indicated that BmArgRS and BmLamin-C were binding-protein of DA with K_D value 5.53 × 10⁻⁵ and 8.64 × 10⁻⁵ M, but not BmPRP1. These interactions were also verified by CD and CETSA tests. In addition, docking model and mutants assay in vitro showed that BmArgRS interacts with DA at the pocket including Lys228, His231, Asp434 and Gln437 in its enzyme active catalysis region, while BmLamin-C binds to DA at His524 and Lys528 in the tail domain. This study might provide new insight and evidence in illustrating molecular mechanism of DA in breaking insect.

An overview of acyclotides: Past, present and future

Acyclotides are plant-based, acyclic miniproteins with cystine knot motif formed by three conserved disulfide linkages and lack head to tail ligation. Acyclotides may not necessarily be less stable, even though they lack cyclic backbone, as the conserved cystine knot feature provides the required stability. Violacin A was the first acyclotide, isolated from Viola odorata in 2006. Until now, acyclotides have been reported from five dicot families (Violaceae, Rubiaceae, Cucurbitaceae, Solanaceae, Fabaceae) and one monocot family (Poaceae). In Poaceae, only acyclotides have been found whereas in dicot families both cyclotides and acyclotides have been isolated. In last 15 years, several acyclotides with antimicrobial, cytotoxic and hemolytic bioactivities have been discovered. Thus, although many naturally expressed acyclotides do exhibit bioactivities, the linearization of the cyclic peptides may result in loss of bioactivities. Although, bioactivities of acyclotides are comparable to their cyclic counterparts, the numbers of isolated acyclotides are still few. Further, those discovered, have the scope to be screened for agriculturally important activities (insecticidal, anti-helminthic, molluscicidal) and pharmaceutical properties (anticancer, anti-HIV, immuno-stimulant). The feasibility of application of acyclotides is because of their relatively less complex biological synthesis compared to cyclotides, as the cyclization step is not needed. This attribute facilitates the production of transgenic crops and/or its expression in heterologous organisms, lacking cyclization machinery. Keeping in view the bioactivities and the wide array of emerging potential applications of acyclotides, the present review discusses their distribution in plants, gene and protein structure, biosynthesis, bioactivities and mechanism of action. Further, their potential applications and future perspectives to exploit them in agriculture and pharmaceutical industries have been highlighted.

Isolation and characterization of the insect growth regulatory substances from actinomycetes

Insect growth regulators (IGRs) are attractive alternatives to chemical insecticides. Since it has been reported that secondary metabolites from actinomycetes show insecticidal activities against various insect pests, actinomycetes could be a potential source of novel IGR compounds. In the present study, insect juvenile hormone antagonists (JHANs) were identified from actinomycetes and their insect growth regulatory and insecticidal activities were investigated. A total of 363 actinomycetes were screened for their insect growth regulatory and insecticidal activities against Aedes albopictus and Plutella xylostella. Among them, Streptomyces sp. AN120537 showed the highest JHAN and insecticidal activities. Five antimycins were isolated as active compounds by assay-guided fractionation and showed high JHAN activities. These antimycins also exhibited significant insecticidal activities against A. albopictus, P. xylostella, F. occidentalis, and T. urticae. Moreover, dead larvae treated with these antimycins displayed morphological deformities that are similar to those of JH-based IGR-treated insects. This is the first report demonstrating that the insecticidal activities of antimycins resulted from their possible JHAN activity. Based on our results, it is expected that novel JHAN compounds potentially derived from actinomycetes could be efficiently applied as IGR insecticides with a broad insecticidal spectrum.

Bioactivity and efficacy of essential oils extracted from Artemisia annua against Tribolium casteneum (Herbst. 1797) (Coleoptera: Tenebrionidae): An eco-friendly approach

Tribolium casteneum is a major stored grains pest causing huge loss by secreting toxic quinones' which make the grains unfit for human consumption. Increasing concern about the fast-growing resistance in T. casteneum against fumigants has evoked more intense research worldwide. Therefore, finding an eco-friendly alternative for the management of the pest is of great importance. In this study, the insecticidal activity of the essential oils (EOs) of Artemisia annua is evaluated. Chemical composition of the EOs eluted with methanol and petroleum ether was analysed through Gas chromatography-mass spectrometry (GC-MS). The result has reported a total of 13 & 16 compounds in the methanol and petroleum ether EOs respectively. In contact toxicity studies, adults were found more susceptible to the petroleum ether EOs (LD₅₀ = 0.43 mg adult-¹) than the methanolic EOs (LD₅₀ = 1.87 mg adult-¹). Petroleum ether EOs was also superior in fumigant assays against both the adults (0.81 mg L air^-1) and larvae (0.65 mg L air^-1). Moreover, the same was also recorded as a strong repellent. The bio-molecular studies conducted to gain an insight into the extent of metabolic disturbances inflicted in the treatment sets has shown a significant increase in Lipid peroxidase and decrease (p˂0.01) in protein, Acetylcholinesterase, Glutathione S Transferees, Reduced Glutathione level. This indicates the major signs of oxidative stress in the treatment sets. The Results ascertain the knowledge to develop natural insecticides from Artemisia annua using a potential solvent to be used in the future as an efficient management tool against T. casteneum.

Ammi Visnaga L., a Potential Medicinal Plant: A Review

Ammi visnaga L. (Visnaga daucoides Gaertn., Family Apiaceae), also known as Khella Baldi or toothpick weed, is an annual or biennial herb indigenous to the Mediterranean region of North Africa, Asia, and Europe. The plant is known to have been used in traditional medicine a long time ago. Nowadays, it is used in modern medicine to treat many aliments such as renal colic and coronary insufficiency, and is used as an antioxidant, antifungal, and antibacterial, with a larvicidal effect on mosquito larvae. Peer-reviewed studies show that these pharmacological activities are due its valuable chemical constituents that include mainly essential oil, polyphenolic compounds including flavonoids, as well as γ-pyrones, represented mainly by khellin and visnagin. Its essential oil is reported to have antiviral, antibacterial, and larvicidal effects, while its flavonoid content is responsible for its antioxidant activity. Its γ-pyrone content has a powerful effect on facilitating the passage of kidney stones and relieving renal colic, in addition to having a relaxant effect on smooth muscle including that of the coronary arteries. The current review represents the progress in research on A. visnaga in terms of either its chemistry or biological activities. This review represents scientific support material for the use of the plant by the pharmaceutical industry.

Secondary Metabolites from Solanum rostratum and Their Antifeedant Defense Mechanisms against Helicoverpa armigera

Solanum rostratum is a worldwide malignant invasive weed, causing serious harm to the ecological environment and biodiversity. Strong chemical defense against herbivorous insects is supposed to be one of the successful invasive mechanisms of this exotic plant. However, the real defense components and their action mechanisms and distributions are still unknown. To address these problems, we bioassay-guided isolated compounds from the aerial part of S. rostratum and determined their structures using high-resolution electrospray ionization mass spectrometry, nuclear magnetic resonance, and electronic circular dichroism calculation. One new and seven known compounds were identified, and all of the isolates exhibited different levels of antifeedant activities, especially compounds 1 and 4. Consistently, compounds 1 and 4 displayed potent inhibitory effects on antifeedant-related enzymes (AchE and CarE). The action mechanisms of active compounds 1 and 4 were revealed by molecular docking and molecular dynamic simulation studies. Furthermore, the distributions of the active compounds in leaves, stems, and flowers were also analyzed by liquid chromatography-mass spectrometry.

Efficacy of biochar in removal of organic pesticide, Bentazone from watershed systems

Bentazone is one of the toxic insecticides used to control forest tent caterpillar moths, boll weevils, gypsy moths, and other types of moths in various field crops. We report the efficacy of biochar prepared from the Azardirachta Indica waste biomass as adsorbent for removal of Bentazone. Biochar material was prepared by pyrolysis process under limited oxygen conditions. Biochar material was characterized by proximate and ultimate analysis, SEM analysis, FTIR analysis and TG/DTA analyses. The Bentazone adsorption capacity by biochar from aqueous solutions was assessed. Effect of time, adsorbent dosage, insecticide concentration and pH on the adsorption characteristics of the biochar were evaluated. Adsorption parameters were obtained at equilibrium contact time of 150 min, with biochar dosage of 0.5 g at pH 8. From the optimization studies, desirability of 0.952 was obtained with response (adsorption uptake) of 79.40 mg/g, for initial concentration of insecticide (50 mg/L), adsorbent dosage (0.448 g), time 30.0 min and pH 2. The adsorption isotherm data for the removal of Bentazone fitted well with the Freundlich isotherm. This study indicates that the biochar produced from the bark of Azardirachta Indica biomass could be employed as a potential adsorbent for removal of synthetic organic pollutants from the water streams.

Evaluation of Toxicity in Four Extract Types of Tuba Root against Dengue Vector, Aedes aegypti (Diptera: Culicidae) Larvae

BACKGROUND AND OBJECTIVE

Since the Dengue virus spreads rapidly and the vector becomes resistant to insecticides and larvicides, exploration of new compounds that overcome resistance problems, are easily degraded and do not lead to bioaccumulation, is needed. This study evaluated four extract types of Derris elliptica represented the polar, semi-polar and nonpolar extract against the 3rd-instar larvae of Ae. aegypti and determined the effective concentration among the extracts.

MATERIALS AND METHODS

The crude extract was obtained from the maceration of root powder of the plant with methanol and subsequently evaporated. The crude extract was diluted in distilled water and partitioned sequentially with ethyl-acetate, n-hexane and water to obtain their fractions. All the fractions were evaporated to obtain their extract types. Initial bioassay test of the extracts with concentration ranges of 50, 100, 500 and 1,000 mg L-1 against Ae. aegypti larvae and resulted in 86-100% larval mortality rates at concentrations of 50 and 100 mg L-1, except for water extract. The lower concentration range of 3, 5, 10, 25, 50 and 100 mg L-1 of three extract types were tested.

RESULTS

Larval mortality rates of 18.4-100, 1.6-99.2 and 0.8-98.4% with LC50 of 4.088, 14.066 and 21.063 mg L-1, respectively for n-hexane, methanol and ethyl-acetate. FTIR analysis indicated nine lead compounds in which rotenone and ceramides were observed in all extract types.

CONCLUSION

The n-hexane extract showed the highest larvicidal toxicity and its specific compounds are necessarily isolated to obtain pure bioactive ingredients.

Hyalodendrins A and B, New Decalin-Type Tetramic Acid Larvicides from the Endophytic Fungus Hyalodendriella sp. Ponipodef12

Two new decalin/tetramic acid hybrid metabolites, hyalodendrins A (1) and B (2) were isolated from plant endophytic fungus Hyalodendriella sp. Ponipodef12. The structures of the new compounds were elucidated by analysis of the spectroscopic data, including NMR, HRMS and ECD, and by chemical conversion. Compounds 1 and 2 were phomasetin analogues, and both showed potent larvicidal activity against the fourth-instar larvae of Aedes aegypti with the median lethal dose (LC₅₀) values of 10.31 and 5.93 μg/mL, respectively.

Insecticidal Activity and Insecticidal Mechanism of Total Saponins from Camellia oleifera

Chemical pesticides are commonly used during the cultivation of agricultural products to control pests and diseases. Excessive use of traditional pesticides can cause environmental and human health risks. There are ongoing searches for new plant-derived pesticides to reduce the use of chemical pesticides. In this study, tea saponin extracts of different purities were extracted from Camellia oleifera seeds using AB-8 macroporous resin and gradient elution with ethanol. The insecticidal effects of the tea saponin extracts were evaluated by contact toxicity tests and stomach toxicity tests using the lepidopteran pest of tea plantation, Ectropis obliqua. The total saponins extracted using 70% ethanol showed strong contact toxicity (LC₅₀ = 8.459 mg/L) and stomach toxicity (LC₅₀ = 22.395 mg/L). In-depth mechanistic studies demonstrated that tea saponins can disrupt the waxy layer of the epidermis, causing serious loss of water, and can penetrate the inside of the intestine of E. obliqua. After consumption of the tea saponins, the intestinal villi were shortened and the cavities of the intestinal wall were disrupted, which resulted in larval death. This study highlights the potential of tea saponins as a natural, plant-derived pesticide for the management of plant pests.

Dual Insecticidal Effects of Adenanthera pavonina Kunitz-Type Inhibitor on Plodia interpunctella is Mediated by Digestive Enzymes Inhibition and Chitin-Binding Properties

The Indianmeal moth, Plodia interpunctella, is one of the most damaging pests of stored products. We investigated the insecticidal properties of ApKTI, a Kunitz trypsin inhibitor from Adenanthera pavonina seeds, against P. interpunctella larvae through bioassays with artificial diet. ApKTI-fed larvae showed reduction of up to 88% on larval weight and 75% in survival. Trypsin enzymes extracted from P. interpunctella larvae were inhibited by ApKTI, which also demonstrated capacity to bind to chitin. Kinetic studies revealed a non-competitive inhibition mechanism of ApKTI for trypsin, which were further corroborated by molecular docking studies. Furthermore, we have demonstrated that ApKTI exhibits a hydrophobic pocket near the reactive site loop probably involved in chitin interactions. Taken together, these data suggested that the insecticidal activity of ApKTI for P. interpunctella larvae involves a dual and promiscuous mechanisms biding to two completely different targets. Both processes might impair the P. interpunctella larval digestive process, leading to larvae death before reaching the pupal stage. Further studies are encouraged using ApKTI as a biotechnological tool to control insect pests in field conditions.

Simultaneous removal of neonicotinoid insecticides by a microbial degrading consortium: Detoxification at reactor scale

Neonicotinoid insecticides show high persistence in the environment, and standard biological approaches such as biopurification systems have shown mostly inefficient removal of such compounds. In this work, soil pre-exposed to imidacloprid was used to obtain presumptive imidacloprid-degrading consortia. Cometabolic enrichment yielded a microbial consortium composed of eight bacterial and one yeast strains, capable of degrading not only this compound, but also thiamethoxam and acetamiprid, as demonstrated in cross-degradation assays. The biological removal process was scaled-up to batch stirred tank bioreactors (STBR); this configuration was able to simultaneously remove mixtures of imidacloprid + thiamethoxam or imidacloprid + thiamethoxam + acetamiprid, reaching elimination of 95.8% and 94.4% of total neonicotinoids, respectively. Removal rates in the bioreactors followed the pattern imidacloprid > acetamiprid > thiamethoxam, including >99% elimination of imidacloprid in 6 d and 17 d (binary and ternary mixtures, respectively). A comprehensive evaluation of the detoxification in the STBR was performed using different biomarkers: seed germination (Lactuca sativa), bioluminescence inhibition (Vibrio fischeri), and acute oral tests in honeybees. Overall, ecotoxicological tests revealed partial detoxification of the matrix, with clearer detoxification patterns in the binary mixture. This biological approach represents a promising option for the removal of neonicotinoids from agricultural wastewater; however, optimization of the process should be performed before application in farms.

Similarities and differences in adsorption mechanism of dichlorvos and pymetrozine insecticides with coconut fiber biowaste sorbent

In this study, the similarities and differences of the adsorption mechanisms between dichlorvos and pymetrozine and coconut fiber biowaste sorbent (CF-BWS) were investigated. CF-BWS was produced using the slow pyrolysis process at 600 °C for 4 h. HCl acid modification was used to improve the specific surface area. The properties of CF-BWS were analyzed by SEM, FT-IR, BET, and pHpzc. The adsorption kinetics of dichlorvos and pymetrozine on the CF-BWS were well explained by the pseudo-second-order model. The adsorption isotherms for both insecticides were followed the Langmuir isotherm. The difference in molecular structures and surface chemistry caused the difference in adsorption mechanisms of both insecticides. The pore-filling and the hydrophobic interactions were the key mechanisms for both insecticide adsorptions. However, the π-π electron donor-acceptor interaction played the major role in the pymetrozine adsorption but hardly impacted on the adsorption of dichlorvos. The hydrogen bonding mechanism was pronounced in the pymetrozine adsorption, but it had little influence on the dichlorvos adsorption. The CF-BWS is exhibited as an excellent material for the removal of both pollutants and has high potential to be used further as the adsorbent in water treatment process.

Entomotoxic Activity of Prasiola crispa (Antarctic Algae) in Nauphoeta cinerea Cockroaches: Identification of Main Steroidal Compounds

Prasiola crispa is a macroscopic green algae found in abundance in Antarctica ice free areas. Prasiola crispan-hexaneextract (HPC) induced insecticidal activity in Nauphoeta cinerea cockroaches after 24 h of exposure. The chemical analysis of HPC revealed the presence of the followingphytosterols: β-sitosterol, campesterol and stigmasterol. The incubation of cockroach semi-isolated heart preparations with HPC caused a significant negative chronotropic activity in the heartbeats. HPC affected the insect neuromuscular function by inducing a complete inhibition of the cockroach leg-muscle twitch tension. When the isolated phytosterols were injected at in vivo cockroach neuromuscular preparations, there was a progressive inhibition of muscle twitches on the following order of potency: β-sitosterol > campesterol > stigmasterol. HPC also provoked significant behavioral alterations, characterized by the increase or decrease of cockroach grooming activity, depending on the dose assayed. Altogether, the results presented here corroborate the insecticide potential of Prasiola crispa Antarctic algae. They also revealed the presence of phytosterols and the involvement of these steroidal compounds in the entomotoxic activity of the algae, potentially by modulating octopaminergic-cholinergic pathways. Further phytochemical-combined bioguided analysis of the HPC will unveil novel bioactive compounds that might be an accessory to the insecticide activity of the algae.

Simultaneous Determination of Five Diamide Insecticides in Food Matrices Using Carbon Nanotube Multiplug Filtration Cleanup and Ultrahigh-Performance Liquid Chromatography-Tandem Mass Spectrometry

In this study, an analytical method was developed and validated for simultaneous determination of five diamide insecticides (chlorantraniliprole, cyantraniliprole, flubendiamide, cyclaniliprole, and tetrachlorantraniliprole) in food matrices. Determination of the latter two diamide compounds is first reported. Samples were cleaned up by multiplug filters containing carbon nanotubes (CNT) or hydrophilic-lipophilic balanced copolymers (HLB) and classic dispersive solid phase extraction (d-SPE) procedures, respectively. The CNT multiplug filter performed the best in terms of process rapidity and cleanup efficiency; thus, it was finally chosen for sample cleanup. Instrumental analysis was completed in 5 min using ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Mean recoveries of the five diamides ranged from 84.3 to 110.0%, with intraday and interday relative standard deviations (RSD) of less than 13.5%. Limits of quantitation (LOQ) of all analytes ranged from 0.005 to 0.01 mg kg^-1 in different matrices. The results indicate this method is reliable for monitoring the five diamide insecticides in various foods.

Reduction of phoxim pesticide residues from grapes by atmospheric pressure non-thermal air plasma activated water

In this study, we propose a novel strategy, plasma activated water (PAW) to reduce pesticide residues on agricultural products. To validate its feasibility and effectiveness, we employee high-performance liquid chromatography (HPLC) to detect phoxim on grapes. HPLC results suggest that the reduction of phoxim on grapes achieve 73.60% after treated 10 min by PAW prepared 30 min, and the concentration of phoxim decreased significantly (p <  0.05) with the preparation time of PAW. Furthermore, HPLC-MS analysis shows that the reduction effect of phoxim by PAW is dominated by the degradation of phoxim. Combined with analyzing the physicochemical properties of PAW, one possible degradation pathway is proposed under the present experimental conditions, mediated by reactive oxygen and nitrogen species. The acidic environment (pH < 3) and high oxidation capacity (ORP > 500 mV) are suggested to be a benefit to the reduction of phoxim. Besides, the experimental results regarding color, firmness, sugar, vitamin C, and superoxide dismutase of grapes demonstrate that the PAW treatment will not significantly affect the quality of grapes. In conclusion, phoxim pesticide residues on grapes could be effectively reduced by the PAW strategy and without a significant (p <  0.05) effect on grapes quality.

Stereoselective Analysis of Chiral Pyrethroid Insecticides Tetramethrin and α-Cypermethrin in Fruits, Vegetables, and Cereals

This manuscript presents an effective and robust method for simultaneous stereoselective determination of two pyrethroid insecticides, tetramethrin and α-cypermethrin in different food products by high-performance liquid chromatography. Enantioseparation was carried out using reversed-phase chromatography, and the influences of four polysaccharide-based chiral columns, mobile phase composition, and column temperature on retention were fully investigated. Satisfactory separation was obtained on Chiralpak IG column using acetonitrile-water (75:25, v/v) under isocratic conditions. To extract and purify the target analytes from food matrices, matrix solid-phase dispersion was employed with C₁₈ as dispersant and primary secondary amine as well as graphitized carbon black as cleanup sorbents. Response surface method based on Box-Behnken design was implemented to assist optimization of the extraction variables. Then, method validation was done in real samples including specificity, linearity, sensitivity, trueness, precision, as well as stability, and its analytical performance fulfills the criteria recommended by the European Union SANTE/11945/2015, demonstrating its applicability in studying the stereochemistry of chiral tetramethrin and α-cypermethrin in food products.

An atoxigenic L-strain of Aspergillus flavus (Eurotiales: Trichocomaceae) is pathogenic to the coffee twig borer, Xylosandrus compactus (Coleoptera: Curculionidea: Scolytinae)

This study isolated and evaluated virulence of fungal entomopathogens of Xylosandrus compactus - an important pest of Robusta coffee in Sub-Saharan Africa. A survey was conducted in five farming systems in Uganda to isolate entomopathogens associated with X. compactus. Four fungal isolates were screened for virulence against X. compactus in the laboratory at 1 × 10⁷ conidia ml^-1 where an atoxigenic L-strain of A. flavus killed 70%-100% of all stages of X. compactus compared with other unidentified isolates which caused 20%-70% mortalities. The time taken by A. flavus to kill 50% of X. compactus eggs, larvae, pupae and adults in the laboratory was 2-3 days; whereas the other unidentified fungal isolates took 4-7 days. The concentrations of A. flavus that killed 50% of different stages of X. compactus were 5 × 10⁵ , 12 × 10⁵ , 17 × 10⁵ and 30 × 10⁵ conidia ml^-1 for larvae, eggs, pupae and adults respectively. A formulation of A. flavus in oil caused higher mortalities of X. compactus larvae, pupae and adults in the field (71%-79%) than its formulation in water (33%-47%). The atoxigenic strain of A. flavus could therefore be developed into a safe biopesticide against X. compactus.

Matrix-Induced Sugaring-Out: A Simple and Rapid Sample Preparation Method for the Determination of Neonicotinoid Pesticides in Honey

In the present work, we developed a simple and rapid sample preparation method for the determination of neonicotinoid pesticides in honey based on the matrix-induced sugaring-out. Since there is a high concentration of sugars in the honey matrix, the honey samples were mixed directly with acetonitrile (ACN)-water mixture to trigger the phase separation. Analytes were extracted into the upper ACN phase without additional phase separation agents and injected into the HPLC system for the analysis. Parameters of this matrix-induced sugaring-out method were systematically investigated. The optimal protocol involves 2 g honey mixed with 4 mL ACN-water mixture (v/v, 60:40). In addition, this simple sample preparation method was compared with two other ACN-water-based homogenous liquid-liquid extraction methods, including salting-out assisted liquid-liquid extraction and subzero-temperature assisted liquid-liquid extraction. The present method was fully validated, the obtained limits of detection (LODs) and limits of quantification (LOQs) were from 21 to 27 and 70 to 90 μg/kg, respectively. Average recoveries at three spiked levels were in the range of 91.49% to 97.73%. Precision expressed as relative standard deviations (RSDs) in the inter-day and intra-day analysis were all lower than 5%. Finally, the developed method was applied for the analysis of eight honey samples, results showed that none of the target neonicotinoid residues were detected.

Phytochemical composition and larvicidal activity of essential oils from herbal plants

The essential oils (EOs) of Plectranthus amboinicus showed the highest larvicidal activity among four herbal plants studied and β-caryophyllene might be the major component responsible for its differential toxicity to the larvae of Culex quinquefasciatus and Aedes Aegypti. Mosquitoes act as vectors for many life-threatening diseases, including malaria, dengue fever, and Zika virus infection. Management of mosquitoes mainly relies on synthetic insecticides, which usually result in the rapid development of resistance; therefore, alternative mosquito control strategies are urgently needed. This study characterized the major component of essential oils (EOs) derived from the vegetative parts of four herbal plants and their larvicidal activity toward important mosquito vectors. The EOs were extracted by hydro-distillation and subjected to gas chromatography-mass spectrometry (GC-MS) analysis and a larvicidal activity assay toward Aedes aegypti, Ae. albopictus and Culex quinquefasciatus. In total, 14, 11, 11 and 9 compounds were identified from the EOs of Plectranthus amboinicus, Mentha requienii, Vitex rotundifolia and Crossostephium chinense, respectively. The EOs derived from four herbal plants exhibited remarkable larvicidal activity against the three mosquito species. In particular, the EOs of P. amboinicus showed the highest larvicidal activity, and the larvae of Cx. quinquefasciatus were more sensitive to the P. amboinicus EOs than that of Ae. Aegypti. Although carvacrol (61.53%) was the predominant constituent of the P. amboinicus EOs, its precursors, γ-terpinene (8.51%) and p-cymene (9.42%), exhibited the most larvicidal activity toward Ae. aegypti and Cx. quinquefasciatus. However, β-caryophyllene (12.79%) might be the major component responsible for the differential toxicity of the P. amboinicus EOs, as indicated by the significant differences in its LC₅₀ values toward both mosquitoes. Information from these studies will benefit the incorporation of EOs into integrated vector management.

Insecticidal Activity of Four Lignans Isolated from Phryma leptostachya

A new lignan (T4) and three known lignans (T1, T2, and T3) were isolated from the methanol extract of the roots of Phryma leptostachya using bioassay-guided method, and their structures were identified as phrymarolin I (T1), II (T2), haedoxan A (T3), and methyl 4-((6a-acetoxy-4-(6-methoxybenzo[d][1,3]dioxol-5-yl)tetrahydro-1H,3H-furo[3,4-c]furan-1-yl)oxy)-1-hydroxy-2,2-dimethoxy-5-oxocyclopent-3-ene-1-carboxylate (T4) byNMR and ESI-MS spectral data. Bioassay results revealed that haedoxan A exhibited remarkably high insecticidal activity against Mythimna separata with a stomach toxicity LC₅₀ value of 17.06 mg/L and a topical toxicity LC₅₀ value of 1123.14 mg/L at 24 h, respectively. Phrymarolin I and compound T4 also showed some stomach toxicity against M. separata with KD₅₀ values of 3450.21 mg/L at 4 h and 2807.10 mg/L at 8 h, respectively. In addition, phrymarolin I and haedoxan A exhibited some stomach toxicity against Plutella xylostella with an LC₅₀ value of 1432.05 and 857.28 mg/L at 48 h, respectively. In conclusion, this study demonstrated that lignans from P. leptostachya are promising as a novel class of insecticides or insecticide lead compounds for developing botanical pesticides.

Biological activity of Dittrichia viscosa (L.) Greuter extracts against adult Sitophilus granarius (L.) (Coleoptera, Curculionidae) and identification of active compounds

Dittrichia viscosa (L.) Greuter, a perennial weed of the Mediterranean area, was reported to be source of active substances. Here, by means of both ingestion and contact assays, the biological activity of three different extracts (n-hexane, methanol, and distilled water) of D. viscosa aerial part has been evaluated against Sitophilus granarius (L.) adults, an important pest of stored grains. Ingestion assays showed negligible mortality and food deterrence for all the extracts, whereas only a slight reduction of some nutritional parameters (relative growth rate, relative consumption rate, food efficiency conversion) was recorded for water extract. High contact toxicity was found only for the n-hexane extract (24 h median lethal dose LD50 = 53.20 μg/adult). This extract was further subfractioned by silica gel column chromatography and then by thin layer chromatography. Further contact toxicity bioassays highlighted two active subfractions which were analyzed by GC-MS. This revealed the occurrence, in both subfractions, of two major peaks that were identified as α- and γ- costic acid isomers. Moreover, D. viscosa active subfractions, did not cause acetylcholinesterase (AChE) inhibition; therefore, in the light of progressive limitation of compounds acting by this mechanism of action, D. viscosa represents a promising eco-sustainable source of natural products for pest control.

Bruceine D Isolated from Brucea Javanica (L.) Merr. as a Systemic Feeding Deterrent for Three Major Lepidopteran Pests

Systemicity is a desirable property for insecticides. Many phytochemicals show good systemic properties and thus are natural sources of novel systemic insecticidal ingredients. Bruceine D, a quassinoid, was identified in Brucea javanica (L.) Merr. and displayed outstanding systemic properties and excellent antifeedant activity against the diamondback moth (DBM, Plutella xylostella L.), beet armyworm ( Spodoptera exigua Hübner), and cotton leafworm ( Spodoptera litura Fabricius). Its antifeedant effect on third instar larvae of DBM was approximately 6.2-fold stronger than that of azadirachtin. When bruceine D was applied to roots at a concentration of 100 μg/mL for 24 and 48 h, its concentration in flowering Chinese cabbage ( Brassica campestris L. ssp. chinensis var. utiliz Tsen et Lee) leaves was 38.69 μg/g (fresh weight, FW) and 108.45 μg/g (FW), respectively. These concentrations could achieve 93.80% and 96.83% antifeedant effects, which were significantly greater than those of azadirachtin. Similar to azadirachtin, bruceine D also posed a potent growth inhibition effect on insect larvae. After feeding with 20 μg/g bruceine D, no pupae were observed. The results demonstrated that bruceine D is an effective botanical insect antifeedant with outstanding systemic properties, causing potent pest growth inhibitory activity.

Comparative extraction of Salmonella bongori derived metabolites and their toxicity on bacterial pathogens, mosquito-larvae, zebrafish-embryo and brine-shrimp: A modified approach

The present study pertains to two different (standard and adapted) extraction-procedures to extract bacterial extracellular metabolites from the cell-free supernatant (CFS) of S. bongori. Metabolites were extracted with the different polarity solvents using lyophilized-CFS mediated procedure, which revealed more number of compounds than standard procedure. The crude-extracts (CEs) were characterized using FTIR, HPLC and GC-MS analyses. The commonly presented compounds in standard (ME, EA & HE) and lyophilization-mediated extracts (LME, LEA & LHE) were identified through Heat-map analysis. Antibacterial assay: all CEs showed considerable activity on tested MTCC-strains, in which, LME and LEA were found preponderant. Larvicidal bioassay: LME resulted maximum mortality than other CEs on Culex-larvae. Zebrafish embryo-toxicity assay: except HE, all CEs exhibited toxicity at 100 ppm after 96 hpf. Brine shrimp-toxicity assay: ME, LME, EA and LEA have shown significant mortality after 24 h. With these observations, the adapted-extraction-procedure could form significance in the drug development process.

Seven herbs against the stored product insect: Toxicity evidence and the active sesquiterpenes from Atractylodes lancea

In this work, the essential oils (EO) were extracted from seven typical Chinese herbs, and their repellent and contact toxicities against Tribolium castaneum adults (red flour beetles) were evaluated. The experimental results showed that the above EOs presented the various levels of repellent and contact toxicities. The EOs extracted from A. lancea and A argyi of the Compositae (Asteraceae) family presented obvious repellent effects (Repellency Percentage > 90% at 3.15 nL/cm² after 4 h exposure) and strong contact toxicity with LD₅₀ values of 5.78 and 3.09 μg/adult respectively. Based on literature researches and screening results, the EO from A. lancea was analyzed by GC-MS and chosen for further identification of bioactive components. Altogether 59 chemical components were identified and 17 of them were recognized as sesquiterpene compounds, accounting for 57.8% of the total weight of the EO. From the identified sesquiterpenes, three individual compounds (β-eudesmol, hinesol, valencene) were selected for the laboratory bioassays of the toxicity against red flour beetles. It was found that all the three compounds expressed some repellent effects. Although β-eudesmol (31.2%) and hinesol (5.1%) were identified as main constituents and had been considered to be symbolic characteristics of high medicinal value, valencene (0.3%) showed strong repellent property which could be comparable to that of DEET (N, N‑diethyl‑3‑methylbenzamide), a powerful commercial pesticides, and it had best toxicity with LD₅₀ values of 3.25 (μg/adult) in the contact test. This work may provide toxicity evidence of seven common herbs against red flour beetles, add the information for the development and comprehensive utilization of A. lancea, and will contribute to the application of grain preservation.

Astratides: Insulin-Modulating, Insecticidal, and Antifungal Cysteine-Rich Peptides from Astragalus membranaceus

Astragalus membranaceus root, Huang Qi in Chinese, is a popular medicinal herb traditionally used to regulate blood glucose. Herein, the identification and characterization of two families of cysteine-rich peptides (CRPs), designated α- and β-astratides, from A. membranaceus roots are reported. Proteomic analysis showed that α-astratide aM1 and β-astratide bM1 belong to two distinct CRP families. The six-cysteine-containing and proline-rich α-astratide aM1 displayed high sequence identity to Pea Albumin 1 Subunit b (PA1b), while the eight-cysteine-containing β-astratide bM1 showed sequence similarity to plant defensins. An antifungal assay revealed that bM1 possessed potent antifungal activity. In contrast, aM1 showed a cytotoxic effect against insect Sf9 cells. More importantly, aM1 decreased insulin secretion in mouse pancreatic β cells, suggesting it could interfere in glucose homeostasis, which accounts for the adaptogenic property of A. membranaceus. Phylogenetic clustering analysis suggested that the proline-rich aM1 is a putative prolyl oligopeptidase inhibitor and belongs to a novel subfamily of PA1b-like peptides, while bM1 belongs to a new subfamily of plant defensins. Together, the study reveals that astratides are multifunctional CRPs in plants, which expand the existing library of PA1b-like peptides and plant defensins and further our understanding of their roles in host-defense system and leads as peptidyl therapeutics.