LC50 Values Research Articles

Discovery of Novel (+)-Nootkatone-Based Amine Derivatives as Potential Insecticide Candidates.

To discover novel natural product-based insecticides, a series of (+)-nootkatone-based amine derivatives 3a-t were prepared and evaluated for their insecticidal activities against Mythimna separata Walker, Myzus persicae Sulzer, and Plutella xylostella Linnaeus. Insecticidal assays showed that most of the title (+)-nootkatone derivatives exhibited stronger insecticidal activities against three insect pests than the precursor (+)-nootkatone after the introduction of amine groups on the parent (+)-nootkatone. Compounds 3a, 3d, 3h, 3m, 3n, 3p, and 3r displayed more promising growth inhibitory (GI) effect against M. separata than the commercially available botanical insecticide toosendanin. Compound 3o exhibited the most potent aphicidal activity with an LD50 value of 0.011 μg/larvae, which was 2.09-fold higher than the positive control rotenone. Additionally, compounds 3g and 3n showed more promising larvicidal activity against P. xylostella with LC50 values of 260 and 230 mg/L, respectively, superior to that of rotenone (460 mg/L). Moreover, derivatives 3g and 3n exhibited better control efficacy toward P. xylostella than rotenone under greenhouse conditions. Preliminary mechanistic studies revealed that derivative 3n could inhibit the activity of glutathione S-transferase (GST) in P. xylostella and thus exerted larvicidal activity, and molecular docking further demonstrated that 3n could interact well with some amino acid residues of GST. Finally, the toxicity assay suggested that derivatives 3g and 3n were relatively less toxic to nontarget organisms. These findings will provide insights into the development of (+)-nootkatone derivatives as green pesticides.

The New Nematicide Cyclobutrifluram Targets the Mitochondrial Succinate Dehydrogenase Complex in Bursaphelenchus xylophilus.

Bursaphelenchus xylophilus is a dangerous quarantine pest that causes extensive damage to pine ecosystems worldwide. Cyclobutrifluram, a succinate dehydrogenase inhibitor (SDHI), is a novel nematicide introduced by Syngenta in 2013. However, the nematocidal effect of cyclobutrifluram against plant-parasitic nematodes remains underexplored. Therefore, here, we aim to address this knowledge gap by evaluating the toxicity, effects, and mode of action of cyclobutrifluram on B. xylophilus. The result shows that cyclobutrifluram is the most effective agent, with an LC50 value of 0.1078 mg·L-1. At an LC20 dose, it significantly reduced the population size to 10.40 × 103 ± 737.56-approximately 1/23 that of the control group. This notable impact may stem from the agent's ability to diminish egg-laying and hatching rates, as well as to impede the nematodes' development. In addition, it has also performed well in the prevention of pine wilt disease, significantly reducing the incidence in greenhouses and in the field. SDH consists of a transmembrane assembly composed of four protein subunits (SDHA to SDHD). Four sdh genes were characterized and proved by RNAi to regulate the spawning capacity, locomotion ability, and body size of B. xylophilus. The mortality of nematodes treated with sdhc-dsRNA significantly decreased upon cyclobutrifluram application. Molecular docking further confirmed that SDHC, a cytochrome-binding protein, is the target. In conclusion, cyclobutrifluram has a good potential for trunk injection against B. xylophilus. This study provides valuable information for the screening and application of effective agents in controlling and preventing PWD in forests.

Efficacy of entomopathogenic nematodes against Cydalima perspectalis and Hyphantria cunea (Lepidoptera), two invasive forest pests in Iran

The box tree moth (BTM), Cydalima perspectalis, and the fall webworm (FWW), Hyphantria cunea are two invasive forest pests in northern Iran. Entomopathogenic nematodes (EPNs) are usually compatible with integrated pest management programs. In this study, the efficacy of five isolates of EPNs was evaluated against the two pests in laboratory and field conditions. LC50 values of Steinernema carpocapsae (IRTabriz), S. feltiae (IRTabriz), S. feltiae (Entonem), Oscheius rugaoensis and Heterorhabditis bacteriophora (IRTabriz) were as follow: 44.8, 66.5, 113.8, 190.7 and 515.9 infective juveniles (IJs) larva−1 on the fifth instar larvae of BTM; and 75.2, 96.6, 131.0, 258.0 and 292.5 IJs larva−1 on fifth instar larvae of FWW, respectively in the laboratory tests 48 h post-treatment at 25 °C and 60% relative humidity. Under field conditions, the foliar applications of S. carpocapsae (IRTabriz), S. feltiae (IRTabriz), and S. feltiae (Entonem) at the rate of 106 IJs L−1 resulted in 36–58% mortality after 48 h against BTM and 15–52% mortality against FWW, respectively. The results demonstrate that EPNs are promising candidates for biocontrol of BTW and FWW.

Toxicological assessment of the Achyrocline satureioides aqueous extract in the Caenorhabditis elegans alternative model

ABSTRACT Achyrocline satureioides, popularly called “marcela” in Brazil, is used in traditional medicine in South America. A. satureioides, inflorescences are used for many conditions, including to minimize the Sars-Cov-2 symptoms. Therefore, the aim of this study was to determine the toxicity profile of A. satureioides aqueous extract (ASAE), using the Caenorhabditis elegans (C. elegans) alternative model. Survival, reproduction, development, and transgenerational assays were performed. The effects of ASAE were investigated under conditions of thermal stress and presence of oxidant hydrogen peroxide (H2O2). In addition, C. elegans strains containing high antioxidant enzyme levels and elevated lineages of daf-16, skn-1 and daf-2 regulatory pathways were examined. The ASAE LC50 value was found to be 77.3 ± 4 mg/ml. The concentration of ASAE 10 mg/ml (frequently used in humans) did not exhibit a significant reduction in worm survival at either the L1 or L4 stage, after 24 or 72 hr treatment. ASAE did not markedly alter the body area. In N2 strain, ASAE (10 or 25 mg/ml) reversed the damage initiated by H2O2. In addition, ASAE protected the damage produced by H2O2 in strains containing significant levels of sod-3, gst-4 and ctl − 1,2,3, suggesting modulation in these antioxidant systems by this plant extract. ASAE exposure activated daf-16 and skn-1 stress response transcriptional pathways independently of daf-2, even under extreme stress. Data suggest that ASAE, at the concentrations tested in C. elegans, exhibits a reliable toxicity profile, which may contribute to consideration for safe use in humans.

Comparison of the acute toxicity and behavioural effects of two pyrethroids on African catfish Clarias gariepinus fingerlings

Two of the most-commonly used pyrethroid insecticides were subjected to static bioassays to determine their acute toxicity to Clarias gariepinus fingerlings, followed by comparisons of their impact on mortality and behavioural changes in the fish. The LC50 values for deltamethrin (DMT) at exposure durations of 24, 48 and 96 h were 12, 9 and 8 µg l−1, respectively; the LC50 values for cypermethrin (CYP) at the same exposure durations were 55, 44 and 26 µg l−1, respectively. The estimated safe limits ranged from 8×10−1 to 8×10−5 µg l−1 for DMT, and 26×10−1 to 26×10−5 µg l-1 for CYP. The tested substances had an acute toxicity effect on fish development as they caused death, and chronic toxicity effects as they changed fish behaviour. Fish exposed to either one of these pesticides showed behavioural alterations, such as loss of static balance, excessive mucous secretion, irregular swimming, gulping of air and skin discolouration. The results reveal that CYP was less toxic (96-h LC50 = 26 µg l−1) than DMT (96-h LC50 = 8 µg l−1) based on the greater LC50 value and a lower percentage of mortality. To avoid potential ecotoxicological risks to aquatic life, use of these pyrethroids in both terrestrial and freshwater ecosystems must be treated with caution.

Two tropical oligochaetes as potential standard test species: a case study evaluating single and combined copper and manganese toxicity

ABSTRACT The lack of toxicity tests using indigenous species in risk assessments of tropical regions has often been discussed. Thus, this study evaluated two tropical oligochaete species (Allonais inaequalis and Dero furcatus) for potential use as test species. To this end, the toxic effects of copper and manganese, both isolated and mixed, were evaluated for both species via acute tests. The test protocol developed by the Organisation for Economic Co-operation and Development (OECD) for temperate sediment-dwelling benthic oligochaetes could be successfully applied for both test species. The 96-h LC50 values (mean ± standard deviation) for D. furcatus were 31 ± 3 µg L−1 and 18 ± 0.061 mg L−1 for copper and manganese, respectively. The corresponding values for A. inaequalis were 26 ± 1 µg L−1 and 28 ± 0.063 mg L−1, respectively. Compared to the toxicity values for temperate arthropods, D. furcatus and A. inaequalis had comparable or greater sensitivity to the evaluated metals. The mixture toxicity tests indicated a dose ratio-dependent deviation of the concentration addition (CA) model, with antagonism occurring especially if the effects in the mixture were provoked by copper. Overall, these findings indicated that these taxa are sensitive candidates for use in tropical ecotoxicity testing. Future studies can elucidate the mechanisms of chemical mixture toxicity.

Bioinspired green synthesis of ZnO nanoparticles by marine-derived Streptomyces plicatus and its multifaceted biomedicinal properties

The present study explores the bioinspired green synthesis of zinc oxide nanoparticles (ZnONPs) using marine Streptomyces plicatus and its potent antibacterial, antibiofilm activity against dental caries forming Streptococcus mutans MTCC and S. mutans clinical isolate (CI), cytotoxicity against oral KB cancer cells, hemolysis against blood erythrocytes and artemia toxicity. The bioinspired ZnONPs showed a distinctive absorption peak at 375 nm in UV–Vis spectra, the FT-IR spectra divulged the active functional groups, and XRD confirmed the crystalline nature of the nanoparticles with an average grain size of 41.76 nm. SEM analysis evidenced hexagonal morphology, and EDX spectra affirmed the presence of zinc. The ZnONPs exerted higher antagonistic activity against S. mutans MTCC (Inhibitory zone: 19 mm; MIC: 75 μg/ml) than S. mutans CI (Inhibitory zone: 17 mm; MIC: 100 μg/ml). Results of biofilm inhibitory activity showed a concentration-dependent reduction with S. mutans MTCC (15 %–95 %) more sensitive than S. mutans CI (13 %–89 %). The 50 % biofilm inhibitory concentration (BIC50) of ZnONPs against S. mutans MTCC was considerably lower (71.76 μg/ml) than S. mutans CI (78.13 μg/ml). Confocal Laser Scanning Microscopic visuals clearly implied that ZnONPs effectively distorted the biofilm architecture of both S. mutans MTCC and S. mutans CI. This was further bolstered by a remarkable rise in protein leakage (19 %–85 %; 15 %–77 %) and a fall in exopolysaccharide production (34 mg–7 mg; 49 mg–12 mg). MTT cytotoxicity of ZnONPs recorded an IC50 value of 22.06 μg/ml against KB cells. Acridine orange/ethidium bromide staining showed an increasing incidence of apoptosis in KB cells. Brine shrimp cytotoxicity using Artemia salina larvae recorded an LC50 value of 78.41 μg/ml. Hemolysis assay substantiated the biocompatibility of the ZnONPs. This study underscores the multifaceted application of bioinspired ZnONPs in dentistry.

Impact of Agricultural Insecticide Vapona on a Freshwater Catfish Heteropneustes Fossilis: A Toxicity Study

This study investigates the critical toxicity of Vapona in the air-breathing freshwater catfish, Heteropneustes fossilis (Bloch). The LC50 values (median lethal concentration) were determined using a static bioassay method over 24, 48, 72, and 96-hour exposure periods. The LC50 values for 24, 48, 72, and 96 hours of Vapona were found to be 400, 378, 320, and 275 ppm, respectively. An increased mucus secretion was observed at higher concentrations, suggesting a physiological response to the toxicant. The potential causes of mortality in the fish were also analyzed and discussed.

The contact toxicity and toxic mechanism of essential oils from Pimenta racemosa and Eugenia caryophyllata against Haemaphysalis longicornis (Acari: Ixodidae)

Haemaphysalis longicornis, which is widely distributed in China, can transmit various tick-borne diseases such as severe fever with thrombocytopenia syndrome, babesiosis, rickettsia disease and so on, and do great harm to human health and the development of animal husbandry. Chemical acaricides are the most traditional tick control method, but because of its many shortcomings, there is an urgent need to find a substitute with high efficiency, environmental protection and low toxicity. It has been found that some plant essential oils (EOs) have good insecticidal activity and environmental safety. In this study, the components of EOs from Pimenta racemosa and Eugenia caryophyllata were analyzed by gas chromatography–mass spectrometry (GC–MS), and their potential for application in the control of Haemaphysalis longicornis were studied. Gas chromatography-mass spectrometry analysis showed that the main components of P. racemosa EO were eugenol (64.07%), those of E. caryophyllata EO were Hexadecanoic acid, 2-methylpropyl ester (51.84%) and eugenol (39.76%). Larval packet test showed that the EOs of P. racemosa and E. caryophyllata had significant acaricidal activity against unfed larvae of H. longicornis, with LC50 values of 1.20 mg/mL and 0.47 mg/mL and LC90 values of 8.76 mg/mL and 2.91 mg/mL, respectively. The P. racemosa EO, E. caryophyllata EO and eugenol showed significant acaricidal activity against unfed nymph H. longicornis, with LC50 values of 1.65 mg/mL, 2.29 mg/mL and 0.93 mg/mL and LC90 values of 5.03 mg/mL, 11.01 mg/mL and 4.77 mg/mL, respectively. The P. racemosa EO, E. caryophyllata EO and eugenol showed significant acaricidal activity against unfed adults H. longicornis, with LC50 values of 0.51 mg/mL, 2.57 mg/mL and 1.83 mg/mL and LC90 values of 2.44 mg/mL, 11.44 mg/mL and 2.54 mg/mL, respectively. Enzyme assays revealed that the E. caryophyllata EO and eugenol significantly inhibited the activity of carboxylesterase (CarE), eugenol significantly inhibited the activity of catalase (CAT), and two EOs and eugenol had no significant effect on acetylcholinesterase (AchE) (p < 0.05). The above results suggest that the essential oils from P. racemosa and E. caryophyllata have great potential for use as alternatives to synthetic acaricides for tick control.

Flavonoids from Mimosa tenuiflora Green Propolis: Chemotaxonomy, Antioxidant, Anti‐Inflammation, Anti‐Bacteria, Mosquito Larvicidal Activity, and In Silico Approach

AbstractPhytochemical study of green propolis alcohol extract of Brazilian Caatinga Mimosa tenuiflora (Willd.) Poir resulted in the separation of six flavonoids, including quercetin 3‐methyl ether (1) and 3,3′‐O‐dimethylquercetin (2), and four flavanones eriodictyol 5‐O‐methyl ether (3), 5,4′‐dihydroxy‐6,7‐dimethoxyflavanone (4), licoflavanone (5), and macarangaflavanone B (6). All these metabolites were first isolated from green propolis and the genus Mimosa. Metabolites 3–4 also established chemotaxonomic significance since they had never been observed in the bean family Fabaceae. Flavones 1–2 showed strong antioxidative activity against DPPH (1,1‐diphenyl‐2‐picryl hydrazyl) radicals with IC50 values of 12.40 and 16.23 μg/mL, respectively. All six isolates showed anti‐inflammatory effects against NO (nitric oxide) production in LPS (lipopolysaccharide)‐stimulated Raw 264.7 cells, in which the activity of flavone 1 was better than the standard dexamethasone (IC50 13.35 μg/mL). Flavonoids 1–3 also strongly controlled the growth of the Gram‐positive bacteria Bacillus subtilis ATCC 6051, and Staphylococcus aureus ATCC 29213 with MIC values of 32–64 μg/mL. Six isolated flavonoids exhibited strong or moderate mosquito larvicidal activity against Aedes aegypti and Ae. albopictus fourth instar larvae with the 24 h LC50 values of 29.62–55.89 μg/mL. By in silico approach, compound 1 was a non‐toxic agent with an LD50 value of 5000 mg/kg.

Glycine-doped metal–organic frameworks as intelligent nanocarriers to enhance pesticide delivery and provide micronutrient in plants

The development of multifunctional pesticide-delivery system is of practical significance for realizing efficient utilization of pesticides and minimizing environmental risks. In this work, methoxyfenozide (Met)-loaded glycine-doped zeolitic imidazolate framework-8 composites (Met@Gly@ZIF-8) for intelligent-release of Met and effective pest management were facilely constructed. The physical properties of Met@Gly@ZIF-8, including ultraviolet (UV) resistance, deposition and release profiles were evaluated. Compared with Met, the residual content after UV irradiation and retention content on cabbage leaves of Met@Gly@ZIF-8 increased by 121.2% and 98.2%, respectively, and the contact angle on foliar decreased by 26.5% compared with Met suspension concentrate (SC), demonstrating better photolysis resistance, deposition and wetting ability. Release experiments indicated that Met@Gly@ZIF-8 possessed significant stimuli-responsive release characteristics which were negatively correlated with pH, due to the acidic degradation of ZIF-8. The biological activity experiments showed that Met@Gly@ZIF-8 possessed elevated control efficacy on Plutella xylostella compared with Met and reduced the LC50 value by 53.2%. The application performance experiments indicated that the penetration amount of Met@Gly@ZIF-8 in cabbage leaves increased by 194.7% and the translocation factor (TFleaf) increased by 63.3%, respectively, as compared with those of Met. Compared with the blank control, Gly@ZIF-8 and Met@Gly@ZIF-8 increased the total biomass of cabbage by 37.8% and 25.7%, respectively, exhibiting nutritional functions for plants. Toxicity test showed that Met@Gly@ZIF-8 was relatively safe for zebrafish compared with Met. The present approach could be strategically promising for constructing functional and environmentally friendly smart-nanopesticide.

Insecticidal activity of Thymus pallescens de Noë and Cymbogon citratus essential oils against Sitophilus zeamais and Tribolium castaneum

The thrust of the study was to determine the chemical composition of the essential oils extracted from Thymus pallescens de Noé and Cymbogon citratus Stapf. as well as to evaluate their efficacy in controlling Sitophilus zeamais Motschulsky and Tribolium castaneum (Herbst) in either single or combined populations. Carvacrol (56.04%) and geraniol (20.86%) were identified as the major constituents of T. pallescens and C. citratus respectively. The tested essential oils showed pronounced insecticidal activity against the pest species in relation with the applied doses. T. pallescens EO had the highest efficacy and S. zeamais was found to be more susceptible to both individual and combined treatments. With reference to the contact and fumigation assessments, T. pallescens EO effectuated corrected mortality rates ranging from 42.5–100% to 25–100% in S. zeamais with corresponding lethal concentration (LC50) values of 17.7 µl/ml and 15µL/L air respectively. Whereas, the T. pallescens EO exhibited corrected mortality rates of 42.5–100% and 20–100% with corresponding LC50 values of 18.1 µl/ml and 15.5 µL/L air against T. castaneum in contact and fumigation assessments, respectively. The corrected mortality rates increased for both insect species when using combination treatments, with significant increases in the LC50 values, ranging from 8.59 to 49.9% for both pest species. Analysis of energy biomarkers in the treated insects indicate significantly increased protein and carbohydrate contents and decreased lipids levels. The study therefore demonstrated the bio-insecticidal toxicity of the EOs from T. pallescens and C. citratus against two important maize post-harvest pests, concurrently revealing significant positive and negative insecticidal activity gradients in relation to single or combined populations.

New Cyclic Pentapeptides from the Mangrove-Derived Aspergillus fumigatus GXIMD 03099.

Four new cyclic pentapeptides, avellanins D-G (1-4), together with four known compounds (5-8), were isolated from a mangrove-derived Aspergillus fumigatus GXIMD 03099 fungus from Acanthus ilicifolius L. Their structures were elucidated by analysis of HRESIMS, NMR, and ESI-MS/MS data. Their absolute configurations were determined by X-ray diffraction analysis and Marfey's method. Compounds 1-8 were screened for insecticidal and antibacterial activities. Compound 2 showed insecticidal activity against newly hatched larvae of Culex quinquefasciatus with an LC50 value of 86.6 µM; compound 4 had weak activity against Vibrio harveyi with an MIC value of 5.85 µM.

Discovery of α-hexyl cinnamaldehyde and its derivatives as novel larvicides against Aedes albopictus

Mosquitoes are the vectors of numerous diseases such as malaria, Dengue and Zika. Controlling mosquito vectors is essential for preventing and managing diseases transmitted by mosquitoes. Larvicides target larvae within their breeding habitats before they mature into adult mosquitoes and disperse. In this study, using α-hexyl cinnamaldehyde (HCA) as a lead compound, three series of derivatives comprising a total of 78 compounds were designed and synthesized. The larvicidal activities of these compounds against Aedes albopictus were evaluated, resulting in the identification of ten promising compounds. Among them, furan-3-ylmethyl cinnamate (compound 2v) and (E)-allyl 3-(4-chlorophenyl)acrylate (compound 4c) exhibited the lowest LC50 values (8.0 ppm and 7.2 ppm respectively). In a 96-h acute toxicity assay conducted on zebrafish, 2v showed no or very low toxicity with an LC50 higher than 100 ppm. To elucidate their mode of action, morphological and histopathologic analyses were performed, and the effects of the compounds on the acetylcholinesterase (AChE) and phosphatase activities were evaluated. Results suggested that the active HCA derivatives induce injury to intestinal epithelial cells by inhibiting phosphatase activity, ultimately resulting in the mortality of mosquito larvae.

Larvicidal Activity of Red Betel Leaves (Piper ornatum) Ethanolic Extract&amp;nbsp;Against Mosquito Larvae

Larvae are the initial carriers of dengue hemorrhagic fever (DHF) and culex, making them significant in disease transmission. Excessive chemical larvicides pose serious risks to human health, thus driving the development of biological alternatives like red betel leaf extract. This study aimed to assess the efficacy of red betel leaf extract in larval control. Using 300 larvae, concentrations of 5%, 6%, and 7% were tested with three replicates over 24 h. The bioassay involved placing the larvae into a plastic container filled with the extract. It was found that ethanol extract from Piper ornatum leaves contained alkaloids, tannins, saponins, flavonoids, and terpenoids. After 24 h, results revealed 83% mortality at 5%, 98% at 6%, and 100% at 7% of extract concentration. Consequently, the 7% concentration showed the fastest efficacy in killing mosquito larvae (100% in 50 min). The LC50 value, representing the concentration at which 50% of larvae are killed, was determined to be 0.04%. Additionally, the LT50 value, indicating the time required to kill 50% of larvae (based on the LC50 value), was found to be 3.34 hours. In conclusion, red betel leaf extract demonstrated promising larvicidal activity against mosquito larvae. Future research is anticipated to prove its safety via in vitro and in vivo test.

Evaluation of Lysinibacillus formulations against banana pseudostem weevil (BPW) Odoiporus longicollis [Olivier.]

ABSTRACT Odoiporus longicollis [Olivier], commonly known as banana pseudostem weevil or BPW has been a predominant pest of bananas, resulting in devastating losses in banana cultivation across India. The current research explores the use and effectiveness of the microbial biopesticide – Lysinibacillus sphaericus against banana pseudostem weevils in field and laboratory conditions. The LC50 value of L.sphaericus was found to be 9.92% of 1 OD (optical density at 600 nm) culture after 24 h of treatment against grubs at in-vitro conditions. L.sphaericus cultures were formulated as liquid, solid, and capsule formulations, and analysed parameters such as viability, shelf life, and pest control efficiency against banana pseudostem weevils. The capsule-based formulation (8 ± 2 × 102a CFU/ml) was most effective against the grubs with a storage period of 120 days to six months under room temperature in air-free containers. The efficacy of a capsule-based formulation at in vivo conditions in the pseudostem revealed that the gelatine coat of the capsule disintegrated within 24hrs after application, leading to the easy release of active ingredients to the pseudostem. The field evaluation observed that in L.sphaericus-based capsule formulations treated plants, there was more than an 80% reduction in the infestation of grubs over control treatments. The current paper describes the application of L.sphaericus against the weevil, its unique formulation as a capsule increasing bacterial shelf life, and ease of application. The development of an easily applicable and effective capsule with a better shelf life of 6 months would increase the marketing possibilities of this biopesticide formulation against Odoiporus longicollis.

Alternanthera sessilis derived fluorescent carbon dots and their sensing and biological applications

Herein, the green synthesis of novel fluorescent carbon dots (CDs) from the Alternanthera sessilis plant by a simple, eco-friendly, and facile hydrothermal method was reported. The developed CDs exhibit green fluorescence and have a size of 5.25 nm. Various analyses reveal outstanding features, including high quantum yield, good photostability, and excellent hydrophilicity of the as-synthesized CDs. It was used as a dual-mode probe for the sensing of Cu2+ ions and Zn2+ ions in an aqueous system. Efficient sensing of Cu2+ ions takes place by static quenching of fluorescence with a detection limit of 28.03 nM. CDs-coated glassy carbon electrode was used to perform the electrochemical detection of Zn2+ ions in an aqueous system with high selectivity and sensitivity, and the LOD value was found to be 2.28 nM. The LC50 value of the fabricated CDs against the human breast cancer cell line is 89.85 µL/mL. Also, the antimicrobial efficacy of the CDs was examined against Escherichia coli, Staphylococcus Aureus, and Aspergillus niger, and the results indicate the high toxicity of the CDs against all tested microbial strains.

Decoding defenses: Biochemical insights into insecticide resistance in tea mosquito bug, Helopeltis theivora Waterhouse (Hemiptera: Miridae) from tea plantations of Eastern India

Helopeltis theivora is one of the major tea pests in India and the strategies of management largely depend on application of different insecticides. Resistance in ten field populations of H. theivora collected from different tea growing regions of Eastern India to three insecticides was evaluated by leaf dip method in the laboratory. The results showed varied levels of susceptibility in nine populations to thiamethoxam and deltamethrin with a resistance coefficient (RC) ranging from 2.04 to 30.95 and 1.56–59.81-fold, respectively. Upper Assam and Central Dooars populations showed high resistance to thiamethoxam and deltamethrin. A high resistance to deltamethrin was also recorded in the Eastern Dooars (RC = 52.74) and Western Dooars (RC = 53.07) populations. There was no resistance to quinalphos in any of the populations (RC = 0.11–0.60). The Darjeeling population was relatively susceptible to the insecticides. Biochemical enzyme assays suggested that glutathione S-transferases (GST), general esterase (GE) and cytochrome P450 (CYP) activities were high in most of the field populations as compared to the susceptible population. However, the expression of CYP was statistically at par between the Cachar, Tripura, Darjeeling and susceptible population. GST and GE activity displayed a strong significant correlation with LC50 values of thiamethoxam and deltamethrin while a moderate to strong linear relationship was recorded between CYP and the LC50s of thiamethoxam and deltamethrin, respectively. A weak positive correlation was established between LC50 of quinalphos and the enzymes. Synergistic assays reveal that the addition of synergists’ piperonyl butoxide and diethyl maleate with thiamethoxam and deltamethrin enhanced the toxicity of these insecticides. The results of this study will contribute to the insecticide resistance management and integrated management of H. theivora.

Characterization and antibacterial evaluation of Eco-friendly silver nanoparticles synthesized by halophilic Streptomyces rochei SSCM102 isolated from mangrove sediment.

Antimicrobial resistance has surged due to widespread antimicrobial drug use, prompting interest in biosynthesizing nanoparticles from marine-derived actinomycetes extracellular metabolites, valued for their diverse bioactive compounds. This approach holds promise for addressing the urgent need for novel antimicrobial agents. The current study aimed to characterize novel bioactive compounds from unexplored biodiversity hotspots, halophilic Streptomyces sp. isolated from mangrove sediment in the Pichavaram region, India. Streptomyces rochei SSCM102 was conclusively identified through morphological and molecular characterization. Synthesis of silver nanoparticles (AgNPs) from Streptomyces rochei SSCM102 was characterized using various techniques, including UV-Vis, XRD, SEM, EDX, and FT-IR. The UV-Vis spectrum of the reduced AgNPs exhibited a prominent peak at 380nm, confirming the AgNPs. The UV-Vis spectrum confirmed the synthesis of AgNP, and SEM analysis revealed a cubic morphology with sizes ranging from 11 to 21nm. The FTIR spectrum demonstrated a shift in frequency widths between 626cm-1 and 3432cm-1. The EDX analysis substantiated the presence of metallic silver, evident from a strong band at 1.44keV. The synthesized AgNPs exhibited antibacterial efficacy against human pathogens Escherichia coli (64 ± 0.32µg/ml), Klebsiella pneumoniae (32 ± 0.16µg/ml), and Pseudomonas aeruginosa (16 ± 0.08µg/ml) by MIC and MBC values of 128 ± 0.64 (µg/ml), 64 ± 0.32 (µg/ml) and 32 ± 0.16 (µg/ml), respectively. Additionally, at a concentration of 400µg/ml, the AgNPs displayed a 72% inhibition of DPPH radicals, indicating notable antioxidant capacity. The LC50 value of 130µg/mL indicates that the green-synthesized AgNPs have lower toxicity by Brine Shrimp Larvae assay. The study's novel approach to synthesizing eco-friendly silver nanoparticles using Halophilic Streptomyces rochei SSCM102 contributes significantly to the field of biomedical research and drug development. By demonstrating potent antibacterial properties and aligning with sustainability goals, these nanoparticles offer promising avenues for novel antibacterial therapies.

Novel synthesis of some heterocycles and their molluscicidal activity against the destructive land snail, Theba pisana

BackgroundTerrestrial snails, specifically Theba pisana, represent significant agricultural pests in the Mediterranean region, particularly in Egypt. They are gastropods that cause substantial damage to a variety of vegetation, rendering them important agricultural pests that result in economic losses. In response, we have developed unique and non-toxic molluscicides. The study assessed nine novel heterocycles compared with methomyl as a reference compound, to study their molluscicidal effects on T. pisana. These heterocycles include 2-pyrazolines, 2-oxocyclohex-3-ene, and 3-cyano-2-ethoxypyridine.ResultsThe obtained data revealed that the majority of the produced chemicals were remarkably effective against T. pisana snails, exhibiting different degrees of toxicity seven days post-treatment. Methomyl exhibited the highest toxicity, followed by prop-2-en-1-one and 1-thiocarbamoyl-2-pyrazoline derivatives, with LC50 values of 44.14, 59.54, and 72.00 ppm, respectively.ConclusionsThese findings will inform the potential of these synthetic compounds as one of the sources for molluscicide development and their integration into pest management strategies.Graphical