2, 3-Dimethylmaleic anhydride (3, 4-Dimethyl-2, 5-furandione): A plant derived insecticidal molecule from Colocasia esculenta var. esculenta (L.) Schott

Pesticides impacts on human health and the environment with their mechanisms of action and possible countermeasures

Pesticides are chemical constituents used to prevent or control pests, including insects, rodents, fungi, weeds, and other unwanted organisms. Despite their advantages in crop production and disease management, the use of pesticides poses significant hazards to the environment and public health. Pesticide elements have now perpetually entered our atmosphere and subsequently contaminated water, food, and soil, leading to health threats ranging from acute to chronic toxicities. Pesticides can cause acute toxicity if a high dose is inhaled, ingested, or comes into contact with the skin or eyes, while prolonged or recurrent exposure to pesticides leads to chronic toxicity. Pesticides produce different types of toxicity, for instance, neurotoxicity, mutagenicity, carcinogenicity, teratogenicity, and endocrine disruption. The toxicity of a pesticide formulation may depend on the specific active ingredient and the presence of synergistic or inert compounds that can enhance or modify its toxicity. Safety concerns are the need of the hour to control contemporary pesticide-induced health hazards. The effectiveness and implementation of the current legislature in providing ample protection for human health and the environment are key concerns. This review explored a comprehensive summary of pesticides regarding their updated impacts on human health and advanced safety concerns with legislation. Implementing regulations, proper training, and education can help mitigate the negative impacts of pesticide use and promote safer and more sustainable agricultural practices.

Endophytic fungi: hidden treasure chest of antimicrobial metabolites interrelationship of endophytes and metabolites

Endophytic fungi comprise host-associated fungal communities which thrive within the tissues of host plants and produce a diverse range of secondary metabolites with various bioactive attributes. The metabolites such as phenols, polyketides, saponins, alkaloids help to mitigate biotic and abiotic stresses, fight against pathogen attacks and enhance the plant immune system. We present an overview of the association of endophytic fungal communities with a plant host and discuss molecular mechanisms induced during their symbiotic interaction. The overview focuses on the secondary metabolites (especially those of terpenoid nature) secreted by endophytic fungi and their respective function. The recent advancement in multi-omics approaches paved the way for identification of these metabolites and their characterization via comparative analysis of extensive omics datasets. This study also elaborates on the role of diverse endophytic fungi associated with key agricultural crops and hence important for sustainability of agriculture.

Insecticidal and biochemical effects of Dillenia indica L. leaves against three major stored grain insect pests

The Last four decades have witnessed the banning of several synthetic insecticides mainly due to the development of resistance to the target pests and due to hazardous effects on humans and the environment. Hence, the development of a potent insecticide with biodegradable and eco-friendly nature is the need of the hour. In the present study, the fumigant property, and biochemical effects of Dillenia indica L. (Dilleniaceae) were studied against three coleopterans stored-products insects. The bioactive enriched fraction (sub-fraction-III) was isolated from ethyl acetate extracts of D. indica leaves and found toxic to rice weevil, Sitophilus oryzae (L.) (Coleoptera); lesser grain borer Rhyzopertha dominica (L.) (Coleoptera) and red flour beetle, Tribolium castaneum (Herbst.) (Coleoptera) with the LC₅₀ values of 101.887, 189.908 and 115.1 µg/L respectively after 24 h exposure. The enriched fraction was found to inhibit the function of acetylcholinesterase (AChE) enzyme when tested against S. oryzae, T. castaneum, and R. dominica with LC₅₀ value of 88.57 µg/ml, 97.07 µg/ml, and 66.31 µg/ml respectively, in in-vitro condition. It was also found that the enriched fraction caused a significant oxidative imbalance in the antioxidative enzyme system such as superoxide dismutase, catalase, DPPH (2,2-diphenyl-1-picrylhydrazyl), and glutathione-S-transferase (GST). GCMS analysis of the enriched fraction indicates three major compounds namely, 6-Hydroxy-4,4,7a-trimethyl-5,6,7,7a-tetrahydrobenzofuran-2(4H)-one, 1,2-Benzisothiazol-3(2H)-one, and Benzothiazole, 2-(2-hydroxyethylthio)-. Finally, we concluded that the enriched fraction of D. indica has insecticidal properties and the toxicity may be due to the inhibition of the AChE enzyme in association with oxidative imbalance created on the insect's antioxidant enzyme systems.

A novel biofumigant from Tithonia diversifolia (Hemsl.) A. Gray for control of stored grain insect pests

For the well-being of human health as well as ecological concerns and the development of insect resistance to conventional chemical insecticides, efforts have increased worldwide, to find eco-friendly, effective and safer insect control agents which are of natural origin. A bioactive biofumigant molecule named dihydro-p-coumaric acid was isolated and characterized from the leaves of Tithonia diversifolia Hemsl. A. Gray following laboratory bioassays against the rice weevil, Sitophilus oryzae L (Coleoptera: Curculionidae); the lesser grain borer, Rhyzopertha dominica F (Coleoptera: Bostrichidae) and the rust-red flour beetle, Tribolium castaneum Herbst (Coleoptera: Tenebrionidae). The isolated compound acted as a fumigant, toxic to adults of stored grain insect pests with LC₅₀ values of 17.86, and 11.49 μg/L (S. oryzae), 19.80 and 10.29 μg/L (R. dominica) and 24.41 and 17.80 μg/L air (T. casatneum) respectively. Further, in vivo data reveal that the percentage of inhibition of acetyl cholinesterase (AChE) was dose-dependent and in vitro results showed potent AChE inhibitor. The isolated compound acts as an efficient biofumigant against the stored grain insect pests and has no adverse effect on seed germination. From this study, we assume that the isolated biofumigant molecule has the ability for used in IPM programs for stored-grain pests because of its biofumigant activity.

Potential of cold plasma to control Callosobruchus chinensis (Chrysomelidae: Bruchinae) in chickpea cultivars during four year storage

Cold plasma has proven itself as a promising method of food preservation by controlling food spoilage bacteria at very low temperatures. It is showing potential for insect control. Synthetic pesticides are mostly used to control Callosobruchus chinensis L. (Chrysomelidae: Coleoptera) to which it has developed resistance. The prospective potential of cold plasma treatment to control pulse beetle infestation of chickpea in the storage for about four years of plasma treatment was studied. The four chickpea cultivars were treated with cold plasma at different power 40, 50, and 60 W each for 10, 15, 20 min. Plasma treated and untreated chickpeas were stored in an airtight ziplock pouch. At regular intervals, the grains were observed for infestation. It was found most effective in controlling the pulse beetle infestation of treated chickpea samples. While plasma untreated chickpeas were attacked and damaged mostly by pulse beetle within the first quarter of the storage study. To avoid the problems created by the use of pesticides cold plasma treatment is found to be the best alternative in the protection of chickpea invasion by pulse beetle during a longer storage period. The findings in the present research may be used for the preparation of legumes which may also soak and cook faster like quick-cooking legumes and preserved for years without invasion of pulse beetle.

Toxicity nanoinsecticide based on clove essential oil against Tribolium castaneum (Herbst)

This study aimed to characterize nanoparticles loaded with clove (Syzygium aromaticum) essential oil-based polyethylene glycol (PEG) and to know their insecticidal activity against red flour beetle (Tribolium castaneum). The nanoparticles have irregular shapes in good dispersion. The nanoformulation could not enhance clove oil contact toxicity to T. castaneum, but could protect the oil from degradation and evaporation while simultaneously allowing sustained release, as indicated by the continued high toxicity for 16 weeks of storage.

Effects of Sublethal Doses of Methyl Benzoate on the Life History Traits and Acetylcholinesterase (AChE) Activity of Aphis gossypii

Safer alternatives to synthetic pesticides are essential for sustainable agriculture. Methyl benzoate (MB) is a volatile essential oil found in several plants. Recent reports of the toxicity of MB to arthropod pests suggest that MB may be a useful alternative insecticide. The present study assessed the effects of a sublethal concentration of MB (LC30, 0.22%) on the life history and reproductive characteristics of the cotton aphid, Aphis gossypii Glover, in both a treated parental generation (F0) and untreated progeny (F1). MB treatment significantly decreased longevity and fecundity in both the F0 and F1 generations, and prolonged the developmental duration of each immature instar of the F1 generations, compared with controls. The intrinsic rate of increase (r), finite rate of increase (λ), and net reproductive rate (R0) of the F1 generation were significantly reduced, compared to controls. The mode of action of MB is not known, but in aphids treated with LC30 MB, the activity of the enzyme acetylcholinesterase (AChE) decreased by more than 65%, compared with untreated controls. AChE activity was rapidly inhibited within 1 h, and remained inhibited for 6 h after in vivo exposure to MB. Moreover, molecular docking analysis revealed that MB had a strong affinity with the catalytic site of AChE, with a binding energy value of −6.2 kcal/mole. Our results suggest that MB targets AChE, and that a sublethal dose of MB can have adverse transgenerational effects on cotton aphids.

Tarin, a Potential Immunomodulator and COX-Inhibitor Lectin Found in Taro (Colocasia esculenta)

Taro (Colocasia esculenta) corm is a rustic staple food, rich in small starch granules, fibers, and bioactive phytoconstituents such as flavonoids, alkaloids, sterols, tannins, phytates, micronutrients, and proteins, including tarin, a GNA-related lectin. Tarin exhibits recognized biocide activities against viruses and insects, has antitumoral properties and is an immunomodulator molecule candidate. It has been isolated in highly purified form (>90%) from taro corms through low-cost and single-step affinity chromatography. It comprises 2-domain 27 to 28 kDa protomer, posttranslational cleaved into 2 nonidentical monomers, 11.9 and 12.6 kDa, held by noncovalent binding. At least 10 tarin isoforms sharing over 70% similarity have been described. The monomers assume the β-prism II fold, consisting of 3 antiparallel β-sheets formed by 4 β-strands each. Tarin exhibits an expanded-binding site for complex and high-mannose N-glycan chains 49, 212, 213, 358, 465, and 477 found on cell surface antigens of viruses, insects, cancer, and hematopoietic cells, explaining its broad biological activities. Tarin may stimulate innate and adaptive immune responses, enabling hosts to recover from infections or immunosuppressed status inherent to several pathological conditions. In a murine model, tarin stimulates the in vitro and in vivo proliferation of total spleen and bone marrow cells, especially B lymphocytes. Granulocyte repopulation has also been demonstrated in long-term mice bone marrow cell cultures. As a potential immunomodulator, tarin, administered to immunosuppressed mice, attenuated cyclophosphamide-induced leukopenia. We propose a molecular model that unites the potential prophylactic and therapeutic action of tarin on hematopoietic and cancer cells, as a potential immunomodulator.

Biochemical efficacy, molecular docking and inhibitory effect of 2, 3-dimethylmaleic anhydride on insect acetylcholinesterase

Evolution of resistance among insects to action of pesticides has led to the discovery of several insecticides (neonicotinoids and organophosphates) with new targets in insect nervous system. Present study evaluates the mode of inhibition of acetylchlonesterase (AChE), biochemical efficacy, and molecular docking of 2,3-dimethylmaleic anhydride, against Periplaneta americana and Sitophilus oryzae. The knockdown activity of 2,3-dimethylmaleic anhydride was associated with in vivo inhibition of AChE. At KD₉₉ dosage, the 2,3-dimethylmaleic anhydride showed more than 90% inhibition of AChE activity in test insects. A significant impairment in antioxidant system was observed, characterized by alteration in superoxide dismutase and catalase activities along with increase in reduced glutathione levels. Computational docking programs provided insights in to the possible interaction between 2,3-dimethylmaleic anhydride and AChE of P. americana. Our study reveals that 2,3-dimethylmaeic anhydride elicits toxicity in S. oryzae and P. americana primarily by AChE inhibition along with oxidative stress.

Effectiveness of carbon dioxide against different developmental stages of Cadra cautella and Tribolium castaneum

Methyl bromide is an excellent fumigant but has been banned because it has high potential for depleting the ozone layer which leads to many environmental and human health hazard issues. In this connection, effectiveness of carbon dioxide (CO₂, 99.9%) was studied as an alternative to methyl bromide under various exposure timings, 25 ± 1 °C, against different developmental stages of the almond moth, Cadra cautella, and red flour beetle, Tribolium castaneum. In case of C. cautella, the LT₉₉ against adult, pupa, and larval stages was achieved after 37.5, 78.1, and 99.9 h of CO₂ application, respectively. While for T. castaneum, the LT₉₉ values were obtained after exposure timings of 29.3, 153.9, and 78.4 h against adult, pupa, and larval stages, respectively. Adults were very susceptible; in contrast, pupae and larvae were more tolerant. The susceptibility order was observed as follows: T. castaneum adult > C. cautella adult > C. cautella pupae > T. castaneum larvae > C. cautella larvae > T. castaneum pupae. This study could be useful in developing the management strategies to prevent stored dates from C. cautella and T. castaneum infestation.

Mode of Action of the Natural Insecticide, Decaleside Involves Sodium Pump Inhibition

Decalesides are a new class of natural insecticides which are toxic to insects by contact via the tarsal gustatory chemosensilla. The symptoms of their toxicity to insects and the rapid knockdown effect suggest neurotoxic action, but the precise mode of action and the molecular targets for decaleside action are not known. We have presented experimental evidence for the involvement of sodium pump inhibition in the insecticidal action of decaleside in the cockroach and housefly. The knockdown effect of decaleside is concomitant with the in vivo inhibition of Na+, K+ -ATPase in the head and thorax. The lack of insecticidal action by experimental ablation of tarsi or blocking the tarsal sites with paraffin correlated with lack of inhibition of Na+- K+ ATPase in vivo. Maltotriose, a trisaccharide, partially rescued the toxic action of decaleside as well as inhibition of the enzyme, suggesting the possible involvement of gustatory sugar receptors. In vitro studies with crude insect enzyme preparation and purified porcine Na+, K+ -ATPase showed that decaleside competitively inhibited the enzyme involving the ATP binding site. Our study shows that the insecticidal action of decaleside via the tarsal gustatory sites is causally linked to the inhibition of sodium pump which represents a unique mode of action. The precise target(s) for decaleside in the tarsal chemosensilla and the pathway linked to inhibition of sodium pump and the insecticidal action remain to be understood.