Antifeedant and larvicidal activity of bioactive compounds isolated from entomopathogenic fungi Penicillium sp. for the control of agricultural and medically important insect pest (Spodoptera litura and Culex quinquefasciatus).

The use of chemical insecticides in agriculture has posed several challenges to environment and ecosystem health. Pesticides of biological origin are considered to be suitable for sustainable environment. In the present study bioactive compounds from Penicillium sp. was isolated and tested for insecticidal activity on Spodoptera litura and Culex quinquefasciatus larvae. Ethyl acetate extract of Penicillium sp. were characterized using GC-MS and FT-IR analysis. GC-MS analysis showed 20 different bioactive compounds namely, Propanoic acid, ethyl ester, Acetic Acid, Propyl Ester, Isopentyl Acetate, Acetic Acid, 2-Methylpropyl Ester, Behenic alcohol, 1-Hexadecene, 1-Octadecene, 1-Hexacosanol, n-Hexadecanoic acid, 1-Tetradecanol, 1-Dodecene, Tetrydamine, and Octadecanoic acid. The presence of functional groups such as, chloroalkanes, sulfonates, phosphines, amines, carboxylic acid, alkanes, and isocyanates was identified by using FTIR. Ethyl acetate extract of Penicillium sp., were tested for larvicidal activity on Spodoptera litura and Culex quinquefasciatus larvae showed significant larval mortality after 48 h of exposure with LC50: 72.205 mg/ml: LC90: 282.783 mg/ml and LC50: 94.701 mg/ml: LC90:475.049 mg/ml respectively. High antifeedant activity was observed in 300 µg/ml at 48 h of crude extract exposure. The present study concludes that Penicillium sp., secondary metabolites are effective for control of Spodoptera litura and Culex quinquefasciatus larvae.

Long-term storage does not affect the infectivity of entomopathogenic nematodes on insect hosts.

Entomopathogenic nematodes (EPNs) are effective biopesticides used in insect control. There are several formulations of entomopathogenic nematodes which are commercially available, but their popularity is low because the requirement of periodic release of stored entomopathogenic nematodes in field has reduced infectivity and is a constraint in large-scale repeated application of entomopathogenic nematodes in field. So, in order to overcome this impediment, the current study focuses on storage of entomopathogenic nematodes for a longer period of time using encapsulating beads. In this study, three EPNs, namely, Steinernema carpocapsae, Steinernema monticolum, and Rhabditis blumi, were encapsulated with Arabic gum and sodium alginate gel beads at different concentrations. Bio-efficacy of stored EPNs at different concentrations (50, 100, 200, 500, and 1000 infective juveniles (IJs)) in varying time intervals of 3, 6, 9, and 12 weeks were tested against Culex quinquefasciatus larvae. The results show that, after 3 weeks of storage, these entomopathogenic nematode species showed survival up to 96%, and in 12-week storage, survival rate was 50%. The virulence of the progeny that emerged from these stored entomopathogenic nematodes was similar to the fresh infective juveniles. The results of the present study show that Arabic gum-sodium alginate combination is a promising approach toward storing entomopathogenic nematodes. Furthermore, semi-field trials showed 70-90% larval mortality at a concentration of 3000 IJs (encapsulated and stored entomopathogenic nematodes in S. monticolum, S. carpocapsae, and R. blumi) on C. quinquefasciatus larvae. KEY POINTS: • Increased survival of stored EPNs (S. carpocapsae, S. monticolum, and R. blumi) in encapsulated gel using Arabic gum, sodium alginate, and yeast cells was assessed. • The efficacy was greater in stored EPNs at different concentrations from 3 to 12 weeks. • Semi-field trials of stored encapsulated EPNs are efficient in mosquito larval control.

Biosynthesis and characterization of silver nanoparticles from symbiotic bacteria Xenorhabdus nematophila and testing its insecticidal efficacy on Spodoptera litura larvae.

Spodoptera litura, one of the polyphagous pests, causes huge economical lose and use of chemical pesticide causes impact to the environmental. The present study deals with the use of cell- free supernatant of bacteria Xenorhabdus nematophila NP-1 strain for synthesizing silver nanoparticles and analyzing its larvicidal ability against Spodoptera litura. Color change from yellow to dark brown specifies the synthesis of AgNPs. UV-Vis spec indicates the presences of AgNPs at 440 nm λmax and functional groups; alcohols, carboxylic acids, aromatics, alkylhalides, ethers and phenols were confirmed by FTIR. SEM revealed the synthesized AgNPs is in spherical shape, EDaX confirms the elemental composition and the crystalline nature were observed using XRD. GC-MS analysis showed presence of Benzencepropanoic acid, 1, 3, 5 Trichloropent-2-ene, 1,1-Dichloro-2,3- dicmethycycloprone and 1,2-benzenedicarboxylic acid bioactive compounds some of which may be responsible for insecticidal and antibacterial activity. The antibacterial activity against S. aureus, B. subtilis and K. pneumoniae showed maximum zone of inhibition at 100 µL/mL. Larvicidal activity of S. litura shows highest mortality at 48 h. In potted plant experiment, AgNPs treated plants showed less damage, with less leaf consumption by S. litura larvae. Further, the synthesis of AgNPs were targeted to zebrafish embryos (non- target organism) and it didn't exhibit any toxic effect even at higher concentration. Our experiment concludes that, AgNPs synthesized using NP-1 strain has highest antimicrobial and insecticidal activity, which can be used in biomedical and biopesticides.

Mycosynthesis of bimetallic zinc oxide and titanium dioxide nanoparticles for control of Spodoptera frugiperda.

Spodoptera frugiperda is an important pest of several crops. Use of chemical insecticides in insect control has not been successful. In the present study, bio-nano formulation of bimetallic nanoparticles were synthesized using fungal metabolites from Metarhizium anisopliae and tested for insecticidal activity. Metarhizium anisopliae metabolites was synthesized along with bimetallic nanoparticles at different volumes for bioassay studies. Bimetallic nanoparticles showed colour change from light greenish to white. Synthesis of bimetallic NPs was confirmed by UV-vis spectrophotometer, with absorption peak at 387 nm. Functional groups in the synthesized BMNPs were analyzed by FTIR, which showed the presence of functional amines, carboxylic acids, alkenes, alkyl halides, phosphine oxides, anhydrides, phosphines, sulfonates, acid chlorides and alkynes. XRD analysis confirms the crystalline nature of nanoparticles. SEM analysis exhibits, the nanoparticles to be spherical in shape with size ranging 9.50 nm. EDaX analysis confirmed the elemental composition of synthesized NPs, while DLS for size distribution ranging at 80 to 137 nm. The larvicidal activity of monometallic and mycogenic bimetallic nanoparticles were tested on third instar S. frugiperda larvae. The highest mortality was observed in BMNPs at a concentration of 100 µg/ml after 48 h exposure. Pupicidal and antifeedant activity was also observed in the tested BMNPs. Detoxification enzymes studies of BMNPs showed considerable lowering these enzyme which may result in toxic manifestation in the insect. These results strongly suggest that, bimetallic nanoparticles synthesized using M. anisopilae can be used for protecting the crops against S. furgiperda.

Neuroprotective Effect of Epalrestat on Hydrogen Peroxide-Induced Neurodegeneration in SH-SY5Y Cellular Model.

Epalrestat (EPS) is a brain penetrant aldose reductase inhibitor, an approved drug currently used for the treatment of diabetic neuropathy. At near-plasma concentration, EPS induces glutathione biosynthesis, which in turn reduces oxidative stress in the neuronal cells. In this study, we found that EPS reduces neurodegeneration by inhibiting reactive oxygen species (ROS)-induced oxidative injury, mitochondrial membrane damage, apoptosis and tauopathy. EPS treatment up to 50 µM did not show any toxic effect on SH-SY5Y cell line (neuroblastoma cells). However, we observed toxic effect at a concentration of 100 µM and above. At 50 µM concentration, EPS showed better antioxidant activity against H2O2 (100 µM)-induced cytotoxicity, ROS formation and mitochondrial membrane damage in retinoic acid-differentiated SH-SY5Y cell line. Furthermore, our study revealed that 50 µM of EPS concentration reduced the glycogen synthase kinase-3 ß (GSK3-ß) expression and total tau protein level in H2O2 (100 µM)-treated cells. Findings from this study confirms the therapeutic efficacy of EPS on regulating Alzheimer's disease (AD) by regulating GSK3-ß and total tau proteins phosphorylation, which helped to restore the cellular viability. This process could also reduce toxic fibrillary tangle formation and disease progression of AD. Therefore, it is our view that an optimal concentration of EPS therapy could decrease AD pathology by reducing tau phosphorylation through regulating the expression level of GSK3-ß.

Effect of food plants on Spodoptera litura (Lepidoptera: Noctuidae) larvae immune and antioxidant properties in response to Bacillus thuringiensis infection.

The larvae of Spodoptera litura (Fabricius) were reared on five host plants, Brassica oleracea, Nicotiana tabacum, Ricinus communis, Gossypium hirsutum, and Arachis hypogaea. The larvae were immunized with Bacillus thuringiensis to observe the immune response. The results of total and differential hemocyte count were increased in B. oleracea, N. tabacum, and R. communis fed S. litura larval hemolymph. Similar results were observed in the parameter of nodulation, melanization, and phenoloxidase. Total protein was higher in R. communis fed larvae. Antioxidant levels like Catalase (CAT), Superoxide dismutase (SOD), Glutathione S- transferase (GST), Peroxidase (POX), Lipid peroxidase (LPO), and Esterase (EST) was found in moreover all plant-feeding insect. High CAT activity was observed 2-6 h in R. communis, G. hirsutum, and A. hypogaea fed S. litura larval midgut and fatbody samples. Increased SOD activity in both midgut and fatbody at 2-12 h of B. oleracea, G. hirsutum, and A. hypogaea fed. GST activity was increased initially 2-6 h in G. hirsutum and A. hypogaea. Increased POX activity was observed initially in all treated groups. Highest LPO observed at 6 h in N. tabacum in both midgut and fatbody. Whereas increased EST activity was observed in N. tabacum and B. oleracea. The results of the present study shows that nature of food influence the immunity against Bt infection. This information can be very useful for incorporating biological control program for insect pest.

Effect of Aspergillus flavus on the mortality and activity of antioxidant enzymes of Spodoptera litura Fab. (Lepidoptera: Noctuidae) larvae.

Insects have developed tolerance against mycoses caused by entomopathogenic fungi through several humoral and cellular mechanisms. Antioxidant enzymes such as superoxide dismutase, lipid peroxidase, and peroxidase can play a role in defense against mycosis, but the physiological interactions between the fungus and the insect are not well characterized. In this study, the effects of infection by entomopathogenic fungus, Aspergillus flavus on the antioxidant defense system of Spodoptera litura, were investigated. The fungi, A. flavus exposure resulted in modification of the levels of antioxidant enzymes, as well as significant decline in phenoloxidase titers and the total hemocyte count 48 h post exposure. A significant increase was observed in detoxifying enzymes. All these results suggest that A. flavus infects S. litura by directly acting on the immune system, resulting in decreased immune function. Bioassay results showed that A. flavus affects third and fourth instar larvae of S. litura. This report supports the importance of A. flavus as a candidate for biological control of S. litura.

Insecticidal and repellent activity of Clausena dentata (Rutaceae) plant extracts against Aedes aegypti and Culex quinquefasciatus mosquitoes (Diptera: Culicidae).

Mosquito control is facing a threat due to the emergence of resistance to synthetic insecticides. Insecticides of botanical origin may serve as suitable alternative biocontrol agents. The present study is to evaluate adulticidal activity of Clausena dentata plant extract against Aedes aegypti and Culex quinquefasciatus mosquitoes. The adult mortality was observed after 24 h of exposure. The highest mortality was found in acetone extracts against Ae. aegypti and Cx. quinquefasciatus with the LC50 and LC90 4.1783 mg/ml (3.8201-7.1026), 9.3884 mg/ml (7. 8258-13.1820) and 4.2451 mg/ml (3.8547-8.0254), 12.3214 mg/ml (10.9287-16.2220), respectively. Smoke toxicity was observed at 10-min interval for 40 min, and the mortality data were recorded. Result shows that Ae. aegypti and Cx. quinquefasciatus are 85 ± 2 and 89 ± 1.5, respectively. A mortality of 100 % was recorded in the commercial mosquito control. These results suggest that the leaf extracts of C. dentata have a potential to be used as an ideal eco-friendly approach for the control of mosquitoes.