Muthugounder Subramanian Shivakumar

Resistance selection and molecular mechanisms of cypermethrin resistance in red hairy caterpillar (Amsacta albistriga walker)

Amsacta albistriga is one of the important pests of oilseed crops in India. This pest has developed high resistance to organophosphate (OP) insecticide in field. Therefore, cypermethrin insecticide was used as an alternative for this pest. After 20 generations of selection with cypermethrin, the LD50 value for A. albistriga was increased by 21.5-folds. The synergism ratio of piperonyl butoxide (PBO) and triphenyl phosphate (TPP) was increased by 10- and 9.6-fold in resistant strains and comparatively, 3.9 and 4.2-fold in susceptible strains. Detoxification enzyme analysis and native PAGE electrophoresis of esterase isoenzyme further revealed that esterase and mixed function oxidase may be involved in cypermethrin resistance in CypRes strain. In addition to enzyme analysis overexpression of CYP4M44, CYP9A77 and CYP6B47 (ortholog) can confer metabolic resistance in the CypRes strain. These data provide a foundation for further study of cypermethrin resistance mechanism observed in A. albistriga.

Ultraviolet-B light induced oxidative stress: effects on antioxidant response of Spodoptera litura.

Ultraviolet light (UV-B), which emits radiation in the range of 280-315 nm, has been used worldwide in light trapping of insect pests. In this article, we test the hypothesis that one of the duration of UV-B exposure has a differential impact on oxidative stress marker enzymes in Spodoptera litura. Effect of UV-B exposure on total protein and antioxidant activities of superoxide dismutase (SOD), catalase (CAT), peroxidases (POX) and glutathione-S-transferase (GST) were investigated in S. litura. The adults were exposed to UV-B light for various time periods (0, 30, 60, 90 and 120 min). We found that exposure to UV-B light for 30 and 60 min resulted in increased activities of POX. When the exposure time lasted for 60 and 90 min, the activities of SOD remained significantly higher than the control. However, the POX, CAT and GST activity decreased to control levels at 90 and 120 min. whereas relatively long duration exposure activates the xenobiotics detoxifying enzymes like GST and POX and CAT enzymes. Longer UV-B exposure may interfere with pesticide detoxification mechanism in insects, making them more susceptible to insecticides.

Mosquitocidal Effect of Glycosmis pentaphylla Leaf Extracts against Three Mosquito Species (Diptera: Culicidae)

Background The resistance status of malaria vectors to different classes of insecticides used for public health has raised concern for vector control programmes. Alternative compounds to supplement the existing tools are important to be searched to overcome the existing resistance and persistence of pesticides in vectors and the environment respectively. The mosquitocidal effects of Glycosmis pentaphylla using different solvents of acetone, methanol, chloroform and ethyl acetate extracts against three medically important mosquito vectors was conducted. Methods Glycosmis pentaphylla plant leaves were collected from Kolli Hills, India. The WHO test procedures for larval and adult bioassays were used to evaluate extracts against mosquito vectors, and the chemical composition of extracts identified using GC-MS analysis. Results The larvicidal and adulticidal activity of G. pentaphylla plant extracts clearly impacted the three species of major mosquitoes vectors. Acetone extracts had the highest larvicidal effect against An. stephensi, Cx. quinquefasciatus and Ae. aegypti with the LC50 and LC90 values of 0.0004, 138.54; 0.2669, 73.7413 and 0.0585, 303.746 mg/ml, respectively. The LC50 and LC90 adulticide values of G. pentaphylla leaf extracts in acetone, methanol, chloroform and ethyl acetate, solvents were as follows for Cx. quinquefasciatus, An. stephensi and Ae. Aegypti: 2.957, 5.458, 2.708, and 4.777, 3.449, 6.676 mg/ml respectively. The chemical composition of G. pentaphylla leaf extract has been found in 20 active compounds. Conclusions The plant leaf extracts of G. pentaphylla bioactive molecules which are effective and can be developed as an eco-friendly approach for larvicides and adulticidal mosquitoes vector control. Detailed identification and characterization of mosquitocidal effect of individual bioactive molecules ingredient may result into biodegradable effective tools for the control of mosquito vectors.

Pre-treatment with melatonin decreases abamectin induced toxicity in a nocturnal insect Spodoptera litura (Lepidoptera: Noctuidae)

AIM Oxidative stress is an important component of the mechanism of pesticide toxicity. The aim of the present study was to investigate the time-dependent melatonin effects against abamectin-induced oxidative stress in a S.litura model. Larvae were divided into 5 different groups; (1) control group,(2) Melatonin group (4.3×10-5M/100ml diet), (3) Abamectin group 1.5ml/L, (4) Pre-melatonin treated group (PM) (4.3×10-5M/100ml diet) before abamectin exposure 1.5ml/L, (5) Post-melatonin treated group (TM) after abamectin exposure. Melatonin was supplemented via artificial diet in PM and TM animals during 24h. MAIN METHODS Midgut, fatbody, and hemolymph, were collected for the analysis of oxidative stress markers (Total ROS, GSH, nitrite, TBARS, LPO), antioxidant enzyme levels (SOD, GST, CAT, POX, APOX) in fifth instar larvae. Midgut damage was examined by using morphological analysis. KEY FINDINGS Our results observed that ABA group showed significant changes (p<0.001) in the ROS and carbonyl content in midgut. The increase of antioxidant enzyme levels (SOD, CAT, POX, and APOX) in midgut was led by the continuous free radical scavenger cascade of melatonin. Significant (p<0.01) increases in CAT and APOX levels were seen in the fatbody of PM and TM treated insects. SIGNIFICANCE In conclusion, the results of the study revealed that abamectin toxicity generates oxidative stress in the insect, while pre-melatonin treatment reduces this damage due to its antioxidant properties, especially POX levels in midgut, fatbody, and hemolymph. Therefore, indoleamine can play a vital role curtailing the abamectin toxicity in time dependent manner in S.litura.

Medicinal Plants for Anopheles stephensi Liston Larvae Management

Abstract Plants contain several secondary metabolites which are known to be effective in controlling a variety of insects. Chemical insecticides have been used for controlling the breeding of mosquitoes. Due to the problem of insecticide resistance and undesirable effects on non target organisms, a search for alternative larvicidal sources is necessary. Plant secondary metabolites are an ideal source for larvicides. In this study, larvicidal efficacy of different solvent (hexane, chloroform, ethyl acetate, acetone and methanol) crude leaf extracts was investigated against fourth-instar larvae of Anopheles stephensi. Larval bioassay tests were carried out as per WHO protocol and mortality was recorded after 24 h exposure. High larval mortality was observed in acetone extract of Elaeagnus indica with LC50 and LC90 values of 41.18 and 96.37 ppm respectively. The chloroform extract of B. maderaspatensis also showed a high larval mortality with LC50 and LC90 values of 49.18 ppm, and 145.45 ppm respectively. The results of this study revealed that larvicidal potential of acetone extract of Elaeagnus indica and chloroform extract of Blepharis maderaspatensis further effort to characterize the bioactive compounds can be used for effective mosquito control.

Circadian clock gene is involved in the photoperiodic response of the Spodoptera litura adults

Circadian clocks govern many metabolic and behavioural processes in an organism. In insects, these clocks and their molecular machinery have been found to influence reproduction in many different ways. In moth Spodoptera litura, we demonstrated the occurrence of circadian clock genes in adult’s heads. We identified different clock genes, period (per), cryptochrome1 (cry1) and cryptochrome2 (cry2) in adult heads, using real-time PCR. Our results show that Cry1 gene and Period gene expression level is high at 8:16 photoperiod as compared with other photoperiod. In Cry2, gene expression level is high at 8:16 and 0:24 photoperiod. We show that expression levels of the clock genes per, cry1 and cry2 fluctuate in a circadian manner in adult heads in S. litura. These results strongly suggest that the occurrence of a circadian clock in S. litura heads.

Synergistic effect of entomopathogenic fungus Fusarium oxysporum extract in combination with temephos against three major mosquito vectors

Abstract Mosquito control using chemical insecticides is facing a major challenge due to development of insecticide resistance. Improving the efficiency of existing insecticides using synergistic secondary metabolites of biological origin is increasingly being researched. Herein, we evaluated the toxicity of Fusarium oxysporum extract alone and in binary combinations with temephos, on larvae and pupae of Anopheles stephensi, Aedes aegypti and Culex quinquefaciatus. F. oxysporum extract was characterized using TLC, FT-IR and GC-MS. After 24 h of exposure, the binary combination of temephos + F. oxysporum extract (1:1 ratio) was highly toxic to larvae of An. stephensi (LC50: 35.927 μg/ml), Ae. aegypti (LC50: 20.763 μg/ml) and Cx. quinquefasciatus, (LC50: 51.199 μg/ml). For pupae LC50 values were 38.668, 26.394, and 72.086 μg/ml, respectively. Histology studies of mosquitoes exposed to F. oxysporum extract showed vacuolation in epithelium, as well as in adipose, and muscle tissues of larval midgut. Overall, our results show that the synergistic combination of temephos and F. oxysporum extract is highly effective to control mosquito young instars.

Changes in light and dark periods affect the arylalkylamine N-acetyl transferase, melatonin activities and redox status in the head and hemolymph of nocturnal insect Spodoptera litura

Abstract The present study was conducted to describe the impact of circadian rhythm on melatonin levels and redox statusunder three photoperiods (12L:12D, 0L:24D, and 24L:0D) in head and hemolymph of Spodoptera litura. Melatonin is an powerful antioxidant and controls the reproduction of organisms. In this study, melatonin levels, Arylalkylamine N-acetyltransferase(AA-NAT), and antioxidant enzyme activities were analyzed. Results showed melatonin, AA-NAT levels in hemolymph were significantly (p < 0.05) higher during the dark period than during LL regime. HPLC chromatogram of the insect head and hemolymph showed 5 peaks while hemolymph showed 6 peaks in LD, and LLregimes. The day–night changes of melatonin increased the antioxidant enzymes (GST, CAT, POX) persisted in the insect hemolymph, but were suppressed by constant light. The present study leads us to speculate that synthesis and release of melatonin in the S.litura head occur as circadian rhythm and light has an inhibitory effect on melatonin synthesis.

Spectral characterization and antibacterial activity of an isolated compound from Memecylon edule leaves

Memecylon edule Roxb. (Melastamataceae family) is a small evergreen tree reported as having ethnobotanical and pharmacological properties. The present study was aimed to investigate the spectral characterization and antibacterial activity of isolated pure compound (3β-hydroxyurs-12-en-28-oic acid (ursolic acid)) from Memecylon edule leaves by performing bioassay guided isolation method. The structure derivation of isolated compound was done by different spectral studies like UV, FT-IR, LC-MS, CHNS analysis, 1D (1H, 13C and DEPT-135) and 2D-NMR (HSQC and HMBC), respectively. About 99.29% purity of the compound was found in LC analysis. 1H NMR spectrum results of compound shown 48 protons appear at different shielded region and most of the protons were present in aliphatic region. Whereas, 13C NMR spectral data resulted seven methyl carbons (CH3), nine methylene carbons (CH2), seven methine carbons (CH) and six non-hydrogenated carbons (C) which are characteristic of pentacyclic triterpene. The isolated pure compound was tested for its antibacterial properties against targeted human pathogens by performing agar well diffusion, MIC and MBC assays and the result exhibits better growth inhibitory effects against S. epidermidis and S. pneumoniae, with the MIC values of 1.56 and 3.15μg/ml. The outcome of this study suggests that the bioactive compound is used for development of plant based drugs in pharmaceutical industry for combating microbial mediated diseases.

In vitro evaluation of antioxidant, antiproliferative potentials of bioactive extract-cum-rutin compound Isolated from Memecylon edule leaves and its molecular docking study

Abstract The current study was planned to investigate the antioxidant and anti-proliferative potential of leaf crude extracts and isolated compound (rutin) from Memecylon edule by performing the standard antioxidant and MTT assays. Results suggested that different solvents crude leaf extracts of M. edule expressed varying degree of antioxidant potential on all tested methods (DPPH, NO, OH, O2•- radicals) based on dose depended manner and they also had good reducing ability. Significant high antiradical potential was found in ethyl acetate extract (DPPH IC50 value 26.77 μg/ml, NO IC50 value 27.04 μg/ml, OH IC50 value 30.94 μg/ml, O2•- IC50 value 50.75 μg/ml and FRAP EC50 value 40.43 μg/ml) followed by other extracts. The anti-proliferative activity of potential extract (ethyl acetate extract) which possess high antioxidant activity, and isolated rutin compound was tested (by MTT assay) against U-937 and HT-60 cell lines and the results show dose dependent activity. In addition, docking studies of reported rutin compound exhibits strong inhibition on the active site of VEGFR2 than the co-crystallized ligand N,2-dimethyl-6-(7-(2-morpholinoethoxy) Quinolin-4-yloxy)benzofuran-3-carboxamide.