Bioassay Studies Research Articles

Design and synthesis of cantharidin derivative DCZ5418 as a TRIP13 inhibitor with anti-multiple myeloma activity in vitro and in vivo

Natural product cantharidin can inhibit multiple myeloma cell growth in vitro, while serious adverse effects limited its clinical application. Therefore, the structural modification of cantharidin is needed. Herein, inspired by the structural similarity of the aliphatic endocyclic moiety in cantharidin and TRIP13 inhibitor DCZ0415, we designed and synthesized DCZ5418 and its nineteen derivatives. The molecular docking study indicated that DCZ5418 had a similar binding mode to TRIP13 protein as DCZ0415 while with a stronger docking score. Moreover, the bioassay studies of the MM-cells viability inhibition, TRIP13 protein binding affinity and enzyme inhibiting activity showed that DCZ5418 had good anti-MM activity in vitro and definite interaction with TRIP13 protein. The acute toxicity test of DCZ5418 showed less toxicity in vivo than cantharidin. Furthermore, DCZ5418 showed good anti-MM effects in vivo with a lower dose administration than DCZ0415 (15 mg/kg vs 25 mg/kg) on the tumor xenograft models. Thus, we obtained a new TRIP13 inhibitor DCZ5418 with improved safety and good activity in vivo, which provides a new example of lead optimization by using the structural fragments of natural products.

Effect of Azadirachta indica Leaf Extract on Some Biochemical Parameters in Wistar Albino Mice Infected with Plasmodium berghei

The use of medicinal plants in combating many tropical diseases including malaria is gaining wide acceptance owing to their many bioactive compounds. Malaria, which is caused by a Plasmodium parasite, and transmitted by the bite of infected mosquitoes is endemic in developing countries especially in Africa where it pose serious health challenge to the populace. This study evaluates the effect of Azadirachta indica leaf extract on some biochemical parameters in Wistar Albino mice infected with Plasmodiumberghei. A total of ninety (90) mature male swiss albino mice (free from infection and weighing between 25-35g) were used for the study. The animals were grouped into six classes (A-F) of fifteen (15) mice per group, per cage. Groups A to C served as the control groups [normal (uninfected plus distilled water), standard (infected plus Lonart (4mg/kg) and negative (infected plus distilled water)] respectively while groups D, E and F served as the treatment groups and were orally administered 100 mg/kg, 200 mg/kg and 400 mg/kg doses of leaf extract of Azadirachta indica for five (5) days consecutively. Malaria parasites (Plasmodium berghei, Anka strain) were inoculated using standard methods. At the end of the experimental periods, the animals were sacrificed and blood collected through cardiac puncture for bioassay studies. Activities of ALT, AST, ALP were determined using standard assay kits and concentrations of bilirubin (total and direct) as well as urea, creatinine, sodium, potassium, chloride and bicarbonate levels were carried out using standard methods. Results showed a significant increase (p<0.05) in serum activities of ALT and AST in extract treated animals when compared with the untreated control while there was significant decrease (p>0.05) in the serum activities of ALP in extract treated animals when compared with the untreated control. Results further showed an increase in the bilirubin (total and direct) levels of the extract treated groups as compared with the untreated control. Similar trends were observed for the levels of urea, creatinine, sodium, potassium and chloride. It could therefore be concluded that administration of Azadirachta indica leaf extract, though potent in fighting against malarial infection, could pose a threat to the liver and other organs of the body if not properly monitored.

Effectiveness of chitosan nanohydrogel mediated encapsulation of EcR dsRNA against the whitefly, Bemisia tabaci Asia-I (Gennedius) (Hemiptera: Aleyordidae)

Bemisia tabaci is a global invasive pest causing substantial loss on several economically important crops and has developed a very high level of resistance to insecticides making current management practices ineffective. Thus, the novel pest management strategy like RNA interference (RNAi) has emerged as a potential molecular tool in the management of insect pests particularly B. tabaci. The present study investigated RNAi mediated silencing of the Ecdysone Receptor (EcR) gene in B. tabaci Asia-I using biodegradable Chitosan Nanoparticles (CNPs) hydrogel containing EcR dsRNA. The formation of nanohydrogel and dsRNA loading were characterized by gel retardation assay, scanning electron microscopy (SEM); transmission electron microscopy (TEM) and Fourier transform infrared microscopy (FTIR). The stability of CNPs/dsRNA was assessed by exposure to direct sunlight and UV light for different time periods. The CNPs/dsRNA exhibited increased stability over the untreated control and further confirmed by bioassay studies which yielded mortality over 80% and effectively down regulated the expression of the EcR gene as confirmed by qRT-PCR analysis. These investigations provide potential avenues for advancing innovative pest management strategies using biopolymer CNPs hydrogel, which can enhance the efficiency of dsRNA as a safe and targeted solution in the management of whiteflies.

Bent π‐Conjugation within a Macrocycle: Asymmetric Total Syntheses of Spirohexenolides A and B

AbstractMacrocycles with bent π‐conjugation motif are extremely rare in nature and synthetically daunting and anticancer haouamines and spirohexenolides were representative of such rare natural products with synthetically challenging bent π‐conjugation within a macrocycle. While the total synthesis of haouamines has been elegantly achieved, spirohexenolides remains an unmet synthetic challenge due to the highly strained bent 1,3,5‐triene conjugation within C15 macrocycle. Inspired by the chemical synthesis of cycloparaphenylenes (CPPs) and haouamines, herein we devise a synthetic strategy to overcome the highly strained bent 1,3,5‐triene conjugation within the macrocycle and achieve the first, asymmetric total synthesis of spirohexenolides A (>20 mg) and B (>50 mg). Our synthesis features strategic design of ring‐closing metathesis (RCM) macrocyclization followed by double dehydration to achieve the C15 macrocycle with the deformed nonplanar 1,3,5‐triene conjugation. In addition, we have developed a new enantioselective construction of highly functionalized spirotetronate fragment (northeast moiety) through RCM and Ireland–Claisen rearrangement. Our in vitro bioassay studies reveal that both spirohexenolides are cytotoxic against a panel of human cancer cells with IC50 1.2–13.3 μM and spirohexenolide A is consistently more potent (up to 3 times) than spirohexenolide B, suggesting the importance of alcohol for their bioactivity and for medicinal chemistry development.

Bent π-Conjugation within a Macrocycle: Asymmetric Total Syntheses of Spirohexenolides A and B.

Macrocycles with bent π-conjugation motif are extremely rare in nature and synthetically daunting and anticancer haouamines and spirohexenolides were representative of such rare natural products with synthetically challenging bent π-conjugation within a macrocycle. While the total synthesis of haouamines has been elegantly achieved, spirohexenolides remains an unmet synthetic challenge due to the highly strained bent 1,3,5-triene conjugation within C15 macrocycle. Inspired by the chemical synthesis of cycloparaphenylenes (CPPs) and haouamines, herein we devise a synthetic strategy to overcome the highly strained bent 1,3,5-triene conjugation within the macrocycle and achieve the first, asymmetric total synthesis of spirohexenolides A (>20 mg) and B (>50 mg). Our synthesis features strategic design of ring-closing metathesis (RCM) macrocyclization followed by double dehydration to achieve the C15 macrocycle with the deformed nonplanar 1,3,5-triene conjugation. In addition, we have developed a new enantioselective construction of highly functionalized spirotetronate fragment (northeast moiety) through RCM and Ireland-Claisen rearrangement. Our in vitro bioassay studies reveal that both spirohexenolides are cytotoxic against a panel of human cancer cells with IC50 1.2-13.3 μM and spirohexenolide A is consistently more potent (up to 3 times) than spirohexenolide B, suggesting the importance of alcohol for their bioactivity and for medicinal chemistry development.

Identification of a Staphylococcus aureus amidase catalytic domain inhibitor to prevent biofilm formation by sequential virtual screening, molecular dynamics simulation and biological evaluation

Staphylococcus aureus (S. aureus) is one of the common causes of implant associated biofilm infections and their biofilms are resistant to antibiotics. S. aureus amidase (AM) protein, a cell wall hydrolase that cleaves the amide bond between N-acetylmuramic acid and L-alanine residue of the stem peptide, is several fold over-expressed under biofilm conditions. Previous studies demonstrated an autolysin mutant in S. aureus that lacks the AM protein, is highly impaired in biofilm development. We carried out a structure-based small molecule design using the crystal structure of AM protein catalytic domain to identify inhibitors that can block amidase activity and therefore inhibits S. aureus biofilm formation. Sequential virtual screening followed by pharmacokinetic analysis and bioassay studies filtered 25 small molecules from different databases. Two compounds from the SPECS database, SPECS-1 and SPECS-2, were selected based on the best docking score and minimum biofilm inhibitory concentration towards S. aureus biofilms. SPECS-1 and SPECS-2 were further tested for their structural/energetic stability in complex with the AM protein using molecular dynamics simulation and MM-GBSA techniques. In vitro, biofilm inhibition studies on different surfaces confirmed that treatment with SPECS-1 and SPECS-2 at a concentration of 250 μg/ml exhibited significant prevention and disruption of S. aureus biofilms. Finally, the in vitro anti-biofilm activities of these two compounds were validated against Methicillin-resistant S. aureus clinical isolates. We concluded that the discovered compounds SPECS-1 and SPECS-2 are safe and exhibit biofilm preventive and disruption activity for inhibiting the S. aureus biofilms and hence can be used to treat implant-associated biofilm infections.

Using Multiple Metal Mixture Models to Predict Toxicity of Riverine Sediment Porewater to the Benthic Life Stage of Juvenile White Sturgeon (Acipenser transmontanus).

Five metal mixture dose-response models were used to predict the toxicity of porewater to young sturgeon at areas of interest in the Upper Columbia River (WA, USA/BC, Canada) and to evaluate these models as tools for risk assessments. Dose components of metal mixture models included exposure to free metal ion activities or metal accumulation by biotic ligands or humic acid, and links of dose to response used logistic equations, independent joint action equations, or additive toxicity functions. Laboratory bioassay studies of single metal exposures to juvenile sturgeon, porewater collected in situ in the fast-flowing Upper Columbia River, and metal mixture models were used to evaluate toxicity. The five metal mixture models were very similar in their predictions of adverse response of juvenile sturgeon and in identifying copper (Cu) as the metal responsible for the most toxic conditions. Although the modes of toxic action and the 20% effective concentration values were different among the dose models, predictions of adverse response were consistent among models because all doses were tied to the same biological responses. All models indicated that 56% ± 5% of 122 porewater samples were predicted to have <20% adverse response, 25% ± 5% of samples were predicted to have 20% to 80% adverse response, and 20% ± 4% were predicted to have >80% adverse response in juvenile sturgeon. The approach of combining bioassay toxicity data, compositions of field porewater, and metal mixture models to predict lack of growth and survival of aquatic organisms due to metal toxicity is an important tool that can be integrated with other information (e.g., survey studies of organism populations, life cycle and behavior characteristics, sediment geochemistry, and food sources) to assess risks to aquatic organisms in metal-enriched ecosystems. Environ Toxicol Chem 2024;43:62-73. Published 2023. This article is a U.S. Government work and is in the public domain in the USA.

Effectiveness of Fungicides against Colletotrichum lindemuthianum Causing Anthracnose of Green Gram [Vigna radiata (L.) Wilczek

Background: Anthracnose is currently a severe threat to green gram cultivation in India. In vitro bioassay and glasshouse studies were performed to evaluate the effectiveness of different fungicides against Collectotrichum lindemuthianum. Methods: The current investigation was conducted at the Department of Plant Pathology, N.M. College of Agriculture, Navsari Agricultural University, Navsari, Gujarat in 2020-21. The poison food technique assessed the efficacy of systemic, non-systemic and combination fungicides against C. lindemuthianum. The management study was also carried out from the best-performing bioassay treatments and evaluated in the glasshouse. Result: At 500 ppm, carbendazim 50 WP and propiconazole 25 EC inhibited 100% of mycelial growth out of six systemic fungicides tested while in non-systemic fungicides, mancozeb 75 WP and chlorothalonil 75 WP inhibited the test pathogen the most at 2500 ppm. Among the combi-fungicides tested at 500 ppm, carbendazim (12%) + mancozeb (63%) 75 WP and captan 70% + hexaconazole 5% 75 WP inhibited pathogen mycelial growth the most significantly more than the untreated control. In glasshouse studies, the lowest disease index was found in two foliar sprays of carbendazim 50 WP @ 1.0 g/l, propiconazole 25 EC @ 2.0 ml/l and captan 70% + hexaconazole 5% @ 0.6 g/l spaced 15 days apart. On the other hand, seed treatment of carbendazim 12% + mancozeb 63% @ 3.0 g/kg seed and mancozeb 75 WP @ 3.0 g/kg seed had the lowest disease index compared to control.

Phytotoxicity Studies of Chromolaena odorata (L.) R.M. King and H. Robinson. Through Seed Germination Bioassays

Invasive or alien weeds are those which are introduced to new areas intentionally or unintentionally. They are undesirable plants which affect crop production, their quality and quantity, other resource utilization and income generation activities of the humans. Chromolaena odorata is one such invasive or alien weed which has invaded Maval region in Pune district. Chromolaena odorata has shown gradual increase in its abundance and decrease in natural Phytodiversity and crop diversity over frequent field visits. The present study was therefore undertaken to investigate allelopathic potential of leachates of root, stem, and leaf of Chromolaena odorata on common legumes in Maval tehsil like Horsegram, Lentil, and Mothbean in seed germination bioassay experiment. Petri plate bioassay study revealed that lower concentrations of leachates promoted root length, shoot length, Vigour index but higher concentration (20%) of aqueous leachates reduced seed germination in Horsegram, Lentil, and Mothbeans significantly as compared to other concentrations (4%, 8%, 12%, 16% and control). Treatment with higher concentration caused a remarkable increase in the rate of inhibition. Phytochemical analysis showed the presence of Flavonoids, Saponins, Tannins, Alkaloids, Steroids and Terpenoids. The inhibitory effects on seed germination revealed allelopathic potential of weed Chromolaena odorata. Toxicity effect was more in 20% concentration of leaf leachates than in root and stem. This may be due to presence of more allelochemicals in leaf than in root and stem.

Discovery of Novel Salicylaldehyde Derivatives Incorporating an α-Methylene-γ-Butyrolactone Moiety as Antifungal Agents.

Plant diseases caused by phytopathogenic fungi and oomycetes pose a serious threat to ensuring crop yield and quality. Finding novel antifungal candidates based on natural products is one of the critical methods for developing effective and environmentally friendly pesticides. In this study, a series of salicylaldehyde derivatives containing an α-methylene-γ-butyrolactone moiety were designed, synthesized, and their fungicidal activities were evaluated. The bioassay studies indicated that compound C3 displayed an excellent in vitro activity against Rhizoctonia solani with an EC50 value of 0.65 μg/mL, higher than that of pyraclostrobin (EC50 = 1.44 μg/mL) and comparable to that of carbendazim (EC50 = 0.33 μg/mL). For Valsa mali and Phytophthora capsici, compound C3 also showed good fungicidal activities with EC50 values of 0.91 μg/mL and 1.33 μg/mL, respectively. In addition, compound C3 exhibited promising protective in vivo activity against R. solani (84.1%) at 100 μg/mL, which was better than that of pyraclostrobin (78.4%). The pot experiment displayed that compound C3 had 74.8% protective efficacy against R. solani at 200 μg/mL, which was comparable to that of validamycin (78.2%). The antifungal mode of action research indicated that compound C3 could change the mycelial morphology and ultrastructure, increase cell membrane permeability, affect respiratory metabolism by binding to complex III, and inhibit the germination and formation of sclerotia, thereby effectively controlling the disease. The present study provides support for the application of these salicylaldehyde derivatives as promising potential pesticides with remarkable and broad-spectrum fungicidal activities against phytopathogenic fungi and oomycetes in crop protection. This article is protected by copyright. All rights reserved.

Biological Preparation, Characterization of CaO Nanoparticles from Egg Shell Waste and Insecticidal Activity against Seed Weevil, Sitophilus oryzae L. in Maize

Calcium oxide (CaO) nanoparticles was biologically synthesized by calcinating egg shells from kitchen waste and characterized using SEM, UV-Vis, XRD and FT-IR. Biosynthesized CaO nanoparticles are found to be an effective insecticide against seed weevil, Sitophilus oryzae in maize. The indiscriminate use of already available commercial pesticides has led to develop resistance among the pests and also occurrence of pesticide residues in produce. The SEM study revealed that the particles are granular in shape with a size of 189 nm. The diffraction peaks of XRD were observed at 2θ = 32.320, 37.48°, 48.40°, 53.96°, 64.18°, 67.52°and exhibited polycrystalline nature. In the FTIR spectrum, a broad band at 1410 cm-1, a sign of a C-O bond which indicated the association between the oxygen atom of carbonate and the calcium atom. The insecticidal activity of CaO nanoparticles was assessed against S. oryzae by contact toxicity bioassay method. The outcomes of the bioassay studies showed that the lethal dose (LD50) for maize seeds was 72.62 mg/100 g. and within seven days of exposure, 100% death of S. oryzae was attained at a dosage of 240 mg/100 gm of maize seeds. The current study concluded that biosynthesized CaO nanoparticles may be used as an effective management technique to successfully manage the S. oryzae under storage conditions as an alternative to chemical pesticides.

Impact of silver nanoparticles against stored product pest Sitophilus oryzae (L.) and effect on agromorphological characteristics of Zea mays (maize seeds)

The present study, comparative entomotoxic efficacy of silver nanoparticles obtained through the chemical and biological route against Sitophilus oryzae L. Physicochemical characterization results revealed that silver nanoparticles (Ag NPs) were spherical morphology with an average size of 20–51 nm having excellent stability. XRD diffraction peaks showed major peaks at (2 theta) 38.19º, 44.37º, 64.56º, and 77.47º confirming their crystalline nature. UV–vis spectra inferred strong absorbance between 410 and 450 nm. Bioassay studies exhibited the LD50 values as 40.16 mg/100 g for c-Ag NPs and 24.69 mg/100 g for b-Ag NPs. The mortality brought by b-Ag NPs at the dose of 130 mg after 6 days of exposure was 100% whereas only 80% of mortality was observed for c-Ag NPs at the same dose. These c-Ag NPs also enhanced seedling characteristics i.e., germination (96%), seedling length (45.33 cm), vigor index (4351.68), and dry matter production (4.20 g). The experiment results shows that the b-Ag NPs are an alternative to insecticides against S. oryzae and improving agromorphological characteristics of maize.

Susceptibility of Selected Crops to Simulated Imazethapyr Carryover: A Morpho-Anatomical Analysis

A bioassay study was conducted to determine the differences in the susceptibility of selected crops to simulated imazethapyr residues based on morphological and anatomical parameters. Sugar beet, white mustard, and rapeseed oil were found to be the most sensitive based on ED50 values for the root length and the root fresh weight. Corn and sunflower were less sensitive, and wheat was the least sensitive. The measured anatomical parameters confirmed the different sensitivities of the tested plants, as evidenced by a shortening of the meristem and elongation zones, a reduction in the distance between the root tip and the absorption zone, and the distance between the root tip and the point where the primordium of the lateral root appears. An imazethapyr residue level equivalent to ED20 (for root length) did not cause serious morphological changes in the less sensitive plants, nor did it cause significant changes in the length of the root cap, the beginning of the root absorption zone (root hair region), the beginning of lateral root formation (i.e., the permanent region), and the number of root primordia per root length. Therefore, ED20 could be proposed as an acceptable residue level (ARL) or herbicide residue level at which these plants can be safely sown.

Hydantoanabaenopeptins from Lake Kinneret Microcystis Bloom, Isolation, and Structure Elucidation of the Possible Intermediates in the Anabaenopeptins Biosynthesis.

Anabaenopeptins are common metabolites of cyanobacteria. In the course of reisolation of the known aeruginosins KT608A and KT608B for bioassay studies, we noticed the presence of some unknown anabaenopeptins in the extract of a Microcystis cell mass collected during the 2016 spring bloom event in Lake Kinneret, Israel. The 1H NMR spectra of some of these compounds presented a significant difference in the appearance of the ureido bridge protons, and their molecular masses did not match any one of the 152 known anabaenopeptins. Analyses of the 1D and 2D NMR, HRMS, and MS/MS spectra of the new compounds revealed their structures as the hydantoin derivatives of anabaenopeptins A, B, F, and 1[Dht]-anabaenopeptin A and oscillamide Y (1, 2, 3, 6, and 4, respectively) and a new anabaenopeptin, 1[Dht]-anabaenopeptin A (5). The known anabaenopeptins A, B, and F and oscillamide Y (7, 8, 9, and 10, respectively) were present in the extract as well. We propose that 1-4 and 6 are the possible missing intermediates in the previously proposed partial biosynthesis route to the anabaenopeptins. Compounds 1-6 were tested for inhibition of the serine proteases trypsin and chymotrypsin and found inactive at a final concentration of ca. 54 μM.

Possible Ameliorative and Preventive Effect of Leaf Extract of Andrographis paniculata on Atherosclerosis: An Experience with Isoproterenol Induced Wistar Rats

Atherosclerosis has been regarded as one of the leading causes of death in modern-day man worldwide. The use of medicinal plants especially Andrographis paniculata in the treatment of chronic diseases, particularly atherosclerotic disorder is becoming popular. This study aimed to evaluate the possible ameliorative and preventive effect of leaf extract of Andrographis paniculata on atherosclerosis in isoproterenol-induced Wistar rats. Thirty animals were randomly divided into five groups (A-E) of six animals per group, per cage. Groups A, B and C served as the treatment groups and were orally pre-treated with 100, 200 and 400 mg/kg body weight extract of A. paniculata for fourteen days, group D served as the positive control group and was administered 10 mg atorvastatin while group E served as the negative control and was administered distilled water. On the fifteenth and sixteenth day, 150 mg/kg isoproterenol was administered intraperitoneal at 24 h intervals to all the animals and were subsequently sacrificed. The sera obtained were used for a bioassay study. Analysis of serum total cholesterol, triglycerides, low density lipoprotein (LDL) and high density lipoprotein (HDL) were carried out using standard methods. The result obtained revealed a significant decrease (p&gt;0.05) in the serum total cholesterol, triglycerides and LDL in the extract treated groups in a dose dependent manner when compared with the untreated control while there was a significant increase in the serum HDL level of extract treated group compared to the untreated control; thereby supporting the protective effect of A. paniculata against atherosclerotic disorder.

Characterization of bacterial pathogens in Muga silkworm, Antheraea assamensis Helfer (Lepidoptera: Saturniidae)

Aim: To identify and characterize the bacterial pathogens associated with bacteriosis in muga silkworm, A. assamensis. Methodology: The mid gut of diseased silkworm, A. assamensis was dissected and bacterial pathogens were cultured. Bacterial pathogens were identified by 16S rRNA gene sequencing. Insect bioassay studies were conducted to understand the pathogenicity of bacterial isolates. Results: Bacterial pathogens were identified as Pseudomonas aeruginosa and Bacillus mycoids. Under laboratory conditions, approximately 70% mortality of A. assamensis larvae was due to P. aeruginosa, while 50% larval mortality was due to B. mycoids. Interpretation: P. aeruginosa was relatively more pathogenic to A. assamensis than B. mycoids. Further, a graph on disease progression was developed to understand the trajectory of bacteriosis in A. assamensis. Key words: Bacteriosis, Disease progression, Muga silkworm, Pseudomonas sp., 16S rRNA sequencing

Isolation characterization and pathogenicity of Helicoverpa armigera single nucleopolyhedrovirus isolate from Türkiye

The cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), is a major pest of agricultural crops, such as cotton, horticultural plants, a range of vegetable crops and forest trees. Many dead and live larvae and pupa samples of H. armigera, an extremely polyphagous pest, were collected from Adana in Türkiye. It was observed that cadaveric integuments were fragile, and their body tissues were also liquefied. Studies with phase-contrast microscopy revealed a very intense baculovirus infection in cadavers. Transmission electron microscopy exhibited that the new baculovirus had one nucleocapsid in an envelope in the occlusion bodies. Therefore, the isolate was named Helicoverpa armigera single nucleopolyhedrovirus-D (HearSNPV-D). The phylogenetic analysis according to the polyhedrin and late expression factor-8 genes appeared that the new isolate was in close relationship with HearSNPV China and Türkiye isolate. The new isolate was tested on six different insects including its own host Helicoverpa armigera, Hyphantria cunea, Malacosoma neustria, Lymantria dispar, Thaumetopea pityocampa and Spodoptera exigua larvae. Bioassay studies showed that HearSNPV-D was virulent to H. armigera and had a narrow host range. The LC50 value was determined as 0.7 × 105 and 1.9 × 107 OBs/ml for H. armigera and S. exigua, respectively. Non-significant mortality was observed in non-host species by HearSNPV-D, which may reveal the highly specific nature of HearSNPV-D. Therefore, HearSNPV-D can be used as a specific, environmentally friendly control agent for H. armigera.

Farnesol dehydrogenase from Helicoverpa armigera (Hübner) as a promising target for pest management: molecular docking, in vitro and insect bioassay studies using geranylgeraniol as potential inhibitor.

Juvenile hormone (JH) plays pivotal roles in several critical developmental processes in insects, including metamorphosis and reproduction. JH-biosynthetic pathway enzymes are considered highly promising targets for discovering novel insecticides. The oxidation of farnesol to farnesal, catalysed by farnesol dehydrogenase (FDL), represents a rate-limiting step in JH biosynthesis. Here, we report farnesol dehydrogenase (HaFDL) from H. armigera as a promising insecticidal target. The inhibitory potential of natural substrate analogue geranylgeraniol (GGol) was tested in vitro, wherein it showed a high binding affinity (kd 595µM) for HaFDL in isothermal titration calorimetry (ITC) and subsequently exhibited dose-dependent enzyme inhibition in GC-MS coupled qualitative enzyme inhibition assay. Moreover, the experimentally determined inhibitory activity of GGol was augmented by the in silico molecular docking simulation which showed that GGol formed a stable complex with HaFDL, occupied the active site pocket and interacted with key active site residues (Ser147 and Tyr162) as well as other residues that are crucial in determining the active site architecture. Further, the diet-incorporated oral feeding of GGol caused detrimental effects on larval growth and development, exhibiting a significantly reduced rate of larval weight gain (P < 0.01), aberrant pupal and adult morphogenesis, and a cumulative mortality of ~ 63%. To the best of our knowledge, the study presents the first report on evaluating GGol as a potential inhibitor for HaFDL. Overall, the findings revealed the suitability of HaFDL as a potential insecticidal target for the management H. armigera.

Modeling integrated biomarker response (IBR) index for the mussel Mytilus galloprovincialis (Lamark 1819) exposed to heavy metal mixture using the CCF design

Marine pollutants such as heavy metals (HMs) are considered among the most copious oxidative stress (OS) inducers in marine organisms which leads to reactive oxygen species (ROS) formation. Complementary to our previous bioassays studies, the present research focuses on Catalase (CAT), Glutathione S-transferase (GST) and Malondialdehyde (MDA) as oxidative stress biomarkers and the integrated biomarker response (IBR) indexes (IBR1 and IBR2) as an ecotoxicological assessment tool in Mytilus galloprovincialis using central composite face centered (CCF) design. The oxidative stress biomarkers were measured in adult mussels (45-55 mm) on 3 days-exposed under different sub-lethal concentrations of cadmium (Cd), zinc (Zn), and copper (Cu). Using multiple regressions, ANOVA analysis revealed that experimental data fitted to second-order (quadratic) polynomial equations. The results showed that types, concentrations and metals combinations has a direct effect in CAT and GST activities, MDA level and IBR indexes. Additionally, metal-metal interactions were found synergistic (supra-additive), antagonistic (infra-additive) or zero interaction in the toxicological effect. As necessary, the optimization of the experimental results was done in order to determine the optimal conditions for the oxidative stress responses and IBR indexes. It was demonstrated that the CCF design combined with the multi-biomarker approach and IBR index can be used as an appropriate tool in ecotoxicological modulation and prediction of oxidative stress and antioxidant status by heavy metals in the mussels Mytilus galloprovincialis.

Insecticidal activity of isolated Purpureocillium lilacinum PL1 against whitefly, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) on cassava plantations in southern Viet Nam

BackgroundWhitefly Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) is a plant-damaging insect in tropical and subtropical regions that causes agricultural damage worldwide, including in Viet Nam. The abuse of pesticides derived from chemicals has resulted in the evolution of insect-resistant strains, polluting the environment and threatening human health. Using entomopathogenic fungi (EPF) for biological control is an alternative strategy in integrated pest management. Hence, an attempt was conducted to isolate, characterize and evaluate the efficacy of EPF, Purpureocillium lilacinum against whitefly B. tabaci under laboratory and field conditions.ResultsPurpureocillium lilacinum PL1 (PL1) was isolated from the whitefly B. tabaci cadavers and subsequently identified using morphological study and internal transcribed spacer sequencing. Purpureocillium lilacinum PL1 had effectively grown and sporulated at temperatures ranging from 25 to 35 °C and throughout a broad pH range, which is particularly advantageous against the harsh tropical monsoon climate. Bioassay study indicated that 1 × 107 conidia/ml of P. lilacinum PL1 had a high lethality against the whitefly B. tabaci nymphs in vitro with efficiency was 88.24% after 7 days of treatment. The median lethal concentration (LC50) of P. lilacinum PL1 to B. tabaci after 7 days of treatment was 1.24 × 105 conidia/ml. In field conditions, 1 × 107 conidia/ml of P. lilacinum PL1 lowered the population of B. tabaci nymphs with efficacy was 78.86% after 2 batches, 7 days after treatments.ConclusionThe findings indicated that P. lilacinum PL1 was effective in the biological control of B. tabaci nymphs, which could be a potential alternative to chemical pesticides for pest management.