Isolation and identification of acaricidal compounds in Inula japonica (Asteraceae)

Phytochemical Composition and Antibacterial Activity of Barleria albostellata C.B. Clarke Leaf and Stem Extracts

Barleria albostellata (Acanthaceae) is a shrub located in South Africa and is relatively understudied. However, plants within this genus are well known for their medicinal and ethnopharmacological properties. This study aimed to characterise the phytochemical compounds and antibacterial efficacies of B. albostellata. Phytochemical analysis, fluorescence microscopy and gas chromatography-mass spectrometry (GC-MS) analysis were performed to determine the composition of compounds that may be of medicinal importance. Crude leaf and stem extracts (hexane, chloroform and methanol) were subjected to an antibacterial analysis against several pathogenic microorganisms. The qualitative phytochemical screening of leaf and stem extracts revealed the presence various compounds. Fluorescence microscopy qualitatively assessed the leaf and stem powdered material, which displayed various colours under bright and UV light. GC-MS chromatograms represents 10-108 peaks of various compounds detected in the leaf and stem crude extracts. Major pharmacologically active compounds found in the extracts were alpha-amyrin, flavone, phenol, phytol, phytol acetate, squalene and stigmasterol. Crude extracts positively inhibited Gram-positive and Gram-negative bacteria. Significance was established at p < 0.05 for all concentrations and treatments. These results indicate that the leaves and stems of B. albostellata are rich in bioactive compounds, which could be a potential source of antibacterial agents for treating various diseases linked to the pathogenic bacteria studied. Future discoveries from this plant could advance the use of indigenous traditional medicine and provide novel drug leads.

Acaricidal Activity of Artemisia nilagirica Leaves Against Rhipicephalus (Boophilus) annulatus Ticks

Since time immemorial, human beings have used various parts of plants in either prevention or treatment of ailments. Plants are rich sources of secondary metabolites such as alkaloids, steroids, terpenoids, flavonoids, and phenolic compounds with a high structural diversity. Many plants/herbs with specific biological activities such as antitumor, antioxidant, anti-inflammatory, antifungal, sedative, and acaricidal activity have been reported. Artemisia nilagirica (C. B. Clarke) Pamp. (Compositae) is a plant traditionally used for insect control in the southern part of India. Previous studies have demonstrated the activity of Artemisia species against pests. The present study thus evaluates the acaricidal activity of crude ethanolic extract of A. nilagirica leaves and its fractions against Rhipicephalus (Boophilus) annulatus. Ticks are ectoparasites that transmit several protozoal, viral, and rickettsial diseases. In south India, R. (B.) annulatus is the commonly observed tick species. Control of these acarine parasites that adversely affect milk and meat production is a tough task. Chemical acaricides such as organophosphates, synthetic pyrethroids, amitraz, and ivermectin are commonly used in tick control. The high cost, environmental hazards, and development of acaricidal resistance are some of the drawbacks of these chemical acaricides. Plant-based formulations are one of the promising approaches for the control of ectoparasites. Previously, extracts from various medicinal/aromatic plants were reported for acaricidal activity from our laboratory, such as Tetrastigma leucostaphylum (Dennst.) Alston, Chassalia curviflora (Wall.) Thwaites, Jatropha curcas L., and Ageratum conyzoides Hieron. Biochemical quantification, fluorescence analysis, and primary phytochemical analysis are already reported for the ethanolic extract and its fractions of areal parts of A. nilagirica. Phytochemical characterization of ethanolic extract of A. nilagirica from Kerala, India was shown to have the presence of terpenoids, flavonoids, steroids, saponins, fixed oils and fats, tannins, and glycosides.

Novel and selective acetylcholinesterase inhibitors for Tetranychus cinnabarinus (Acari: Tetranychidae)

The carmine spider mite, Tetranychus cinnabarinus (Acari: Tetranychidae), is an economically important and extremely polyphagous herbivorous pest, with the title of "resistance champion" among arthropods. Anticholinesterase insecticides such as organophosphate and carbamate account for more than one-third of global insecticide sales. The non-target toxicity and resistance problem of organophosphate and carbamate have become of growing concern, which may be due to the fact that they target the ubiquitous catalytic serine residue of acetylcholinesterase (AChE) in mammals, birds, and beneficial insects. In this study, the structural differences between T. cinnabarinus AChE and human AChE, at or near the catalytic pocket, were illustrated. From the SPECS chemical lead-compound database, 55 AChE inhibitor candidates were screened for high affinity for T. cinnabarinus AChE, but low affinity for human AChE, using the DOCK 6 and AutoDock Vina software. Three of the fifty-five candidates had inhibitory activity greater than that of the reversible AChE inhibitor eserine, with no observed inhibitory activities against human AChE. Two of the three had toxicity to T. cinnabarinus comparable to that of natural insecticidal pyrethrins. However, their potency is low compared with that of etoxazole, and further work is needed to optimize their potency. The selectivity of the three compounds over human and mite AChE may be due to their interaction with the mite-specific residues, as analyzed by Cyscore. The three compounds are potential lead compounds for development of novel acaricides against T. cinnabarinus with reduced toxicity to non-target species and a low propensity for resistance.

Transcriptome Analysis of the Carmine Spider Mite, Tetranychus cinnabarinus (Boisduval, 1867) (Acari: Tetranychidae), and Its Response to β-Sitosterol

Tetranychus cinnabarinus (Acari: Tetranychidae) is a worldwide polyphagous agricultural pest that has the title of resistance champion among arthropods. We reported previously the identification of the acaricidal compound β-sitosterol from Mentha piperita and Inula japonica. However, the acaricidal mechanism of β-sitosterol is unclear. Due to the limited genetic research carried out, we de novo assembled the transcriptome of T. cinnabarinus using Illumina sequencing and conducted a differential expression analysis of control and β-sitosterol-treated mites. In total, we obtained >5.4 G high-quality bases for each sample with unprecedented sequencing depth and assembled them into 22,941 unigenes. We identified 617 xenobiotic metabolism-related genes involved in detoxification, binding, and transporting of xenobiotics. A highly expanded xenobiotic metabolic system was found in mites. T. cinnabarinus detoxification genes-including carboxyl/cholinesterase and ABC transporter class C-were upregulated after β-sitosterol treatment. Defense-related proteins, such as Toll-like receptor, legumain, and serine proteases, were also activated. Furthermore, other important genes-such as the chloride channel protein, cytochrome b, carboxypeptidase, peritrophic membrane chitin binding protein, and calphostin-may also play important roles in mites' response to β-sitosterol. Our results demonstrate that high-throughput-omics tool facilitates identification of xenobiotic metabolism-related genes and illustration of the acaricidal mechanisms of β-sitosterol.

In vitro growth-inhibitory effect of Brazilian plants extracts against Paenibacillus larvae and toxicity in bees

American foulbrood (AFB) is a serious worldwide spreading disease in bees caused by Paenibacillus larvae. Plants extracts are known to decrease or inhibit the growth of these bacteria. The purpose of this study was to evaluate the antimicrobial activity of Calendula. officinalis, Cariniana domestica, and Nasturtium officinale extracts against the P. larvae and to evaluate the toxicity of the extracts in bees. In vitro activity against P. larvae of the extracts was evaluated by micro dilution method and the minimal inhibitory concentrations (MICs) were also determined. The concentrations used in the toxicity test were established based on the MIC values and by the spraying application method. The P. larvae was susceptible to the evaluated crude extract of C. officinalis and N. officinale. To C. domestica, only the ethyl acetate (EtAc) fraction and n-butanol (BuOH) fractions had activity against P. larvae. Toxicity analysis in bees showed no toxicity for N. officinale crude extract and for C. domestica BuOH fraction during 15 days of treatment, however, some deaths of bees occurred during the first three days of treatment with C. officinalis and C. domestica EtAc fraction. The results with these species were firstly described and showed that N. officinale crude extract and C. domestica BuOH fraction both presented not toxic effects in the concentration tested by the spraying application method, and can be a useful alternative for treatment or prevention of AFB.

Cloning and Characterization of the Acetylcholinesterase1 Gene of Tetranychus cinnabarinus (Acari: Tetranychidae)

The carmine spider mite, Tetranychus cinnabarinus (Boisduval), is a major agriculture pest. It can be found worldwide, has an extensive host plant range, and has shown resistance to pesticides. Organophosphate and carbamate insecticides account for more than one-third of all insecticide sales. Insecticide resistance and the toxicity of organophosphate and carbamate insecticides to mammals have become a growing concern. Acetylcholinesterase (AChE) is the major targeted enzyme of organophosphate and carbamate insecticides. In this study, we fully cloned, sequenced and characterized the ace1 gene of T. cinnabarinus, and identified the differences between T. cinnabarinus AChE1, Tetranychus urticae Koch AChE1, and human AChE1. Resistance-associated target-site mutations were displayed by comparing the AChE amino acid sequences and their AChE three-dimensional (3D) structures of the insecticide-susceptible strains of T. cinnabarinus and T. urticae to that of a T. urticae-resistant strain. We identified variation in the active-site gorge and the sites interacting with gorge residues by comparing AChE1 3D structures of T. cinnabarinus, T. urticae, and humans, though their 3D structures were similar. Furthermore, the expression profile of T. cinnabarinus AChE, at the different developmental stages, was determined by quantitative real-time polymerase chain reaction; the transcript levels of AChE were higher in the larvae stage than in other stages. The changes in AChE expression between different developmental stages may be related to their growth habits and metabolism characteristics. This study may offer new insights into the problems of insecticide resistance and insecticide toxicity of nontarget species.