The effect of 1-pentadecene on Tribolium castaneum behaviour: Repellent or attractant?

Green solvent-based extraction of three Fabaceae species: A potential antioxidant, anti-diabetic, and anti-leishmanial agents

The Fabaceae is renowned for its diverse range of chemical compounds with significant biological activities, making it a valuable subject for pharmacological studies. The chemical composition and biological activities of three Fabaceae species were investigated using methanol separately and in combination with dimethyl sulfoxide (DMSO) and glycerol for extraction. The results revealed the highest phenolic (49.59 ± 0.38 mg gallic acid equivalent/g), flavonoid (29.16 ± 0.39 mg rutin equivalent/g), and alkaloid (14.23 ± 0.54 mg atropine equivalent/g) contents in the Caesalpinia decapetala methanol extracts. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity and DNA protection activity were the highest (0.88 ± 0.43 μg/mL IC50 and 2149.26 band intensity) in Albizia julibrissin methanol extracts. The α-amylase activity was highest in all methanol extracts (<15 μg/mL IC50 values), while the α-glucosidase inhibition potential was highest (<1 μg/mL IC50 value) in the methanol-glycerol and methanol-DMSO extracts. Pearson coefficient analysis showed a strong positive correlation between the DPPH and α-amylase assays and phytochemicals. Anti-leishmanial activity was observed in decreasing order: A. julibrissin (74.75 %) > C. decapetala (70.86 %) > Indigofera atropurpurea (65.34 %). Gas chromatography-mass spectrometry revealed 33 volatile compounds and, aamong these (Z)-9-octadecenamide was detected in the highest concentration ranging from 21.85 to 38.61 %. Only the methanol extracts of the examined species could be assessed for in vivo studies for immediate applications.

Influences of compound age and identity in the effectiveness of insect quinone secretions against the fungus Beauveria bassiana

Chemical defences against parasites and pathogens can be seen in a wide range of animal taxa, including insect pests such as the red flour beetle Tribolium castaneum. Antimicrobial quinone-based secretions can be used by these beetles to defend against various parasites, particularly the fungal entomopathogen Beauveria bassiana. While quinone secretions can inhibit B. bassiana growth, it is unknown how long they remain effective or how individual secretion compounds contribute to growth inhibition. Here, we tested each individual component of the quinone secretions (methyl-1,4-benzoquinone, ethyl-1,4-benzoquinone, and 1-pentadecene), as well as two mixed solutions that represent the composition range found in natural T. castaneum secretions, after aging for 0, 24, or 72 h. The two quinone compounds equally contributed to B. bassiana inhibition, but their efficacy was significantly reduced after 24 h, with no growth inhibition after 72 h. This indicates that quinones protect insects against B. bassiana for only a limited time, perhaps requiring constant secretion into the environment to effectively defend against this fungal threat. Future investigations may consider the extent to which quinone secretions are effective against other parasites, as well as how their ability to cause parasite damage changes with compound age.

Bioactive Analysis of Antibacterial Efficacy and Antioxidant Potential of Aloe barbadensis Miller Leaf Extracts and Exploration of Secondary Metabolites Using GC-MS Profiling

Aloe barbadensis Miller (ABM) is a traditional medicinal plant all over the world. Numerous studies were conducted to exhibit its medicinal properties and most of them were concentrated on its metabolites against human pathogens. The current research work evaluates the attributes of different polar-based extracts (ethanol, methanol, ethyl acetate, acetone, hexane, and petroleum ether) of dried Aloe barbadensis leaf (ABL) to investigate its phytochemical constituents, antioxidant potential (DPPH, ABTS), phenolic, tannin, flavonoid contents, identification of bioactive compounds, and functional groups by gas chromatography-mass spectrometry (GC-MS) and fourier transform infrared spectroscopy (FT-IR) respectively, and comparing antibacterial efficacy against human pathogens, aquatic bacterial pathogens, and zoonotic bacteria associated with fish and human. The present results showed that the methanolic extract of ABL showed higher antioxidant activity (DPPH-59.73 ± 2.01%; ABTS-74.1 ± 1.29%), total phenolic (10.660 ± 1.242 mg GAE/g), tannin (7.158 ± 0.668 mg TAE/g), and flavonoid content (49.545 ± 1.928 µg QE/g) than that of other solvent extracts. Non-polar solvents hexane and petroleum ether exhibited lesser activity among the extracts. In the case of antibacterial activity, higher inhibition zone was recorded in methanol extract of ABL (25.00 ± 0.70 mm) against Aeromonas salmonicida. Variations in antibacterial activity were observed depending on solvents and extracts. In the current study, polar solvents revealed higher antibacterial activity when compared to the non-polar and the mid-polar solvents. Diverse crucial bioactive compounds were detected in GC-MS analysis. The vital compounds were hexadecanoic acid (30.69%) and 2-pentanone, 4-hydroxy-4-methyl (23.77%) which are responsible for higher antioxidant and antibacterial activity. Similar functional groups were identified in all the solvent extracts of ABL with slight variations in the FT-IR analysis. Polar-based solvent extraction influenced the elution of phytocompounds more than that of the other solvents used in this study. The obtained results suggested that the ABM could be an excellent source for antioxidant and antibacterial activities and can also serve as a potential source of effective bioactive compounds to combat human as well as aquatic pathogens.

Effects of insect host chemical secretions on the entomopathogenic nematode Steinernema carpocapsae

Given the threat presented by parasites and pathogens, insects employ various defences to protect themselves against infection, including chemical secretions. The red flour beetle Tribolium castaneum releases a secretion containing the benzoquinones methyl-1,4-benzoquinone (MBQ) and ethyl-1,4-benzoquinone (EBQ) into the environment. These compounds have known antimicrobial effects; however, their role in defence against macroparasites is not known. Entomopathogenic nematodes, such as Steinernema carpocapsae, present a serious threat to insects, with successful infection leading to death. Thus, quinone-containing secretions may also aid in host defence. We tested how exposure to the individual components of this quinone secretion, as well as a mix at naturally-occurring proportions, affected the survival and thrashing behaviour of S. carpocapsae, as well as their virulence to a model host (Galleria mellonella). Exposure to high concentrations of MBQ and EBQ, as well as the quinone mix, significantly increased nematode death but did not consistently reduce thrashing, which would otherwise be expected given their toxicity. Rather, quinones may act as a host cue to S. carpocapsae by triggering increased activity. We found that exposure to quinones for 24 or 72 hours did not reduce nematode virulence, and surviving nematodes remained infective after non-lethal exposure. Our results indicate that quinone secretions likely serve as a defence against multiple infection threats by reducing S. carpocapsae survival, but further research is required to contextualize their roles by testing against other nematodes, as well as other helminths using insects as hosts.

Detection of Specific Volatile Organic Compounds in Tribolium castaneum (Herbst) by Solid-Phase Microextraction and Gas Chromatography-Mass Spectrometry

The red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), is a major storage pest that could lead to a wide range of damage. Its secretions have a significant impact on the quality of stored grain and food, leading to serious food safety problems such as grain spoilage and food carcinogenesis. This study investigates new detection techniques for grain storage pests to improve grain insect detection in China. The primary volatile organic chemicals (VOCs) in these secretions are identified using headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). The specific VOCs that are unique to T. castaneum are selected as criteria for determining the presence of T. castaneum in the granary. To obtain more specific VOCs, experiments were designed for the analysis of T. castaneum samples under different extraction times, two types of SPME fibers and two GC-MS devices of different manufacturers. The experimental results showed that 12 VOCs were detected at relatively high levels, seven of which were common and which were not detected in other grains and grain insects. The seven compounds are 1-pentadecene, 2-methyl-p-benzoquinone, 2-ethyl-p-benzoquinone, 1-hexadecene, cis-9-tetradecen-1-ol, m-cresol and paeonol. These seven compounds can be used as volatile markers to identify the presence of T. castaneum, which could serve as a research foundation for the creation of new techniques for T. castaneum monitoring.

The Correlation between Volatile Compounds Emitted from Sitophilus granarius (L.) and Its Electrophysiological and Behavioral Responses

Simple Summary

Postharvest loss has become a crucial issue for the grain supply chain. Storage of grain without losses in quality is a critically important aspect of global food security. The monitoring and detection of insect infestations in stored grain is essential to inform pest management decisions. Insect olfaction is a principal sensory modality for sensing semiochemicals from their external environment and regulates their behaviors. Some semiochemicals function as attractants or repellents, which could be used for insect surveillance and pest control. In this study, the granary weevil Sitophilus granarius (L.), was used as an example to evaluate volatile compounds released from the weevils’ and their initiated electrophysiological and behavioral responses. An improved understanding of S.granarius chemical ecology will lead to developing more efficient and environmentally friendly pest control strategies and technologies.

Abstract

The granary weevil Sitophilus granarius (L.) is one of the most serious primary insect pests of stored products. When S. granarius present in grains, various volatile organic compounds are released as chemical signals which can be used to detect the insects. In this study, volatile chemical compounds released from S. granarius were analyzed using the headspace solid phase micro-extraction (HS-SPME) coupled with gas chromatography (GC)–mass spectrometry (MS) techniques. Two key compounds, 3-hydroxy-2-butanone and 1-pentadecene, were identified from mixed gender of S. granarius adults at high density. Moreover, both male and female adults showed dose-dependent electroantennography (EAG) responses to 3-hydroxy-2-butanone. In behavioral assays, S. granarius was attracted to 3-hydroxy-2-butanone at 0.001 µg/10 µL but repelled at 10 µg/10 µL or higher. S. granarius was consistently repelled by 1-pentadecene at concentrations at 0.001 and 1000 µg/10 µL. 3-hydroxy-2-butanone and 1-pentadecene have considerable potential to offer in the development of new approaches for the monitoring and management of this destructive stored grain insect pest.

Identification of Biomarker Volatile Organic Compounds Released by Three Stored-Grain Insect Pests in Wheat

Monitoring and early detection of stored-grain insect infestation is essential to implement timely and effective pest management decisions to protect stored grains. We report a reliable analytical procedure based on headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry (HS-SPME-GC-MS) to assess stored-grain infestation through the detection of volatile compounds emitted by insects. Four different fibre coatings were assessed; 85 µm CAR/PDMS had optimal efficiency in the extraction of analytes from wheat. The headspace profiles of volatile compounds produced by Tribolium castaneum (Herbst), Rhyzopertha dominica (Fabricius), and Sitophilus granarius (Linnaeus), either alone or with wheat, were compared with those of non-infested wheat grains. Qualitative analysis of chromatograms showed the presence of different volatile compound profiles in wheat with pest infestation compared with the wheat controls. Wheat-specific and insect-specific volatile compounds were identified, including the aggregation pheromones, dominicalure-1 and dominicalure-2, from R. dominica, and benzoquinones homologs from T. castaneum. For the first time, the presence of 3-hydroxy-2-butanone was reported from S. granarius, which might function as an alarm pheromone. These identified candidate biomarker compounds can be utilized in insect surveillance and monitoring in stored grain to safeguard our grain products in future.

Volatilome and Essential Oil of Ulomoides dermestoides: A Broad-Spectrum Medical Insect

Ulomoides dermestoides are used as a broad-spectrum medical insect in the alternative treatment of various diseases. Preliminary volatilome studies carried out to date have shown, as the main components, methyl-1,4-benzoquinone, ethyl-1,4-benzoquinone, 1-tridecene, 1-pentadecene, and limonene. This work focused on the production of metabolites and their metabolic variations in U. dermestoides under stress conditions to provide additional valuable information to help better understand the broad-spectrum medical uses. To this end, VOCs were characterized by HS-SPME with PEG and CAR/PDMS fibers, and the first reported insect essential oils were obtained. In HS-SMPE, we found 17 terpenes, six quinones, five alkenes, and four aromatic compounds; in the essential oils, 53 terpenes, 54 carboxylic acids and derivatives, three alkynes, 12 alkenes (1-Pentadecene, EOT1: 77.6% and EOT2: 57.9%), 28 alkanes, nine alkyl disulfides, three aromatic compounds, 19 alcohols, three quinones, and 12 aldehydes were identified. Between both study approaches, a total of 171 secondary metabolites were identified with no previous report for U. dermestoides. A considerable number of the identified metabolites showed previous studies of the activity of pharmacological interest. Therefore, considering the wide variety of activities reported for these metabolites, this work allows a broader vision of the therapeutic potential of U. dermestoides in traditional medicine.