Putative ligand binding sites of two functionally characterized bark beetle odorant receptors.

BACKGROUND: Bark beetles are major pests of conifer forests, and their behavior is primarily mediated via olfaction. Targeting the odorant receptors (ORs) may thus provide avenues towards improved pest control. Such an approach requires information on the function of ORs and their interactions with ligands, which is also essential for understanding the functional evolution of these receptors. Hence, we aimed to identify a high-quality complement of ORs from the destructive spruce bark beetle Ips typographus (Coleoptera, Curculionidae, Scolytinae) and analyze their antennal expression and phylogenetic relationships with ORs from other beetles. Using 68 biologically relevant test compounds, we next aimed to functionally characterize ecologically important ORs, using two systems for heterologous expression. Our final aim was to gain insight into the ligand-OR interaction of the functionally characterized ORs, using a combination of computational and experimental methods. RESULTS: We annotated 73 ORs from an antennal transcriptome of I. typographus and report the functional characterization of two ORs (ItypOR46 and ItypOR49), which are responsive to single enantiomers of the common bark beetle pheromone compounds ipsenol and ipsdienol, respectively. Their responses and antennal expression correlate with the specificities, localizations, and/or abundances of olfactory sensory neurons detecting these enantiomers. We use homology modeling and molecular docking to predict their binding sites. Our models reveal a likely binding cleft lined with residues that previously have been shown to affect the responses of insect ORs. Within this cleft, the active ligands are predicted to specifically interact with residues Tyr84 and Thr205 in ItypOR46. The suggested importance of these residues in the activation by ipsenol is experimentally supported through site-directed mutagenesis and functional testing, and hydrogen bonding appears key in pheromone binding. CONCLUSIONS: The emerging insight into ligand binding in the two characterized ItypORs has a general importance for our understanding of the molecular and functional evolution of the insect OR gene family. Due to the ecological importance of the characterized receptors and widespread use of ipsenol and ipsdienol in bark beetle chemical communication, these ORs should be evaluated for their potential use in pest control and biosensors to detect bark beetle infestations.

Local, Geographical, and Contextual Variation in the Aggregation Pheromone Blend of the Spruce Beetle, Dendroctonus rufipennis (Coleoptera: Curculionidae).

Prior research from trapping experiments using synthetic pheromone components suggested the existence of local and geographical variation in the pheromone system of the spruce beetle, Dendroctonus rufipennis (Kirby). To test hypotheses concerning variation in the spruce beetle's aggregation pheromone blend, we extracted volatiles from the hindguts of individual spruce beetles sampled from sites in eastern Canada (Nova Scotia and Newfoundland) and western Canada (British Columbia and Alberta) and quantified the amounts of four known aggregation pheromone components within each sample. Chiral analyses were performed on a subset of samples. Frontalin (1,5-dimethyl-6,8-dioxabicyclo[3.2.1]octane) was more dominant in western Canada, whereas MCOL (1-methyl-2-cyclohexen-1-ol) and seudenol (3-methyl-2-cyclohexen-1-ol) were more dominant in the east. Verbenene (4-methylene-6,6-dimethylbicyclo[3.1.1]hept-2-ene) was prevalent only in one of our six sites (Rocky Mountain House, AB). Female beetles in Rocky Mountain House (AB) also produced a higher proportion of (+)-frontalin than females from the other sites, and a comparison to previously published data suggests additional geographic variation that was not captured among our sites. When paired with a male in a gallery, female spruce beetles produced pheromone blends with more frontalin and less MCOL compared to solitary female beetles. Our results show that variation in the spruce beetle's pheromone blend exists at both large and small spatial scales, possibly a consequence of local selective pressures and assortative mating.

Chemical composition and antimicrobial activity of cuticular and internal lipids of the insect Rhynchophorus palmarum.

Insect cuticle lipids are involved in various types of chemical communication between species, and reduce the penetration of insecticides, chemicals, and toxins, as well as provide protection against the attack of microorganisms, parasitic insects, and predators. Ecological studies related to the insect Rhynchophorus palmarum are well-known; however, very little is known about its resistance mechanisms, which includes its lipid composition and its importance, specifically the cuticle layer. This study aimed to characterize the cuticle and internal lipid compounds of the male and female R. palmarum adult insects and to evaluate the presence of antimicrobial activity. We performed by gas chromatography coupled to mass spectrometry (GC-MS) analyzes of lipid extracts fractions and we identified 10 methyl esters of fatty acids esters of C14 to C23, with variation between the sexes of C22:0, C21:0, present only in male cuticle, and C20:2 in female. The lipid content of this insect showed relevant amount of C16:1, C18:1, and C18:2. The antimicrobial activity of the cuticular and internal fractions obtained was tested, which resulted in minimum inhibitory concentrations between 12.5 and 20 µg/ml against Gram-positive bacteria (Staphylococcus epidermidis, Enterococcus faecalis), Gram-negative (Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumonia), and fungal species (Candida albicans e Candida tropicalis). The antimicrobial effect of the R. palmarum cuticle open perspectives for a new source to bioinsecticidal strategies, in addition to elucidating a bioactive mixture against bacteria and fungi.

Profile of Terpenoid Compounds Mediating a Plant-Herbivore Interaction: Screening by Static Headspace Solid-Phase Microextraction-Gas Chromatography/Q-ToF Mass Spectrometry.

Conotrachelus dimidiatus (Coleoptera: Curculionidae) interacts with immature guava fruits (Psidium guajava L.) for feed, sleep, mate and oviposit. Determination of the volatile organic compounds (VOCs) emitted by the insect and immature fruits can help improve understanding of plant-insect and intraspecific insect interactions between females and males of C. dimidiatus. Daytime fruit setting emissions of immature guava consist mainly of limonene, caryophyllene, and aromadendrene. In addition to the host's volatiles, the aim of this study was to assess the VOCs released by the insect. Static headspace-solid phase microextraction (SHS-SPME), combined with gas chromatography/quadrupole time of flight mass spectrometry (GC/Q-ToF-MS), allowed the identification of the C10 terpenoids: grandlure I, II, II, IV, grandisoic acid, papayanol and papayanal bioactive compounds released by female and male C. dimidiatus under laboratory conditions. These chemical compounds are candidates for the preparation of a lure formulation.

Anthonomus grandis aggregation pheromone induces cotton indirect defence and attracts the parasitic wasp Bracon vulgaris.

Insect-derived volatiles seem to provide reliable chemical cues that plants could employ to defend themselves. Here we investigated the effect of pheromone emission from a closely associated (Anthonomus grandis; boll weevil) and an unassociated (Tibraca limbativentris) herbivore on cotton volatile emission. Exposure to A. grandis aggregation pheromone induced cotton defence response by enhancing the emission of volatiles attractive to the natural enemy of A. grandis, the parasitic wasp Bracon vulgaris, but only when the pheromonal blend was complete (all four components). Individual components of A. grandis aggregation pheromone were not able to induce cotton plants to increase the release of volatiles. On the other hand, T. limbativentris sex pheromone did not induce any change in the cotton constitutive volatile profile. Our results support the hypothesis that plants are able to detect pheromones of tightly co-evolved herbivores. Moreover, A. grandis pheromone exposure induced similar volatile compounds to herbivore-induced cotton, such as linalool, (E)-ocimene, (E)-4,8-dimethylnona-1,3,7-triene (DMNT), and (E,E)-4,8,12-trimethyltrideca-1,3,7,11-tetraene (TMTT). We also showed that the larval ectoparasitoid B. vulgaris relies on boll weevil's aggregation pheromone and pheromone-induced plant volatiles as kairomones to locate suitable hosts.

Evaluation of guanylhydrazone derivatives as inhibitors of Candida rugosa digestive lipase: Biological, biophysical, theoretical studies and biotechnological application.

This work aimed to evaluate the inhibition of Candida rugosa lipase by five guanylhydrazone derivatives through biological, biophysical and theoretical studies simulating physiologic conditions. The compound LQM11 (IC50 = 14.70 µM) presented the highest inhibition against the enzyme. Therefore, for a better understanding of the interaction process, spectroscopic and theoretical studies were performed. Fluorescence and UV-vis assays indicate a static quenching mechanism with non-fluorescent supramolecular complex formation and changing the native protein structure. The binding process was spontaneous (ΔG < 0) and electrostatic forces (ΔH < 0 and ΔS > 0) played a preferential role in stabilizing the complex ligand-lipase. The compounds were classified as non-competitive inhibitors using orlistat as a reference in competition studies. Based on the 1H NMR assays it was possible to propose the sites of ligand (epitope) that bind preferentially to the enzyme and the theoretical studies were consistent with the experimental results. Finally, LQM11 was efficient as a lipase inhibitor of the crude intestinal extract of larvae of Rhynchophorus palmarum, an important agricultural plague, showing potential for control of this pest. Within this context, the real potential of this biotechnological application deserves further studies.

Aggregation Pheromone of the Bearded Weevil, Rhinostomus barbirostris (Coleoptera: Curculionidae): Identification, Synthesis, Absolute Configuration and Bioactivity.

The bearded weevil, Rhinostomus barbirostris (Coleoptera: Curculionidae: Dryophthorinae), attacks coconut trees, oil palms and other species of Arecaceae. Besides direct damage, R. barbirostris may be a vector of diseases in coconut and oil palms, such as stem bleeding (resinosis) and red ring disease. Currently, the only method to control this weevil is by visual observation of damage and removal of infected plants. Semiochemical-based trapping could improve the effectiveness of monitoring and management of R. barbirostris. In comparisons of volatiles released by R. barbirostris males and females by gas chromatography (GC) two male-specific compounds were observed. GC-mass spectrometry (MS) and GC-Fourier transform-infrared (FTIR) analyses of the natural compounds suggested these were diastereoisomers of 5-hydroxy-4-methylheptan-3-one, also known as sitophilure, a pheromone component of other dryophthorine species. Synthesis of the mixture of all four stereoisomers of sitophilure was performed in two steps, and the chemical structures were confirmed by comparing GC retention times and MS and FTIR spectra of natural and synthetic compounds. The absolute configurations of the two male-specific compounds were elucidated by enantioselective GC; the major component was the (4S,5R)-isomer, and the minor component (4S,5S)-sitophilure. In analyses by GC-electroantennography (EAG) the antennae of male and female R. barbirostris only responded to the (4S,5R)-isomer of the synthetic sitophilure. The stereoisomeric mixture of sitophilure was attractive to both sexes of R. barbirostris in laboratory experiments in the presence of sugar cane volatiles, and a similar result was obtained in a preliminary field trapping test.

n-Pentacosane Acts as both Contact and Volatile Pheromone in the tea Weevil, Myllocerinus aurolineatus.

Insect cuticular hydrocarbons (CHCs) play important roles in chemical communication, as well as having ecological and physiological roles. The use of CHCs for mate recognition has been shown in many insect genera, but little is known about their use in the tea weevil Myllocerinus aurolineatus. Here, we provide evidence that CHCs on the surface of sexually mature M. aurolineatus females act as contact sex pheromones, facilitating mate recognition and eliciting copulatory behavior in male weevils. Using gas chromatography-mass spectrometry, we identify n-pentacosane and n-heptacosane as two potential contact pheromone components. Results from arena bioassays showed that n-pentacosane is a component of a contact pheromone of M. aurolineatus. Further results from the Y-tube olfactometer bioassays showed that n-pentacosane also acts as a volatile attractant. Our results greatly improve our understanding of the chemical ecology of M. aurolineatus.

Male-Produced Aggregation Pheromone of Coffee Bean Weevil, Araecerus fasciculatus.

The coffee bean weevil (CBW), Araecerus fasciculatus (De Geer, 1775), is a cosmopolitan stored-product pest, especially in tropical and subtropical areas. Previous reports showed evidence for aggregation behavior of CBW and this study aimed to identify and evaluate the aggregation pheromone of this pest. Whole-body solvent extractions were analyzed by coupled gas chromatography-mass spectrometry and comparison of male and female extracts showed a male-specific compound which was identified as squalene, 2,6,10,15,19,23-hexamethyl-2,6,10,14,18,22-tetracosahexaene. This compound was shown to attract male and female CBW in Y-tube olfactometer and storage trap assays. The longevity of septum lures was also evaluated in a warehouse. Squalene could be useful in monitoring and controlling this pest.

Identification of male-produced aggregation pheromone of the curculionid beetle Acrotomopus atropunctellus.

The sugarcane stem weevil, Acrotomopus atropunctellus (Boheman) (Curculionidae: Molytinae: Cholini) is an important economic pest from the Northwestern region of Argentina. Analyses of the headspace volatiles produced by separated males and females revealed one male-specific compound. Its structural identification is reported here in using gas chromatography coupled with mass spectroscopy analysis and chemical micro-reactions. Besides, two laboratory olfactometry assays allowed us to propose 6-methyl-5-hepten-2-one (sulcatone) as an aggregation pheromone for this insect, being attractive to both conspecific males and females. This compound is reported for the first time as involved in the Curculionidae family communication.

Reproductive Isolation of Ips nitidus and I. shangrila in Mountain Forests of Western China: Responses to Chiral and Achiral Candidate Pheromone Components.

Eastern Palearctic conifers are subject to frequent bark beetle outbreaks. However, neither the species responsible nor the semiochemicals guiding these attacks are well understood. Two high-mountain Ips species on Qinghai spruce, Picea crassifolia, I. shangrila and I. nitidus, are typical in this regard. Six synthetic candidate pheromone components that we earlier identified from hindguts of unmated males of these two Ips species were tested for field activity in Qinghai province, P. R. China. For I. nitidus, racemic ipsdienol ((±)-Id) could replace the naturally-produced blend of enantiomers containing 74% (-)-(S)-Id (74:26 S:R), in attractive ternary or binary blends. In contrast, sympatric I. shangrila were attracted mainly to blends including Id of opposite chirality, 97%-(+)-(R)-Id. Of the verbenols, (-)-trans-verbenol was inactive for I. nitidus or inhibitory for I. shangrila, but (-)-cis-verbenol (cV) was a key component of the pheromone in both species. Two fully factorial experiments demonstrated that (±)-Id, cV, and 2-methyl-3-buten-2-ol (MB) are components of the aggregation pheromone of I. nitidus, whereas only (+)-Id and cV are essential components of the aggregation pheromone of I. shangrila. While MB is not necessary for attraction of I. shangrila, it is an active antagonist and likely functions in species isolation. A review of the pheromone production and responses in Palearctic Ips and Pseudoips showed that cV is more common than methylbutenols, and both elicit qualitatively variable responses. Ipsdienol is the most common component with variable chirality, and is a necessary, but often not sufficient, factor for determining pheromone specificity.

Comparative analysis of Quercus suber L. acorns in natural and semi-natural stands: Morphology characterization, insect attacks, and chemical composition.

The present study aims to investigate the differences between cork oak acorns from natural and semi-natural stands in terms of morphology, insect attack rate, and acorn chemical composition. Moreover, it examines the metabolic responses induced by insect attacks. The results show that acorns from the semi-natural stand in our study are larger than those from the natural stand. In addition, the insect attack rate was higher in the natural stand (8.25%) than in the semi-natural stand (6.25%). Furthermore, acorns in the semi-natural stand exhibit high total flavonoid content (TFC), whereas those in the natural stand are rich in total phenolic content (TPC). In terms of biochemical changes in acorns, the study revealed a remarkably significant difference in TPC, TFC, and antioxidant activity subsequent to infestation by Cydia and Curculio insects. Cydia-infested acorns from the natural stand had higher TPC levels, with a value of 93.96±0.39 mg GAE/g, showing a 17.7% increase over healthy acorns. Acorns from the semi-natural stand attacked by Curculio show the highest TFC with a value of 0.288±0.004 mg EQ/g, showing a 121.5% increase over healthy acorns. Moreover, both DPPH and FRAP methods revealed that antioxidant activity of the acorns from the semi-natural stand attacked by Curculio was more effective. This research is crucial for providing a solid foundation for the selection of highquality cork oak germplasm resources and exploring the potential valorization of insect-affected acorns in the realms of food and agriculture.

Ancient pests: the season of the Santorini Minoan volcanic eruption and a date from insect chitin.

Attributing a season and a date to the volcanic eruption of Santorini in the Aegean has become possible by using preserved remains of the bean weevil, Bruchus rufipes, pests of pulses, from the storage jars of the West House, in the Bronze Age settlement at Akrotiri. We have applied an improved pre-treatment methodology for dating the charred insects, and this provides a date of 1744-1538 BC. This date is within the range of others obtained from pulses from the same context and confirms the utility of chitin as a dating material. Based on the nature of the insect material and the life cycle of the species involved, we argue for a summer eruption, which took place after harvest, shortly after this material was transported into the West House storeroom.

Identification and electrophysiological studies of (4S,5S)-5-hydroxy-4-methyl-3-heptanone and 4-methyl-3,5-heptanedione in male lucerne weevils.

An investigation to identify a sex or aggregation pheromone of Sitona discoideus Gyllenhål (Coleoptera: Curculionidae) is presented. Antenna flicking and attraction behaviors evoked by conspecifics of both sexes were recorded in arena bioassays, where attraction of females to males was observed. Air entrainment of both males and females was conducted in separate chambers. Gas chromatographic-mass spectrometric analysis of headspace volatiles revealed that two male-specific compounds, 4-methyl-3,5-heptanedione (major) and (4S,5S)-5-hydroxy-4-methyl-3-heptanone (minor), were emitted during the autumnal post-aestivatory flight period. The stereoisomers of the minor component were separated by enantioselective gas chromatography and their absolute configurations assigned by NMR (diastereomers) and the known preference of enantioselective transesterification reactions catalyzed by Candida antarctica lipase B. Electroantennogram and single sensillum recording studies indicate that 4-methyl-3,5-heptanedione as well as all individual stereoisomers of 5-hydroxy-4-methyl-3-heptanone are detected by the antennae of male and female S. discoideus. Further, single sensillum recordings suggest that both sexes of S. discoideus have specialized olfactory receptor neurons (ORNs) for detecting 4-methyl-3,5-heptanedione and different populations of stereoselective ORNs for detecting the stereoisomers of 5-hydroxy-4-methyl-3-heptanone. Some of these stereoselective ORNs appear to be sex-specific in S. discoideus.

Transcriptome analysis of the entomopathogenic fungus Beauveria bassiana grown on cuticular extracts of the coffee berry borer (Hypothenemus hampei).

The coffee berry borer (CBB; Hypothenemus hampei) is a major pest of coffee responsible for significant crop losses worldwide. The entomopathogenic fungus Beauveria bassiana represents a natural means of controlling this insect pest; however, little is known concerning the molecular determinants that contribute to the virulence of the fungus towards the CBB. In order to examine genes involved in insect virulence, two expressed sequence tag (EST) libraries, representing germinating conidia and growing hyphae/mycelia of B. bassiana cells grown on cuticular extracts of the CBB were constructed and analysed. In total, 4186 cDNA transcripts were obtained, which included 2141 from the cuticle-germinated conidia and 2045 from the cuticle-grown mycelium libraries, respectively. The average sequence length obtained was 470 bp and transcript assembly resulted in a set of 1271 and 1305 unique gene sequences for the conidial and mycelia libraries, respectively. Around 50 % of the sequences in each library could be annotated by gene ontology terms. An analysis of the two generated libraries as well as a previously reported EST library of B. bassiana grown on chitin was performed. Between the cuticle-germinated conidia and the cuticle-grown mycelia libraries, 322 unique gene sequences were shared, of which 90 % could be annotated, leaving 949 unique cuticle-germinated conidial genes and 983 unique growing hyphae/mycelia genes of which around 65 % were annotated. ESTs shared between the libraries indicated a basic response pattern for B. bassiana against H. hampei, which included genes implicated in pathogenicity. The expression profiles of four genes were evaluated with a cyclophilin, an alkaline-like serine protease and a mitogen-activated protein kinase (MAPK), showing elevated expression during initial phases of infection, i.e. conidia germinating on insect extracts. These data provide clues and gene candidates for further exploration concerning the biology and molecular mechanisms of entomopathogenicity by this fungus.

Identification of male-produced aggregation pheromone of the curculionid beetle Sternechus subsignatus.

Analyses of the headspace volatiles produced by males and females of Sternechus subsignatus Boheman (Coleoptera: Curculionidae) revealed seven male-specific compounds. The major component was (E)-2-(3,3-dimethylcyclohexylidene)-ethanol, and the minor components were 1-(2'-hydroxyethyl)-1-methyl-2-isopropenylcyclobutane (grandisol), 7-methyl-3-methyleneoct-6-en-1-ol, (Z)-2-(3,3-dimethylcyclohexylidene)-ethanol, (Z)- and (E)-2-(3,3-dimethylcyclohexylidene)-acetaldehyde, and (E)-2-(3,3-dimethylcyclohexylidene) acetic acid. The latter compound is described for the first time as a natural product. Only four of the seven identified compounds showed electrophysiological activity. Enantioselective gas chromatography showed that the natural grandisol is the (1R,2S)-stereoisomer. The major component, (E)-2-(3,3-dimethylcyclohexylidene)-ethanol, attracted S. subsignatus in olfactometer bioassays. Studies are in progress to evaluate the biological activity of the major component and the EAD-active mixture under field conditions.

Oleoresin chemistry mediates oviposition behavior and fecundity of a tree-killing bark beetle.

Many herbivores are sensitive to the secondary chemistry of their host plants. However, the influence of pine secondary chemicals (monoterpenes) on bark beetle fitness is poorly understood. We tested the hypothesis that the monoterpene composition of the phloem oleoresin of ponderosa pine, Pinus ponderosa var scopulorum, mediates rates of host acceptance, oviposition behavior, and fecundity of the western pine beetle, Dendroctonus brevicomis. We performed reciprocal rearing experiments, controlling for the monoterpene composition (chemotype) of host material. We tested the effects of two geographically interspersed host chemotypes on beetles with unknown (wild) and known (reared F(1)) chemical histories. Host chemotype and insect chemical history did not affect rates of acceptance of host material by female beetles. Insect chemical history affected egg gallery construction, and beetles constructed egg galleries that were on average 24.3% longer when reared in host material that was chemically similar to their natal host material. However, mean egg gallery lengths did not differ between host chemotypes. Insect chemical history also influenced fecundity: F(1) beetles produced 52.7% more offspring on average when reared in host material that was chemically similar to their natal host. Our experiments demonstrate that the chemical history of bark beetles mediates egg gallery construction and fecundity, but not host acceptance. This implicates chemical history as a more important factor than host chemotype in the oviposition behavior and fecundity of D. brevicomis.

Chemical evaluation of African palm weevil, Rhychophorus phoenicis, larvae as a food source.

The chemical properties of the African palm weevil, Rhychophorus phoenicis (F.) (Coleoptera: Curculionidae), larvae were evaluated using standard methodology. The chloroform-methanol extract yielded 37.12% on a dry basis. The oil was liquid at room temperature with a flash point of 36.0 °C. Analysis of the physical constants indicated values of 192.25 Wijs and 427.70 mg KOH/g as iodine and saponification, respectively. Fatty acid analysis of the extracted oil showed the presence of unsaturated fatty acids at low levels. Palmitic acid and stearic acid constituted 35.3 and 60.5% of the oil, respectively. The usual behaviour of the oil at room temperature, irrespective of the level of unsaturation of its constituent fatty acid was noted. The total protein content of the defatted palm weevil larva (dry basis) was estimated at 66.3%. The amino acid values compared favourably to FAO reference protein, except for tryptophan, which was limiting. All the other essential amino acids were adequate. Mineral analysis revealed high levels of potassium (1025 mg/100 g) and phosphorus (685 mg/100 g). The dried and defatted palm weevil lava represents a very good source of protein, and a good complement of essential amino acids.

Isolation and characterization of chitosan from Ugandan edible mushrooms, Nile perch scales and banana weevils for biomedical applications.

Of recent, immense attention has been given to chitosan in the biomedical field due to its valuable biochemical and physiological properties. Traditionally, the chief source of chitosan is chitin from crab and shrimp shells. Chitin is also an important component of fish scales, insects and fungal cell walls. Thus, the aim of this study was to isolate and characterize chitosan from locally available material for potential use in the biomedical field. Chitosan ash and nitrogen contents ranged from 1.55 to 3.5% and 6.6 to 7.0% respectively. Molecular weight varied from 291 to 348KDa. FTIR spectra revealed high degree of similarity between locally isolated chitosan and commercial chitosan with DD ranging from 77.8 to 79.1%. XRD patterns exhibited peaks at 2θ values of 19.5° for both mushroom and banana weevil chitosan while Nile perch scales chitosan registered 3 peaks at 2θ angles of 12.3°, 20.1° and 21.3° comparable to the established commercial chitosan XRD pattern. Locally isolated chitosan exhibited antimicrobial activity at a very high concentration. Ash content, moisture content, DD, FTIR spectra and XRD patterns revealed that chitosan isolated from locally available materials has physiochemical properties comparable to conventional chitosan and therefore it can be used in the biomedical field.

Identification and metabolite profiling of Sitophilus oryzae L. by 1D and 2D NMR spectroscopy.

The polyphagous insect Sitophilus oryzae L. (Coleoptera:Curculionidae) has a tremendous adaptability in feeding behaviour, making it a serious invasive pest of stored cereals. The present study identifies the metabolite composition of Sitophilus oryzae (S. oryzae) using Nuclear Magnetic Resonance (NMR) spectroscopy. Assignment of 1D-proton by NMR, 1H-1H COSY, 2D-TOCSY 1H-1H, had been done. Amongst the various biochemically important metabolites isoleucine, valine, leucine, beta-hydroxybutyrate, lysine, glutamate, glutamine, proline, lactate, alanine, di-methylamine, alpha-glucose, beta-glucose, choline, glycerophosphorylcholine and tyrosine are present in S. oryzae. In wheat-fed S. oryzae, the presence of threonine and the absence of lactate is observed. In rice-fed S. oryzae, however, the presence of lactate and the absence of threonine were observed. Barley-fed S. oryzae shows presence of both tyrosine and lactate. It is concluded that the pest S. oryzae has adaptability on different stored cereals and grains, depicting the presence of earlier reported metabolites. The present study aims to identify the key metabolic components and associated enzymes in Sitophilus oryzae fed on different cereals.