First insights into insecticidal activity against Aedes aegypti and partial biochemical characterization of a novel low molecular mass chymotrypsin‐trypsin inhibitor purified from Lonchocarpus sericeus seeds

BACKGROUND

Arboviroses such as dengue, Zika and chikungunya represent a serious public health issue as a consequence of the absence of approved vaccines or specific antiviral drugs against the arboviruses that cause them. One way to prevent these diseases is by combating the vector mosquito, Aedes aegypti (Diptera), which has serine proteases in the midgut. Protease inhibitors are molecules that can block enzyme activity, impairing digestion and nutrition, which can lead to death. Thus, we purified and characterized a novel chymotrypsin‐trypsin inhibitor (LsCTI) from Lonchocarpus sericeus seeds and investigated its effect upon Ae. aegypti egg hatching, larval development and digestive proteases.

RESULTS

LsCTI showed a single protein band in sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS‐PAGE), and the molecular mass determined by matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry (MALDI‐TOF‐MS) was 8870.45 Da. Kinetics analyses revealed a noncompetitive type of inhibition and low inhibition constant (K_i) for chymotrypsin (8.24 x 10^‐8 m ). The thermal resistance was remarkable, even at 100 °C for 180 min. The inhibitor concentration required for 50‐percent enzyme inhibition (IC₅₀) of LsCTI was 4.7 x 10^‐7 m for Ae. aegypti midgut larval enzymes. LsCTI did not affect egg hatchability at 0.3 mg mL^‐1, but caused a high larval mortality rate (77%) and delayed development (37%).

CONCLUSIONS

LsCTI is a novel protease inhibitor with remarkable biochemical characteristics and is a potential tool to control Ae. aegypti development. © 2017 Society of Chemical Industry

     

Frequency and intensity of pyrethroid resistance through the CDC bottle bioassay and their association with the frequency of kdr mutations in Aedes aegypti (Diptera: Culicidae) from Mexico

BACKGROUND

The control of Aedes aegypti (L.), the main urban vector that causes arboviral diseases such as dengue, Chikungunya and Zika, has proved to be a challenge because of a rapid increase in insecticide resistance. Therefore, adequate monitoring of insecticide resistance is an essential element in the control of Ae. aegypti and the diseases it transmits. We estimated the frequency and intensity (Resistance Frequency Rapid Diagnostic Test [F‐RDT] and Resistance Intensity Rapid Diagnostic Test [I‐RDT]) of pyrethroid resistance in populations of Ae. aegypti from Mexico using the bottle bioassay and results were related to the frequencies of knockdown resistance (kdr) mutations V1016I and F1534C.

RESULTS

All populations under study were resistant to the pyrethroids: bifenthrin (99%), d‐(cis–trans)‐phenothrin (6.3% cis, 91.7% trans) and permethrin (99.5%) according to F‐RDT, and showed moderate to high‐intensity resistance at 10× the diagnostic dose (DD) in I‐RDT. Frequencies of the kdr mutation V1016I in Ae. aegypti populations were correlated with moderate permethrin resistance at 10× DD, whereas F1534C mutation frequencies were correlated with high bifenthrin resistance at 5× DD. Both I1016 and C1535 were highly correlated with high‐intensity phenothrin resistance at 1× to 10× DD.

CONCLUSIONS

This study showed that high frequencies of kdr mutations V1016I and F1534C are reflected in the results of F‐RDT and I‐RDT tests. Bioassays in conjunction with the characterization of genetic resistance mechanisms are indispensable in the strategic and rational management of resistance in mosquitoes. © 2018 Society of Chemical Industry

     

Synthesis and structure–activity relationships of carbohydrazides and 1,3,4‐oxadiazole derivatives bearing an imidazolidine moiety against the yellow fever and dengue vector,Aedes aegypti

BACKGROUND

1,3,4‐Oxadiazole and imidazolidine rings are important heterocyclic compounds exhibiting a variety of biological activities. In this study, novel compounds with oxadiazole and imidazolidine rings were synthesized from 3‐(methylsulfonyl)‐2‐oxoimidazolidine‐1‐carbonyl chloride and screened for insecticidal activities. The proposed structures of the 17 synthesized compounds were confirmed using elemental analysis, infrared (IR), proton nuclear magnetic resonance (¹H‐NMR), and mass spectroscopy.

RESULTS

None of the compounds showed larvicidal activity at the tested concentrations against first‐instar Aedes aegypti larvae. However, nine compounds exhibited promising adulticidal activity, with mortality rates of ≥80% at 5 µg per mosquito. Further dose–response bioassays were undertaken to determine median lethal dose (LD₅₀) values. Compounds 1 , 2b , 2c , 2d , 2 g , 3b , 3c , 3 g, and 3 h were effective, with typical LD₅₀ values of about 5 ? 10 µg per mosquito against female Ae. aegypti. Compounds 2c (bearing a nitro group on the aromatic ring; LD₅₀ = 2.80 ± 0.54 µg per mosquito) and 3 h ( double halogen groups at 2,4 position on the phenyl ring; LD₅₀ = 2.80 ± 0.54 µg per mosquito) were the most promising compounds.

CONCLUSION

Preliminary mode of action studies failed to show consistent evidence of either neurotoxic or mitochondria‐directed effects. Further chemical synthesis within this series may lead to the development of new effective insecticides. © 2017 Society of Chemical Industry

     

PM 4/10(2): Certification scheme for Rubus

Specific scope

This standard describes the production of certified pathogen‐tested material of Rubus.

Specific approval and amendment

First approved in 2004–09. Revised in 2009–09.

     

PM 9/1(2): Bursaphelenchus xylophilus and its vectors: procedures for official control

Specific scope

This standard describes the procedures for official control with the aim of containing and eradicating Bursaphelenchus xylophilus in areas where infestation of susceptible coniferous species by B. xylophilus leads to wilt symptoms.

Specific approval and amendment

First approved in 2002–09. Revision approved in 2009‐09.

     

PM 7/90(1): Anisogramma anomala

Specific scope

This standard describes diagnostic protocols for Anisogramma anomala ¹ 1 Use of brand names of chemicals or equipment in these EPPO Standards implies no approval of them to the exclusion of others that may also be suitable.
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Specific approval and amendment

Approved in 2009‐09.

     

Curtobacterium flaccumfaciens pv. flaccumfaciens

Specific scope

This standard describes a diagnostic protocol for Curtobacterium flaccumfaciens pv. flaccumfaciens. ¹ 1 Use of names of chemicals or equipment in these EPPO Standards implies no approval of them to the exclusion of others that may also be suitable.

Specific approval and amendment

Approved in 2011‐09.

     

PM 4/16(2): Certification scheme for hop

Specific scope

This standard describes the production of certified pathogen‐tested material of hop.

Specific approval and amendment

First approved in 1996–09. Revised in 2009–09.

     

PM 7/40(2): Globodera rostochiensis and Globodera pallida

Specific scope

This standard describes a diagnostic protocol for Globodera rostochiensis and Globodera pallida ¹ 1 Use of brand names of chemicals or equipment in these EPPO Standards implies no approval of them to the exclusion of others that may also be suitable.
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Specific approval and amendment

This Standard was developed under the EU DIAGPRO Project (SMT 4‐CT98‐2252) by partnership of contractor laboratories and intercomparison laboratories in European countries. Approved as an EPPO Standard in 2003–09. Revision approved in 2009–09.

     

PM 9/9(1): Heracleum mantegazzianum,H. sosnowskyi and H. persicum

Specific scope

This standard describes national regulatory control systems for Heracleum mantegazzianum, Heracleum sosnowskyi and Heracleum persicum. In the text the three species are referred to as Heracleum spp. in order to reduce repetitions.

Specific approval and amendment

First approved in 2009–09.

     

PM 7/91(1): Gibberella circinata

Specific scope

This standard describes a diagnostic protocol for Gibberella circinata ¹ 1 Use of brand names of chemicals or equipment in these EPPO Standards implies no approval of them to the exclusion of others that may also be suitable.
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Specific approval and amendment

Approved in 2009–09.

     

PP 7/94(1): Hirschmanniella spp.

Specific scope

This standard describes a diagnostic protocol for the genus Hirschmanniella ¹ 1 Use of names of chemicals or equipment in these EPPO Standards implies no approval of them to the exclusion of others that may also be suitable.
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Specific approval and amendment

Approved in 2009–09.

     

PM 7/95(1): Xiphinema americanum sensu lato

Specific scope

This standard describes a diagnostic protocol for Xiphinema americanum sensu lato ¹ 1 Use of names of chemicals or equipment in these EPPO Standards implies no approval of them to the exclusion of others that may also be suitable.
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Specific approval and amendment

Approved in 2009–09.

     

PM 7/92(1): Gremmeniella abietina

Specific scope

This standard describes a diagnostic protocol for Gremmeniella abietina ¹ 1 Use of brand names of chemicals or equipment in these EPPO Standards implies no approval of them to the exclusion of others that may also be suitable.

Specific approval and amendment

Approved in 2009–09.

     

PM 7/5(2): Nacobbus aberrans sensu lato

Specific scope

This standard describes a diagnostic protocol for Nacobbus aberrans sensu lato ¹ 1 Use of brand names of chemicals or equipment in these EPPO Standards implies no approval of them to the exclusion of others that may also be suitable.
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Specific approval and amendment

Approved in 2000–09. Revision approved in 2009–09.

     

PM 7/23 (2): Xanthomonas axonopodis pv. dieffenbachiae

Specific scope

This standard describes a diagnostic protocol for Xanthomonas axonopodis pv. dieffenbachiae ¹ 1 Use of brand names of chemicals or equipment in these EPPO Standards implies no approval of them to the exclusion of others that may also be suitable.
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Specific approval and amendment

First approved in 2003–09. Revised in 2009–09.

     

PM 3/74(1): EPPO guidelines on the development of a Code of conduct on horticulture and invasive alien plants

Specific scope

This standard describes guidelines for the development of a Code of conduct on horticulture and invasive alien plants.

Specific approval

First approved in 2009–09.

     

PM 9/8(1): Eichhornia crassipes

Specific scope

This standard describes the procedures for control of Eichhornia crassipes.

Specific approval and amendment

First approved in 2009–09.

     

PM 10/14 (1): Disinfestation of production site against Liriomyza sativae

Specific scope

This standard describes a treatment programme aimed at eradication of Liriomyza sativae in those parts of the EPPO region where it is not established. It is recognized that not all treatments (active substances) will be available in EPPO countries and emergency procedures (special restrictions) may be required to permit implementation of such an intensive treatment programme. It is recognized that in implementing this intensive treatment programme maximum residue levels may be exceeded and as such the product(s) may not be suitable for consumption. A risk assessment of this programme will need to be made by individual countries in order to assess a particular situation.

Specific approval and amendment

First approved in 2009–09.

     

Ceratitis capitata

Specific scope

This standard describes a diagnostic protocol for Ceratitis capitata. ¹ 1 Use of brand names of chemicals or equipment in these EPPO Standards implies no approval of them to the exclusion of others that may also be suitable.

Specific approval and amendment

Approved in 2011–09.