Assessment of larvicidal and genotoxic potentials of extracts of Hyptis suaveolens against Culex quinquefasciatus based on enzyme profile and RAPD-PCR assay

Oviposition Deterrence and Larvicidal Activity of Propyl Ether Dillapiole and Piperidyl Dillapiole Against Aedes (Stegomyia) aegypti (Diptera: Culicidae)

The study of substances of botanical origin is fundamental for the development of new effective alternatives for the control of Aedes (Stegomyia) aegypti (Culicidae), a vector of arboviruses in humans. In this study, the potential of two new dillapiole derivatives, propyl ether dillapiole and piperidyl dillapiole, was tested to determine their ability to deter oviposition and their larvicidal and residual effects against Ae. aegypti under simulated field conditions, as alternatives for the control of this mosquito. The ability of these substances to deter oviposition by pregnant Ae. aegypti females was assessed in the laboratory, and then the larvicide and residual effects of different concentrations were tested under simulated field conditions. The determination of the enzymatic activity in exposed larvae was carried out using sublethal concentrations. The LC50 values of propyl ether dillapiole after 24 and 48 h were 24.60 µg/mL and 14.76 µg/mL, and those of piperidyl dillapiole were 31.58 µg/mL and 24.85 µg/mL, respectively. After 48 h of exposure to aged, treated water, the mortality of propyl ether dillapiole (100 µg/mL) and piperidyl dillapiole (200 µg/mL) fell to 81.7% and 75% on the second day, and to 73.3% and 66.7% on the fourth day, respectively. The concentrations of 100 µg/mL of propyl ether dillapiole and 200 µg/mL of piperidyl dillapiole caused oviposition rates of only 3.80% and 4.63% of the eggs of the females, respectively, compared to 22.01% in the negative control (water and DMSO at 2%). In the larvae exposed to propyl ether, piperidyl dillapiole, dillapiole, or the chemical insecticide temephos (positive control), inhibition of acetylcholinesterase (AChE) occurred. Propyl ether dillapiole and piperidyl dillapiole have potential for use as alternative forms of control of Ae. aegypti, with propyl ether dillapiole being the most promising molecule. Further studies are needed to understand the effects of these substances on this mosquito and on non-target organisms.

Bioactive components in Psidium guajava extracts elicit biotoxic attributes and distinct antioxidant enzyme modulation in the larvae of vectors of lymphatic filariasis and dengue

Control of mosquito vectors, which have caused a global disease burden, has employed various methods. However, the challenges posed by current physical and chemical methods have raised concerns about vector control programs, leading to the search for alternative methods that are less toxic, eco-friendly, and cost-effective. This study investigated the larvicidal potential of aqueous, methanol, and ethylacetate extracts of Guava (Psidium guajava) against Aedes aegypti and Culex quinquefasciatus larvae. Functional group and phytochemical characterization were performed using Fourier-Transform Infrared Spectroscopy (FTIR) and GC-MS analysis to identify the bioactive compounds in the extracts. Larval bioassays were conducted using WHO standard procedures at concentrations of 12.5, 25, 50, 125, and 250 mg/L, and mortality was recorded after 24, 48, and 72 h. Additionally, antioxidant enzyme profiles in the larvae were studied. All of the solvent extracts showed larvicidal activity, with the methanol extract exhibiting the highest mortality against Ae. aegypti and Cx. quinquefasciatus larvae, followed by aqueous and ethylacetate extracts. FTIR spectroscopic analysis revealed the presence of OH, C-H of methyl and methylene, CO and CC. The GC-MS analysis indicated that the methanol, aqueous, and ethylacetate extracts all had 27, 34, and 43 phytoactive compounds that were effective at causing larvicidal effects, respectively. Different concentrations of each extract significantly modulated the levels of superoxide dismutase, catalase, glutathione peroxidase, and reduced glutathione in larvae. This study's findings indicate the potential for developing environmentally friendly vector control products using the bioactive components of extracts from P. guajava leaves.

Phytomediated stress modulates antioxidant status, induces overexpression of CYP6M2, Hsp70, α-esterase, and suppresses the ABC transporter in Anopheles gambiae (sensu stricto) exposed to Ocimum tenuiflorum extracts

The incorporation of phytoactive compounds in the management of malarial vectors holds promise for the development of innovative and efficient alternatives. Nevertheless, the molecular and physiological responses that these bioactive substances induce remain underexplored. This present study investigated the toxicity of different concentrations of aqueous and methanol extracts of Ocimum tenuiflorum against larvae of Anopheles gambiae (sensu stricto) and unraveled the possible underlying molecular pathways responsible for the observed physiological effects. FTIR and GCMS analyses of phytoactive compounds in aqueous and methanol crude extracts of O. tenuiflorum showed the presence of OH stretching vibration, C = C stretching modes of aromatics and methylene rocking vibration; ring deformation mode with high levels of trans-β-ocimene, 3,7-dimethyl-1,3,6-octatriene in aqueous extract and 4-methoxy-benzaldehyde, 1,3,5-trimethyl-cyclohexane and o-cymene in methanol extract. The percentage mortality upon exposure to methanol and aqueous extracts of O. tenuiflorum were 21.1% and 26.1% at 24 h, 27.8% and 36.1% at 48 h and 36.1% and 45% at 72 h respectively. Using reverse transcription quantitative polymerase chain reaction (RT-qPCR), down-regulation of ABC transporter, overexpression of CYP6M2, Hsp70, and α-esterase, coupled with significantly increased levels of SOD, CAT, and GSH, were observed in An. gambiae (s.s.) exposed to aqueous and methanol extracts of O. tenuiflorum as compared to the control. Findings from this study have significant implications for our understanding of how An. gambiae (s.s.) larvae detoxify phytoactive compounds.

Chemical Composition, Antioxidant, and Mosquito Larvicidal Activity of Essential Oils from Hyptis capitata Jacq

Background

Mortality and morbidity associated with vector-borne diseases, particularly those caused by mosquitoes, are increasing and new means of controlling them, including bio-larvicides, are needed. Malaria is a serious threat in many countries of Africa and Asia, and eco-friendly vector preventing measures are very much essential. Plant-derived larvicides are of great importance in this context. Hyptis capitata is an aromatic medicinal plant which is widely distributed in tropical countries. The aim of the present study is to examine the chemical composition, antioxidant and mosquito larvicidal effects of essential oils of this plant, extracted by hydro-distillation.

Methods

Chemical compositions of essential oils were analyzed using gas chromatography–mass spectrometry (GC-MS). Antioxidant activity was tested by the 2,2-diphenyl-1-(2,4,6-trinitrophenyl) hydrazyl (DPPH) assay and the mosquito larvicidal activity was checked against the fourth instar larvae of the malarial vector Anopheles stephensi. Fingerlings of Oreochromis mossambicus were used as a bio-model for toxicity studies.

Results

A total of 48 constituents, inclusive of 44 (94.67%) from inflorescence and 19 (97.09%) from leaf oil were identified; δ-cadinene (14.68%) and linalool (6.99%) were the major constituents of the inflorescence oil, while leaf oil contained 1-octen-3-ol (34.08%), methyl linoleate (17.2%), and germacrene D (11.16%). Antioxidant analysis showed an effective concentration (EC₅₀) value of 22.76 μg/mL for leaf oil and 26.18 μg/mL for the inflorescence oil, corresponding to 17.57 μg/mL of ascorbic acid. Both oils showed a respectable larvicidal effect and the lethal concentrations (LC₅₀) are 39.08 μg/mL and 33.19 μg/mL for the inflorescence and leaf oil, respectively. Notably, both the inflorescence and leaf oils are not very toxic to fish with respect to the concentrations tested.

Conclusion

This study showed that the essential oils extracted from the leaves and inflorescences of H. capitata are effective antioxidants and can act as inexpensive mosquito larvicidal agents.