Chemical screening, insecticidal and reprotoxic activities of Tecoma stans ethanolic leaf extract against the vector mosquito Culex pipiens

Abstract

To select potential plant‐based insecticides, Tecoma stans (Bignoniaceae) leaf extract was screened for its larvicidal and delayed effects against a medically important mosquito species Culex pipiens L. (Diptera: Culicidae). First, gas chromatography–mass spectrometry (GC–MS) was conducted on T. stans extract, collected in ethanol for its chemical characterization and detection of active constituents. Second, insecticidal bioassays were made with several concentrations on earlier fourth instar larvae (L4) of Cx. pipiens for 24 h as recommended by WHO, in order to determine the lethality parameters of the tested extract. For that, two concentrations (LC30 and LC50) were applied on L4 for 24 h, and emerged adults were observed for their reproductive performance success like fecundity, percentage of hatching (fertility), body and gonads' volume. The biochemical composition of whole bodies of adults was investigated. Also, the specific activities of acetylcholinesterase (AChE) and glutathion S‐transferase (GST), biomarkers of neurotoxicity and detoxification, respectively, were also determined in L4 at different time intervals. Qualitative and quantitative phytochemical analysis (GC–MS) of the extract unveiled nine phytoconstituents with 2‐[4‐cyclohexylbutanoylamino]‐3‐chloro‐1,4‐naphthoquinone (36.24%) and 1,2‐Benzenedicarboxylic acid, mono(2‐ethylhexyl) ester (22.65%) as major components. The early L4 of Cx. pipiens were exposed to LC30 and LC50, and after 24 h, surviving individuals have been further reared until adult emergence. All over, T. stans leaves ethanolic extract impairs adults reproductive traits; it adversely affected gonad's size, fecundity and fertility, which negatively affected the survival of their offspring. Lipids contents were found to increase in both male and female adults. T. stans ethanolic extract increased GST activity and slightly inhibited AChE activity in L4. In conclusion, the ethanolic extract of T. stans could be a potential candidate used as a sustainable botanical insecticide for controlling mosquito.

Larvicidal and Biochemical Effects of Some Essential Oils and Bee Products Against Culex pipiens Larvae (Diptera: Culicidae)

“…The increase in the case of garlic treatment was significant. Our findings agreed with similar studies indicating that lipid content increased after larval treatment with Azadirachta indica extract (Sharma et al, 2011) and adult treatment with Tecoma stans ethanolic extracts (Hafsi et al, 2022).…”

“…It was reported a non-significant increase in carbohydrate content after treatment of Cx. pipiens adults by Tecoma stans ethanolic extracts (Hafsi et al, 2022). Garlic and marjoram oils significantly decreased carbohydrate contents to 11.2 and 11.43 mg/g, respectively.…”

Phytochemical composition of almond oil from Melia azedarach L. and its larvicidal, ovicidal, repellent and enzyme activities in Culex pipiens L.

“…Our results are in agreement with the work of Hafsi et al (2022) who used ethanolic extract of Tecoma stans leaf against the fourth instar larvae of Cx. pipiens which showed an induction of GST activity.…”

“…The photochemicals derived from plant sources can act as larvicides, insect growth regulators, repellents and ovipositional attractants. They have deterrent activities observed by many researchers (Thanigaivel et al, 2017;Hafsi et al, 2022). The interest in new botanical compounds for biological control is based on their bioefficiency, their biodegradability, their respect for the environment, their physiological activity (Baranitharan et al, 2020;Kharoubi et al, 2020;Zeghib et al, 2020;Rechek et al, 2021) and usually their low mammalian toxicity (El-Sabrout et al, 2020).…”