BIOACTIVITY EVALUATION OF SARCOPHYTON CRUDE EXTRACT AS A LARVICIDAL AGENT AGAINST CULEX PIPIENS (DIPTERA; CULICIDAE) LARVAE

Abstract

Culex pipiens (Cx. pipiens L.) mosquitoes play a crucial role as vectors for many diseases. The persistent application of synthetic insecticides for controlling mosquitoes in developing insect resistance. The marine ecosystem has garnered considerable interest in exploring new insecticide alternatives with low resistance. This work evaluated the larvicidal effect of Sarcophyton soft coral crude extract against third-instar larvae of Cx. pipiens as a safe insecticidal agent. To conduct this objective, the determination of the Sarcophyton extract's phytochemicals and its gas chromatography-mass spectrometric (GC-MS) fatty acid profile. The mortality rate induced by Sarcophyton extract against larvae was assessed in a dose-dependent manner at 24, 48, and 72-hr post-exposure. Also, the larvae were observed for any behavioral and morphological alterations, along with an estimation of acetylcholinesterase (AChE) and glutathione-S-transferase (GST) activities in larvae. Chemical characterization of Sarcophyton extract revealed different bioactive phytochemicals and three primary fatty acids: linoleic acid, oleic acid, and palmitic acid. The median lethal concentrations (LC50) of Sarcophyton extract were recorded at 745.418, 370.064, and 232.017 µg/ml after 24, 48, and 72hr exposure time, respectively. Treatment with 24hr-LC50 of Sarcophyton extract revealed neurobehavioral toxicity and morphological aberrations against Cx. pipiens larvae. The application of 24 hr-LC50 of Sarcophyton extract displayed a neurotoxic effect, as evidenced by the significant inhibition of AChE activity and suppression of GST detoxification activity. The larvicidal action mechanism of Sarcophyton could be attributed to its bioactive components. This study concluded that Sarcophyton extract could be a natural candidate for controlling Culex larvae.