Investigation of Larvicidal Activity and Histopathological Variations of Brown Algae Spatoglossum asperum J. Agardh against Aedes aegypti, Culex quinquefasciatus, and Anopheles stephensi

Abstract

The purpose of the current study was to determine whether the methanolic extract of Spatoglossum asperum has larvicidal properties against Aedes aegypti, Culex quinquefasciatus, and Anopheles stephensi. Various doses of methanolic seaweed extract (50, 100, 150, and 200 ppm) were applied to chosen larvae in the early 4^th instar. Each test was carried out in triplicate, with a control group present simultaneously. The mortality rate was observed at regular 24 hr intervals. FTIR and GC-MS studies analyzed the methanolic extract's functional groups and phytochemical compounds. The standard plate procedure was used to test the antibacterial capacity using clinically isolated pathogens; the extract effectively killed bacteria of all types, according to findings. FTIR peaks confirmed the presence of carbonyl groups, amino acids, hydroxyl groups, and alkynes. The GC-MS study of the seaweed extract found 14 major bioactive compounds, such as citronellol and diethyl phthalate, found to have insecticidal, nematocidal, antibacterial, antioxidant, cytotoxic, antifungal, and hepatoprotective properties. DPPH radical scavenging and nitric oxide assays showed that the efficacy grew as the extract level was raised. Total phenol and flavonoid content of the methanol extract was estimated at 73.2±02 μg/mL and 89.1±0.03 μg/mL, respectively. Against 4^th instar Ae. aegypti, Cx. quinquefasciatus, and An. stephensi larvae, methanolic extract of S. asperum showed LC₅₀ values of 2.56 mg/L, 3.32 mg/L, and 2.84 mg/L, respectively. These studies suggest methanolic extracts of S. asperum have more potential use as a larvicidal agent against vectors of Aedes, Culex, and Anopheles mosquitoes.