In-vitro Larvicidal Efficacy and GC-MS Analysis of Carica papaya Ethanol Leaf Extract against Anopheles gambiae Larvae

Infections due to mosquito vectors such as the female Anopheles gambiae constitute a significant threat to public health, especially in tropical and sub-tropical regions. This study aimed to evaluate the in vitro larvicidal efficacy of Carica papaya ethanol leaf extract against A. gambiae larvae. Freshly obtained leaves were carefully washed, air-dried and ground into powder. Bioactive constituents were extracted by maceration, while phytochemical compounds were characterised using gas chromatography-mass spectrometry. Five concentrations ranging from 50% to 10% were prepared by serial dilution and used for the larval bioassay. Data were analysed using one-way ANOVA, the chi-square test and probit regression analysis. The GC-MS analysis revealed the presence of 30 bioactive compounds in the ethanol leaf extract of C. papaya. Vitamin E was the most abundant compound (34.59%) followed by 1H-Indole, 5-methyl-2-phenyl- (10.16%), while Decanoic acid, hexyl ester was the least abundant compound (0.71%). The larval bioassay showed significant larvicidal activity of C. papaya leaf extract against the studied larvae. The highest percentage mortality (100%) and mean larval mortality (3.00±1.00 – 20.00±0.00) occurred at the 50% extract concentration, while the lowest percentage mortality (16.6%) and mean larval mortality (0.67±0.58 – 3.33±1.53) were recorded at the 10% extract concentration. Exposure time showed that the highest mean larval mortality (3.33±1.53 - 20.00±0.00) occurred after 24 h of larval exposure to the plant extract, while the lowest mean larval mortality (0.67±0.58 – 3.00±1.00) was recorded at 3 h of larval exposure. The lethal concentrations (LC50 and LC90) required to induce 50% and 90% mortality were (LC50=24.11 mg/ml; LC90=56.79 mg/ml), while the lethal times (LT50 and LT90) were (LT50=17.44 h; LT90=87.31 h). These findings suggest that C. papaya possesses enormous potential as a green larvicide and can be utilised, following standardisation, as a plant-based alternative agent for mosquito larval control.