Concentration-Dependent Larvicidal Activity of Nutmeg Seed (Myristica fragrans Houtt.) Extract against Third-Instar Aedes aegypti Larvae

Abstract

Dengue prevention continues to depend on integrated vector management, including control of immature Aedes aegypti in water-holding containers. Plant-derived larvicides may provide locally available candidates, but their activity must be established through controlled bioassays before practical use. This study evaluated the concentration-dependent larvicidal activity of nutmeg seed (Myristica fragrans Houtt.) extract against third-instar A. aegypti larvae. A posttest-only controlled experiment involved five groups: 10%, 20%, 30%, and 40% (v/v) ethanolic nutmeg seed extract and an aquadest negative control. Each group comprised three independent vessels containing 25 larvae, yielding 375 larvae in total. Nutmeg seed simplicia was macerated in 96% ethanol for 5 × 24 hours and concentrated using a rotary evaporator. Larval mortality was observed every four hours for 24 hours. Data were analyzed using ANOVA, followed by exploratory least significant difference pairwise comparisons; a Kruskal-Wallis test was applied as a sensitivity analysis. Mortality increased from 0% in the control to 42.7%, 52.0%, 64.0%, and 82.7% at 10%, 20%, 30%, and 40%, respectively. Mean mortality differed significantly among groups, F(4,10) = 34.753, p<0.001, with a large effect size (η²=0.933). The sensitivity analysis supported an overall group difference (H=11.932, p=0.018). The 40% extract differed significantly from all lower concentrations, whereas differences between 10% and 20% and between 20% and 30% were not significant. Nutmeg seed extract demonstrated concentration-dependent larvicidal activity, with the highest mortality at 40%. However, the absence of a positive control, chemical standardization, lethal-concentration estimates, and non-target safety testing means that household or field application cannot yet be recommended.