Larvicidal Effects of Methanolic Extract of Ocimum gratissimum Leaves on Anopheles spp. Larva in Gombe, Gombe State, Nigeria

Mosquitoes are among the most notorious insect vectors responsible for transmitting numerous life-threatening diseases, posing serious public health challenges and hindering development in many of the world’s poorest nations. Effective vector control remains a crucial component in managing these diseases. However, the widespread emergence of insecticide resistance, along with the negative impacts of chemical insecticides on non-target organisms and the environment, underscores the urgent need for safer, eco-friendly, and sustainable mosquito control strategies. This study evaluated the larvicidal potential of Ocimum gratissimum (scent leaf) methanolic extract against Anopheles species larvae. The extract was prepared using the cold extraction method, while phytochemical screening was carried out through standard qualitative procedures. Larvicidal assays were performed following the World Health Organization (WHO) guidelines. The methanolic extract yielded 8.14% and revealed the presence of several bioactive compounds, including alkaloids, flavonoids, tannins, steroids, saponins, anthraquinones, phenolics, and glycosides. Bioassay results indicated strong larvicidal activity, with LC₅₀ and LC₉₀ values of 4.38 mg/ml and 25.40 mg/ml after 72 hours, respectively. These findings suggest that O. gratissimum possesses significant potential as a natural larvicide against Anopheles species, offering a promising alternative to synthetic insecticides. The aromatic plant extract could serve as a safe, economical, and environmentally friendly mosquito control agent.