Larvicidal and antiplasmodial studies of Eucalyptus camaldulensis (Myrtaceae) leaf

Abstract

Eucalyptus camaldulensis is a medicinal plant used as insect repellant and antimalarial agent in ethnomedicine. This study examined the antiplasmodial and larvicidal potential of E. camaldulensis leaf extract and also identified the plant extract's most active fraction(s). The acute oral toxicity test of the methanol extract was evaluated using Lorke’s method. The larvicidal assay was performed on the extract and partitioned fractions according to the 2005 World Health Organization guidelines, while the 4-day chemosuppressive and curative antimalarial assays were carried out against Plasmodium bergei bergei. Endosulphan and chloroquine (10 mg/kg) was used as the positive controls for the larvicidal and antiplasmodial assays, respectively, while tween 80 in normal saline (1%) was the negative control. The methanol leaf extract of EC showed good larvicidal activity across all tested concentrations (LC50 3.79 ± 0.64 mg/mL), while the aqueous fraction with LC50 of 2.80 ± 0.14 mg/mL was the most active. Its acute toxicity test showed it was safe up to 5000 mg/kg. The extract significantly increased dose-dependent antiplasmodial activity for the chemosuppressive and curative models (p < 0.05) than the negative control. At 800 mg/kg, EC gave chemosuppressive (53.69 ± 1.62%) and curative (81.26 ± 1.87%) activities, which was significantly lower than that of 10 mg/kg chloroquine (82.00 ± 0.57% and 92.51 ± 0.22% respectively). The aqueous partitioned fraction gave the highest chemosuppression (73.84 ± 2.73%) at 80 mg/kg, which was comparable to the positive control. The methanol extract of E. camaldulensis leaf is a promising larvicidal and antimalarial agent that could proffer a solution to vector control and the prevalence of malaria.