Abstrait

Phytochemical analysis and toxicity of Annona muricata stem bark and leaf extracts on Anopheles gambiae larvae.

Paschal Chiedozie Amakiri, Edith Nonye Nwankwo, Augustine Chukwuemeka Amakiri, Chukwudi Micheal Egbuche, Ikenna Fabian Osuagwu, Izunna Somadina Okwelogu, Vivian Onyinyechi Offor, Chineme T Acha

Global efforts to control mosquitoes have relied heavily on the use of synthetic insecticides which have negatively impacted the ecosystem. With the continuous campaign on sustainability and the need to preserve the ecological balance, it has become imperative to develop alternative measures to contain the spread of mosquitoes which are efficient, sustainable and less impactful on the environment. It is in light of these, that laboratory investigations were conducted to determine the phytochemical components present in A. muricata stem bark and leaf extracts. The toxicity effects of various concentrations (200 mg/ml, 100 mg/ml, 50 mg/ml and 25 mg/mL) of A. muricata stem bark and leaf extracts to An. gambiae complex (Diptera: Culicidae) were evaluated by exposing the mosquito larvae at ambient temperature of 29 ± 2°C and 29.5 ± 5% r.h and photoperiod 12:12 light and dark hours. Three replicates of each of the concentrations were used to treat 20 active larvae of An. gambiae in a completely randomized design. Mortality resulting from eclosion inhibition was monitored at 3 hourly intervals for 48 hours, post-treatment and adult emergence were recorded. Data were analysed using log-probit regression and analysis of variance. Results of the qualitative phytochemical analysis revealed the presence of saponins, flavonoids, phenols, cardiac glycosides and alkaloids in both stem bark and leaf extracts. The toxicity result showed that the different concentrations of the extracts resulted in considerable mortality of the larvae. The stem bark and leaf extracts caused significant (p<0.05) mortalities of 100% and 70% respectively at highest concentration of 200 mg/mL while at lowest concentration of 25 mg/mL caused mortalities of 30% and 20% respectively. The percentage inhibition of emergence for stem bark and leaf extracts at highest concentrations were respectively 100% and 70.00%. The LC50 and LC90 are (36.64 and 79.82 mg/mL) and (67.03 and 570.96 mg/mL) respectively for stem bark and leaf extracts. This study suggests that the stem bark and leaf extracts of A. muricata could perhaps be good alternatives to synthetic pesticides that adversely contaminate the environment while also suggesting that the active phytochemicals present in these plant parts could be saponins, flavonoids, alkaloids acting individually or synergistically.