Hyptis suaveolens extract exhibits larvicidal activity against Anopheles gambiae larvae

Abstract

Hyptis suaveolens (Lamiaceae) is traditionally used to repel insects. The aim of this study was to determine the larvicidal activity of dichloromethane aerial part extract of H. suaveolens against 4th instar Anopheles gambiae (Diptera: Culicidae) larvae by establishing dose response of the extracts, determining the lethal concentrations (LC50 and LC90) of the extracts and the efficacy of the plant as a mosquito larvicide following the World Health Organization guidelines for laboratory testing of mosquito larvicides. Two samples of the aerial parts were collected and used for the test; sample Z1 was collected in the morning and sample Z2 in the afternoon. Concentrations ranging from 10-100 mg/mL of the extract were used. The results showed that there is a very high significant difference between the two samples in relation to the concentrations (df = 4, P < 0.0001). The larvae were resistant at 24th hour and at 48th hour but became susceptible to the extracts at 72nd hour with 99% and 97% mortality rates with both samples. There was significant difference in mortality rates between the two samples (P < 0.05). LC50 at 72nd hour for Z1 and Z2 was 3.51 mg/mL. LC90 at 72nd hour for Z1 was 1.52 mg/mL and 33.47 mg/mL for Z2. The result of this study indicates that H. suaveolens possesses larvicidal properties and supports its traditional application as a repellant/insecticide. Thus, the plant extract could be applied to mosquito breeding sites as a measure to control malaria vector, particularly A. gambiae.