Larvicidal and phytochemical analysis of Hypoestes forskaolii extracts against Anopheles gambiae, Aedes aegypti and Culex quinquefasciatus

Abstract

This research evaluated larvicidal potencies and phytochemical analysis of Hypoestes forskaolii (vahl) R. Br root extracts. Larvicidal activities were tested to Anopheles gambiae, Aedes aegypti and Culex quinquefasciatus. World Health Organization protocol for evaluating and testing insecticides was adopted with minor modification. Larvae of these mosquitoes were allowed to interact with extracts prepared in different concentration ranging between 25 to 750 μg/mL and the death rate were noted subsequent to 24 h, 36 h and 72 h. Root extracts of H. forskaolii displayed its effectiveness towards larva’s of A. gambiae, A. aegypti and C. quinquefasciatus 3 rd instars having LC 50 between 3.8989 to 220.4789 μg/mL for A. aegypti, LC 50 of 2.0322 to 69.6596 μg/mL for A. gambiae and LC 50 of 6.0004 to 177.5595 μg/mL for C. quinquefasciatus. The chloroform extract results indicated high mortality of larvae subsequent to 72 h of contact for the three species of mosquitoes tested. Anopheles gambiae had the LC 50 of 2.0322 μg/mL where by A. aegypti had LC50 of 3.8989 μg/mL while C. quinquefasciatus showed LC50 of 6.0004 μg/mL. Analysis of the organic compounds found in Hypoestes forskaolii chloroform extract was performed using gas chromatography-mass spectrometry technique (GC-MS). Twenty three compounds were identified namely; piperonal, caryophyllene, caryophyllene oxide, β-humulene, α-farnesene, Nerolidol, patchoulane, γ-cadinene, viridiflorol, n-hexadecanoic acid, octadecanoic acid, bicyclo [5.2.0] nonane, 2-methylene-4,8,8-trimthyl-4vinyl, Kaurene, 9,12-octadecadienoic acid Z, Z, eicosane, allo- aromadendrene oxide, Epiglobulol, Longipinane, curcumene, Globulol, Calamenene, α-cedrene and Copaene. The larvicidal activity of Hypoestes forskaolii extracts is likely due to the presence of one or some of these compounds. Further study is needed to establish the compound(s) responsible for the displayed larvicidal potencies.