Globimetula cupulata as a Potential Source of Larvicides for the Control of Culex quinquefasciatus

Abstract

Aim: Globimetula cupulata, a parasitic shrub that grows widely in Nigeria, is commonly used in ethnomedicine to treat fever, malaria, high blood pressure and diabetes mellitus. This plant was investigated for probable activity against Cx. quinquefasciatus larvae as there is currently no such report. Study Design: The methanol extracts of G. cupulata leaf, stem and flower were separately tested against Cx. quinquefasciatus larvae. The most active extract was partitioned in order to identify the most active fraction from which the active compound could be isolated. Place and Duration of Study: Department of Pharmacognosy, Faculty of Pharmacy, Obafemi Awolowo University, Ile-Ife, Nigeria; between November 2023 and August 2024. Methodology: The leaf, stem and flower of G. cupulata growing on Leucaena leucocephala were collected from the university’s research farm. It was authenticated and deposited under reference number FPI 2513. They were air dried separately, weighed and macerated in methanol for 72 hours, filtered, concentrated in vacuo at 35°C and tested against the fourth instar larvae of Cx. quinquefasciatus according to WHO, 2005 guidelines. The most active extract was reconstituted in water and successively partitioned into n-hexane and ethylacetate. Each fraction was tested for activity. The methanol extract of Nicotiana tabacum leaf and Tween 80 in water (0.2%v/v) were the positive and negative controls respectively. Results: After 48 hours of exposure, the flower extract was the most active, followed by the leaf while the stem was the least active. Also, throughout the period of exposure, the hexane and the ethylacetate fractions had comparable activities while the aqueous fraction was inactive.  Conclusion: The methanol extract of G. cupulata flower has activity against the fourth instar larvae of Cx. quinquefasciatus. This activity is concentrated in the n-hexane and ethylacetate fractions. Globimetula cupulata therefore is a potential source of larvicidal compounds.