Abstract
Dengue fever, which is transmitted by Aedes aegypti L. (Diptera: Culicidae), is one of the most important diseases affecting human health and the economy in the western part of Saudi Arabia. This study has aimed to investigate the biological activities of three different extracts (ethanol, acetone and water) from leaves of Rhanterium epapposum Oliv. (Asteraceae) (commonly known as Arfaj). Results obtained indicate that the tested extracts had significant varying effects on A. aegypti larvae. The larvicidal potency of the ethanolic extract at a high concentration of 50000 ppm was up to 98% after 24 hours of application. In contrast, the acetonic and aqueous extracts caused 72% and 30% mortalities of the larvae, respectively, at the same concentration and exposure time. After 48 hours of exposure, the mortalities of the larvae increased by 99%, 86% and 35%, respectively, for the ethanolic, acetonic and aqueous extracts. Moreover, this study has illustrated that the ethanolic extract had a higher larvicidal effect with a lower LC50 value (168.15 ppm) after 24 hours. This effect was also higher than those of the acetonic (847.75 ppm) and aqueous (2278.22 ppm) extracts. Further investigations have revealed that the chemical composition of the essential oils, such as alkaloids, flavonoids, triterpenes, cumarins and tannins, in the ethanolic leaf extracts of R. epapposum could be responsible for their higher toxicity against the larvae of the dengue fever mosquito vector. Thus, conducting studies on the chemical constituents and bioactive chemical ingredients constancy of R. epapposum ethanolic extract would give good insights for developing a sustainable mosquito control method.