Oviposition Deterrent Efficacy and Characteristics of a Botanical Natural Product, Ocimum gratissimum (L.) Oil-Alginate Beads, against Aedes aegypti (L.)

Abstract

This study was aimed at investigating the oviposition deterrent activity of Ocimum gratissimum (L.) essential oil (O. gratissimum oil) and its product, Ocimum gratissimum (L.)- alginate beads (beads), against Aedes aegypti (Ae. aegypti) mosquitoes. Chemical analysis of O. gratissimum oil obtained by hydrodistillation, using gas chromatography-mass spectroscopy techniques, presented eugenol (67.38%) and Z-β-ocimene (14.95 %) as major constituents. Good characteristics of beads were obtained by the orifice-ionic gelation method with calcium chloride as hardening agent and Tween®20 as emulsifier. The beads exhibited a good spherical shape and good hardness and flexibility with an average size of 1.49 ± 1.36 mm. The oil content, the yield percentage, and the entrapping efficiency were also examined. The beads (formulation code, F2) could prolong the essential oil release until the 10th d. This beads provided a remarkably longer oviposition deterrence activity against gravid Ae. aegypti with high percentage for 27 d, whereas free O. gratissimum oil showed a short period of time (8 d) in this activity. The stability study showed the stability of oil content and its compositions in storage condition. These results are very affordable approaches to control the dengue fever.