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

Abstract

This study was aimed at investigating the oviposition deterrent activity ofOcimum gratissimum(L.) essential oil (O. gratissimumoil) and its product,Ocimum gratissimum(L.)- alginate beads (beads), againstAedes aegypti(Ae. aegypti) mosquitoes. Chemical analysis ofO. gratissimumoil 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 the10thd. This beads provided a remarkably longer oviposition deterrence activity against gravidAe. aegyptiwith high percentage for 27 d, whereas freeO. gratissimumoil 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.