Bioprospection for Repellent Effect of Natural Volatiles from Ocimum suave Willd Growing in Dar es Salaam, Tanzania against Anopheles Mosquitoes

Essential oil was extracted from Ocimum suave Willd leaves by water distillation and tested for repellency effectiveness against Anopheles gambiae adult mosquitoes. The percentage yield of the essential oil was 0.2%. Six concentrations of O. suave essential oil were applied on human skin of four volunteers, and the repellency effectiveness which was analyzed by PoloPlus (LeOra software version 1.0, 2002-2014), revealed promising RC50, RC75, RC90 and RC99 with their confidence limits as 0.1161 mg/cm2 (0.02067 - 0.1767 mg/cm2), 0.2823 mg/cm2 (0.22328 - 0.3654 mg/cm2), 0.4319 mg/cm2 (0.35226 - 0.58862 mg/cm2) and 0.98934 mg/cm2 (0.54731 - 0.99972 mg/cm2), respectively. O. suave essential oil exhibited high Anopheles mosquitos’ repellency effectiveness which merits further scientific attention for the development of natural repellents for the control of malaria and other mosquito borne diseases. These findings provides a scientific evidence and base for formulation for further mosquito repellency semi-field and field trials for the development of cheaper and affordable new mosquito repellent product(s) to meet human healthcare needs in the prevention and control of malaria and other mosquito transmitted infections.