Analysis by GC (Ir), GC/MS and mosquito repellent effect of essential oils against Anopheles gambiae: Case of stem bark of Sterculia tragacantha Lindl (Sterculiaceae) from Cte dIvoire

The objectives of this study were to determine the chemical composition and to evaluate the mosquito repellent property of essential oils extracted from the bark of the stem of Sterculia tragacantha Lindl on Anopheles gambiae, vector of malaria. The essential oil of the stem bark of S. tragacantha Lindl is extracted by hydrodistillation and their chemical compositions were identified by GC (Ir) and GC-MS. This oil has been tested on sensitive « kisumu » strains of A. gambiae adults, according to the World Health Organization (WHO) guidelines for laboratory testing of the repellency of chemicals. The extraction yield obtained from this oil is 0.12%. By means of GC (Ir) and GC-MS, 29 compounds representing 88.4% of the HE were identified. β-elemol (40.54%) is the major compound of this oil. It is rich in sesquiterpenes (79.47%) with a predominance of oxygenated sesquiterpenes (55.86%). As for the oxygenated monoterpenes, they represent 8.93%. The repellency test against adult female Anopheles, revealed that the EO of S. tragacantha (10%) has repellent properties against mosquitoes. Indeed, it induces an average reduction of 98.2% of the blood meal (TIRS) of mosquitoes on guinea pigs with a complete protection time (CPT) of 5 h compared to 3 h 30 min for the natural reference substance (Cymbopogon citratus). In view of its extractive value and prolonged repellent properties, S. tragacantha could be a good alternative in the vector borne diseases control if used as natural repellents for skin application. Key words: Anopheles gambiae, Sterculia tragacantha Lindl, essential oil, chemical composition, mosquito repellent.