Acaricidal Activity of Essencial Oil from Ocimum gratissimum (Lamiaceae)

The house dust mite (Dematophagoides farina, Dermatophagoides pteronyssinus) is the greatest source of indoor allergens causing symptoms like: asthma, rhinitis and atopic dermatitis. Reducing exposure to these mite strains may alleviate clinical symptoms. One way to control indoor mite infestation is spraying acaricidal substances. Plants may be an alternative source for dust mite control once they contain a range of bioactive compounds. The objectives of this study were to verify the acaricidal activity of essential oil from Ocimum gratissimum and to find out it's most effective concentrations. The HPLC analysis showed eugenol to be the major constituent of the essential oil of O. gratissimum obtained from Southern Brazil (74.6%). The acaricidal activity was conducted using D. pteronyssinus cultures, in which the different concentrations of essential oil (100%, 75%, 50% and 25%) were directly applied in Petri dishes where a number of mites were placed in contact with the essential oil. The 95% ethanol and a commercial acaricidal solution were used as the negative and positive controls, respectively. Mite mortality was counted and used as comparison standard. Observations were carried out 24, 48, 72 and 96h after treatment and the number of dead mites was recorded. This study showed that the acaricidal activity of essencial oil extracted from O. gratissimum was most effective than the commercial acaricidal solution, suggesting that this essential oil could be a simple and alternative approach to control house dust mites.