Biotoxicity of essential oil of <i>Eucalyptus citriodora</i> Hook (Myrtaceae) to dust mites.

Abstract

<h4>Introduction</h4>Dust mites are a prevalent indoor allergen contributing to respiratory diseases like allergic rhinitis and asthma. <i>Eucalyptus citriodora</i> essential oil, known for its balsamic odor and repellent effects on various pests, has been scantily investigated for its impacts on dust mites.<h4>Methods</h4>The chemical composition of the essential oil and its head-space extracted from <i>E. citriodora</i> was determined using gas chromatography-mass spectrometry (GC-MS). The toxicity of the oil and its compounds were assessed through contact-fumigant and vapor-phase mortality bioassays. Repellent effects were evaluated using a fabric-contact assay. Data were analyzed using probit regression to determine LC₅₀ values.<h4>Results</h4>The essential oil contained seven main compounds, and citronellal, citronellol and citronellyl acetate were the most abundant in the oil's volatile, accounting fora total of 88.22%. Citronellal exhibited the highest toxicity, and the essential oil itself showed strong toxicity with the LC₅₀ of 63.94 and 84.53 μL/cm against <i>Dermatophagoides pteronyssinus</i>, 60.72 and 75.88 μL/cm against <i>Dermatophagoides farinae</i>, respectively. In vapor-phase assays, citronellal and ethyl phenylacetate caused 100% mortality.<h4>Discussion</h4>Citronellol had the highest repellent effect, and the essential oil, 1,8-cineole, and citronellyl acetate also showed significant repellency rates. <i>E. citriodora</i> essential oil and its compounds particularly citronellal and citronellol, showed high potential for effective dust mite control due to their natural origin, strong toxicity and repellency impacts. Thus, <i>E. citriodora</i> essential oil is a natural, eco-friendly alternative to synthetic acaricides, providing a scientific basis for the control of indoor dust mite allergies.