High quality bergamot oil from Greece: Chemical analysis using chiral gas chromatography and larvicidal activity against the West Nile virus vector

Abstract

The essential oils contained in the rind of the fruit and the leaves of bergamot from Greece (Citrus aurantium subsp. bergamia) were studied. The bergamot trees in question were cultivated on Kefalonia Island. The plant material (leaves and fruits in different stages of maturity) was collected between December and March for a two year period. The rind of the fruit was separated manually and the essential oil was obtained either by cold pressing or by hydrodistillation. The maximum yield calculated on a wet weight of fresh rinds basis was 1.8%. The essential oils were first analyzed by GC-MS with a DB-5 column and then with a β-Dex™ enantiomeric column. The main constituent of the cold pressed essential oil of the rind was (-)-linalyl acetate with optical purity >99.9%. Other important constituents were (-)-linalool, (+)-limonene and γ-terpinene. The best value of linalool/linalyl acetate ratio was 0.38 and the maximum sum of linalool+linalyl acetate was found to be 55.8%. The larvacidal activities of the obtained essential oils and the compounds (±)-linalyl acetate, (±)-linalool and (-)-linalool were evaluated against larvae of the mosquito species Culex pipiens (Diptera: Culicidae), the West Nile virus vector, under laboratory conditions. The cold pressed essential oil showed an LC50 value of 58 mg/L, while the LC50 value of the corresponding essential oil obtained by hydrostillation was 106 mg/L. The essential oil of the leaves presented similar larvicidal toxicity with the cold pressed oil of the rind (LC50=68 mg/L).