Chemical composition, antioxidant activity and inhibitory effects of essential oil of Eucalyptus teretecornis grown in north-western Himalaya against Alternaria alternata

The essential oil obtained from fresh leaves of Eucalyptus teretecornis (family Myrtaceae) was analysed by gas chromatography/mass spectrometry (GC/MS). Twenty eight compounds were identified and ??-pinene (22.55%), ??-pinene (22.50%), 1,8-cineole (19.84%), limonene (5.62%), ??-fenchol (3.10%), ??-phellandrene (2.90%), ??-eudesmol (2.66%) and 4-(2-methylcyclohex-1-enyl)-but-2-enal (2.34%) were the main components. The antifungal activity of the essential oil was assayed against Alternaria alternata using bioautography. Two main bioactive components namely a₁ (R _f ?=?0.27) and a₂ (R _f ?=?0.33) were observed that produced inhibition zone of 4?mm and 8?mm in diameter respectively. The minimum inhibitory amount (MIA) of a₁ and a₂ against A. alternata was determined as 28???g and 10???g, respectively using bioautography assay. Components corresponding to a₁ and a₂ were determined as ??-fenchol (oxygenated monoterpene) and ??-eudesmol (oxygenated sesquiterpene) respectively using GC/MS analysis. The antioxidant activity of the essential oil and its bioactive fraction was evaluated by DPPH radical scavenging assay, ??-carotene/linoleic acid bleaching assay, reducing power assay and metal chelating assay. In addition fraction of the essential oil that showed antioxidant activity was analyzed using GC/MS and ??-fenchol, 4-terpineol and carvacrol were the main components.