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 beta-pinene (22.55%), alpha-pinene (22.50%), 1,8-cineole (19.84%), limonene (5.62%), beta-fenchol (3.10%), alpha-phellandrene (2.90%), alpha-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 a(1) (R (f) = 0.27) and a(2) (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 a(1) and a(2) against A. alternata was determined as 28 mu g and 10 mu g, respectively using bioautography assay. Components corresponding to a(1) and a(2) were determined as beta-fenchol (oxygenated monoterpene) and alpha-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, beta-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 alpha-fenchol, 4-terpineol and carvacrol were the main components.