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

Abstract

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 β-pinene (22.55%), α-pinene (22.50%), 1,8-cineole (19.84%), limonene (5.62%), β-fenchol (3.10%), α-phellandrene (2.90%), α-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 (Rf = 0.27) and a2 (Rf = 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 μg and 10 μg, respectively using bioautography assay. Components corresponding to a1 and a2 were determined as β-fenchol (oxygenated monoterpene) and α-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, β-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 α-fenchol, 4-terpineol and carvacrol were the main components.