Chemical characterization, antioxidant and antifungal activity of essential oil from Eucalyptus tereticornis

Eucalyptus tereticornis (red gum tree, family Myrtaceae), is extensively grown throughout India under various afforestation programmes, primarily for the supply of wood, timber. Unlike, other species of eucalypt known for the presence of volatile oil in their foliage, not much information is available regarding the volatile oils of E. tereticornis and their bioactivity. We extracted and characterized the essential oils from its mature (adult) leaves and determined its antioxidant and antifungal activity against phytopathogenic fungi. Gas chromatography mass spectrometry (GC/GC-MS) analyses revealed that the oil, in general, was monoterpenoid in nature with 37 constituents. Among these, alpha-pinene was the major component (similar to 30%) followed by 1,8-cineole (similar to 22%). We determined the antioxidant activity of the oil (25-200 mu g/ml) in terms of free radical scavenging (as DPPH activity), and H2O2 quenching. Further, the essential oil (0.5 - 10.0 ppm) exhibited a strong fungitoxicity against three phytopathogenic fungi viz. Fusarium oxysporum, Rhizoctonia solani and Heminthosporium oryzae. The antioxidant and fungitoxicity of the oil was compared to commercially used antioxidant (BHT) and fungicide mancozeb, respectively. The study concludes that essential oil from foliage of E. tereticornis possesses a strong antioxidant and antifungal activity worth exploitation.