ANTIBACTERIAL AND ANTIOXIDANT ACTIVITIES OF ESSENTIAL OILS FROM LEAVES OF SEVEN EUCALYPTUS SPECIES GROWN IN PAKISTAN

The chemical composition of essential oils from leaves of seven Eucalyptus species, viz., Eucalyptus crebra; Eucalyptus kitsoniana; Eucalyptus melanophloia; Eucalyptus microtheca; Eucalyptus pruinosa; Eucalyptus rudis and Eucalyptus tereticornis (Pakistan) was analysed by GC-FID and GC-MS. The main component of E. crebra, E. microtheca and E. rudis essential oils was 1,8-cineole (31.6-49.7 %). Eucalyptus melanophloia and E. tereticornis contained p-cymene (41.8-58.1 %) as a major component while E. kitsoniana and E. pruinosa essential oils were dominated by a-pinene (25.8-31.4 %). In vitro antimicrobial activity of the essential oils was studied by agar well diffusion method at concentration range 8-2501 mu g/ml. The Eucalyptus oils inhibited the growth of Gram positive bacteria (Bacillus spizizenii, Staphylococcus aureus) significantly with zones of inhibition (IZ) ranging from 15.3-46.0 mm. The studied oil demonstrated moderate inhibitory effect against Gram negative bacteria (Enterobacter aerogenes, Escherichia coli, Salmonella enterica, Klebsiella pneumoniae and Pseudomonas aeruginosa) with IZ (0.0-22.2 mm). The oils exhibited bactericidal effects at 8 mu g/ml in agreement with minimum inhibitory concentration against all tested foodborne pathogens except Pseudomonas aeruginosa (8-250 mu g/ml). Time kill assay based on four weeks studies authenticated the potency of oils as food preservatives. Antioxidant assays (free radical scavenging activity and ferric reducing power test) demonstrated good activity of the oils. The evaluated essential oils exhibited strong antioxidant activity by 45.3-75.1 % inhibition of 2, 2'-diphenyl-l-picrylhydrazyl radical (DPPH) and ferric reducing power (1.04 +/- 0.05-1.95 +/- 0.04 %) at 100 mu g/ml. The good antioxidant and antibacterial activities of Eucalyptus essential oils validate their potential use as food preservatives.