Antimicrobial and Antiradical Potential of Four Agro-waste Citrus Peels Cultivars

The peels essential oil profiles of four new cultivars of Citrus species have been studied by GC-MS. The hydro-distilled oils yield was 0.1 - 1.0 % (w/w) with the highest yield in lime peel. Out of the forty-one characterized components, limonene was the major monoterpene hydrocarbons detected in all tested samples (89.3 +/- 0.0, 88.5 +/- 0.2, 78.1 +/- 0.3 and 53.0 +/- 0.0 % in grapefruit, orange, mandarin and lime oils, respectively). Both beta-pinene (16.0 +/- 0.5 %) and p-cymene (13.9 +/- 0.2%) were major in lime oil, while mandarin oil was rich with gamma-terpinene (9.0 +/- 0.5 %). Concentration of volatile oils constituents was calculated based on the average of 3 determination +/- standard deviation (S.D.). Three citrus oils; orange (100 mu l/ml), lime and grapefruit (250 mu l/ml), demonstrate relatively equivalent antiradical potential (inhibit 70 % of DPPH) as vitamin E (5.2 mu l/ml), having IC50 of 110 +/- 10.0, 142 +/- 2.5 and 155 +/- 5.0 mu l/ml, respectively. Lime peel essential oil showed the highest antimicrobial activity recording MIC90 of 14, 11, 12 and 9 mu l/ml against Staphylococcus aureus, E. coli, Candida albicans and Aspergillus flavus, respectively, while other tested oils demonstrated moderate antimicrobial activity against the eight pathogenic microorganisms.