Chemical composition and antioxidant and antibacterial properties of the essential oils extracted from Citrus sinensis peels by hydrodistillation and microwave methods

The present study is devoted to evaluate in vitro the chemical composition and the antioxidant and antibacterial properties of essential oils (Eo) extracted by hydrodistillation (HD) and microwave (MW) from the plant peels of Citrus sinensis . The extraction provided yields of 0.26% and 0.02%, respectively. The essential oils were analyzed by GC–MS whose major component is limonene that has a remarkable percentage (78.192% and 58.6%, respectively) for the essential oil extracted by HD and MW. The results of the antioxidant potential were noticeable in each of the essential oils with a higher priority to that extracted by hydrodistillation. The evaluation of the antioxidant power by the free radical scavenging method (DPPH) showed that the essential oils studied have good antioxidant activity, especially for the oil extracted by HD having presented an IC 50 of (13.07 ± 0.169) mg/ml, while BHT and ascorbic acid showed very potent and effective anti-free radical activity with IC 50 of the order of (19.54 ± 0.32) µg/ml and (1.17 ± 0.05) µg/ml respectively. According to the β-carotene/linoleic acid test, the oxidation of β-carotene was effectively inhibited by the two essential oils of Citrus sinensis peels with a percentage of inhibition of (56.46 ± 0.76) % and (31.39 ± 1.49) % respectively for HD and MW. Eo extracted by HD is more active than ascorbic acid (15.43%). In the antibacterial test, the activity was evaluated by the disc-diffusion method, the two types of sweet orange essential oils inhibited the growth of five bacterial strains out of six: The best activity was obtained against E. coli , Listeria monocytogenes , and Agrobacterium with a diameter of the zone of inhibition between 70 and 84 mm, with the exception of the strain of Bacillus subtilis , there is no zone of inhibition has been observed.