Comparative analysis of antioxidant and antibacterial activities of leaf and zest essential oils from "Citrus limon”

This work is part of the study of the antibacterial and antioxidant activity of Algerian aromatic and medicinal plants. We conducted a study on a plant widely used by the local population, Citrus limon, an aromatic plant from the Ghardaïa region. Essential oils were extracted from Citrus limon (zest and leaves) using hydrodistillation, yielding 1.12% for the zest and 0.71% for the leaves. The essential oils were analyzed using GC/MS, identifying 35 constituents in the leaf oils, with 19.41% L-Limonene and 15.02% Nerol acetate, and 25 constituents in the zest oils, with 45.62% L-Limonene, 9.40 Beta-Pinene and 8.3% 3-Carene as major compounds. The antioxidant activity of the essential oils was evaluated using three methods. The first method was the DPPH free radical scavenging test, where the zest showed an IC50 of 135.678 mg/mL, higher than that of the leaf essential oil (IC50 of 34.238 mg/mL). The second method, potassium ferricyanide reduction (FRAP), showed that the essential oils of the leaves had an antioxidant activity of EC50 = 63.3773 mg/mL, and the zest showed EC50 = 200.875 mg/mL. The third method, ammonium phosphomolybdate, based on molybdate reduction (TAC), gave antioxidant activities for the leaves and zest, respectively, of EC50 = 1.5722 mg/mL and EC50 = 1.9604 mg/mL. The antibacterial activity was tested against six reference bacterial strains, with Klebsiella pneumoniae being the most sensitive to both essential oils, showing inhibition zones of 48 mm for the leaf oil and 40 mm for the zest oil. According to the obtained results, the essential oils appear to exhibit excellent antioxidant and antibacterial activity.