The present work aims to study the chemical composition and the antimicrobial and antioxidant properties of the essential oil of Senecio longiscapus (SLEO) leaves. SLEO was extracted from fresh leaves by hydrodistillation with a yield of 3%. It is clear, yellow, with a relative density of 0.7466 at 20°C, a refractive index of 1.4959, an optical rotation of +3°47, an acid number of 1.53 and an ester number of 12.49. Gas chromatography/mass spectrometry (GC/MS) analysis of the SLEO identified 17 components, representing more than 99.09% of the overall composition. The main component of SLEO was sabinene (53.28%) and elemicin (15%), β-pinene (9.85%), methyleugenol (5.58%), α-pinene (4.84%) and mircene (2.37%) were the major components. At 7.48 mg/disk, SLEO inhibited the growth of all germs tested including four GRAM (+) and five GRAM (-) bacteria and one yeast. The zones of inhibition (ZI) ranged from 12 mm (Yersinia enterolitica) to 40 mm (Bacillus subtilis). The antioxidant activity of SLEO by the DPPH method was IC50 = 4.601 µg/ml. When administered orally at doses as high as 5 g/kg body weight, SLEO was not toxic to mice. Its non-toxicity, antimicrobial and antioxidant activities could make SLEO an alternative in the treatment of infectious diseases.

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