Antimicrobial and Antioxidant Activities of the Essential Oils of Some Aromatic Medicinal Plants (Pulicaria inuloides-Asteraceae and Ocimum forskolei-Lamiaceae)

Purpose: To determine the antimicrobial and antioxidant activities of Pulicaria inuloides and Ocimum forskolei essential oils. Methods: Steam distillation of the aerial parts of P. inuloides and O. forskolei was performed using a Clevenger apparatus. Essential oils were analyzed by gas chromatography–mass spectrometry. Total phenolic content and antioxidant activities were determined by 2,2-diphenyl-1,1-picrylhydrazyl (DPPH) and β-carotene bleaching assays. Disc diffusion and microtiter broth microdilution assays were employed to determine antimicrobial activity. Results: The chemical compounds in P. inuloides essential oil include 2-cyclohexen-1-one, 2-methyl-5(1-methyl) (55.1 %) and benzene, methyl(20.6 %). The major components identified in O. forskolei essential oil included bicyclo [3.1.1] hept-2-ene,2, (22.4 %) and naphthalene 1,2,3,4,4a,5,6, (19.3 %). P. inuloides showed a higher total phenol content than O. forskolei (144 ± 5.32 vs. 54.6 ± 30 mg GAE/g extract), higher antioxidant activity (92.92 ± 0.10 % vs. 26.76 ± 0.11 % scavenging activity; IC50, 4.5 ± 0.05 vs. 73.03 ± 0.05) and β-carotene bleaching (90.77 ± 0.21 % vs. 41.03 ± 6.35 % inhibition). P. inuloides essential oil inhibited all tested microorganisms except Salmonella typhimurium and Shigella dysenteriae with a minimum inhibitory concentration (MIC) of 3.0 μg/mL against Escherichia coli. O. forskolei essential oil inhibited only Candida albicans. Conclusion: P. inuloides essential oil possesses significant antioxidant and antimicrobial activities.