Antimicrobial, Antiradical Capacity and Chemical Analysis of Conyza incana Essential Oil Extracted from Aerial Parts

Abstract

This study was designed to examine the chemical composition, antimicrobial and antioxidant activity of the essential oil extracted from the Conyza incana plant from Yemen. The essential oil was obtained from the aerial parts of the plant using a Clevenger apparatus by hydrodistillation for 4 hours. Seven compounds were identified using GC-MS analysis of the oil representing 96.0% of the oil. The identified main components are 3-hydroxy-4-methoxy cinammic acid (72.6%), thymol acetate (11.3%), thymol (3.4%), palmitic acid (3.0%) and geranylisobutrate (2.9%). Antibacterial activity of the essential oil was evaluated in vitro against four bacterial strains of which two are Gram-positive (Staphylococcus aureus and Bacillus subtilis), two are Gramnegative (Escherichia coli, Pseudomonas aeruginosa). The antifungal activity was examined on Candida albicans as common fungal strain. The antimicrobial capacity of the oil was determined using disc diffusion method and through measuring the diameter of the zone of complete inhibition and MIC values. The extracted oil showed pronounced fungal activity and bacterial activity against Gram-positive bacteria, while negative test was shown against the Gram-negative bacteria strains. The results indicated highest potency against C. albicans with MIC value of 40 μg/mL, while a substantial efficiency was indicated for B. subtilus and S. aureus Grampositive bacterial strains with MIC(s) values of 150 μg/mL and 234 μg/mL respectively. The oil showed strong in vitro antioxidant activity in 2,2-diphenyl-1-picrylhydrazyl (DPPH)-assay with IC₅₀ value of 5.2 μg/mL.

Key words:

• Conyza incana
• essential oil
• chemical composition
• antimicrobial activity
• antiradical capacity