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

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 Gram-negative (Escherichia colt, 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 Grain-negative bacteria strains. The results indicated highest potency against C. albicans with MIC value of 40 mu g/mL, while a substantial efficiency was indicated for B. subtilus and S. aureus Gram-positive bacterial strains with MIC(s) values of 150 mu g/mL and 234 mu g/mL respectively. The oil showed strong in vitro antioxidant activity in 2,2-diphenyl-1-piciylhydrazyl (DPPH)-assay with IC50 value of 5.2 mu g/mL.