Title: Evaluation of the antimicrobial and antioxidant activities of essential oils, extracts and their main components from oregano from Madeira Island, Portugal
Abstract: Origanum vulgare subsp. virens growing wild in Madeira Island, Portugal was studied within the ongoing investigations on polymorphic Lamiaceae species. The antimicrobial activity of the essential oils and n-hexane extracts of origanum was determined against 10 strains of bacteria and yeasts, found as human pathogenic or food spoilage microorganisms. The essential oils, n-hexane extracts and isolated compounds showed moderately activity, compared to standard antibiotics, inhibiting all tested bacteria except Pseudomonas aeruginosa. The most sensitive microorganism was Mycobacterium smegmatis, reaching MIC = 25 μg mL−1. The results obtained suggest a potential application of these oils in preventing the human pathogenic and food spoilage due to microorganism's growth. The essential oils and n-hexane extracts have greater RSC than polar extracts, probably due to the high contents in thymol, which demonstrated the highest activity in the DPPH assay. All studied origanum samples showed a large content in non-esterified 1-hexacosanol, C26H54O, accumulated mainly in bracts and flowers.