Vapor-phase antifungal activity of Ocimum micranthum from Ecuadorian Amazon rainforest

Food grade chemicals are being investigated for their potential as preservative, in order to extend the spectrum of food preservation techniques. Studies on protective atmosphere for food packaging purposes is lately gaining more attention. The present study aimed at investigating the potential of Amazonian essential oils as preservative compounds in food industry. The antifungal activity of volatile organics components (VOCs) of Amazonian Ocimum micranthum essential oil was evaluated over three concentrations (10, 100, 500 mL/mL), through the vapor diffusion assay. The essential oil was tested against three fungi (Aspergillus niger, Cladosporium cladosporioides, Candida albicans); Thymus vulgaris essential oil has been used as positive control. PDA solidified medium was inoculated with fungal agar disks (0.5 mm) on the center of Petri dishes. The EO was diluted in DMSO to obtain dilutions. Then, 10mL of each concentration was distributed on 10 mm sterile paper filter disks, then placed on the Petri dish cover, in order to spread the EO vapors. The Petri dishes were carefully closed with sealing tape. Fungi were stored at 27±2°C during 7 days and then colony diameters were measured. A. niger was the most sensitive at the highest concentration of EO (500 mL/mL), showing inhibition of 67%. C. cladosporioides followed with 64% inhibition, while C. albicans did not show any. These results concerning the vapor-phase antifungal activity of O. micranthum have been reported for the first time.