In-vitro Assessment of Antifungal and Antioxidant Activities of Olive Leaves and Fruits at Various Extraction Conditions

Abstract   Background and Objective: Nowadays, there is a growing interest for use of plant-based products such as extracts in various industrial sectors. Therefore, optimization of conditions for ideal extraction of bioactive compounds is highly important. Olive leaves and fruits include biophenols, which can be used as natural antimicrobial and antioxidant agents. Therefore, extraction of these bioactive compounds can create value-added products, which can be used as natural preservatives in food industries. The aim of this study was to investigate effects of various extraction parameters (type of solvent, solvent volume, temperature, time and pH) on in-vitro antioxidant and antifungal activities of Iranian olive leaf and fruit extracts against five Candida species. Material and Methods: Olive fruit and leaf extracts were achieved using maceration method at various extraction conditions. Antioxidant activity of the prepared extracts was assessed by cupric reducing antioxidant capacity method. The phenolic profile in olive leaf extract was assessed using high performance liquid chromatography. Antifungal activity of the olive leaf extract was assessed using disk diffusion method and minimum inhibitory concentration and minimum fungicidal concentration values. Results and Conclusion: Results showed that the highest antioxidant activity was recorded in olive leaf extract prepared by 100 ml of 96% ethanol at pH 7 and 80 °C for 6 h. Moreover, HPLC analysis of the ethanolic olive leaf extract showed that oleuropein was the major compound of the extract. Antioxidant activity of the olive leaf extract was higher than that of the fruit extract in various conditions. Regarding antifungal activity, the olive leaf extract showed a higher activity, compared to olive fruit extract at all concentrations. In olive leaf extract, the highest (62.5 µg ml-1) and the lowest minimum fungicidal concentration (15.6 µg.ml-1) values were reported for Candida tropicalis and Candida albicans, respectively. The minimum fungicidal concentration of the olive leaf extract was 250 µg ml-1 for Candida albicans, Candida parapsilosis, Candida glabrata and Candida krusei and 500 µg ml-1 for Candida tropicalis. It can be concluded that olive leaf extract is a source of antioxidant and antifungal substances with potential uses in food industries. Conflict of interest: The authors declare no conflict of interest