Biological activity of Satureja montana L. ethanolic extracts and their effect on oxidative stability of cold pressed sunflower oil in long-term storage conditions

Abstract

Medicinal plants represent a rich source of phytochemicals, many of which possess diverse biological activities, including antioxidants. The objectives of this study were to assess antioxidant, antibacterial and anticancer activities of savory (Satureja montana L.) ethanolic extracts and to monitor the changes of oxidative status during long-term storage conditions of the cold pressed sunflower oil (CPSU) with the addition of extracts at various concentrations. Extracts were obtained by Soxhlet extraction and ultrasound-assisted maceration, using 70% and 96% ethanol. Antioxidant activity was evaluated by DPPH and ꞵ-carotene bleaching assays. In both assays, extracts showed remarkable antioxidative properties which were equal or stronger than those of BHT and BHA. Also, regardless of the extraction method and assay applied, the 70% ethanol extracts proved to be more potent than 96% ethanol ones. For antibacterial activity assay, minimal inhibitory concentrations (MIC) were obtained by the microdilution method. Tested Gram-negative bacteria (E. coli and S. typhimurium) were more resistant than Gram-positive (S. aureus and L. monocytogenes) with MIC=1,25–10 μg/mL and 0,0781–0,3125 μg/mL, respectively. As results obtained by MTT test, the extracts didn’t show anticancer activity (IC50>100 μg/L) against tested tumor cell lines: PC-3 (prostate), HT-29 (colon) and HeLa (cervix) in the applied concentration range. For investigation of oxidative stability of CPSU, only 70% ethanol extracts were used. Samples of CPSU (with addition of 250, 500 and 1000 ppm of extracts), as well as control samples (with addition of 200 ppm of BHT and CPSU without any additives), were stored at room temperature for six months. In order to determine the level of oxidative changes, samples were analyzed for peroxide, anisidine value and conjugated dienes and trienes. Based on obtained results, it can be concluded that savory extracts are powerful natural antioxidants that can delay the oxidative deterioration of CPSU and whose effectiveness is comparable to the synthetic antioxidant BHT.