Determination of stability and shelf life in different propolis extracts

The increasing demand for natural products and biotechnological activities from bees facilitate their widespread use in food preservation and beneficial effects on humans. Propolis, a bee product, is the material used by bees to protect their hives. It is a glue-like substance composed of plant resins, bee waxes and pollens. Nowadays propolis is widely used by dissolving it in solvents such as ethyl alcohol, water, propylene glycol, glycerol, olive oil, and its biological activities differ in each solvent. This thesis study aimed determine the biological active properties of these extracts, which are frequently used in apitherapy applications, and to carry out shelf life studies. The biological activities of the pure water, etyhl alcohol, monopropylene glycol (MPG), polyethylene glycol (PEG) and glycerol extracts were evaluated by determining their antioxidant potential (2,2-diphenyl-1-picrylhydrazyl radical (DPPH•); iron reducing antioxidant potency (FRAP) method). The antimicrobial activity of the extracts were demonstrated by agar well diffusion method against gram-positive (Staphylococcus aureus, Staphylococcus epidermidis, Bacillus cereus) and gram-negative (Escherichia coli) bacteria and yeast (Candida albicans) strains. The total phenolic substance and flavonoid contents were determined, and the phenolic substance profile was determined by reversed-phase high performance liquid chromatography photodiode array detector (RP-HPLC-PDA). After the initial values were determined, the tests were repeated by applying accelerated stabilization test to the extracts. The initial values were compared with the values after accelerated stability. As a result of the comparison, it was observed that there was a statistically significant decrease in the phenolic substance content, antioxidant capacity and flavonoid amount in general (p≤0.05). In terms of antimicrobial activity, at the end of the shelf life ethanol extract was found to be effective against all gram-positive, gram-negative and yeast strains. It was concluded that ethanol extract may be advantageous in terms of shelf life length and quality, while polyethylene glycol extracts can also be evaluated.