Abstract:
Although natural phenolic and flavonoid compounds have demonstrated a broad spectrum of biological activities, there are few studies focused on the enzyme inhibitory activity of these compounds. Honey, olive leaf extract, and propolis are rich sources of phenolic and flavonoid compounds, and could be reasonably expected to inhibit a range of enzymes. The enzymes studied were selected as myeloperoxidase, tyrosinase, and glucose oxidase. Myeloperoxidase is expressed in neutrophil cells in response to tissue inflammation, and is a suitable target for inhibition in oral spray designed to alleviate the symptoms of throat inflammation; tyrosinase has important role for protection from direct UV damage, but overexpression may lead to skin darkening and various other skin conditions, and consequently is a target for cosmetic skin whitening products; and glucose oxidase is a well-researched enzyme, which has a range of important applications including glucose detection and used as a food additive. The compounds present in honey, olive leaf extracts and propolis inhibited all three enzymes, the most sensitive enzyme was myeloperoxidase, followed by glucose oxidase, and tyrosinase was the most resistant to inhibition. All examined products displayed greater inhibition on myeloperoxidase than tyrosinase, generally 10 to 100 times more concentrated inhibitors were required to cause the same level of inhibition on tyrosinase than myeloperoxidase. The study have found the 3,4-dihydroxyphenol structure present in most phenolic compounds in olive leaf extract displayed high level of inhibition on myeloperoxidase and glucose oxidase, but the structure was not very effective against tyrosinase; manuka honey exhibited elevated levels of myeloperoxidase inhibition relative to the other honey types, and this may be related to the presence of leptosin; and propolis displayed the greatest inhibition against tyrosinase among all examined products. This study provided information on the pattern and effectiveness of inhibition from natural products, and identified candidate inhibitors for each of the examined enzyme. The potential for developing into commercial anti-inflammatory and skin-whitening products is discussed in terms of theoretical effectiveness and possible improvements.