Phenolic Profile, Antioxidant Capacities and Enzymatic Inhibitory Activities of Propolis from Different Geographical Areas: Needs for Analytical Harmonization

Propolis is a resinous vegetal exudate modified by bees, and is interesting as a preservative and potentially functional product. This work dealt with studying the common phenolic profiles and antioxidant capacities of 13 bee propolis from different geographical areas. Both hyaluronidase and angiotensin converting enzyme (ACE) inhibitory activities were also assessed and related when possible with particular phenolic compounds. High performance liquid chromatography-ultraviolet detection (HPLC-UV) analysis showed that every propolis contained p-coumaric acid (1.2-12.2 mg/g) and ferulic acid (0.3-11.0 mg/g). Pinocembrin, catechin, and caffeic acid phenethyl ester (CAPE) plus galangin were the main flavonoids. Antioxidant activities were higher than 280 µmol trolox/g for trolox equivalent antioxidant capacity (TEAC), 0.099 mmol uric acid/g for radical-scavenging effect on hydroxyl radicals, and 0.19 mg/mL for half maximal inhibitory concentration (IC₅₀) of antioxidant activity against superoxide anion radical. Working with solutions of 10 mg/mL propolis, hyaluronidase inhibitory activity ranged between 0% and 68.20%, being correlated to ferulic acid content. ACE inhibitory effect determined by HPLC was higher than 78%, being correlated with catechin and p-coumaric acid. Therefore, propolis could be useful for food, pharmaceutical, and cosmetic companies, also helping to reduce risk factors for diseases related to oxidative damage, inflammatory processes, and hypertension. This research also highlights the necessity for harmonized analysis methods and the expression of results for propolis.