Chemical composition and antioxidant activity of propolis, stored for more than 30 years

¹ University of Ruse “Angel Kanchev”, Branch-Razgrad, 7200 Razgrad, Bulgaria
² Agrobiotechnology Department, Agrobioinstitute, Agricultural Academy, 1164 Sofia, Bulgaria
³ Trakia University, Stara Zagora, Faculty of Technics and Technology, 8600 Yambol, Bulgaria
⁴ University of Ruse “Angel Kanchev”, Ruse, Bulgaria
⁵ Technical University of Sofia, Sliven Faculty and College, Sliven, Bulgaria
⁶ University of Food Technologies, Plovdiv, Bulgaria

^* Corresponding author: inikolova@uni-ruse.bg

Abstract

The propolis is a unique natural product that has been used by people in traditional medicine since ancient times. The aim of the present work is to determine the chemical composition and antioxidant activity of propolis, originating in 1993 from North-Eastern Bulgaria. The stored raw material has unchanged physical and chemical parameters - appearance, color, smell, content of mechanical impurities, wax content (19.6%), oxidizability index (16), active acidity (5.5), acid number (42.3 mg KOH/ g), ester number (152 mg KOH/g), boiling point (107°C). The data show that 40 components were identified, representing 99.14% of the total composition. The main components (over 2%) are: chrysin (18.37%), pinobanksin-3-etenoate (13.38%), pinobanksin-3-propanote (11.38%), pinobanksin-3-pentanoate (9.36%), squalene (6.36%), galangin (5.91%), dihydrochrysin (4.11%), pinobanksin-3-butenoate (2.94%), caffeic acid isomer 2 (2.74%), and (E)-sinapic acid (2.23%). Total phenols were 23.91 mg GAE/g. Antioxidant activity was determined by three methods: DPPH (1874.12 mMTE/g), FRAP (1039.18 mMTE/g), and ABTS (1539.52 mMTE/g). The antioxidant effect was monitored against goose fat and sunflower oil. The obtained data show maximally preserved physical parameters, chemical composition and antioxidant activity of the propolis sample stored for more than 30 years, which can be used in various products, an object of future research.