Biologically active compounds from different herbs used as additives in honeybee feeding.

Abstract

Different herb preparations (alcoholic extracts and water infusions) were tested for total phenol and flavonoid content and antioxidant properties. The Folin Ciocalteu test was used to determine the phenol content, Kim method with some modifications was used for total flavonoid content and 1,1-diphenyl-2-picryl-hydrazyl (DPPH) assay for radical scavenging activity. Sugar profile for herb preparations was determined by HPLC with refractive index detection. The highest content of total polyphenols was registered in fresh nettle infusion (689 mgGAE/100g DW sample), followed by PROTOFIL (570 mgGAE), infusion of Echinacea (570 mgGAE), thyme extract (555 mgGAE), Echinacea extract (549 mgGAE), thyme infuzion (530 mgGAE), dry nettle infuzion (510 mgGAE) and fresh nettle extract (426,7 mgGAE). Smaller quantities were registered for dry nettle extract and fresh juice of onion. Regarding the flavonoid content, higher quantities were registered for fresh nettle infusion (668 mgQE in 100 g DW sample), followed by dry nettle infusion (482 mgQE), PROTOFIL (378,9 mgQE), fresh nettle extract (368 mgQE) and Echinacea infusion (326 mgQE). Smaller quantities were obtained for Echinacea, thyme, dry nettle extract and thyme infusion (183–123 mgQE). Antioxidant activity was not correlated with total polyphenols and flavonoid content, the highest antioxidant activity being registered in fresh juice of garlic and onion (95,1% and 84,85% inhibition of DPPH radical). High percentages of inhibition present the extracts and infusions of every analised plants (50,7% - 75,47%), exception was registered in onion and garlic extracts, which inhibit the DPPH radical in proportion of 29,84% and 20,98% respectively