Qualitatively prepared dry extracts are advantaged over conventional fluid extracts. Extracts of Betula pendula Roth leaves possess mild diuretic effects and anti-inflammatory activity. In this work, the spray-drying and lyophilisation processes were evaluated for producing dry extracts of birch leaves. The purpose was to identify the best drying method that provides the highest content of phenolic compounds and possesses greatest antioxidant activity. Predominant compounds hyperoside and chlorogenic acid were chosen as markers for the quantitative control of phenolic compounds. Their determined amounts in hydroalcoholic birch leaf extract were 15.85 and 8.77 mg/g of dry residue, respectively. Insignificant differences were determined in spray- and freeze-dried extracts. In the antioxidant profile, hyperoside (28.9 μmol TE/g dw) and chlorogenic acid (22.8 μmol TE/g dw) possessed strongest ferric-reducing activity. Also, no significant differences of antioxidant activity were determined in the spray- and freeze-dried extracts.
Keywords: Betula pendula; FRAP; antioxidant; birch; dry extract; phenolic.