CHARACTERIZATION OF ANTIOXIDANT ACTIVITY AND TOTAL PHENOLIC COMPOUND CONTENT OF BIRCH OUTER BARK EXTRACTS USING MICRO PLATE ASSAY

In modern plants, 2.7 to 2.8 m 3 of solid volume veneer blocks are consumed to produce 1 m 3 of plywood. After the hydrothermal treatment and debarking of blocks, waste bark is obtained, which makes up 12.5% of the wood mass, while 16-20% of bark is composed of birch outer bark (BOB). Recalculating, BOB makes up 2.0-3.4% of the veneer log mass. Bark is currently burned in boiler houses that is not rational. BOB contains large amount of valuable extractives (up to 34% from o.d. BOB) consisting of various secondary metabolites such as terpenes, flavonoids, hydrocarbons, polyphenols, tannins etc. BOB extractives exhibit antioxidant properties as well as wound-healing and anti-inflammatory activity. The objective of this paper was to compare amount of total phenolic content (TPC) and antiradical activity (ARA) in ethanol extracts from silver birch ( Betula pendula Roth.) outer bark using micro plate assay. Among 11 fractions, fraction of average BOB had the highest DPPH free radical scavenging activity with IC50 of 39.28 μg/mL and the highest TPC 7.42 ± 0.52 g GAE/100 g of dry extract.