Lignin as natural radical scavenger. Study of the antioxidant capacity apple tree pruning lignin obtained by different methods

In the present work, the antioxidant activity of lignin obtained from apple tree pruning was studied. Different procedures were used in order to fractionate the raw material and extract the lignin (autohydrolysis, organosolv and soda processes) and several operation conditions, techniques and methodologies were applied (ultrafiltration and differential precipitation). The obtained lignin samples were characterized by ATR-IR spectroscopy and TGA techniques. Further analyses were done in order to determinate main components and total phenolic contents (Folin-Ciocalteau method). The antioxidant activity results (evaluated by ABTS assay) showed that: (1) the lignin obtaining process highly affects this property and (2) that the antiradical behaviour of lignin could reach similar efficiency than two powerful natural antioxidants, gallic acid and catechin, and a commercial one, Trolox®.