Soda lignin, dioxane lignin and milled lignin were isolated from Alfa grass (Stipa tenacissima L.). The physico-chemical characterization of three different lignins: one industrial lignin precipitated from soda spent liquor and two lignin preparations isolated under laboratory conditions from Alfa grass (also know as Esparta grass) was performed. The structures of lignins were studied by three non-destructive (FT-IR, solid state (13)C NMR and UV/visible spectroscopy) and two destructive (nitrobenzene oxidation and thermogravimetric analysis) methods. Elemental analysis and the methoxyl content determination were performed in order to determine the C(9) formulae for the studied lignins. The total antioxidant capacity of the studied lignins has been determined and compared to commercial antioxidants commonly used in thermoplastic industry. (C) 2009 Elsevier Ltd. All rights reserved.