A study on the efficiency of natural antioxidants from agri-food industry wastes as long-term antioxidants for polypropylene (PP) is reported. Special attention is paid to the usage of vegetal wastes as a source of natural antioxidants such as alternatives to synthetic long-term antioxidants. The potential of the lignin-derived fractions generated during autoydrolysis processing of lignocellulosic agricultural, forestal, and food wastes was assessed. The measurements of oxidation induction time were used for obtaining information on long-term antioxidant effectiveness, showing the protective effect of natural extracts. The protective effect was improved in combinations of natural extracts with 0.1% and 0.2% of Irgafos 168 (short-term antioxidant) besides a synergistic effect was exhibited when 0.4% of Irgafos 168 is added. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012