Lignin constitutes up to one-third of the material found in plant cell walls and is considered the second most abundant natural polymer in the world. Despite unique characteristics of lignin, it is mostly used for low-value commercial applications. In this study, lignin obtained after alkaline treatment of steam-exploded sugarcane bagasse was submitted to an acidification process. The soluble fractions produced at different pH values were comprehensively characterized and in vitro antioxidant capacity against reactive oxygen (ROO and H2O2) and nitrogen (ONOO-) species was evaluated. The soluble fraction obtained at pH 2 exhibited the highest scavenging capacities against all species tested (10.2±0.7mmol Trolox equivalent g-1 for ROO, IC30=14.9μgmL-1 for H2O2 and IC50 =2.3μgmL-1 for ONOO-) and the lowest polydispersity value (1.2) compared to others fractions. 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