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The variation in water availability can cause oxidative stress in plant species, which respond by producing antioxidants. Phenolic compounds are among the primary substances responsible for antioxidant activities. Thus, the goal of this study was to evaluate whether rainfall in a dry forest in Brazil affects the antioxidant activity and the major phenolic compounds in the stem bark of Anadenartthera colubrina, an economically important species from the semi-arid region of Brazil. Monthly samplings were performed over one year for the analysis of free radical sequestration by the DPPH method and for the identification and quantification of major phenolic compounds by HPLC. These data were correlated with each other and with the monthly rainfall. Three major phenolic compounds were identified, one of which was hyperin. The stem bark was highly capable of scavenging free radicals. The antioxidant activity and the production of the three compounds only slightly varied during the year, despite the significant differences among a few of the months studied. These differences are apparently unrelated to rainfall. No correlation was found between the major compounds and free radical scavenging. Our results suggest that rainfall was not the environmental factor responsible for monthly differences in the antioxidant activity of and concentrations of major phenolic compounds in the bark of A. colubrirta. (C) 2015 Elsevier B.V. All rights reserved.