This research has been done to evaluate the kinetic of DPPH (2,2 diphenyl-1-picryl-hidrazil) radical scavenge by some tropical fruits (acerola - Malpighia emarginata), açaí - Euterpe oleracea, mangaba - Hancornia speciosa and uvaia - Eugenia pyriformis) extracts. The fruits were harvested in the Ceará and Piauí States, Brazil. The capacity to reduce 50% the DPPH (EC50) concentration by different fruit extracts was evaluated. The absorbance at 515 nm decreased until stabilization was reached. Reaction stabilized at 10 minutes for acerola, 30 minutes for mangaba, and 120 minutes for açaí and uvaia. Acerola had the highest antioxidant activity (AA) (670 g/g DPPH), followed by uvaia (3246 g/g DPPH), mangaba (3385 g/g DPPH) and açaí (3778 g/g DPPH). Antioxidant potential of these fruits could be attributed to different compounds evaluated, such as vitamin C (1357 mg/100 g) and phenolics (1063 mg/100 g) in acerola.