The antioxidant capacities of ascorbic acid and phenolic compounds present in camu camu fruit were screened during ripening. Ascorbic acid decreased, and anthocyanin, flavonol and flavanol contents, and DPPH antioxidant capacity increased during ripening. Antioxidant compounds from camu camu were fractionated in two fractions: an ascorbic acid-rich fraction (F-I) and a phenolics-rich fraction (F-II). F-I was the major contributor to the DPPH antioxidant capacity (67.5-79.3%) and F-II played a minor role (20.7-32.5%). A total of 30 different phenolic compounds were detected by HPLC-PAD. The presence of catechin, delphinidin 3-glucoside, cyanidin 3-glucoside, ellagic acid and rutin was elucidated. Other phenolic compounds, such as flavan-3-ol, flavonol, flavanone and ellagic acid derivatives, were also present. For the three ripening stages the flavan-3-ols and ellagic acid group were the most representative phenolic compounds in this fruit. Acid hydrolysis of F-II revealed the presence mainly of gallic and ellagic acids, suggesting that camu camu fruit possesses important quantities of hydrolysed tannins (gallo- and/or ellagitannins). These results confirm that camu camu fruit is a promising source of antioxidant phenolics. © 2009 Elsevier Ltd. All rights reserved.