The antioxidant activity of the crude n-hexane, dichloromethane, and methanol extracts from 25 species belonging to the Asteraceae, Euphorbiaceae, Rubiaceae, and Solanaceae families collected at natural reserves from the Eje Cafetero Ecorregión Colombia, were evaluated by using the spectrophotometric 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical-scavenging method.The strongest antioxidant activities were showed by the methanol and dichloromethane extracts from the Euphorbiaceae, Alchornea coelophylla (IC 50 41.14 mg/l) and Acalypha platyphilla (IC 50 111.99 mg/l), respectively. These two species had stronger DPPH radical scavenging activities than hydroquinone (IC 50 151.19 mg/l), the positive control. The potential use of Colombian flora for their antioxidant activities is discussed.Key words: Asteraceae -1,1-diphenyl-2-picrylhydrazyl (DPPH) -Euphorbiaceae -radical-scavenging -Rubiaceae -Solanaceae ternative, once it has been suggested that there is an inverse relationship between dietary intake of antioxidants and the incidence of diseases caused by the deficiency on these substances (Antolovich et al. 2002). In recent years, synthetic antioxidants such as buthylated hydroxyanisole (BHA) and buthylated hydroxytoluene (BHT) are added to food preparations because they are good free radical scavengers, even though there are some experimental evidences that they induce DNA damage (Sasaki et al. 2002). Therefore, there is an increasing interest in searching antioxidants from natural origin to scavenge free radicals to prevent human body from oxidative stress produced by ROS and RNS species (Gonçalves et al. 2005).According to Hostettmann and Terreaux (2000), the estimated number of higher plant species in the world is of 400,000, the fact that plant secondary metabolites are characterized by an enormous chemical diversity and that currently one-fourth of all prescribed pharmaceuticals compounds in developed countries are directly or indirectly (semi-synthetic) derived from plants. Then, the above statement in conjunction with the great Colombian biodiversity can make possible to discover new important antioxidant agents from such plethora of plant resources.As plants produce a huge amount of antioxidants they can represent a source of new compounds with antioxidant activities (Cuendet et al. 2000, Bassman 2004. From this point of view, the main goal of this research was to study the antioxidant activities through the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging method of the crude n-hexane, dichloromethane, and methanol extracts from 25 plant species belonging to four botanical families (Asteraceae, Euphorbiaceae, Rubiaceae, and Solanaceae) collected from natural reserves on the Eje Cafetero Ecorregión (ECE), Colombia.The ECE is an area constituted by the departments of Caldas, Quindío, and Risaralda, which are located on the Central Andean Colombian mountain chain, with an extension of 13.873 km 2 . Most of the ECE area is constituted by mountains with high mountain valleys, high pluviosity, and ...