FOLK MEDICINE OF TRÁS-OS-MONTES (PORTUGAL). TRADITIONAL USES AND BIOACTIVE COMPOUNDS OF SIX COMMON MEDICINAL SPECIES 1.CIMO and Instituto Politécnico de Bragança, Campus de Santa Apolónia 5301-855 Bragança, Portugal anacarv@ipb.pt 2.CRIA and Faculdade de Ciências Sociais e Humanas da Universidade Nova de Lisboa, Av. Berna 26 C. 1069-061 Lisboa, Portugal Ethnobotanical surveys conducted in north-eastern Portugal reported plant knowledge and uses of several wild species in folk medicine, based on field studies using participant observation, unstructured and structured interviews, including freelisting and free pile-sorting. Taking advantage of a multidisciplinary team, besides botanical inventories and sociocultural and anthropological studies, we set out applied phytochemical research on locally used medicinal plants (more frequently cited, i.e. frequency of citation > 50%) that have special cultural significance. Considering the use reports and informants' selected sites, as well as, local consumers' criteria and the optimal growth stage of each species, samples were collected for analysis with informants' permission and cooperation.Epidemiological and experimental studies have consistently shown an inverse association between consumption of greens and fruits and the risk for chronic diseases. These physiological functions may be partly attributed to the abundance of antioxidants such as vitamin C, vitamin E, â-carotene and phenolics.This study reports the first approach to the antioxidant potential evaluation of six species (Glechoma hederaceae, Foeniculum vulgare, Malva sylvestris, Oregano virens, Rosa canina, Thymus mastichina), often used in folk medicine, accessed by biochemical assays used as models for the lipid peroxidation damage in biomembranes. Bioactive compounds such as phenolics, flavonoids, vitamin C and vitamin E were also determined. Significantly negative linear correlations were observed between the bioactive compounds and antioxidant activity EC50 values. Experimental phytochemical research points to pharmacological effects that confirm the importance of the empirical use of these species and their contribution to a good health condition. Carvalho Ana Maria 1, Lillian Barros1, Isabel C.F.R. Ferreira1 & Amélia Frazão-Moreira2 CONGRESO INTERNACIONAL DE ETNOBOTANICA V V INTERNATIONAL CONGRESS OF ETHNOBOTANY