Bidens segetum Martius ex Colla known as the "picão do mato", is an herbaceous plant that occurs in the Cerrado biome of some Brazilian states. Among the species of Bidens, we highlight B. pilosa known as "picão preto", of which several activities are reported as antioxidant and antibacterial. Ethanolic extract from Bidens segetum (EEBs) showed antioxidant potential when analyzed by free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and antifungal activity against Cladosporium cladosporiodes and C. sphareospermum fungi. PFFR3.3 subfraction from EEBs has 81.5% of 5-O caffeoylquinic acid (5-CQA) and potential antioxidant (DPPH). However, PFFR3.3 did not decrease superoxide anion in metastatic melanoma cells by dihydroethidium assay (DHE). PP4 subfraction is a mixture of polyacetylenes that has antifungal (Cladosporium) and antioxidant activity, since reduced superoxide anion amount in melanoma cells after 5 min of treatment. However, no dose-response and time-response curve were observed, not even with the authentic standard (5-CQA). Complementary chemical studies will be performed to confirm the polyacetylenes and 5-CQA structures present in the EEBs from B. segetum and new methodologies should be performed to confirm the antioxidant activity of these compounds and the effects on melanocytes and melanomas.