The kingdom Fungi has great diversity. A study indicates that there are more than 5 million species, of which approximately 70,000 have been described1. Among the different fungal habitats, there are those living in association with other organisms, such as endophytic fungi, which spend the whole or part their life inside the plant tissue, without causing damages1,2. Endophytic fungi are interesting because exist a lack of knowledge of their diversity, and also they are a prolific source of natural products with various bioactivities, such as antitumor and antibacterial3. Studies of extracts from endophytic fungi associated with Asteraceae are scarce and have shown a wide diversity of compounds and bioactivities4. Guided by cytotoxic assay, the aim of this work was to evaluate the crude extracts of endophytic fungi from Baccharis oxyodonta (Asteraceae) and identify the produced compounds. Healthy leaves of B. oxyodonta were sterilized and fragments were deposited on Petri dishes containing PDA and antibiotic. After incubation, 20 endophytic fungi were isolated. The crude extracts (EtOAc) were obtained and submitted to HPLC analysis and cytotoxic activity using MTT assay and colon adenocarcinoma cells (HCT-116). Six extracts showed significant inhibition results ( 50%) at concentration of 5µg.mL⁻¹ (Table 1). Crude extract of morphotype F11 was submitted to semi-preparative HPLC to isolate the components. From 1H NMR, 13C NMR and Mass spectrometry analysis were identified the polyketides alternariol and alternariol-9-methyl ether (Figure 1). The strain was identified through internal transcribed spacer ITS1 and ITS4 regions as belonging to the genus Phomopsis sp. (Figure 2).