In this work, we conducted the characterization and antibacterial activity test of alkaloid compounds isolated from fungi mangrove sediments. These sediment samples were acquired randomly from the ecotourism region of the Gebang Petengoran mangrove forest (coordinates: -5.570759°S 105.240765°E) and the Dewi Mandapa beach area (coordinates: -5.571889°S 105.243494°E), Pesawaran Regency, Province of Lampung, Indonesia. The findings of the isolation of fungi mangrove sediment obtained four single fungal isolates, which were cultivated and co-cultivated on a solid rice medium. The crude extracts that were macerated from these fungi were tested for screening bioactivity against Staphylococcus aureus and Pseudomonas aeruginosa. Using the chromatography technique, the crude extracts selected then were fractionated and purified to obtain the target compound, called RSM1 fraction (1.691 mg). The findings of the RSM1 fraction (Rf = 0.6) were confirmed using FTIR, TIC, and LC-MS. The FTIR measurement revealed absorption at wave numbers of 1371.7 cm-1 (C-N group); 1744.4 cm-1 (C=O group); and 2922.2 cm-1 (aliphatic C-C or C-H group), which indicated absorption originated from the alkaloid groups. From the TIC analysis, obtained 12 peaks with retention times (9.85 min) that indicated an alkaloid compound (Triazine). In addition, the findings of the alkaloid compound of the RSM1 fraction were also confirmed via the LCMS analysis with a base peak of 365 m/z (C17H33N8O). Furthermore, the RSM1 fraction showed antibacterial activity with % inhibition of 3.8% (S. aureus); 5.8% (P. aeruginosa) from cultivated extract, and 21.2% (S. aureus); 26.8% (P. aeruginosa) from co-cultivated extract, respectively. Therefore, Triazine-an alkaloid compound isolated from fungi sediment mangrove has the potential use as antibacterial. © 2024 Author(s).