Four new alkaloids, Brazoides A-D, together with three known compounds squalene, β-sitosterol and lupeol, were isolated from leaves of Justicia gendarussa. These structures were established by spectrometric techniques, mainly high-resolution electrospray ionization mass spectrometry (HRESIMS) and 1D and 2D nuclear magnetic resonance (NMR), including comparative analysis with literature values. Structural determination of the compounds, Brazoides A-D, was strengthened by molecular modeling and density functional theory (DFT) calculations to predict the NMR data and compare with the experimental NMR values of these natural products. The new compounds were tested against three human cancer cell lines (glioblastoma, prostate and colon), but none exhibited activity. ©2017 Sociedade Brasileira de Química.