A bioassay-guided investigation of Gustavia hexapetala led to the isolation of a new cancer cell growth inhibitor designated gustastatin (1) and four previously known cancer cell growth inhibitors that included betulinic acid (2). The structures were assigned on the basis of analyses of HRMS combined with 1D and 2D NMR data. The structure of portentol (5) was confirmed by an X-ray crystal structure determination.