The n-hexane and carbon tetrachloride soluble fractions of a methanolic extract of the stem bark of the Couroupita guianensis furnished three compounds, identified as $eta$-amyrin (1), betulin-$3{eta}$-caffeate (2) and lupeol-$3{eta}$-caffeate (3). The structures of the isolated compounds were deduced by extensive spectroscopic analysis as well as by comparison with published values. Compounds 1-3 were subjected to antioxidant screening through free radical scavenging activity by DPPH (1,1-diphenyl-2-picrylhydrazyl), where compound 2 showed moderate antioxidant activity with $IC_{50}$ value $108.0{mu}g/ml$.