Croton belongs to the Euphorbiaceae genus, one of the major Angiosperms families, and is widely distributed throughout the world, especially in the tropics. In this study, the hydroalcoholic extract (70% EtOH) of Croton echinocarpus leaves afforded two alkaloids: corydine and norisoboldine, and their structures were established by spectroscopic data interpretation (UV, IR, NMR and LREIMS). Both alkaloids displayed significant in vitro anti-HIV potential, inhibiting 40% of the HIV-1 reverse transcriptase enzyme activity at a concentration of 100 μg mL -1 of norisoboldine and 450 μg mL -1 of corydine. Corydine showed IC 50 of 356.8 μg mL -1 , while norisoboldine was more efficient on inhibiting the RT activity, showing IC 50 of 153.7 μg mL -1 .