Phytochemical investigation of the aerial parts of Mussaenda saigonensis led to the isolation of 6 compounds, including 3,5,6,7,8,3′,4′-heptamethoxyflavone (1), nobiletin (2), quercetin (3), -amyrin (4),oleanolic acid (5) và maslinic acid (6). The chemical structures of the substances were determined by the analysis of spectroscopic data and by comparing them with existing literature. All the individual substances were documented for the first time from Mussaenda saigonensis, to the best of our understanding. The isolated compounds were assessed for their ability to prevent the formation of nitric oxide (NO). Compounds 3, 5 showed NO inhibition with the IC50 values ranging from 34.57, to 35.55 µM while other compounds were weak or inactive compared to the positive control L-NMMA (IC50 29.32 μM).