Caesalpinia sappan is a potent source of multi-functional bioactive compounds.

Traditional Chinese medicinal (TCM) plants have become an important source for screening natural bioactive compounds. This study aimed to compare the phenolic profiles, and antioxidant, antiproliferative, and antibacterial activities of sixteen TCM extracts, to evaluate their effects on intracellular reactive oxygen species (ROS), and to characterize the major bioactive constituents in the most promising plants. Wide ranges of variation were found in methanolic plant extracts for total phenolics (31.3-1247 mg gallic acid equivalent (GAE)/100 g dry extract (DE)), total flavonoids (1.12-346 mg catechin equivalent (CE)/100 g DE), antioxidant activities, antiproliferative effects against four cancer cell lines with IC50 values of 3.74 to more than 200 µg DE/mL, and antibacterial activities against five bacteria with MIC values of 0.313-5.00 mg DE/mL. Caesalpinia sappan L. had the highest total phenolics, flavonoids, antioxidant, antiproliferative and antibacterial activities. It exerted an antiproliferative effect by reducing the intracellular ROS generation. Thirty-two compounds, including two organic acids, two phenolic acids, two chromones, eight flavonoids, four lactones, and 14 other phenolic compounds were tentatively identified from the heartwood of C. sappan. This study's results indicated that C. sappan's heartwood is a potential natural source of excellent antibacterial and anticancer compounds.