Investigation of chemical constituents of Dalbergia candenatensis, Alstonia scholaris
and Alstonia macrophylla led to the isolation of 26 compounds. Nine compounds were
isolated from the air-dried heartwood of D. candenatensis including five new phenolic
compounds (DC1-DC5) and four known compounds (DC6-DC9). The other new indole
alkaloids (AM1, AM2 and AM4) were isolated from the bark of A. macrophylla together with
eight known componds (AM3, AM5-AM11), whereas six known compounds (ASB1-ASB5,
ASL1) were isolated from the bark and leaves of A. scholaris. Structures of new compounds
were characterized by spectroscopic methods including UV, IR, 1D- and 2D-NMR and MS
whereas all known compounds were characterized by NMR and comparison of their
spectral data with reported values. Alstonisine (AM9) exhibited antiplasmodial activity
against Plasmodium falciparum, with an IC50 of 7.6 PM. Candenatenin K (DC5) exhibited
potent activity against DPPH radical scavenging with IC50 value of 25.7 PM, whereas
candenatenin H (DC2) showed cytotoxicity against NCI-H187 cell line with IC50 value of
14.8 PM