Diarylheptanoid Glucosides from Pyrostria major and Their Antiprotozoal Activities

Eight new diarylheptanoid glucosides 1–8 have been isolated from the leaves of Pyrostria major (A. Rich & DC.) Cavaco [syn. Canthium major (A. Rich & DC.)] Cavaco. Their structures were determined by 1D and 2D NMR spectroscopic and HRMS analyses. The absolute configurations of the diarylheptanoids 1–4 were determined to be 3S and 5S by the application of the CD exciton chirality method to the corresponding 3,5‐bis(p‐bromobenzoyl) (1–3) and 3,5‐bis(p‐dimethylaminobenzoyl) (4) derivatives. Their antiparasitic activities against Plasmodium falciparum, Leishmania donovani (amastigote forms), and Trypanosoma brucei (trypomastigote bloodstream forms) as well as their cytotoxic activities against the HL‐60, KB, and MRC5 cell lines of naturally occurring diarylheptanoid glucosides and their derivatives are reported. A story of serendipity: biologically inactive natural diarylheptanoid glucosides have been isolated from Pyrostria major. Their absolute configurations were determined to be 3S and 5S by the application of the CD exciton chirality method to the corresponding benzoyl derivatives. The study led to the discovery of new compounds possessing selective antiprotozoal activity.