Ziziphine N, O, P and Q, new antiplasmodial cyclopeptide alkaloids from Ziziphus oenoplia var. Brunoniana

Bioassay-guided fractionation of the EtOAc extract of the roots of Thai Ziziphus oenoplia var. brunoniana resulted in the isolation of four new 13-membered cyclopeptide alkaloids of the 5(13) type, ziziphine N–Q. The structures of the new metabolites were elucidated on the basis of spectroscopic analyses and the stereochemical assignments were established by comparison with other related compounds of known stereochemistry. Ziziphine N and Q exhibited significant antiplasmodial activity against the parasite Plasmodium falciparum with the inhibitory concentration (IC50) values of 3.92 and 3.5 μg/mL, respectively. Ziziphine N and Q also demonstrated weak antimycobacterial activity against Mycobacterium tuberculosis with the same MIC value of 200 μg/mL.