Occurrence of stilbene oligomers in Cyperus rhizomes

Investigation of the chemical constituents of Rhizoma Cyperi (Cyperus rotundus Linneus)resulted in the isolation of novel enantiomeric andmeso-stilbene trimers [i.e., (+)- and (−)-(E)-cyperusphenol A (1, 2 respectively) and (E)-mesocyperusphenol A (3)], a trimer bearing a novelhexacyclic ring system [cyperusphenol B (5)], aswell as knownstilbenoids (cyperusphenols C (4)and D (6), scirpusins A (7) and B (8), and piceid (9)) and luteolin. HPLC was used for the opticalresolution of 1 and 2 as well as for the identification of cooccurrence of enantiomers of 7. Thestructures of the isolates were established by spectroscopic analyses, including a detailed NMRspectroscopic investigation. The isolates were evaluated in terms of their antiproliferative activityemploying the Jurkat cell line (human T-cell leukemia cells), while the IC50 potencies of aracemate of 1 and 2, 3, 5, and 6 were estimated as 27.4, 40.5, 26.4, and 26.3 μM, respectively. Thesuppression of cell growth by 6 was due to the induction of apoptosis,whichwas characterized bynuclear changes and PARP-1 cleavage determined bywestern blotting.We also evaluated the freeradical scavenging activity of the isolates.