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 and meso-stilbene turners [i.e., (+)- and (-)-(E)-cypensphenol A (1.2 respectively) and (E)-mesocyperusphenol A (3)], a trimer bearing a novel hexacyclic ring system [cyperusphenol B (5)1, as well as known stilbenoids (cyperusphenols C (4) and D (6), scirpusins A (7) and B (8), and piceid (9)) and luteolin. HPLC was used for the optical resolution of 1 and 2 as well as for the identification of cooccurrence of enantiomers of 7. The structures of the isolates were established by spectroscopic analyses, including a detailed NMR spectroscopic investigation. The isolates were evaluated in terms of their antiproliferative activity employing the jurkat cell line (human T-cell leukemia cells), while the IC50 potencies of a racemate of 1 and 2, 3, 5, and 6 were estimated as 27.4, 40.5, 26.4, and 263 mu M, respectively. The suppression of cell growth by 6 was due to the induction of apoptosis, which was characterized by nuclear changes and PARP-1 cleavage determined by western blotting. We also evaluated the free radical scavenging activity of the isolates. (C) 2012 Elsevier B.V. All rights reserved.