Six
flavonoids, persicogenin (1),
artemetin (2),
luteolin (3),
penduletin (4),
vitexicarpin (5) and
chrysosplenol-D (6), have been isolated for the first time as new cell cycle inhibitors from Vitex trifolia L., a Chinese
folk medicine used to treat
cancers, through a bioassay-guided separation procedure. They were identified by spectroscopic methods. The inhibitory effects of 1-6 on the proliferation of mammalian
cancer cells have been evaluated by the SRB (
sulforhodamine B) method and their effects on cell cycle and apoptosis investigated by flow cytometry with the morphological observation under light microscope and by
agarose-gel electrophoresis to detect internucleosomal DNA fragmentation. Compounds 1-6 inhibited the proliferation of mouse tsFT210
cancer cells with the IC50s (microg ml(-1)) > 100 (inhibition rate at 100 microg ml(-1), 47.9%) for 1, >100 (inhibition rate at 100 microg ml(-1), 49.6 %) for 2, 10.7 for 3, 19.8 for 4, 0.3 for 5, and 3.5 for 6. Flow cytometric investigations for 1-6 demonstrated that 1-5 mainly inhibited cell cycle at the G2/M phase in a dose-dependent manner with a weak induction of apoptosis on the tsFT210 cells, while 6 induced mainly apoptosis of the same tsFT210 cells also in a dose-dependent manner together with a weak inhibition of the cell cycle at the G0/G1 and G2/M phases, demonstrating that 1-6 exert their anti-proliferative effect on tsFT210 cells through inhibiting cell cycle and inducing apoptosis. In contrast to the cell cycle G2/M phase inhibitory main effect on tsFT210 cells, 5 induced mainly apoptosis on human
myeloid leukemia K562 cells with a weak inhibition of the cell cycle at the G2/M phase. The present result provides
flavonoids 1-6 as new cell cycle inhibitors and 1 and 4 as new anticancer
flavonoids, which not only provide the first example of cell cycle G2/M phase inhibitory and apoptosis-inducing constituents of V. trifolia L. but also explain the use of Vitex trifolia L. by Chinese people to treat
cancers.