Induction of apoptosis by puerarin in colon cancer HT-29 cells
Puerarin was isolated from Pueraria radix and has beneficial effects on cardiovascular, neurological, and hyperglycemic disorders. The current study showed that puerarin also possessed anti-cancer properties. Methyl thiazolyl tetrazolium assay (MTT) assay revealed a dose-dependent reduction of HT-29 cellular growth in response to puerarin treatment. Apoptosis was observed following treatments with ≥25μM puerarin, as reflected by the appearance of the subdiploid fraction and NDA fragmentations. We then investigated effects of puerarin on expression of apoptosis-associated genes and the results revealed an increase of bax and decreases of c-myc and bcl-2. Finally, puerarin treatment significantly increased the activation of caspase-3, a key executioner of apoptosis. These findings indicate that puerarin may act as a chemopreventive and/or chemotherapeutic agent in colon cancer cells by reducing cell viability and inducing apoptosis.
Zl & Li Wj. Cancer Letters. Volume 238, Issue 1, Pages 53-60 (8 July 2006)

Puerariae radix isoflavones and their metabolites inhibit growth and induce apoptosis in breast cancer cells
Puerariae radix (PR) is a popular natural herb and a traditional food in Asia, which has antithrombotic and anti-allergic properties and stimulates estrogenic activity. In the present study, we investigated the effects of the PR isoflavones puerarin, daidzein, and genistein on the growth of breast cancer cells. Our data revealed that after treatment with PR isoflavones, a dose-dependent inhibition of cell growth occurred in HS578T, MDA-MB-231, and MCF-7 cell lines. Results from cell cycle distribution and apoptosis assays revealed that PR isoflavones induced cell apoptosis through a caspase-3-dependent pathway and mediated cell cycle arrest in the G2/M phase. Furthermore, we observed that the serum metabolites of PR (daidzein sulfates/glucuronides) inhibited proliferation of the breast cancer cells at a 50% cell growth inhibition (GI50) concentration of 2.35 μM. These results indicate that the daidzein constituent of PR can be metabolized to daidzein sulfates or daidzein glucuronides that exhibit anticancer activities. The protein expression levels of the active forms of caspase-9 and Bax in breast cancer cells were significantly increased by treatment with PR metabolites. These metabolites also increased the protein expression levels of p53 and p21. We therefore suggest that PR may act as a chemopreventive and/or chemotherapeutic agent against breast cancer by reducing cell viability and inducing apoptosis.
Lin Y-J, Hou YC, Lin C-H, et al. Biochemical and Biophysical Research Communications. Volume 378, Issue 4, 23 January 2009, Pp 683-8. doi:10.1016/j.bbrc.2008.10.178

The Effects of Plant Flavonoids on Mammalian Cells:Implications for Inflammation, Heart Disease, and Cancer
Flavonoids are nearly ubiquitous in plants and are recognized as the pigments responsible for the colors of leaves, especially in autumn. They are rich in seeds, citrus fruits, olive oil, tea, and red wine. They are low molecular weight compounds composed of a three-ring structure with various substitutions. This basic structure is shared by tocopherols (vitamin E). Flavonoids can be subdivided according to the presence of an oxy group at position 4, a double bond between carbon atoms 2 and 3, or a hydroxyl group in position 3 of the C (middle) ring. These characteristics appear to also be required for best activity, especially antioxidant and antiproliferative, in the systems studied. The particular hydroxylation pattern of the B ring of the flavonoles increases their activities, especially in inhibition of mast cell secretion. Certain plants and spices containing flavonoids have been used for thousands of years in traditional Eastern medicine. They are usually subdivided according to their substituents into flavanols, anthocyanidins, and flavones, flavanones, and chalcones (See Table).
In spite of the voluminous literature available, however, Western medicine has not yet used flavonoids therapeutically, even though their safety record is exceptional. Suggestions are made where such possibilities may be worth pursuing.
Middleton Jr E, Kandaswami C, & Theoharides TC. Pharmacological Reviews December 1, 2000 vol. 52 no. 4 673-751

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