We speculate that some unknown binding www.selleckchem.com/products/Vorinostat-saha.html factors may form a complex with STAT1 3 5 proteins in vivo in the presence of chrysin to facilitate STAT1, 3 5 for easy recognition and accessibility to the two STAT binding sites. It could be very interesting to identify such chrysin regulated proteins that bind to STAT binding sites. In fact, our studies indicate that modification of chro matin structure in response to histone acetylation and methylation of the two responsive sites is sufficient to allow the transcriptional activation of p21WAF1 presum ably via STAT proteins. These findings dem onstrate a possible working model of chrysin for not only regulating cell cycle but also connect epigenetic modulation of p21WAF1 promoter and STAT signaling pathway as well.

The functional importance of STAT region in the promoter activation was highly elucidated. In this study we found that chrysin treatment caused decrease in the protein level of NF kB dependent genes such as Bcl xL, survivin that lead to cell death by enhancing the activity of caspase 3. Thus chrysin can be used as a single drug when compared with combinatorial therapy such as recently used HDAC inhibitor and demethylating agent. Conclusions In summary, we have shown that chrysin posses potent invitro anti cancer activity by suppressing cell prolifera tion, inducing G1 cell cycle arrest with the upregulation of p21 and decrease in cyclin D1, cdk2 protein levels. This compound caused inhibition of HDAC 8 activity with no effect on the activity of HDAC 1 2.

The protein levels of HDAC 2, 3 and 8 were found to be drastically reduced with no change in HDAC 4 6 upon chrysin treat ment. Chrysin caused histone modifications such as acetylation and methylation at p21 promoter particu larly at STAT binding site and resulted in increased p21 promoter activity. More over chrysin as a HDAC inhibitor cause apoptosis by decreasing the levels of NF kB targeted and HDACi related genes such as Bcl xL, survivin and increased the level of caspase 3 proteins. Methods Chemical structure and extraction of natural compounds The dried stem bark of dundilum tree, Oroxylum indicum was grinded and extracted consecutively with hexane in a soxhlet apparatus. Solid residue in the hexane extract was filtered and subjected to silica gel column chromatography to isolate two major frac tions.

Fraction F1 was purified on silica gel column chromatography eluted with 0. 5 % MeoH in Chloroform to isolate methoxy chrysin. Simi larly, Fraction F2 was subjected to repeated column chro matography with the elution of 2 % MeoH in Chloroform to isolate oroxylin A and chrysin. The purifi cation, Carfilzomib chemical structure and characterization of all three compounds were determined via extensive spectroscopic NMR, ESI MS, and HPLC methods. The conserved methyl oxide and hydroxyl group are shown in the chemical struc ture of small flavonoid compounds.