Background:

Sirtinol is an inhibitor of SIRT with IC50 value of 48.6 μM (24 h) and 43.5 μM (48 h) in MCF-7 cells [1].

Sirtinol significantly reduces the growth of MCF-7 cells in a concentration- and time-dependent manner. Meanwhile, the expression level of SIRT1 is notably decreased by sirtinol results in an induction of acetylated p53. It is found that sirtinol decreases the the expression of cell cycle-regulated proteins such as cyclin B1, cyclin D1, CDK2 and CDK6 and subsequently induces G1 phase arrest which indicates cell apoptosis. Furthermore, sirtinol is also demonstrated to induce autophagy in MCF-7 cells. Other in vitro assays show that sirtinol inhibits SIRT2 (amino acids 18–340) with IC50 value of 45 μM while it does not inhibit HDAC1 at 50 and 100 μM [1, 2].

Reference:
[1] Wang J, Kim TH, Ahn MY, Lee J, Jung JH, Choi WS, Lee BM, Yoon KS, Yoon S, Kim HS.  Sirtinol, a class III HDAC inhibitor, induces apoptotic and autophagic cell death in MCF-7 human breast cancer cells. Int J Oncol. 2012 Sep;41(3):1101-9.
[2] Grozinger CM, Chao ED, Blackwell HE, Moazed D, Schreiber SL.  Identification of a class of small molecule inhibitors of the sirtuin family of NAD-dependent deacetylases by phenotypic screening. J Biol Chem. 2001 Oct 19;276(42):38837-43.