Fig. 3

Structures of known histone deacetylase (HDAC) inhibitor and 4-hexylresorcinol (4HR). Most HDAC inhibitors have 4–6 carbon length alkyl group. This alkyl group is a hydrophobic chain and corresponds to hydrophobic domain of HDAC. As zinc ion is required for HDAC activation, some HDAC inhibitors have functional group (FG). To block any introduction of substrate into HDAC enzymatic site cap domain (Cap) can be found in some HDAC inhibitor. Interestingly, hydroxyl-benzene in 4HR can be behaved like FG or Cap (modified from author’s own work [32])