Xanthorrhizol derivatives and their biological properties as caspase-7 inhibitors

Xanthorrhizol (1) is known as the major terpenoid component of the rhizome of Curcuma xanthorrhiza and having some interesting biological activities. In this report, we synthesised five derivatives of 1 containing nitrogen-functional groups. Four of them are new synthesised compounds, including (R)-4-(3-(2-methyl-5-(6-methylhept-5-en-2-yl)phenoxy)propyl)morpholine (2), (R)-N-benzyl-3-(2-methyl-5-(6-methylhept-5-en-2-yl)phenoxy)propan-1-amine (3), (R)-6,7-dimethoxy-3-(3-(2-methyl-5-(6-methylhept-5-en-2-yl)phenoxy)propyl)quinazolin-4(3H)-one (4), and (R)-6-methyl-3-(6-methylhept-5-en-2-yl)-2-nitrophenol (5) groups. Meanwhile the other is the known compound, that is (R)-2-methyl-5-(6-methylhept-5-en-2-yl)-4-nitrophenol (6). The caspase-7 inhibitory activity of compounds 1-6 was evaluated as well. In comparison to other derivatives, compounds 5 and 6 exhibited higher activity. Consequently, compounds 5 and 6 may be a promising lead compound for further development as a caspase-7 inhibitor.