ABSTRACT
Lycii Cortex, a popular herb medicine in traditional Chinese medicine, is used to treat different inflammation-related diseases. The aim of our work is to find the key constituents inhibiting NF-kappaB, a key regulator of inflammation. In the investigations of cell-based in vitro assays of extracts, we found that both ethyl acetate extract and methanol extract of Lycii Cortex inhibited the TNF-alpha-induced activation of NF-kappaB. Through bioassay-guided fractionation, we identified 4 phenolic amides including trans-N-(p-coumaroyl) tyramine (1), trans-N-feruloyltyramine (2), trans-N-caffeoyltyramine (3), and dihydro-N-caffeoyltyramine (4). Four phenolic amides showed differently inhibitory activities on TNF-alpha-induced NF-kappaB activation. Trans-N-caffeoyltyramine (3) was identified as the key component with an IC50 of 18.41 micromol x L(-1). It was suggested that the hydroxyl group at C-3 in trans-N-caffeoyltyramine might be a key binding site and its C-7,8-double bond might play an important role on NF-kappaB inhibitory activities as the link of the conjugation of pi electrons leading to a partial planar conformation. It might be inferred that the biological activity of compound 3 is attributed to the structure of Michael reaction acceptor containing alpha, beta-unsaturated ketones and benzene along with hydroxyl group in o-diphenol.