Technical Abstract: N-caffeoyltyramine is a phenylpropenic acid amide found in numerous plants, including Lycium chinense (Chinese Wolfberry). In this study, N-caffeoyltyramine and its natural analogues (N-cinnamoyltyramine, N-coumaroyltyramine, N-feruloyltyramine, and N-sinapoyltyramine) were investigated to determine their potency as beta-adrenoceptors in human monocytic U937 cells because they have chemical structures strikingly similar to a beta-adrenergic drug, dobutamine. Among the phytochemicals tested in this study, N-caffeoyltyramine was the most potent compound, increasing cAMP at concentrations lower than 0.5 microM via beta-adrenoceptors. Several beta-adrenoceptor agonists were compared with N-caffeoyltyramine in producing cAMP in U937 cells, and the decreasing order of the potency was isoproterenol N-caffeoyltyramine salbutamol > arterenol > dobutamine. Using beta subtype selective antagonists (atenolol (beta1) and butoxamine (beta2)), N-caffeoyltyramine was found to increase cAMP mainly via beta 2-adrenoceptor in U937 cells. cAMP is involved in numerous cellular processes including monocyte activation leading to severe insults to a site of vascular injury. Therefore, effects of N-caffeoyltyramine on monocyte activation markers were also investigated in this study.