Inhibitory activity of Pimenta dioica extracts and constituents on recombinant human histidine decarboxylase

Histamine, a bioactive amine, is formed from histidine through histidine decarboxylase (HDC). The agent that controls histamine synthesis, i.e. activity of HDC, is beneficial for controlling histamine-related physiological actions, such as inflammation. In the present study, the ethyl acetate (EtOAc) extract of the berries of Pimenta dioica was investigated for its potency as an HDC inhibitor. Two quercetin glycosides from P. dioica, quercetin 3-O-β-d-glucuronide 6″-methyl ester and quercetin 3-O-(2-O-galloyl)glucoside were identified as potent HDC inhibitors (64% and 55% inhibition at 1 mM, respectively). The inhibitory rates of these quercetin glycosides were nearly comparable to that of epigallocatechin gallate, another HDC inhibitor (75% at 1 mM). The approach to seek active components from natural products is useful for obtaining HDC inhibitors.