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A primary functional receptor screening assay was performed to examine the effects of methanolic extracts from ten Vietnamese medicinal plants on the human neurokinin-1 receptor expressed from Semliki Forest virus vectors in Chinese hamster ovary cells. Extracts from Piper nigrum, Stephania cambodica and Styphnolobium japonicum were found to exert inhibition on agonist-induced human neurokinin-1 receptor activity. Secondary assays and high performance liquid chromatography of the lead compounds addressed a possible association between pharmacological responses and these chemical compounds. Strong inhibition of human neurokinin-1 receptor was observed for extracts revealing the highest inhibitory potency for rotundine (tetrahydropalmatine) in S. cambodica extracts with IC 50 of 0.88 µM, followed by piperine and capsaicin in P. nigrum extracts with IC 50 values of approximately 2 µM, whereas rutin in S. japonicum extracts failed to inhibit hNK1R up to 100 µM.