Piper longum L. is widelycultivatedfor food, medicine, and other purposes in tropical and subtropicalregions. Sixteen compounds including nine new amide alkaloids wereisolated from the roots of P. longum. The structures of these compounds were determined by spectroscopicdata. All compounds showed better anti-inflammatory activities (IC50 = 1.90 & PLUSMN; 0.68-40.22 & PLUSMN; 0.45 & mu;M) comparedto indomethacin (IC50 = 52.88 & PLUSMN; 3.56 & mu;M). Amongthe isolated compounds, five dimeric amide alkaloids exhibited synergisticeffects with three chemotherapeutic drugs (paclitaxel, adriamycin,or vincristine) against cervical cancer cells. Moreover, these dimericamide alkaloids also enhanced the efficacy of paclitaxel in paclitaxel-resistantcervical cancer cells. The combination treatment of one of these dimericamide alkaloids and paclitaxel promoted cancer cell apoptosis, whichis related to the Src/ERK/STAT3 signaling pathway.