Selected plants documented as medicinal in an ethnobotanical study with the Nahua of the Sierra de Zongolica (Veracruz, Mexico) were evaluated for anti-inflammatory and antibacterial activity. One of the potential sides of action of anti-inflammatory drugs is the transcription factor NF-κB. This factor is essential for the immune, inflammatory, and acute phase responses. We therefore tested extracts from a total of 28 plants used by the Nahua Indians for their potential effect on the activation of the transcription factor NF-κB. The leaves of Tithonia diversifolia (Hemsl.) A. Gray (Asteraceae) was the only extract which showed inhibitory activity. Nonspecific DNA binding activities were not noticably influenced. Phytochemical studies to isolate the active principle and further biochemical studies in order to better understand the mode of action of this NF-κB inhibitor have been initiated. Five plants showed noteworthy antibacterial activity against some pathogenic (Staphylococcus aureus ATCC 25933 and Yersinia enterocolitica 03) and nonpathogenic (E. coli DSM 1077, Micrococcus luteus DSM 348) microorganism: Acacia cornigera, Cuscuta tinctoria, Ludwigia octovalvis, Lysiloma divaricata, and Tithonia diversifolia.