| Summary: | Diverse plants of ethnobotanic interest in Amazonia are commonly used in traditional medicine. We determined the antioxidant potential against lipid peroxidation, the antimicrobial activity, and the polyphenol composition of several Amazonian plants (<em>Brownea rosademonte</em>, <em>Piper glandulosissimum</em>, <em>Piper krukoffii</em>, <em>Piper putumayoense</em>, <em>Solanum grandiflorum</em>, and <em>Vismia baccifera</em>). Extracts from the plant leaf, bark, and stem were prepared as aqueous infusions, as used in folk medicine, and added to rat liver microsomes exposed to iron. The polyphenolic composition was detected by reverse-phase HPLC coupled to diode-array detector and MS/MS analysis. The antimicrobial activity was tested by the spot-on-a-lawn method against several indicator microorganisms. All the extracts inhibited lipid oxidation, except the <em>P.</em> <em>glandulosissimum</em> stem. The plant extracts exhibiting high antioxidant potential (<em>V. baccifera </em>and <em>B. rosademonte</em>) contained high levels of flavanols (particularly, catechin and epicatechin). By contrast, <em>S. grandiflorum</em> leaf, which exhibited very low antioxidant activity, was rich in hydroxycinnamic acids. None of the extracts showed antimicrobial activity. This study demonstrates for the first time the presence of bioactive polyphenolic compounds in several Amazonian plants, and highlights the importance of flavanols as major phenolic contributors to antioxidant activity.
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