Objective: To evaluate the anti-bacterial activity of more than 2,000 plant extracts against commensal Streptococcus sanguinis, which is related to the ffirst steps of biofilm formation, claimed to be a sign of oral health, but has been associated to the development of infectious endocarditis, artheroschlerosis and ischemia, after reaching blood stream. Also, nature plays an important role as source of new antibacterial substances likely to assist good oral health conditions. Methods: More than 2,000 Brazilian Amazon plant extracts were tested against S. sanguinis using the disk diffusion assay. Results: Twenty six out of 2,000 extracts (1.3%) showed activity against the micro-organism when evaluated by their growth inhibition zone. All the extracts showed equal or higher antibacterial activity when compared to chlorhexidine digluconate 0.12, 1% and 2%, such as EB271, obtained from Casearia spruceana (growth inhibition zone of 24.65±0.50mm), or EB1129, obtained from Psychotria sp. (growth inhibition zone of 21.63±0.88mm). Conclusions: The screening of Amazon plant extracts showed that Casearia sprucena and Psychotria sp. are potential sources of preventive agents that can be used in preventive are against Streptococcus sanguinis.