379 Braz J Med Biol Res 37(3) 2004 Screening of antibacterial Brazilian plant extracts Brazilian Journal of Medical and Biological Research (2004) 37: 379-384 ISSN 0100-879X Screening of antibacterial extracts from plants native to the Brazilian Amazon Rain Forest and Atlantic Forest 1 Laboratório de Extração, Universidade Paulista, São Paulo, SP, Brasil 2 Laboratório Especial de Microbiologia Clínica, Universidade Federal de São Paulo, São Paulo, SP, Brasil 3 Centro de Ciências Biológicas e da Saúde, Universidade Federal do Maranhão, São Luís, MA, Brasil I.B. Suffredini 1 , H.S. Sader 2 , A.G. Gonçalves 3 , A.O. Reis 2 , A.C. Gales 2 , A.D. Varella 1 and R.N. Younes 1 Abstract More than 20% of the world’s biodiversity is located in Brazilian forests and only a few plant extracts have been evaluated for potential antibacterial activity. In the present study, 705 organic and aqueous extracts of plants obtained from different Amazon Rain Forest and Atlantic Forest plants were screened for antibacterial activity at 100 µg/ml, using a microdilution broth assay against Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa and Esche- richia coli. One extract, VO581, was active against S. aureus (mini- mum inhibitory concentration (MIC) = 140 µg/ml and minimal bacte- ricidal concentration (MBC) = 160 µg/ml, organic extract obtained from stems) and two extracts were active against E. faecalis, SM053 (MIC = 80 µg/ml and MBC = 90 µg/ml, organic extract obtained from aerial parts), and MY841 (MIC = 30 µg/ml and MBC = 50 µg/ml, organic extract obtained from stems). The most active fractions are being fractionated to identify their active substances. Higher concen- trations of other extracts are currently being evaluated against the same microorganisms. Correspondence I.B. Suffredini Laboratório de Extração Universidade Paulista Av. Paulista, 900, 1º andar 01310-100 São Paulo, SP Fax: +55-11-3170-3978 E-mail: extractlab@unip.br Presented at the XXI Congresso Brasileiro de Microbiologia, Foz do Iguaçu, PR, Brasil, October 21, 2001. Research supported by FAPESP (No. 99/05904-6). Received May 24, 2002 Accepted October 20, 2003 Key words • Plant extract • Antibacterial activity • Screening • Amazon Rain Forest • Atlantic Forest Introduction The Brazilian Amazon Rain Forest is home to 17% of the biodiversity found within the country (1). The Atlantic Forest contains approximately 35% of the world’s Angios- permae, and more than 8% of the Pterido- phytae (2). In view of this wealth of species and that the Atlantic Forest is one of the world’s foci for conservation (3), this biomas should be studied in terms of pharmacologi- cal or biological activity. Approximately 20% of the plants found in the world have been submitted to pharma- cological or biological test, and a substantial number of new antibiotics introduced on the market are obtained from natural or semisyn- thetic resources. It has been reported that between the years 1983 and 1994, of 93 new antibacterial agents submitted to analysis by the FDA six were natural products (teicopla- nin, mupirocin, miokamycin, carumonam, isepamicin, and RV-11), 45 were semisyn- thetic products modeled on a natural product lead, and 7 antivirals were synthetic com- pounds based on natural product models (4). The systematic screening of antibacterial plant extracts represents a continuous effort to find new compounds with the potential to act against multi-resistant bacteria.