In vitro antibacterial effects of Zanthoxylum tingoassuiba root bark extracts and two of its alkaloids against multiresistant Staphylococcus aureus

The emergence of multiresistant strains of bacteria reinforces the need to search for new compounds able to combat resistant organisms. Medicinal plants are a great resource of bioactive substances, pro-viding the possibility of obtaining molecules with potential antimicrobial activity. The aim of the present study is the evaluation of the antibacterial activity of extracts and alkaloids isolated from the root bark of Zanthoxylum tingoassuiba A. St.-Hil., Rutaceae, against four resistant clinical isolates and Staphylococcus aureus ATCC 25923. The dichloromethane and methanol extracts were fractionated by chromatographyon silica gel, leading to the isolation of dihydrocheleryhtrine and N-methylcanadine, identified by Nuclear Magnetic Resonance spectroscopy. The antibacterial activity of the extracts and isolated compounds was evaluated by the disc diffusion method and the minimum inhibitory concentration was determined. The dichloromethane extract was the most active against all the tested strains and the two pure alkaloids were more active than the extracts. The anti-MRSA activity of the two benzophenanthridine alkaloids is demonstrated for the first time in this study. These compounds appear as potential leads for the development of new anti-MRSA compounds and could be responsible for the antibacterial activity, justifying the ethnobotanical use of Z. tingoassuiba and other species for the treatment of various infectious diseases. (C) 2016 Published by Elsevier Editora Ltda. on behalf of Sociedade Brasileira de Farmacognosia.