Journal of Ethnopharmacology 105 (2006) 255–262 Antibacterial activity of Tabebuia impetiginosa Martius ex DC (Taheebo) against Helicobacter pylori Byeoung-Soo Park a , Hyun-Kyung Lee a , Sung-Eun Lee b , Xiang-Lan Piao c , Gary R. Takeoka d , Rosalind Y. Wong d , Young-Joon Ahn a , Jeong-Han Kim a,∗ a School of Agricultural Biotechnology, Seoul National University, Seoul 151-742, Republic of Korea b Department of Molecular Biosciences and Bioengineering, University of Hawaii at Manoa, Honolulu HI 96822, USA c College of Pharmacy, Seoul National University, Seoul 151-742, Republic of Korea d Western Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Albany CA 94710, USA Received 18 June 2005; received in revised form 22 October 2005; accepted 14 November 2005 Available online 15 December 2005 Abstract The growth-inhibiting activity of Tabebuia impetiginosa Martius ex DC dried inner bark-derived constituents against Helicobacter pylori ATCC 43504 was examined using paper disc diffusion and minimum inhibitory concentration (MIC) bioassays. The activity of the isolated compounds was compared to that of the commercially available anti-Helicobacter pylori agents, amoxicillin, metronidazole, and tetracycline. The biologically active components of Tabebuia impetiginosa dried inner bark (taheebo) were characterized by spectroscopic analysis as 2-(hydroxymethyl)anthraquinone, anthraquinone-2-carboxylic acid, and 2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinone (lapachol). With the paper disc diffusion assay 2- (hydroxymethyl)anthraquinone exhibited strong activity against Helicobacter pylori ATCC 43504 at 0.01 mg/disc. Anthraquinone-2-carboxylic acid, lapachol and metronidazole were less effective, exhibiting moderate anti-Helicobacter pylori activity at 0.1 mg/disc. Amoxicillin and tetra- cycline were the most potent compounds tested, displaying very strong activity at 0.005 mg/disc. 2-(Hydroxymethyl)anthraquinone exhibited moderate activity at this dose. Tetracycline still had strong activity at 0.001mg/disc while amoxicillin had little activity at this dose. In the MIC bioassay, 2-(hydroxymethyl)anthraquinone (2 g/mL), anthraquinone-2-carboxylic acid (8 g/mL), and lapachol (4 g/mL) were more active than metronidazole (32 g/mL) but less effective than amoxicillin (0.063 g/mL) and tetracycline (0.5 g/mL). The anti-Helicobacter pylori activity of seven 1,4-naphthoquinone derivatives (structurally related to lapachol), 1,4-naphthoquinone, 5,8-dihydroxy-1,4-naphthoquinone (naphthazarin), 2-methyl-1,4-naphthoquinone (menadione), 2-hydroxy-1,4-naphthoquinone (lawsone), 5-hydroxy-2-methyl-1,4-naphthoquinone (plumbagin), 5-hydroxy-1,4-naphthoquinone (juglone), and 2,3-dichloro-1,4-naphthoquinone (dichlone) was also evaluated using the paper disc assay. Menadione and plumbagin were the most potent compounds tested with the later still exhibiting very strong activity at 0.001mg/disc. Menadione, juglone and tetracycline had strong activity at this low dose while the latter two compounds and amoxicillin had very strong activity at 0.005 mg/disc. Lawsone was unusual in that it had very strong activity at 0.1 and 0.05 mg/disc but weak activity at doses of 0.01 mg/disc and lower. Naphthazalin, lapachol and dichlone had similar activities while metronidazole had the lowest activity of all compounds tested. These results may be an indication of at least one of the pharmacological actions of taheebo. The Tabebuia impetiginosa dried inner bark- derived materials, particularly 2-(hydroxymethyl)anthraquinone, merit further study as potential Helicobacter pylori eradicating agents or lead compounds. © 2005 Elsevier Ireland Ltd. All rights reserved. Keywords: Tabebuia impetiginosa; Taheebo; Helicobacter pylori; 2-(Hydroxymethyl)anthraquinone; Anthraquinone-2-carboxylic acid; Lapachol; 1,4-Naphtho- quinone derivatives ∗ Corresponding author. Tel.: +82 2 880 4644; fax: +82 2 880 4421. E-mail address: kjh2404@snu.ac.kr (J.-H. Kim). 1. Introduction In humans, Helicobacter pylori is a microaerophilic gram- negative bacterium that colonizes the stomachs of about half of the population (Dunn et al., 1997). Helicobacter pylori infection is recognized as an important casual agent in gastroduodenal disease such as chronic gastritis, peptic ulceration, gastric 0378-8741/$ – see front matter © 2005 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.jep.2005.11.005