|Piao, Xiang lan|
Submitted to: Journal of Ethnopharmacology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/14/2005
Publication Date: 3/1/2006
Citation: Park, B., Lee, H., Lee, S., Piao, X., Takeoka, G.R., Wong, R.Y., Ahn, Y., Kim, J. 2005. Antibacterial activity of tabebuia impetiginosa martius ex dc (taheebo) against helicobacter pylori. Journal of Ethnopharmacology 105:255-262. Interpretive Summary: Helicobacter pylori is a microaerophilic gram-negative bacterium that colonizes the stomachs of about half of the human population. Researchers believe that H. pylori is responsible for the majority of peptic ulcers. Though conventional treatments with a mixture of two antibiotics and bismuth, or a proton pump inhibitor have been effective in attaining high cure rates, repeated use of these chemical drugs may lead to development of resistance and resistant strains, and eradication failure rates range from 5 to 20%. Such treatments have had undesirable effects on non-target organisms such as intestinal microorganisms and have sometimes caused serious side effects such as diarrhea, nausea, abnormal taste, dyspepsia, abnormal pain/discomfort, headache, and angiodema. Therefore, there is a strong demand for compositions having all of the beneficial properties of current therapy agents but with less side effects. In this study, methanol extract from the dried inner bark of T. impetiginosa (taheebo) exhibited potent antibacterial activity against H. pylori. The biologically active constituents were identified as 2-(hydroxymethyl)anthraquinone, anthraquinone-2-carboxylic acid and lapachol.
Technical 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-H. pylori agents, amoxicillin, metronidazole and tetracycline. The biologically active components of T. 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 H. pylori ATCC 43504 at 0.01 mg/disc. Anthraquinone-2-carboxylic acid, lapachol and metronidazole were less effective, exhibiting moderate anti-H. pylori activity at 0.1 mg/disc. Amoxicillin and tetracycline 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 0.001 mg/disc while amoxicillin had little activity at this dose. In the MIC bioassay, 2-(hydroxymethyl)anthraquinone (2 µg/mL), anthraquinone-2-carboxylic acid (8 µg/mL), and lapachol (4 µg/mL) were more active than metronidazole (32 µg/mL) but less effective than amoxicillin (0.063 µg/mL) and tetracycline (0.5 µg/mL). The anti-H. 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 0.001 mg/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 T. impetiginosa dried inner bark-derived materials, particularly 2-(hydroxymethyl)anthraquinone, merit further study as potential H. pylori eradicating agents or lead compounds.