β-Glucuronidase inhibitory activity of bromophenol isolated from red alga Grateloupia lancifolia

Abstract

The human gastrointestinal (GI) tract plays an important role in disease and health. The overexpression of β -glucuronidase, an enzyme produced in the gastrointestinal tract, has been found to cause the retoxification of potentially damaging substances already detoxified by liver glucuronidation. Thus, β -glucuronidase has been implicated in a number of diseases including colon cancer, liver disease and Crohn s disease. This study investigated β -glucuronidase inhibitory activity of a bromophenol purified from the red alga Grateloupia lancifolia . Using an assay-guided fractionation technique, a bromophenol, bis(2, 3-dibromo-4, 5-dihydroxybenzyl) ether, a bromophenol, was isolated from the red alga G. lancifolia . Its structure was elucidated on the basis of extensive 1D- and 2D-NMR studies, high resolution EI-MS analysis and comparisons with literature data. Bis(2, 3-dibromo-4, 5-dihydroxybenzyl) ether showed potent β -glucuronidase inhibitory activity. The IC50 and KI values of bromophenol against E. coli β -glucuronidase were 0.54 and 0.53 mM, respectively. This bromophenol inhibited β -glucuronidase competitively and was stable at pH 2 up to 40 min at 37 ℃.