Effects of sponge-derived polybrominated diphenyl ethers on human cancer cell α-N-acetylgalactosaminidase and bacterial α-d-galactosidase and their antioxidant activity

During the search for glycosidase inhibitors among marine natural products that are environmental contaminants, we evaluated for the first time the potency of polybrominated diphenyl ethers 1–7 (5: OH-BDE47, 6: OH-BDE85, 7: OH-BDE137) isolated from Dysidea sponges on the hydrolyzing activity of cancer α-N-acetylgalactosaminidase (α-NaGalase) and the potency of dihydroxylated PBDEs 1 and 2 on the hydrolyzing activity of the recombinant α-D-galactosidase (α-PsGal) from the marine bacterium Pseudoalteromonas sp. KMM 701. The antioxidant activity of the spongean metabolites was assessed to test whether the antioxidant activity affects the activity of the enzymes under study. All OH-PBDEs/MeO-PBDEs tested had no effects on human cancer cell α-N-acetylgalactosaminidase. Dihydroxylated PBDEs 1 and 2 at micromolar levels quickly and irreversibly inhibited the bacterial α-D-galactosidase. Compounds 1–7 were shown to have low antioxidant activity at millimolar levels. It is likely that antioxidant activity is not responsible for the effectiveness of α-D-galactosidase inhibition due to the large difference in the concentrations required to display antioxidant activity (millimolar) and to inhibit an enzyme (micromolar).