Protein tyrosine phosphatase 1B (PTP1B) plays an important role as a negative regulator in insulin signaling pathways. PTP1B is an effective target for the treatment of type 2 diabetes mellitus. Four bromophenol derivatives from red algae Rhodomela confervoides, 2,2′,3,3′-tetrabromo-4,4′,5,5′-tetra- hydroxydiphenyl methane (1), 3-bormo-4,5-bis(2,3-dibromo-4,5-dihydroxybenzyl) pyrocatechol (2), bis(2,3-dibromo-4,5-dihydroxybenzyl) ether (3) and 2,2′,3-tribromo-3′,4,4′,5-tetrahydroxy-6′-ethyloxy- methyldiphenylmethane (4) showed significant inhibitory activity against PTP1B (IC50 were 2.4, 1.7, 1.5 and 0.84 μmol/L, respectively) as potential therapeutical agents for the treatment of type 2 diabetes mellitus. The anti-hyperglycemic effects of the ethanol extracts from R. confervoides on streptozoto- cin-induced diabetes (STZ-diabetes) in male Wistar rats fed with high fat diet were investigated. The STZ-diabetic rats treated with medium-dose and high-dose alga extracts showed remarkable reductions in fasting blood glucose (FBG) as compared with the STZ-diabetic control. The results indicate that the in vivo anti-hyperglycemic activity of the R. confervoides extracts can be partially attributed to the in- hibitory actions against PTP1B of the bromophenol derivatives and that may be of clinical importance in improving the management of type 2 diabetes mellitus.
