Inhibition of protein tyrosine phosphatase 1B by prenylated isoflavonoids isolated from the stem bark of Erythrina addisoniae

It has been suggested that protein tyrosine phosphatase 113 (PTP1B) inhibitors might be a therapeutic target for the treatment of type 2 diabetes and obesity. A bioassay-guided phytochemical study of the EtOAc extract of the stem bark of Erythrina addisoniae (Leguminosae) resulted in the identification of a new PTP1B inhibitory compound, 5,2,4 -trihydroxy-6-(gamma,gamma-dimethylallyl)-2"',2" -dimethyldihydropyrano[5"',6... ]isoflavanone (6), along with five known prenylated isoflavonoids, orientanol E (1), senegalensin (2), warangalone (3), warangalone 4 methyl ether (4) and 2,3-dihydroauriculatin (5). Compounds 1, 5 and 6 inhibited PTP1B with IC50 values ranging from 2.6 +/- 0.5 to 10.1 +/- 0.3 mu M. Our results indicate that hydroxylation at both 2 - and 4-positions in the B-ring and cyclization between a hydroxy group at C-7 and one of the prenyl groups at C-6 or C-8 in the A-ring may be important for activity. Thus, compounds 5 and 6 could be a new class of natural PTP1B inhibitors.