New prenylated flavanones from erythrina abyssinica with protein tyrosine phosphatase 1B (PTP1B) inhibitory activity

As the insulin and leptin signaling pathway can be regulated by PTP1B, it has been suggested that compounds that reduce PTP1B activity or expression levels can be used for treating type 2 diabetes and obesity. In the course of our screening efforts on new PTP1B inhibitors, six new flavanones (16) with dihydrofuran moiety and two known flavanones (7 and 8) were isolated from the stem bark of Erythrina abyssinica (Leguminosae). Their structures were elucidated on the basis of spectroscopic (including UV, CD, MS, 1D, and 2DNMR) and physicochemical analyses. With the exception of 3 and 5, the compounds inhibited PTP1B activity in an in vitro assay with IC₅₀ values ranging from 15.2±1.2 to 19.6±2.3μM, whereas RK-682 as a positive control displayed an IC₅₀ value of 4.7±0.5μM.