METHODS AND RESULTS:
An EtOAc-soluble partition of the MeOH extract of a branch of Tetracera scandens (Dilleniaceae family) was subjected to a glucose-uptake assay, which led to the isolation and identification of five isoflavones of previously known structure namely, genistein (1), its derivatives 3',5'-Diprenylgenistein (2), 6,8-diprenylgenistein (3), derrone (4) and alpinumisoflavone (5). Of these, compounds 2--5 exhibited significant glucose-uptake activity in basal and insulin-stimulated L6 myotubes. The findings from adenosine monophosphate-activated kinase (AMPK) activation and glucose transport protein4 (GLUT4) and GLUT1 over-expression revealed certain characteristics of compounds 2--5. CONCLUSIONS: These compounds inhibited protein tyrosine phosphatase 1B (PTP1B) activities with IC50 values ranging from 20.63 +/- 0.17 to 37.52 +/- 0.31 microM. No muscle cell toxicity was reported with compounds 3--5, while compounds 1 and 3',5'-Diprenylgenistein reduced muscle cell viability with IC50 values of 34.27 +/- 0.35 and 18.69 +/- 0.19 microM, respectively. |