Bioorganic Chemistry ( IF 5.1 ) Pub Date : 2018-03-07 , DOI: 10.1016/j.bioorg.2018.02.026 Zuo Peng Li , Hyeong-Hwan Lee , Zia Uddin , Yeong Hun Song , Ki Hun Park
Four new caged xanthones (1–4) and two known compounds (5, 6) were isolated from the roots of Cratoxylum cochinchinense, a polyphenol rich plant, collected in China. The structures of the isolated compounds (1–6) were characterized by obtaining their detailed spectroscopic data. In particular, compounds 1 and 6 were fully identified by X-ray crystallographic data. The isolated compounds (1–6) were evaluated against protein tyrosine phosphatase 1B (PTP1B), which plays an important role in diabetes, obesity, and cancer. Among these compounds, 3, 4, and 6 displayed significant inhibition with IC50 values of 76.3, 43.2, and 6.6 µM, respectively. A detailed kinetic study was conducted by determining Km, Vmax, and the ratio of Kik and Kiv, which revealed that all the compounds behaved as competitive inhibitors.