Two New Flavanols from Glycosmis pentaphylla and Their Cytotoxic Activities

Two new flavanols, (8S,9R)‐9,10‐dihydro‐5,9‐dihydroxy‐8‐(3,4,5‐trimethoxyphenyl)‐2H,8H‐benzo1,2‐b:3,4‐b′]dipyran‐2‐one ( 1 ) and (2S,3R)‐3,4‐dihydro‐3,5‐dihydroxy‐2‐(3,4,5‐trimethoxyphenyl)‐2H,8H‐benzo1,2‐b:3,4‐b′]dipyran‐8‐one ( 2 ), were isolated from the stems of Glycosmis pentaphylla. The structures of these compounds were determined by extensive spectroscopic (UV, IR, HR‐ESI‐MS, 1D‐ and 2D‐NMR) analyses. The cytotoxic activities of these compounds were evaluated using the MTT method. The results showed that compounds 1 and 2 exhibited considerable cytotoxic activities against HL‐60 and A549 cell lines.