Three novel compounds from the flowers of Bombax malabaricum

Two unusual 9'-norneolignans, bombasin (1) and bombasin 4-O-beta-glucoside (2), and a novel D-gulono-gamma-lactone derivative, bombalin (3), were isolated from the flowers of Bombax malabaricum, together with the three known compounds dihydrodehydrodiconiferyl alcohol 4-O-beta-D-glucopyranoside (4), trans-3-(p-coumaroyl)quinic acid (5), and neochlorogenic acid (6). Their structures were elucidated by extensive spectroscopic methods as well as chemical transformation. Compounds 1-3 were evaluated against the HGC-27 gastrointestinal and Hela cervical human cancer cell lines, but all were inactive in both lines (IC50 > 50 mu m).