Three Novel Compounds from the Flowers of Bombax malabaricum

Two unusual 9′‐norneolignans, bombasin ( 1 ) and bombasin 4‐O‐β‐glucoside ( 2 ), and a novel D ‐gulono‐γ‐lactone derivative, bombalin ( 3 ), were isolated from the flowers of Bombax malabaricum, together with the three known compounds dihydrodehydrodiconiferyl alcohol 4‐O‐β‐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 μM ).