Chemical investigation on the root bark of Bombax malabarica

Ten compounds were isolated from the root bark of Bombax malabarica, including two new compounds, bombamalin (1) and 3,4,5-trimethoxyphenol-1-[β-xylopyranosyl-(1 → 2)]-β-glucopyranoside (3), and shorealactone (4), a rare dehydroascorbic acid fused l-ε-viniferin. Compound 1 is an unusual bissesquiterpene, containing a 1,4-dioxene ring formed by fusing isohemigossypol with ent-cadinen-2-one. Their structures were elucidated by extensive spectroscopic analysis. This chemical reinvestigation is of value for chemotaxonomy of the Bombax genus, in particular the finding of the unusual 1 and rare 4. Among the isolates, shorealactone (4), l-epicatechin 5-O-β-D-xyloside (5), and 2-C-[β-D-apiosyl-(1 → 6)]- β-D-glucosyl]-1,3,6-trihydroxy-7-methoxyxanthone (6) displayed some inhibition against α-glucosidase with IC₅₀ values of 224, 345, and 285 μM, respectively.