4-Alkyl-5,7-dihydroxycoumarins from the flowering buds of Mesua ferrea.

Five new 4-alkyl-5,7-dihydroxycoumarins, Mesuaferol G-K (1-5), together with four known 4-alkyl-5,7-dihydroxycoumarins (6-9) were isolated from the methanol extraction of the flowering buds of Mesua ferrea by flash extraction. Their structures were established on the basis of extensive analyses of HR-ESI-MS, UV, IR and NMR methods, the absolute configurations were confirmed by the Mosher's method and circular dichroism (CD) measurement and theoretical calculation (ECD) methods. Additionally, a putative biogenetic relationship of these compounds was also proposed. The cytotoxicity of all these isolates against HepG2, MCF-7 and Hela cancer cell lines was evaluated. In MCF-7 and Hela cell lines, all compounds exhibited strong activity (IC₅₀ in the range of 3.21-13.54 μM and 4.69-14.47 μM, respectively), while almost all compounds showed moderate cytotoxic activities against HepG2 cell lines.