Two new carboxyethylflavanones from the heartwood of Dalbergia tonkinensis and their antimicrobial activities

Abstract

Two new carboxyethylflavanone derivatives, (2S)-8-carboxyethylnarigenin (2) and (2S)-6,8-dicarboxyethylpinocembrin (3) were isolated from the heartwood of Dalbergia tonkinensis Prain, along with four known compounds 1, and 4-6. The chemical structures of two new compounds 2 and 3 were elucidated based on analyses of the spectroscopic data, including 1D and 2D NMR, HR-ESI-MS, IR, UV, and CD spectroscopies. By carrying out antimicrobial assay, CH3OH and CHCl3 fractions exhibited weak MIC value at 200 μg/mL against filamentous fungus A. Niger (439), whereas the known flavanone 1 and the new carboxyethylflavanone 2 had MIC at 100 μg/mL.