A new β-hydroxydihydrochalcone from Tephrosia uniflora, and the revision of three β-hydroxydihydrochalcones to flavanones

The CH2Cl2/MeOH (1:1) extract of the stems of Tephrosia uniflora yielded the new β-hydroxydihydrochalcone (S)-elatadihydrochalcone-2'-methyl ether (1) along with the three known compounds elongatin (2), (S)-elatadihydrochalcone (3), and tephrosin (4). The structures were elucidated by NMR spectroscopic and mass spectrometric data analyses. Elongatin (2) showed moderate antibacterial activity (EC50 of 25.3 μM and EC90 of 32.8 μM) against the Gram-positive bacterium Bacilus subtilis, and comparable toxicity against the MCF-7 human breast cancer cell line (EC50 of 41.3 μM). Based on the comparison of literature and predicted NMR data with that obtained experimentally, we propose the revision of the structures of three β-hydroxydihydrochalcones to flavanones.