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

The CH2Cl2/MeOH (1:1) extract of the stems of Tephrosia uniflora yielded the new ß-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 ß-hydroxydihydrochalcones to flavanones.

Antibacterial and cytotoxic prenylated dihydrochalcones from Eriosema montanum.

Two new prenylated dihydrochalcones (1,2) and eighteen known secondary metabolites (3-20) were isolated from the CH2Cl2-MeOH (1:1) extracts of the roots, the stem bark and the leaves of Eriosema montanum Baker f. (Leguminosae). The structures of the isolated compounds were characterized by NMR, IR, and UV spectroscopic and mass spectrometric analyses. The structures of compounds 5, 10, 11 and 13 were confirmed by single crystal X-ray diffraction. The antibacterial activity of the crude extracts and the isolated constituents were established against Gram-positive and Gram-negative bacteria. Among the tested compounds, 1-4 and 10 showed strong activity against the Gram-positive bacterium Bacillus subtilis with minimum inhibitory concentration (MIC) ranging from 3.1 to 8.9 µM, as did the leaf crude extract with an MIC of 3.0 µg/mL. None of the crude extracts nor the isolated compounds were active against Escherichia coli. Compounds 1, 3 and 4 showed higher cytotoxicity, evaluated against the human breast cancer cell line MCF-7, with EC50 of 7.0, 18.0 and 18.0 µM, respectively. These findings contribute to the phytochemical understanding of the genus Eriosema, and highlight the pharmaceutical potential of prenylated dihydrochalcones.