Polyoxygenated cyclohexene derivatives and flavonoids from the leaves of Uvaria pandensis.

Three new oxygenated cyclohexene derivatives, pandensenol D - F (1-3), two new flavanoids, pandensone A and B (4-5), and seven known compounds (6-12) were isolated from the methanol extract of the leaves of Uvaria pandensis Verdc. (Annonaceae). The structures were characterized by NMR spectroscopic and mass spectrometric analyses. The isolated metabolites were evaluated for their antibacterial activity against the Gram-positive bacteria Bacillus subtilis and Staphylococcus epidermidis, the Gram-negative bacteria Enterococcus raffinosus, Escherichia coli, Paraburkholderia caledonica, Pectobacterium carotovorum and Pseudomonas putida, and for cytotoxicity against the MCF-7 human breast cancer cell line. Out of the tested compounds, pandensenol D (1) and (6',7'-dihydro-8'α,9'ß-dihydroxy)-3-farnesylindole (12) showed weak activity, whereas (8'α,9'ß-dihydroxy)-3-farnesylindole (11) strong activity against B. subtilis. Four of the isolated compounds (1, 4, 11 and 12) showed moderate cytotoxicity against MCF-7 breast cancer cells (EC50 > 100 µM).

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.

Oxygenated Cyclohexene Derivatives from the Stem and Root Barks of Uvaria pandensis.

Five new cyclohexene derivatives, dipandensin A and B (1 and 2) and pandensenols A-C (3-5), and 16 known secondary metabolites (6-21) were isolated from the methanol-soluble extracts of the stem and root barks of Uvaria pandensis. The structures were characterized by NMR spectroscopic and mass spectrometric analyses, and that of 6-methoxyzeylenol (6) was further confirmed by single-crystal X-ray crystallography, which also established its absolute configuration. The isolated metabolites were evaluated for antibacterial activity against the Gram-positive bacteria Bacillus subtilis and Staphylococcus epidermidis and the Gram-negative bacteria Enterococcus raffinosus, Escherichia coli, Paraburkholderia caledonica, Pectobacterium carotovorum, and Pseudomonas putida, as well as for cytotoxicity against the MCF-7 human breast cancer cell line. A mixture of uvaretin (20) and isouvaretin (21) exhibited significant antibacterial activity against B. subtilis (EC50 8.7 µM) and S. epidermidis (IC50 7.9 µM). (8'α,9'ß-Dihydroxy)-3-farnesylindole (12) showed strong inhibitory activity (EC50 9.8 µM) against B. subtilis, comparable to the clinical reference ampicillin (EC50 17.9 µM). None of the compounds showed relevant cytotoxicity against the MCF-7 human breast cancer cell line.

Antibacterial and cytotoxic biflavonoids from the root bark of Ochna kirkii.

The new isoflavonoid kirkinone A (1) and biflavonoid kirkinone B (2) along with six known compounds (3-8) were isolated from the methanolic extract of the root bark of Ochna kirkii. The compounds were identified by NMR spectroscopic and mass spectrometric analyses. Out of the eight isolated natural products, calodenin B (4) and lophirone A (6) showed significant antibacterial activity against the Gram-positive bacterium Bacillus subtilis with MIC values of 2.2 and 28 µM, and cytotoxicity against the MCF-7 human breast cancer cell line with EC50 values of 219.3 and 19.2 µM, respectively. The methanolic crude extract of the root bark exhibited cytotoxicity at EC50 8.4 µg/mL. The isolated secondary metabolites and the crude extract were generally inactive against the Gram-negative Escherichia coli (MIC ≥400 µg/mL). Isolation of biflavonoids and related secondary metabolites from O. kirkii demonstrates their chemotaxonomic significance to the genus Ochna and to other members of the family Ochnaceae.

Biflavanones, Chalconoids, and Flavonoid Analogues from the Stem Bark of Ochna holstii.

Two new biflavanones (1 and 2), three new bichalconoids (3-5), and 11 known flavonoid analogues (6-16) were isolated from the stem bark extract (CH3OH-CH2Cl2, 7:3, v/v) of Ochna holstii. The structures of the isolated metabolites were elucidated by NMR spectroscopic and mass spectrometric analyses. The crude extract and the isolated metabolites were evaluated for antibacterial activity against Bacillus subtilis (Gram-positive) and Escherichia coli (Gram-negative) as well as for cytotoxicity against the MCF-7 human breast cancer cell line. The crude extract and holstiinone A (1) exhibited moderate antibacterial activity against B. subtilis with MIC values of 9.1 µg/mL and 14 µM, respectively. The crude extract and lophirone F (14) showed cytotoxicity against MCF-7 with EC50 values of 11 µg/mL and 24 µM, respectively. The other isolated metabolites showed no significant antibacterial activities (MIC > 250 µM) and cytotoxicities (EC50 ≥ 350 µM).

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.