Application of Residual Dipolar Couplings and Selective Quantitative NOE to Establish the Structures of Tetranortriterpenoids from <i>Xylocarpus rumphii</i>

Nine triterpenoid derivatives were isolated from the heartwood of <i>Xylocarpus rumphii</i> and were identified as xylorumphiins E (<b>1</b>), C (<b>2</b>), L (<b>3</b>), and M–R (<b>4</b>–<b>9</b>). Compounds <b>4</b>–<b>9</b> have a hemiacetal group in the triterpenoid side chain, making them impossible to purify. Purification was achieved after acetylation and subsequent separation of the epimeric mixtures of acetates; however differentiaition of the <i>R</i> and <i>S</i> epimers was not possible using standard NMR techniques. In one case, the relative configuration of a remotely located stereocenter with respect to the stereocenters in the main skeleton was unambiguously determined using residual dipolar couplings. Dipolar couplings were collected from the sample oriented in compressed poly­(methyl methacrylate) gels swollen in CDCl₃. In another case, the relative configuration was determined using 1D selective quantitative NOE experiments. Xylorumphiin K (<b>10</b>), xyloccensin E, taraxer-14-en-3β-ol, (22<i>S</i>)-hydroxytirucalla-7,24-diene-3,23-dione, and 25-hydroxy-(20<i>S</i>,24<i>S</i>)-epoxydammaran-3-one were isolated from the bark of the same plant. Compounds <b>3</b>–<b>10</b> are new compounds. Compounds <b>1</b>–<b>6</b> and xyloccensin E were tested at one concentration, 1 × 10^–5 M, in the NCI59 cell one-dose screen but did not show significant activity

Application of Residual Dipolar Couplings and Selective Quantitative NOE to Establish the Structures of Tetranortriterpenoids from <i>Xylocarpus rumphii</i>

Nine triterpenoid derivatives were isolated from the heartwood of <i>Xylocarpus rumphii</i> and were identified as xylorumphiins E (<b>1</b>), C (<b>2</b>), L (<b>3</b>), and M–R (<b>4</b>–<b>9</b>). Compounds <b>4</b>–<b>9</b> have a hemiacetal group in the triterpenoid side chain, making them impossible to purify. Purification was achieved after acetylation and subsequent separation of the epimeric mixtures of acetates; however differentiaition of the <i>R</i> and <i>S</i> epimers was not possible using standard NMR techniques. In one case, the relative configuration of a remotely located stereocenter with respect to the stereocenters in the main skeleton was unambiguously determined using residual dipolar couplings. Dipolar couplings were collected from the sample oriented in compressed poly­(methyl methacrylate) gels swollen in CDCl₃. In another case, the relative configuration was determined using 1D selective quantitative NOE experiments. Xylorumphiin K (<b>10</b>), xyloccensin E, taraxer-14-en-3β-ol, (22<i>S</i>)-hydroxytirucalla-7,24-diene-3,23-dione, and 25-hydroxy-(20<i>S</i>,24<i>S</i>)-epoxydammaran-3-one were isolated from the bark of the same plant. Compounds <b>3</b>–<b>10</b> are new compounds. Compounds <b>1</b>–<b>6</b> and xyloccensin E were tested at one concentration, 1 × 10^–5 M, in the NCI59 cell one-dose screen but did not show significant activity

Application of Residual Dipolar Couplings and Selective Quantitative NOE to Establish the Structures of Tetranortriterpenoids from <i>Xylocarpus rumphii</i>

Nine triterpenoid derivatives were isolated from the heartwood of <i>Xylocarpus rumphii</i> and were identified as xylorumphiins E (<b>1</b>), C (<b>2</b>), L (<b>3</b>), and M–R (<b>4</b>–<b>9</b>). Compounds <b>4</b>–<b>9</b> have a hemiacetal group in the triterpenoid side chain, making them impossible to purify. Purification was achieved after acetylation and subsequent separation of the epimeric mixtures of acetates; however differentiaition of the <i>R</i> and <i>S</i> epimers was not possible using standard NMR techniques. In one case, the relative configuration of a remotely located stereocenter with respect to the stereocenters in the main skeleton was unambiguously determined using residual dipolar couplings. Dipolar couplings were collected from the sample oriented in compressed poly­(methyl methacrylate) gels swollen in CDCl₃. In another case, the relative configuration was determined using 1D selective quantitative NOE experiments. Xylorumphiin K (<b>10</b>), xyloccensin E, taraxer-14-en-3β-ol, (22<i>S</i>)-hydroxytirucalla-7,24-diene-3,23-dione, and 25-hydroxy-(20<i>S</i>,24<i>S</i>)-epoxydammaran-3-one were isolated from the bark of the same plant. Compounds <b>3</b>–<b>10</b> are new compounds. Compounds <b>1</b>–<b>6</b> and xyloccensin E were tested at one concentration, 1 × 10^–5 M, in the NCI59 cell one-dose screen but did not show significant activity

Antiangiogenic Pterocarpan and Flavonoid Constituents of <i>Erythrina lysistemon</i>

The roots of Erythrina lysistemon, growing in Egypt, yielded 24 flavonoid compounds, including 17 pterocarpans, two isoflavanones, one flavanone, two isoflavans, one 2-arylbenzofuran, and an isoflava-3-ene. Nine pterocarpans have not been reported previously (7–9, 11–14, 19, and 20), and 11 are reported here for the first time from this species. Structures were established using HRESIMS, NMR, and circular dichroism techniques. Selected compounds were tested for their ability to block the growth of human retinal endothelial cells and antiangiogenic activity in vitro. The isoflavonoids 5 and 6, and the pterocarpans 1, 2, 4, 20, and 22 demonstrated selective antiproliferative activities on endothelial cells compared to a nonendothelial cell type, with concentration-dependent antiangiogenic effects in vitro against HRECs, a cell type relevant to neovascular eye diseases

Phytochemical Investigations of Three <i>Rhodocodon</i> (Hyacinthaceae Sensu APG II) Species

The genus <i>Rhodocodon</i> (Hyacinthaceae sensu APG II) is endemic to Madagascar, and its phytochemistry has not been described previously. The phytochemistry of three species in this genus has been investigated, and eight compounds, including three bufadienolides (compounds <b>1</b>, <b>4</b>, and <b>5</b>), a norlignan (<b>2</b>), and four homoisoflavonoids (compounds <b>3</b> and <b>6</b>–<b>8</b>), have been isolated and identified. Compounds <b>1</b>–<b>3</b> and <b>6</b>–<b>8</b> have not been described previously. The COX-2 inhibitory activity of compound <b>6</b> and compound <b>7</b> acetate (compound <b>7A</b>) was investigated on isolated colorectal cancer cells. Compounds <b>6</b> and <b>7A</b> inhibited COX-2 by 10% and 8%, respectively, at a concentration of 12.5 μM compared to 12% for 1 mM aspirin (the positive control)