Bioassay-guided isolation of proanthocyanidins with antiangiogenic activities.

The proangiogenic members of the vascular endothelial growth factor (VEGF) family and related receptors play a central role in the modulation of pathological angiogenesis. In order to identify plant compounds able to interfere in the VEGFs/VEGFR-1 (Flt-1) recognition by VEGF family members, the extracts of the aerial parts of Campsiandra guayanensis and Feretia apodanthera were screened by a competitive ELISA-based assay. By using this bioassay-oriented approach five proanthocyanindins, including the new natural compounds (2S)-4',5,7-trihydroxyflavan-(4β→8)-afzelechin (1) and (2S)-4',5,7-trihydroxyflavan-(4β→8)-epiafzelechin (2) and the known geranin B (3), proanthocyanidin A2 (4), and proanthocyanidin A1 (5), were isolated.

Phenolic derivatives from Ruprechtia polystachya and their inhibitory activities on the glucose-6-phosphatase system.

Two new compounds, 5-methyl-2-(2-methylbutanoyl)phloroglucinol 1-O-(6-O-β-D-apiofuranosyl)-β-D-glucopyranoside (1) and trans-2,3-dihydrokaempferol 3-O-(4-O-sulfo)-α-L-arabinopyranoside (2), together with 14 known flavonoids, trans-dihydrokaempferol 3-O-α-L-arabinopyranoside (3), trans-taxifolin 3-O-α-L-arabinofuranoside (4), quercetin 3-O-α-L-rhamnopyranoside (5), quercetin 3'-O-α-L-arabinofuranoside (6), catechin 3-O-α-L-rhamnopyranoside (7), trans-taxifolin 3-O-α-L-arabinopyranoside (8), cis-dihydrokaempferol 3-O-α-L-arabinopyranoside (9), catechin (10), myricetin 3-O-α-L-rhamnopyranoside (11), quercetin 3-O-α-L-arabinopyranoside (12), quercetin 3-O-α-L-arabinofuranoside (13), quercetin 3-O-(3″-galloyl)-α-L-rhamnopyranoside (14), quercetin 3-O-(2″-galloyl)-α-L-rhamnopyranoside (15), and epicatechin 3-O-gallate (16), were isolated from the leaves of Ruprechtia polystachya Griseb. (Polygonaceae). Their structures were established on the basis of extensive 1D- and 2D-NMR experiments as well as MS analyses.

A new iridoid from Adenosma caeruleum R. Br.

A new iridoid glycoside, adenosmoside, together with five known phenylpropanoids, crenatoside, verbascoside, cistanoside F, campneoside I, and campneoside II and two known flavonoids, apigenin 7-O-beta-D-glucuronopyranoside and apigenin 7-O-beta-D-glucopyranoside, were isolated from the aerial parts of Adenosma caeruleum R. Br. Their structures were elucidated by spectral evidence.

Gypsins A-D from Gypsophila arabica.

Four new cyclopeptides, named gypsins A-D (1- 4), together with one known oleanane saponin, were isolated from the roots of Gypsophila arabica. The structures of cyclo(-Leu(1)-Pro(2)-Leu(3)-Trp(4)-Pro(5)-Gly(6)-) (1), cyclo(-Leu(1)-Pro(2)-Tyr(3)-Phe(4)-Pro(5)-Gly(6)-) (2), cyclo(-Ala(1)-Pro(2)-Tyr(3)-Leu(4)-Leu(5)-Pro (6)-Pro(7)-Ala(8)-) (3), and cyclo(-Leu(1)-Trp(2)-Pro(3)-Gly(4)-Gly(5)-Ser(6)-Ser(7)-) (4) were elucidated by 1D and 2D NMR spectroscopy including 1D-TOCSY, DQF-COSY, 2D-ROESY, HSQC, and HMBC experiments, as well as ESI tandem mass spectrometric fragmentation analysis and chemical evidence.