Urotensin II (U-II; cyclo [5][6][7][8][9][10] [H-Glu-Thr-Pro-Asp-Cys-Phe-TrpLys-Tyr-Cys-Val-OH]) is a potent vasoconstrictor in mammals, and it is postulated that it plays a central role in cardiovascular homeostasis. Thus, we initiated a structure-to-function analysis of this peptide characterized by a N-terminal tail and a cyclic core formed through a disulfide bridging. A total of 41 analogs focusing on these characteristics were developed and evaluated using a binding assay on membranes from a stable HEK-293 cell line containing the human or rat U-II receptor, a functional assay for Ca 2ϩ mobilization on transiently transfected CHO-K1 cells with the human or rat U-II receptor, and a rat thoracic aorta bioassay. At first, the focus was applied on peptide compounds containing exocyclic modifications. From this series, it appeared that only valine-11 played a significant role although it is not an essential amino acid. Similarly, endocyclic and ring transformations of hU-II were also studied. In most cases, a detrimental effect on affinity and biological activity was observed. However, two compounds, [Tyr 6 ]hU-II and [Phe 9 ]hU-II, retained affinity and activity. So far, our binding, functional, and pharmacological data clearly demonstrated the minor contribution of the N-terminal segment and the essential role of the cyclic structure. More particularly, three residues within the loop, i.e., Trp-7, Lys-8, and Tyr-9, are required for receptor recognition and activation. This three-pole feature, kept by the disulfide bond in a correct spatial arrangement, appears as the key pharmacophore for the U-II receptor.

The cyclic peptide human urotensin II (U-II) has been recently recognized as the endogenous ligand of an orphan GPCR, subsequently named the UT receptor. No synthetic ligands are available for investigating this novel peptide-receptor system. A novel UT receptor ligand, [Orn 8 ]U-II, was synthesized and evaluated in calcium functional assays performed on HEK293 cells expressing the recombinant rat and human UT receptor and in the rat aorta bioassay. [Orn 8 ]U-II behaves as a full agonist (pEC 50 &8) at both human and rat UT receptors in the FlipR calcium assay eliciting similar maximal eects as the natural ligand U-II. On the contrary, in the rat aorta bioassay, [Orn 8 ]U-II behaves as a competitive and selective antagonist (pA 2 =6.56) showing however a small but consistent residual agonist activity. It is therefore proposed that [Orn

The separation and quantification of the flavonoids occurring in Achillea nobilis L. by a CE-method is described. Using 20 mM sodium borate at pH 9.5 with 20 % of methanol as buffer, the flavonoids were sufficiently separated within 11 minutes. Kaempferol-7-O-neohesperidoside was used as internal standard for the quantification. Analysis of six different samples showed the flavon-C-glycosides isoorientin, orientin and vitexin as the characteristic main compounds. The contents of flavon-C-glycosides determined by this CE-method correlated with the results achieved by a spectrophotometric determination.