Ketamine enantiomers differentially relax isolated coronary artery rings.

BACKGROUND AND OBJECTIVE: It has been shown that racemic ketamine increases coronary blood flow and that this effect is at least in part due to a direct vasorelaxing effect of this substance. This study was designed to determine whether ketamine might stereoselectively relax isolated porcine coronary arteries. METHODS: Using the model of isolated vessels we studied the effects of S(+) ketamine, R(-) ketamine, and racemic ketamine (5-500 microg mL(-1)) on artery strips pre-contracted by either potassium chloride (KCl) or prostaglandin F2alpha (PGF2alpha). To elucidate possible mechanisms of action these experiments were repeated in the presence of one of the following compounds: N(omega)-nitro-L-arginine (L-NNA), indomethacin, glibenclamide, and tetraethylammonium (TEA) chloride, an inhibitor of the BK(Ca) K+ channel. RESULTS: Both isoforms and racemic ketamine relaxed isolated coronary arteries in a concentration-dependent manner in concentrations beyond those used in clinical practice. S(+) ketamine exerted the strongest vasorelaxing effect, followed by racemic ketamine and R(-) ketamine. Pretreatment with L-NNA, indomethacin, or glibenclamide did not alter the vasodilating properties of ketamine, whereas TEA chloride significantly attenuated the vasorelaxing effects of all the three forms of ketamine. CONCLUSIONS: Ketamine dilates coronary arteries in vitro when administered in high concentrations. There is a stereoselective difference with a stronger vasorelaxing effect of S(+) ketamine compared to racemic and R(-) ketamine. The impact of TEA chloride suggests that the activation of the BK(Ca) channel may contribute to the vasodilating effect of ketamine.

The significance of lichens and their metabolites.

Lichens, symbiontic organisms of fungi and algae, synthesize numerous metabolites, the "lichen substances," which comprise aliphatic, cycloaliphatic, aromatic, and terpenic compounds. Lichens and their metabolites have a manifold biological activity: antiviral, antibiotic, antitumor, allergenic, plant growth inhibitory, antiherbivore, and enzyme inhibitory. Usnic acid, a very active lichen substance is used in pharmaceutical preparations. Large amounts of Pseudevernia furfuracea and Evernia prunastri are processed in the perfume industry, and some lichens are sensitive reagents for the evaluation of air pollution.

In vitro inhibition of 5-lipoxygenase by protolichesterinic acid from Cetraria islandica.

The aliphatic α-methylene-γ-lactone (+)-protolichesterinic acid (1), isolated from Cetraria islandica, has been shown to exhibit inhibitory effects on the enzyme 5-lipoxygenase in an in vitro assay in which porcine leucocytes are used as a source of the enzyme system. The isomeric compounds (+)-lichesterinic acid (2) and (-)-lichesterinic acid (4), prepared from (+)-protolichesterinic- and (-)-allo-protolichesterinic acids, respectively, exhibited anti-5-lipoxygenase activity of the same order of magnitude. (+)-Methyl lichesterinate (3) was, however, inactive. It was shown that despite its lipophilic nature, protolichesterinic acid is extractable into an aqueous medium, the concentration being dependent on the length of extraction.

Acetylenes and Other Constituents from Artemisia dracunculus.

The aerial parts of ARTEMISIA DRACUNCULUS afforded several known compounds as well as three new acetylenes, two phenylpropane derivatives, two monoterpenes, hex-3 Z-en-1-ol and vomifoliol A glucosides. The structures were elucidated by spectroscopic methods and a few chemical transformations.

Constituents of Evolvolus arbuscula ssp. canus.

From the aerial parts of EVOLVOLUS ARBUSCULA ssp. CANUS (Convolvulaceae) the nor-sesquiterpenoids, 15-norpanasinsan-5beta-ol-8-one, 15-nor-panasinsan-5,8-dione, and caryophyllenoxide, have been isolated together with some aliphatic compounds and sterols.

[Further Compounds from Centaurea stoebe.]. / Weitere Inhaltsstoffe aus Centaurea stoebe.

From CENTAUREA STOEBE the following compounds have been isolated: cnicin, salonitenolide, salonitenolid-8- O-(4'-acetoxy-5'-hydroxyangelate), stoebenolide, 3-hydroxy-2-methylbutyrolactone, and 3-(3, 4-dihydroxy-5-methoxyphenyl)-prop-1-yl 3-hydroxy-11-methyloctadecanoate.