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Biomedical subjects

G Rücker

Publications and source records attributed to G Rücker.

101 records · Page 6Linked to original sources
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Antimalarial activity of 1,4-epidioxy-bisabola-2,12-diene derivatives.

1,4-Epidioxy-bisabola-2,12-diene (3) and aromatic hydroperoxides (4, 5) were prepared by photoxidation of gamma-curcumene (1). Reduction and esterification of 6 and 7 afforded compounds 9 to 10. All compounds were tested in vitro for antimalarial activity. The activity could not be increased significantly, compared with 3. The most active compounds, 3 and 9, did not show in vivo antimalarial activity in mice.

Animals↗
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On finding nonisomorphic connected subgraphs and distinct molecular substructures.

The problem of finding all nonisomorphic subgraphs of a given graph (all distinct substructures of a given molecular structure) is discussed. A computer program is introduced that first generates all connected subgraphs and then uses a combination of well-discriminating graph invariants to eliminate duplicates. The program is broadly applicable, in particular for molecular graphs which may or may not contain unsaturation or heteroatoms. The number of distinct substructures (Ns), proposed earlier as a measure of a compound's complexity which takes into account its symmetry, is thus automatically obtained. As was to be expected, due to the nature of the problem the computational effort increases exponentially with problem size, whence in most cases complexity measures other than Ns are to be preferred.

Journal Article↗
PubMedDate not supplied

On walks in molecular graphs.

Walks in molecular graphs and their counts for a long time have found applications in theoretical chemistry. These are based on the fact that the (i, j)-entry of the kth power of the adjacency matrix is equal to the number of walks starting at vertex i, ending at vertex j, and having length k. In recent papers (refs 13, 18, 19) the numbers of all walks of length k, called molecular walk counts, mwc(k), and their sum from k = 1 to k = n - 1, called total walk count, twc, were proposed as quantities suitable for QSPR studies and capable of measuring the complexity of organic molecules. We now establish a few general properties of mwc's and twc among which are the linear dependence between the mwc's and linear correlations between the mwc's and twc, the spectral decomposition of mwc's, and various connections between the walk counts and the eigenvalues and eigenvectors of the molecular graph. We also characterize the graphs possessing minimal and maximal walk counts.

Journal Article↗
PubMedDate not supplied

Substructure, subgraph, and walk counts as measures of the complexity of graphs and molecules.

In discussions of unsaturated compounds represented by multigraphs it is necessary to distinguish between the notions of substructure and subgraph. Here the difference is explained and exemplified, and a computer program is introduced which for the first time is able to construct and count all substructures and subgraphs for a colored multigraph (a molecular compound which may contain unsaturation and heteroatoms). Construction of all substructures and subgraphs is computationally demanding; therefore, two alternatives are pointed out for the treatment of large sets of compounds: (i) Often it will suffice to consider counts of substructures/subgraphs up to a certain number of edges only, information which is provided by the program much more rapidly. (ii) It is shown that information equivalent to that gained from substructure or subgraph counts is often far more easily available using walk counts. Some problems and their consequences for substructure/subgraph/walk counts are discussed that arise from the models used in organic chemistry for certain compounds such as aromatics and from the necessity to express qualitative features of molecular structures numerically.

Journal Article↗
PubMedDate not supplied

Reduction of ischaemic rest pain in advanced peripheral arterial occlusive disease. A double blind placebo controlled trial with iloprost.

Severe pain at rest is a major symptom of advanced peripheral arterial occlusive disease (PAOD). Preliminary studies of treatment with iloprost, a prostacyclin analogue, showed encouraging results in patients with ischaemic rest pain. Therefore a randomized, placebo-controlled multicentre study was undertaken in 113 patients admitted to hospital with rest pain of at least 2 weeks duration caused by severe PAOD. The patients were randomly assigned to receive 2-week placebo or iloprost infusions for 6 hours per day at a dose of 0.5-0.2 ng/kg/min in addition to conventional care. Demographic data and arteriographic findings were similar in the two groups. Eleven patients withdrew from the study before completion and 102 patients could be included in the final analysis. Significantly more patients in the iloprost group (62.5% of 48) than in the placebo group (42.6% of 54) had complete relief of pain without analgesic therapy during at least five consecutive days at the end of the treatment period (p less than 0.05, chi 2-test). Facial flush, headache and nausea were the most common side effects during iloprost infusion. Serious adverse reactions did not occur. Thus, a 2-week iloprost infusion was shown to be safe and effective as a treatment for ischaemic rest pain caused by PAOD.

Adult↗
PubMedDate not supplied

[Quantitative determination of alpha-peroxyachifolide in yarrow by HPLC with amperometric detection].

A HPLC method with amperometric detection is established for the contact allergen alpha-peroxyachifolid (1) from yarrow (Achillea millefolium L., s. str.). The amounts of 1 are between 0.25 and 0.60% in blossoms, dried 2 h at room temperature, and between 0.01 and 0.05% in the leaves. In completely dried material and in some preparations from the market 1 could also be quantified.

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