Synnøve Assev

Facile synthesis of 5-(alkylidene)thiophen-2(5H)-ones. A new class of antimicrobial agents

5-(Chloromethylene)- and 5-(bromoalkylidene)thiophen-2(5H)-ones are easily prepared from readily available 2-acyl-5-methoxythiophenes in one step by reaction with excess acetyl chloride or acetyl bromide. Other 5-(methylidene)thiophen-2(5H)-ones have been made from 5-(bromomethylene)thiophene-2(5H)-one by treatment with different nucleophiles. Eighteen thiophenones were tested for capacity to reduce biofilm formation by the marine bacterium V. harveyi. All but three compounds reduced biofilm formation markedly. For all effective compounds but one, the relative biofilm reducing capacity was greater than inhibition of bacterial planktonic growth.

Combined effect of xylitol, NaF and ZnCl2 on growth and metabolism of Streptococcus sobrinus OMZ 176

Xylitol, NaF and ZnCl2 in combination inhibited the growth of S. Sobrinus OMZ 176 when added to Brain Heart Infusion broth. Thin‐layer chromatography, followed by autoradiography of cell extracts, was used to study the inhibiting mechanism. Glucose uptake was reduced, the glycolysis inhibited at the glucose 6‐phosphate‐ and fructose‐ 1.6‐diphosphate level and the accumulation of xylitol metabolites was increased. These effects in combination probably accounted for the inhibition of growth.

Effects of xylitol/sorbitol combinations on bacterial growth and metabolism in Streptococcus sobrinus OMZ 176

Combinations of the non‐cariogenic sugar alcohols xylitol and sorbitol are widely used as sucrose substitutes in lozenges and chewing‐gums. In S. sobrinus OMZ 176 xylitol inhibits the metabolism of sorbitol, and the xylitol‐induced bacterial growth inhibition of S. sobrinus OMZ 176 has been shown to be enhanced by sorbitol. In combination with xylitol the sorbitol transport changes from a pts‐to a non‐pts transport, while the transport of xylitol is unaffected by the presence of sorbitol. It would be of interest to know how much xylitol has to be added to a sorbitol‐containing medium to inhibit the metabolism of this sugar alcohol. In the present study no optimal inhibitory concentrations of xylitol/sorbitol combinations were found. Growth and acid production in S. sobrinus OMZ 176 are essentially the same for xylitol: sorbitol ratios in the range from 1:7 to 7:1. The presence of intracellular xylitol metabolites seems to be essential.

Effects of protein synthesis inhibitors on the induction of a labile chicken plasma coagulation factor by preparations of phytoene and substituting factors.

Abstract The phytoene-dependent component of the labile coagulation factor activity complex in chicken plasma (the π -factor) responds uniformly to intravenous administration of preparations of phytoene, and of three unidentified “phytoene-substituting” factors: one occuring in lard, and two others in hog liver fat. In all cases there was an initial lag of about 10 min, followed by a rapid increase in π -factor concentration, reaching the maximum level about 35 min after the injection. The configuration of “active phytoene” and the structures of the phytoene-replacing factors remain unknown. The π -factor response was blocked and arrested by simultaneous and delayed injections, respectively, of cycloheximide and puromycin, whereas simultaneous or prior injection of actinomycin D had no effect on the response to the dietary factors. The data suggest that a post-transcriptional step in π -factor biosynthesis is regulated by the dietary factors or a common metabolite. Control of a specific pre-translational step and of an early step in reactions governing a specific post-translational process are considered as possible modes of action.