Effects of coadministration of natural polyphenols with doxycycline or calcium modulators on acute Chlamydia pneumoniae infection in vitro.

Besides small molecules from medicinal chemistry, natural products are still major sources of innovative therapeutic agents for various conditions, including infectious diseases. Here we present the first attempt to design a combination treatment targeted against Chlamydia pneumoniae infection using coadministration of natural phenolics with calcium (Ca(2+)) modulators, and also the concomitant administration of these compounds with doxycycline. An in vitro acute C. pneumoniae model in human lung epithelial cells was used and Loewe additivity model was applied to evaluate the effects. In general, the phenolic compounds, quercetin, luteolin, rhamnetin and octyl gallate did not improve the antichlamydial effect of doxycycline, and, in some cases, resulted in antagonistic effects. The combination of doxycycline and Ca(2+) modulators (isradipine, verapamil and thapsigargin) was at most additive, and at subinhibitory concentrations of doxycycline, often even antagonistic. The Ca(2+) modulators showed no inhibitory effects on C. pneumoniae growth alone, whereas the coadminstration of Ca(2+) modulators with phenolic compounds resulted in potentiation of the antichlamydial effect of phenolic compounds. Verapamil (100 µM) was synergistic with low quercetin and luteolin concentrations (0.39 and 1.56 µM), whereas 10 µM isradipine was synergistic with high quercetin, rhamnetin and octyl gallate concentrations (12.5 µM and 100 µM). Use of thapsigargin with the phenolic compounds resulted in the most intense synergism. Interaction indices 0.12 and 0.14 were achieved with 0.39 µM luteolin and 10 and 100 nM thapsigargin, respectively. To conclude, the observed results indicate that the Ca(2+) modulators potentiate the antichlamydial effects of the phenolic compounds.

Triterpenoid acids and lactones from the leaves of Fadogia tetraquetra var. tetraquetra (Rubiaceae).

Four triterpenoids isolated from the leaves of Fadogia tetraquetra var. tetraquetra, 3beta-hydroxy-11alpha, 12alpha-epoxyoleanan-28,13beta-olide (1), 3beta-hydroxyurs-11-en-28,13beta-olide (2), oleanolic acid (3), and ursolic acid (4), were evaluated for their antiviral and antibacterial properties. Compound 4 showed potent activity against the Semliki Forest virus with an IC50 of 14.7 microM, but was also found to be significantly cytotoxic (68% reduction in cell viability after 24 hours exposure at 50 microM) towards baby hamster kidney (BHK21) host cells. A viability assay on the mammalian human hepatocellular carcinoma (Huh-7) cell line showed no significant effects on intracellular ATP content after 48 hours exposure to compounds 1-4 at this concentration. Compound 4 also inhibited Staphylococcus aureus (MIC 12.5 microM), but was inactive against Enterobacter aerogenes, Escherichia coli, and Pseudomonas aeruginosa. Compounds 1-3 were inactive against all tested bacterial strains at 50 microM concentration.

The binding of synthetic retinoids to lipocalin beta-lactoglobulins.

The binding of therapeutically relevant synthetic retinoid derivatives to bovine and reindeer beta-lactoglobulin (betaLG) is demonstrated using fluorescence quenching and ultrafiltration/HPLC methods. Furthermore, synthesis of methyl (E)-3-[4-[(E)-2-(2,6,6-trimethylcyclohex-1-enyl)vinyl]phenyl]-acrylate 4 and (E)-3-[4-[(E)-2-(2,6,6-trimethylcyclohex-1-enyl)vinyl]phenyl]acrylic acid 5 is described. All studied compounds bind to both betaLG homologues with nanomolar K(d) values, and the interaction diminishes the pH-dependent aggregation of retinoids. Thus, betaLG may show benefits in improving the bioavailability of retinoid derivatives.