Losses of metabolically incorporated selenium in common digestion procedures for biological material.

Two common procedures for wet destruction of biological materials for subsequent determination of selenium have been investigated. Rat organs and biological fluids were endogenously labelled with (75)Se to monitor losses during the procedures. Addition of nitric and perchloric acids with gradual heating up to 210 degrees seemed to be the best method: at this temperature the labelled selenium was still recovered quantitatively, and the destruction was fast and efficient.

Effect of temperature on in vitro proliferative activity of human umbilical vein endothelial cells.

Human umbilical vein endothelial cells, skin fibroblasts, and retinal pigment epithelial cells are cultivated in medium supplemented with 15 to 20% serum in our laboratory. The effects of various incubation temperatures on the proliferation of these cells was examined. Our study shows that the mitogenic response of the endothelial cells to a change of temperature differed markedly from that of the fibroblasts and epithelial cells. Cultivation of human umbilical vein endothelial at 37 degrees C required seeding densities as high as 1-2 x 10(4) cells/cm2, and yet resulted in a low growth rate and premature senescence. However, under the same culture conditions, but at 33 degrees C, the proliferative capacity of these endothelial cells was potentiated. The results were striking; at 33 degrees C the cells grew actively and the life span was extended. The number of cumulative population doublings increased fourfold compared with that for the same cells cultivated at 37 degrees C. The inoculum size could be reduced, since at 33 degrees C the endothelial cells were able to replicate at seeding densities as low as 20 cells/cm2. The cells serially subcultured at 33 degrees C retained morphological features and specific immunological markers of endothelial cells.

Synthesis and evaluation of caffeic acid amides as antioxidants.

A series of amides of caffeic acid has been synthesised and their antioxidant properties evaluated as lipid peroxidation inhibitors. Anilides of caffeic acid were found to be very efficient antioxidants with IC50's of 0.3 microM.

Chemical and biological investigations on Zizyphus spina-christi L.

Different extracts and fractions of the leaves, fruits and seeds of Zizyphus spina-christi L. grown in Egypt were investigated in vitro for their antiviral, antifungal and antibacterial activities. The flavonoids quercetin, hyperoside, rutin and quercetin-3-O-[beta-xylosyl-(1-2)-alpha-rhamnoside] 4'-O-alpha- rhamnoside) were isolated.

In vitro biological activities of alkaloids from Cryptolepis sanguinolenta.

In our biological screening of higher plants, an aqueous and an 80% EtOH extract from the root bark of Cryptolepis sanguinolenta showed potent antibacterial, anticomplementary, and moderate antiviral activities, but no antifungal effect could be detected. Bioassay-guided fractionation of the 80% EtOH extract led to the isolation of three alkaloids: quindoline (1), hydroxycryptolepine (2), cryptolepine.HCl (3), and the corresponding base cryptolepine (4). All compounds strongly inhibited the growth of Gram-positive bacteria (MIC < or = 100 micrograms/ml) and showed a moderate (MIC = 125 or 250 micrograms/ml), a weak (MIC = 500 micrograms/ml), or no activity (MIC > 500 micrograms/ml) against selected Gram-negative bacteria. They also possessed a bactericidal effect depending on the bacterial strain. Compounds 1, 2 and 3 displayed a dose-dependent inhibitory effect on the classical pathway of the complement system while compounds 2 and 3 activated the alternative pathway, except for compound 1. Compound 3 was found to possess an antiherpetic activity. Compounds 1 and 4 showed no antiviral effect, but were quite cytotoxic in the antiviral test system down to a concentration of 1 microgram/ml.

Antibacterial and antifungal activities of neocryptolepine, biscryptolepine and cryptoquindoline, alkaloids isolated from Cryptolepis sanguinolenta.

From the 80% EtOH extract of Cryptolepis sanguinolenta (Lindl.) Schlechter (Periplocaeae) root bark, a cryptolepine isomer named neocryptolepine, and two dimeric alkaloids named biscryptolepine and cryptoquindoline were isolated. These compounds were tested for their putative antibacterial and antifungal activities. Results have indicated that neocryptolepine showed an antibacterial activity against Gram-positive bacteria (MIC < 100 µg/ml), but was less acive against Gram-negative bacteria. It also inhibited the growth of the yeast C. albicans. Biscryptolepine exhibited only an activity against some Gram-positive bacteria (MIC = 62.5 or 31 µg/ml) while cryptoquindoline did not shown an activity against all selected microorganisms. The antibacterial activity of neocryptolepine and biscryptolepine is bacteriostatic rather than bactericidal. No antifungal activity could be observed for all alkaloids in our test system at the highest test concentration of 100 µg/ml.