Past mastering of metal transformation enabled physicians to increase their therapeutic potential.

BACKGROUND: Metals are trace elements, vital in some instances or toxic in others. Due to this toxicity, they have been used since ancient time as antimicrobials, and prescribed when plant-only remedies were not efficient enough. These remedies could still contain secrets that may lead to the discovery of new therapeutically interesting combinations. The objective of this study was to give a proof of concept that such remedies combining metals and plants are worth studying again. METHODS: We exploited 4 medical formularies (aqrabadhin), from three Arab authors from the 9-12th century. We reproduced a remedy, and analyzed the role of each ingredient. We further looked for the minimum inhibitory concentration against three pathogenic bacteria, and we analyzed toxic and inflammatory effects of this remedy on macrophages. RESULTS: Even if plants were extensively used (almost 80 % of all ingredients), more than 36 different minerals have been found in these 4 aqrabadhin. When it came to remedies against infections that could be applied externally, the use of metals grew to 70 %. We focused on a remedy, containing mainly metals. We have been able to attribute a role for each ingredient, to show that this skin remedy helped to combat the infection and to resorb the wound, and to highlight the mastering of metal transformation by these physicians. CONCLUSIONS: With a very simple recipe, mainly composed of metals, these past physicians designed a complete and synergistic remedy to combat abscesses, while restricting the toxic effect of metals to the site of infection. It is a first example showing that different metal manufactures were evolved to improve their therapeutic potentials. The knowledge acquired by these physician should deserve more attention, and unexpected features, original organo-metallic compounds or therapeutic synergy could still be found from such research.

Removal of NOx from lean exhaust gas by storage/reduction on H3PW12O40 x 6H2O supported on Ce(x)Zr4-xO8.

We have demonstrated the interest of using Zr-Ce mixed oxides as supports for the system H3PW12O40 x 6H2O (HPW) and Pt for the storage (absorption into HPW and adsorption on Zr-Ce support)-reduction of NOx. Zr-Ce oxides adsorb NOx (mainly NO2) as nitrates, which are desorbed thermally as NO2 and NO (12 mg of NOx x g(-1)). On (HPW-Pt)/Zr-Ce system, NO and NO2 are stored equimolarly by substitution of water molecules of the HPW structure. The Zr/Ce support molar ratio has an important influence on the quantity of NOx stored with a maximum for the system Zr/Ce = 0.5. The presence of Pt has no influence on storage capacity but rather on its efficiency, and it is essential when reducing. Pt strongly accelerates both NOx desorption and reduction processes. Reduction of NOx occurs with H2, CO, or an H2/CO mixture. With H2, NO2 is reduced to NO. With CO, it seems reasonable that the mechanism of NO2 reduction concerns its reaction with CO to produce CO2 and NO. Addition of H2 to CO accelerates the reduction process. However, the difference between NOx stored and desorbed implies also the presence of another reduction step. This could be related to an NO interaction with an active site which produces its decomposition with nitrogen as product. The catalytic system proposed is highly selective since no N2O formation was detected.