In-vivo and in-vitro assessment of the free-radical-scavenger activity of Ginkgo flavone glycosides at high concentration.

Free radicals are involved in numerous skin diseases, especially inflammatory reactions and photosenescence. To identify possible free-radical scavenging by an original terpene-free Ginkgo biloba extract containing 33% Ginkgo flavone glycosides, mostly quercetin and kaempferol derivatives, we studied its activity by means of in-vitro and in-vivo experiments, using superoxide dismutase (SOD) as a positive control. By means of an in-vitro electron-spin resonance (ESR) assay we compared the activity of the Ginkgo extract with that of its two aglycones, quercetin and kaempferol. Quercetin and Ginkgo extract had significant antioxidant properties without pro-oxidant effect. In contrast, kaempferol, above an optimum antioxidant concentration, behaved as a pro-oxidant. The in-vivo experiments were conducted on an anti-inflammatory model. The cutaneous blood flux which reflects the skin inflammatory level was recorded by means of a laser Doppler perfusion imager. The data confirmed the free-radical-scavenging property of both Ginkgo extract and SOD. The Ginkgo extract significantly inhibited (37%) cutaneous blood flux to the same extent as SOD. These data confirmed the antioxidant property of Ginkgo extract. A complementary spin-trapping technique would enable identification of the free radicals involved. This Ginkgo extract should be useful for protection of the skin against free radicals.

LDV assessment of methyl nicotinate biological response in aqueous solution against that of a w/o microemulsion system.

Synopsis The aim of this work was to check if the specific microstructure of a water/oil nonionic microemulsion could induce a modification of the bioavailability of a probe (methyl nicotinate). The vasodilatory drug effects were recorded by laser doppler velocimetry in vivo, in man. The results show a quicker activity, and a better release of the drug in the microemulsion, than in the well-known kinetics of an aqueous solution.

Assessment of topical non-steroidal anti-inflammatory drugs.

A new non-invasive technique for assessing the efficacy of topical non-steroidal anti-inflammatory drugs (NSAID) in man is proposed. The NSAID are initially applied to the skin under occlusion before inflammation is induced by a methyl nicotinate solution. The inflammatory response is quantified in terms of cutaneous blood flow by a laser Doppler velocimeter (LDV). The efficacy of NSAID preparations is calculated by comparing the responses of the LDV to the methyl nicotinate challenge on the pretreated and the non-treated skin sites. This protocol has been used to investigate the effect of three different NSAID preparations (indomethacin, niflumic acid, palmitoyl collagenic acid) and the influence of the vehicle on the efficacy of indomethacin. The three preparations tested gave positive results but with different amplitudes in response. The efficacy of indomethacin varied with the vehicle used.