EFFECT OF SOME NATURAL UV-ABSORBERS ON THE PHOTOSTABILIZATION OF ACTIVE INGREDIENTS IN GERMAN CHAMOMILLE FLORAL EXTRACTS: PART I

the effect of some natural uv absorbers on the photostabilization of spiroketal enol ethers (en-yn-dicycloethers) present in german chamomille extracts pre-coated on glass plates (solid phase) was examined. plates were exposed to sunlight radiation from a uv-sun radiation lamp, in the presence and absence of gallic acid, cinnamic acid, caffeic acid, ferulic acid and aloin, all natural uv absorbers. at particular intervals the remaining concentration of the en-yn-dicycloethers was analyzed by hplc. using first-order kinetic equation, the dissipation half-life values (dt50) for the degradation of the en-yn-dicycloethers under uv-sun radiation were obtained. the results showed that the addition of cumaric acid and caffeic acid provided moderate degree of photostabilization of the en-yn-dicycloethers and that addition of ferulic acid provided the best photostabilization among the uv absorbers studied. photostabilization effect appears to be due to a competitive energy absorption of uv photons by the absorber molecules.