AUTOSENSITIZED PHOTOOXIDATION OF THE ROSE HIP (WILD ROSE) OIL - MECHANISM AND QUANTUM YIELD FOR SINGLET MOLECULAR-OXYGEN O-2 (1)DELTA) GENERATION

The autosensitized photooxidation of the fatty acid components of rose hip (Wild Rose) oil was studied. Two important facts arise from the p resent investigation: a) Fatty acids of rose hip oil decompose upon vi sible light irradiation in the absence of external sensitizers by a me chanism that involves O2(1DELTA(G)). The pigments present in rose hip oil themselves efficiently sensitize the generation Of O2(1DELTA(g)) w ith a quantum yield of 0.038 (upper limit). b) Visible irradiation als o produces the degradation of the anthocyanines, native pigments which could behave as O2(1DELTA(g)) sensitizers in the oil. In this case a mechanism involving the production of superoxide ions by the pigment a nd further attack of the radicals on the phenol groups of the anthocya nine could account for the observed experimental evidences. These resu lts should be carefully considered in a practical sense when rose hip oil is stored or employed under daylight conditions. Exposure to visib le radiation may cause irreversible transformations in rose hip oil.