Comparison Of Photophysico-chemical Properties Of Four Perylenequinonoid Derivatives

Perylenequinonoid derivatives (PQD) are a kind of naturally occurring pigments. They have attracted much attention recently owing to their excellent properties of photosensitization and great potential of being developed as a photodynamic medicine to kill tumor cells and human immunodeficiency virus (HIV). At present, they are found to have good antibiotic property and their effect can be enhanced by illumination. The pesticide developed by PQDs also has good foreground in applicationIn order to industrialize the technology relating PQDs, the availability of material is the most important question. The chemical synthesization of this kind of compounds is insufficient to large scale production. But fermentation is the most effective way. We study four PQDs-hypocrellin A, ElsinochromeA, Ek C (HA, EA, EB, EC) extracted from the fermentation products. The investigations include their photophysical, photochemical characters and photosensitive activity in micelle and organic system. Quantum chemical calculation is used to HA and EA. to study their physical chemistry properties. It is expected to give some theoretical instructions to the industrialization of the PQDs based on fermentation technology.Triton X-100 and TweenSO are used to make the micelles. The absorption and fluorescence spectrometers are used in the experiments. We use chemical trapping methodto detect the yield of 1O2- and (V .Quantum chemical analysis do as follow: Molecular mechanics methods in software PCModel are employed to get the initial structure. Further quantum chemistry optimization is performed with program Gaussian 94. Single point energies are obtained through HF/6-31G** methodThe most important findings are as follows:1. PQDs have three characteristic absorption peaks both in organic and micelle system. Just the peaks move to longer wavelength and the intensity is much lower than in organic system. As to HA, the absorption bands in longer wavelength reverse, but EA, EB, EC have not such phenomenon.2. There is not much difference in the fluorescence spectrum peak of PQDs in micelle and homogeneous system, but the intensity in micelle system is much lower. This indicates that water has great quenching effect on PQDs' excited state and the micelle has protective effect for it. The study on quenching of water proves that it is a dynamic process.3. In micelle the fluorescence quantum yield of HA is a little lower than EA, EB, EC. The relative yield is similar to that in organic system, but the absolute value is much lower. The protective effect of Tween-80 and TX-100 is similar.4. In micelle the yield of active oxygen is much higher than that in the water-organic system. The photosensitive activity of the four PQDs we studied is similar and the Elsinochrome is a little higher. This indicate that these four PQDs are all effective in practical use.5. The O2 quantum yield of PQDs in dark is also high with the presence of reducing agents. This indicates that the dark reaction should be given much attention in practical use. And that the sterilization experiment approve that PQDs have good effect when there is no illumination.6. Theoretical calculation elucidates the difference in stability of isomers of HA in solution and indicates that HA is more stable than EA under illumination.