Study On Biological Effects Of Chlorophyll-a Derivatives As Photosensitizers And Proxidants

Photosensitization means substrates give rise to other compounds to be oxidated after absorbed specific wavelength through a series of chemical reactions in the presence of oxygen. Studies and development of photosensitizer are becoming the hotspot in the field of insecticide and bactericide and PDT (Photodynamic therapy) in the moment. As making us go deep into mechanism of porphyrin bioactivity . It has been becoming more and more popular applications in agriculture. So far, porphyrins have been considered as the best photodynamic pesticides.In order to investigate availability of porphyrins as photodynamic pesticide, in the present paper, we extracted Chlorophyl-a from silkworm excrement with different solvents and compared their extractable efficiency in two systems. Also, derivatives of Chlorophyl-a: Phaeophorbide-a. Phaeophorbide-a methyl ester, Pyropheophorbide-a. Pyropheophorbide-a methyl ester. Chlorin e6 was synthesized at the same time. Silica gel column chromatography was employed to purify each derivative as mentioned above. HPLC and FT-IR was used to estimate the purity and their structure.In addition, UV-Visible absorbance, chemiluminescence and ESR (Electron Spin-Resonance) were also employed to study the photosensitized pro-oxidation of porphyrin derivatives. UV-visible absorbance assay showed the porphyrin derivatives have good absorbance to visible light. Chemiluminescence confirmed that porphyrins could produce free radicals under the condition of photosensitized pro-oxidation. Further, ESR results showed that plentiful singlet oxygen was formed during photosensitized pro-oxidation. Photosentization of pyropheophorbide-a was correspondence with the way of Model II of photosensitized and pro-oxidation.To evaluate the biological effect of pyropheophorbide-a under the condition of photosensitization, photodynamci toxicity of pyropheophorbide-a was analyzed by MTT assay. By estimating the viability of Tn-5Bl-4 cells and mortality of Plutella xylostella L under illumination, we found that pyropheophorbide-a significantly influenced on the growth of Tn-5B1-4 cells and Plutella xylostella. Pyropheophorbide-a could reduce the viability of Tn-5B1-4 cells exposure to pyropheophorbide-a for 48h with 30min light irradiation at the concentration of 10μM to 3.6336 %. Fed Plutella xylostella L with pyropheophorbide-a and irradiated for 30 min, mortality of Plutella xylostella L after treatment with pyropheophorbide-a for 48 h was 60% and 100% under irradiation of ultraviolet for 30 min. This finding indicated that pyropheophorbide-a was an excellent photosensitizer and pro-oxidant.