Porphyrin Synthesis

The porphyrin is a group of compounds with substituted tetra pyrrole rings linked together by four methine bridging groups [1]. Each pyrrole ring itself consists of a five member ring with four Carbon atoms and one Nitrogen atom. Further modification of these tetra pyrrole rings with conjugated pi-bond system brings these structures to highly conjugated structures with absorption and emission making them fluorescent in nature [64]. Some natural porphyrin [25], synthetic porphyrin and porphyrin derivatives have been used as photosensitizing agent for photo dynamic therapy treatment [2]. The chelation of different metal ions like magnesium and iron to porphyrin in the last stage of synthesis pathway results in the formation of Chlorophyll and

5-Aminolaevulinic acid (ALA) and porphobilinogen are reported as the early precursors in the haem biosynthetic pathway [11]. Using ALA in both aerobic and anaerobic organism after their biosynthesis in a specific way depending on the type of organism involve, the formation of the porphyrin and haem from the precursor ALA species are commonly proceeded with same sequence of reactions in all these species .The condensation of two molecules of ALA by the enzyme dehydratase gives first ring structure, porphobilinogen (PBG) [12]. The condensation of four PBG molecules in the presence of two enzymes, PGB deaminase and pophyrinogen cosynthetase results in formation of a four ring structure, uroporphyrinogen with side chain mainly comprising of acetic and propanoic acid. The decarboxylation of the acetic acid side chain of uroporphyrinogen to methyl group by enzyme uroporphyrinogen decarboxylase results in the formation of coproporphyrinogen. The oxidative decarboxylation of the propanoic side chain to vinyl group in the presence of enzyme coproporphyrinogen oxidase gives rise to Protoporphrinogen IX [13]. At this stage all the corresponding Uroporphyrinogen, coproporphyrinogen and protoporphyrinogen are non-fluorescent in nature. The oxidation of each specific porphyrinogen results into the corresponding porphyrin by converting the methylene

It is commonly suggested that the oral bacteria have endogenously prepared porphyrin that may be used as inherent photosensitizer. In literature it has been widely documented that some cancer cell and malignant tissue can be photosensitized by using some photosensitizing agent followed by cell decay in order to get rid of the infected cells using the concept of phototherapy. The photosensitizing agent like porphyrin derivative or precursor 5ALA that can sensitize the growth of endogenous porphyrin, have been incorporated into the cells by using some mobile vehicle to eradicate the infected cells[ 65]. Much attention has been given to 5-aminolevulinic acid (ALA) as porphyrin precursor which is converted to photosensitizing porphyrin mainly protoporphyrin (PPIX) after uptake by cells [20]. Main photosensitizers found in the literature are hematoporphyrin derivative (620-650nm), cyanine (600-805nm), phenothiazine, like toluidine blue, methylene blue (620-700nm) and photofrin [22]. The inherent porphyrin may be used as potential photosensitizer to kill bacteria. Jose M. Becerril et al. has investigated protoporphyrin as a natural photodynamic pigment in some herbicides and showed a correlation between the concentration of PPIX and herbicidal damage