Alagar Srinivasan

meso-Tetrakis(p-sulfonatophenyl)N-Confused Porphyrin Tetrasodium Salt: A Potential Sensitizer for Photodynamic Therapy

A water-soluble derivative of N-confused porphyrin (NCP) was synthesized, and the photodynamic therapeutic (PDT) application was investigated by photophysical and in vitro studies. High singlet oxygen quantum yield in water at longer wavelength and promising IC(50) values in a panel of cancer cell lines ensure the potential candidacy of the sensitizer as a PDT drug. Reactive oxygen species (ROS) generation on PDT in MDA-MB 231 cells and the apoptotic pathway of cell death was illustrated using different techniques.

Spectroscopic and electrochemical studies on oxaporphyrins and oxathiaporphyrins

The synthesis and characterization of oxaporphyrins (OTPP and O2TPP) containing one and two furan rings in place of pyrrole and a mixed oxathiaporphyrin (OSTPP) is reported. Spectroscopic and electrochemical studies reveal that oxaporphyrins exhibit optical and emission characteristics closer to the parent H2TPP, while their electrochemical behaviour parallels that reported for mono and dithiaporphyrins. However the characteristics of the mixed oxathia derivative resemble that of monothiaporphyrin. Protonation studies reveal weaker resonance interaction between the β-hydrogens and meso-phenyl substituents in sharp contrast to thiaporphyrins. The reduction potentials for OSTPP and O2TPP indicate stabilization and destabilization of their LUMOs relative to the parent H2TPP in the ground and excited states, respectively.

NOVEL HETEROATOM CONTAINING RUBYRINS

Synthesis of rubyrins containing two or three heteroatoms (O, S, Se) in the core is accomplished using modified diols and tetrapyrromethanes. Substitution of heteroatoms leads to significant reductions in HOMO-LUMO gap and easier oxidations and reductions reflecting the changes in electronic structure of the rubyrin skeleton.

Synthesis of meso-substituted core modified expanded porphyrins; Effect of acid catalysts on the cyclization

[3+2] condensation between modified tripyrromethane and bithiophene or bifurandiol leads to the formation of 18π, 22π, 26π macrocycles under Lewis acid conditions while only 22π macrocycle is formed under protic acid conditions.

One step synthesis of sapphyrin and N-confused porphyrin using dipyrromethane

Reaction of dipyrromethane in trifluoroacetic acid produces sapphyrin while the same reaction in toluene p-sulfonic acid gave N-confused porphyrin.

Improved synthesis of meso substituted 21-Oxa and 21-Thia tetra phenyl porphyrins

Abstract An efficient method for the exclusive formation of 21-Oxa and 21-Thia tetra phenyl porphyrins in high yields by condensation of dipyrromethane and furan or thiophene diols is described.

Characterization of a new meso-aryl rubyrin isomer: [26]hexaphyrin (1.1.1.0.1.0) with an inverted heterocyclic ring

The synthesis and characterization of new aromatic 26π macrocycles obtained from the acid catalyzed 4+3 coupling reaction of core modified tripyrrane and tetrapyrrane are described.

ONE POT SYNTHESIS OF CORE MODIFIED EXPANDED PORPHYRINS

Abstract Reaction of various diols with pyrrole in TFA CH 2 Cl 2 leads to formation of core modified expanded porphyrins.

Structural Diversity in Rubyrins: X-ray Structural Characterisation of Planar and Inverted Rubyrins

Meso aryl rubyrins exhibit three different structures. A planar (7) and two unusual inverted structures (8 and 9) have been characterised by X-ray and NMR spectroscopy.

In Vitro and In Vivo Investigations on the Photodynamic Activity of Core-modified Expanded Porphyrin—Ammonium Salt of 5,10,15,20-tetrakis-(meso-p-sulfonato phenyl)-25,27,29-trithia Sapphyrin¶,†

Abstract The core modification of expanded porphyrins has been proved to have better photochemical properties, which are favorable for photodynamic therapy (PDT) applications. In this context, this study was aimed to investigate the in vitro and in vivo photodynamic activity of one such core-modified expanded porphyrin, namely, ammonium salt of 5,10,15,20-tetrakis-(meso-p-sulfonato phenyl)-25,27,29-trithia sapphyrin. For the in vitro studies, human erythrocytes were used as a membrane semimodel system to investigate the partitioning ability and drug-uptake characteristics. The partition studies on the membrane semimodel system revealed that maximum partitioning occurs at 12 µgm/mL concentration, and from the drug-uptake studies it is observed that maximum amount of the sensitizer is bound to the erythrocyte membranes during a 45 min incubation period. Photohemolysis studies at different concentrations of the sensitizer and exposure time showed maximum damage at 5 µgm/mL and 30 min exposure time. In vivo studies were performed on 7,12-dimethylbenz-(a)nthracene–induced superficial squamous cell carcinoma on mouse skin. The sensitizer at a concentration of 2.5% in 2.0% dimethyl sulfoxide was applied topically on the tumor spot. After 1 h incubation the tumor spot was exposed to laser irradiation from Nd–YAG laser at its second harmonic wavelength of 532 nm. The photodynamic efficacy was estimated by tumor volume measurements at regular intervals after the treatment. One month after PDT exposure a 3.9-fold decrease in the tumor volume was observed with respect to the tumor volume before treatment. The treatment efficacy was further confirmed by histological and fluorescence spectroscopic evaluations of the tissue biopsy sample from the treated area. The results of our study suggest that the ammonium salt of 5,10,15,20-tetrakis-(meso-p-sulfonato phenyl)-25,27,29-trithia sapphyrin may find possible applications in the new modality of cancer treatment.