Synthesis and biological activity of meso -tetrakis (2,10-dioxo-2 H , 10 H -pyrano [2,3-f ] chromene-9-yl) porphyrins

Synthesis of meso -tetrakis (2, 10-dioxo-2 H , 10 H -pyrano[2,3-f ] chromene-9-yl) porphyrins are synthesized directly by reaction of pyrrole with substituted 4-methyl-2,10-dioxo-2 H , 10 H - pyrano[2,3-f ]chromene-9-carbaldehydes in dichloromethane / acid media. The aldehyde’s molar ratio was controlled to optimize the synthesis and purification of the desired porphyrins. This new series of porphyrins was characterized by TLC, Mass Spectrometry (FAB mass), 1 H NMR, UV and IR


Introduction
The synthesis of porphyrins has gained special attention in recent years because of its importance in bioorganic and bioinorganic chemistry 1 and its application in biomedical sciences.Porphyrin type compounds have been actively investigated as sensitizing drugs for application in cancer diagnosis and treatment using photodynamic therapy (PDT).The meso-tetraphenyl porphyrins offer attractive features in this context and have been used in a wide variety of model studies. 2,35][6][7] Here we describe the synthesis of porphyrins substituted at the meso positions by heteroaryl chromenes, wherein both chromone and coumarin moieties are present at meso positions.Earlier, we reported 8 the synthesis of simple porphyrins substituted with chromene-4-ones in the meso position, from our laboratories.3][14][15][16] In the present work, we reported a study on cytotoxic and antiviral activities, in vitro, against tumor cell lines and viruses.This paper aims at elucidating the preliminary structure activity relationships by simple chemical structural modifications and probing structural requirement for the marked antitumor activity of these compounds.
The IR spectra of all the compounds showed a broad band at 3448 cm -1 , and bands at 1630 (the chromone carbonyl stretching), 1720 (the lactone carbonyl stretching), 2950, 2830 (aliphatic str), 940 cm -1 (ω-porphyrin macrocyclic bending).The FAB mass spectra confirmed the composition and the complete structures were assigned by detailed 1 H NMR experiments.For 6a, pyrrole β-CH protons appear as a singlet at 9.12 ppm.The C-2H protons of chromene-4-one are shown as a singlet at 8.0 ppm.The two inner NH protons resonate at -2.5 ppm.

Antitumor activity
The compounds 6a-f were screened for antitumor activity against L1210 murine leukemia cells as well as human T-lymphocyte cells molt 4/C8 and CEM/0 and the results are portrayed in Table 1.Etoposide was used as a standard drug.
0][21] In simple porphyrin 6a antitumor activity was lower in murine leukemia cells and higher in human T-lymphocyte cells.Remarkable enhancement of antitumor activity was observed when a halogen group is located in position 3 of the coumarin (6c).The compound (.6f) displayed intermediate cytotoxic activity, and others (6b, 6e) only had marginal or no activity.

Antiviral activity
Compounds 6 were evaluated for their antiviral activity against HEL, Hela and Vero cell cultures.The cytotoxicity was verified in mock-infected HEL, Hela and Vero cells.The antiviral activity assays were based on inhibition of virus-induced cytopathicity in the above mentioned cultures.The activity of these compounds was compared with that of standard Brivudin, Ribavirin, Acyclovir and Ganciclovir.Briefly, the confluent cell culture in 96 well microliter plates was inoculated with 100 CC1D50 of virus, ICC1D50 being the virus dose required to infect 50% of the cell cultures.After 1h virus adsorption period, the residual virus was removed, and the cell cultures were incubated in the presence of varying concentrations, i.e. 400, 200 and 100 ug/ml, of the test compounds.Viral cytopathicity was recorded as soon as reached completion in the control virus in treated cell cultures.As shown in tables 2, 3 and 4, some compounds (6b, 6d) showed significant antiviral activities while others (6f, 6a) displayed medium antiviral activities.Compounds (6c, 6e) only had marginal or no antiviral activities against HEL, Hela and Vero cell cultures.

Experimental Section
General Procedures.Melting points were determined in open capillaries and are uncorrected.UV-Vis spectra were recorded on a Shimadzu UV-160A UV-Vis-NIR spectrophotometer using methanol as solvent.IR spectra were recorded as KBr discs using a Shimadzu FTIR model 8010 spectrophotometer, 1 H NMR spectra were recorded on a Varian FT 200 MHz instrument using CDCl 3 and d 6 -DMSO as solvent TMS as an internal standard.FABS mass spectra were recorded on YG Micromass 7070H (F1 or C1) auto spectrometer.The C, H and N analysis of compounds was performed on a Carlo Erba Model EA1108 CHNS-O elemental analyzer.Porphyrins were purified by flash column chromatography using 230-400 mesh silica gel (Aldrich make).

Table 1 .
Inhibitory effects on the proliferation of murine leukemia cells (L1210/0) and human T- a 50% inhibitory concentration.

Table 2 .
Cytotoxicity and antiviral activity of compounds (6a-f) in HEL cell cultures a Required to cause a microscopically detectable alteration of normal cell morphology.b Required to reduce virus-induced cytopathogenicity by 50%.

Table 3 .
Cytotoxicity and antiviral activity of compounds (6a-f) in Vero cell cultures a Required to cause a microscopically detectable alteration of normal cell morphology.b Required to reduce virus-induced cytopathogenicity by 50%.

Table 4 .
Cytotoxicity and antiviral activity of compounds (6a-f) in HeLa cell cultures a Required to cause a microscopically detectable alteration of normal cell morphology.b Required to reduce virus-induced cytopathogenicity by 50%.