Discovery of a new anilino-3H-pyrrolo[3,2-f]quinoline derivative as potential anti-cancer agent.

The newly synthesized 1-[4-(3H-pyrrolo[3,2-f]quinolin-9-ylamino)-phenyl]-ethanone hydrochloride showed high antiproliferative activity by mixed mechanisms of action. The compound acts by forming an intercalative complex with DNA and inhibiting DNA topoisomerase II (topo II) and by blocking the cell cycle in G(2)/M phase. Probable cell death by apoptosis is also suggested by flow cytometry analysis.

4'-Methyl derivatives of 5-MOP and 5-MOA: synthesis, photoreactivity, and photobiological activity.

The synthesis and photobiological activity of four new 4'-methyl derivatives of 5-MOP (5-methoxypsoralen) and 5-MOA (5-methoxyangelicin), i.e., 4,4'-dimethyl-5-methoxypsoralen, 3,4'-dimethyl-5-methoxypsoralen, 4,4'-dimethyl-5-methoxyangelicin, and 3,4'-dimethyl-5-methoxyangelicin, are described. All these compounds photobind efficiently to DNA. The DNA-photobinding process was investigated using various nucleic acid structures such as double-helix DNA, bacterial DNA, and synthetic polydeoxyribonucleotides. Photoreaction experiments showed that, unlike 8-MOP (8-methoxypsoralen) and 5-MOP, both angular derivatives bind thymine and cytosine with the same efficiency. The principal nucleoside-psoralen monoadducts were isolated and characterized after enzymatic digestion or acid hydrolysis. Biological activity studies revealed a good correlation with the extent of covalent photoaddition. Moreover, the two angular derivatives and the 4,4'-dimethyl-5-methoxypsoralen were unable to induce skin erythema, in striking contrast with the reference drugs, 8-MOP and 5-MOP; only the 3,4'-dimethyl-5-methoxypsoralen caused erythema, although to a substantially lower extent than that induced by the two parent compounds.

New tetracyclic analogues of photochemotherapeutic drugs 5-MOP and 8-MOP: synthesis, DNA interaction, and antiproliferative activity.

The synthesis of new tetrahydrobenzo- and benzopsoralen derivatives carrying at position 5 or 8 of the furocoumarin moiety a methoxy, hydroxy, or dimethylaminopropoxy side chain is reported. The study of their photoantiproliferative activity and ability to induce erythema on guinea pig skin allows us to state that the derivatives carrying the dimethylaminopropoxy side chain exhibit a very interesting photobiological pattern. Indeed, if compared with the lead compounds 5-MOP and 8-MOP, they exert a higher cytotoxic activity devoid of significant skin phototoxicity. Between them, the more interesting appears to be 16, a nonphototoxic compound whose antiproliferative activity on HeLa cells is 2 orders of magnitude higher than that of the reference drug 8-MOP. Photoreaction experiments have revealed that, like classic furocoumarins, A-T is the preferred nucleic base pair in its photobinding. Moreover, the extent of covalent photoaddition to DNA correlates well with the photobiological activity. For this compound a certain effect was also observed in the dark. Evaluation of the ability to induce DNA cleavage in the presence of human topoisomerase II has suggested that this enzyme is probably the target accountable for this effect.

Sequence specificity of tetrahydrobenzopsoralen photobinding to DNA.

The sequence specificity of photobinding to DNA of two tetrahydrobenzopsoralen derivatives has been investigated by testing the photoreactivity toward a number of self-complementary oligonucleotides. The thermodynamic constant for noncovalent binding to each DNA sequence was evaluated. The extent of photoreactivity was greatly dependent upon base composition. The two tetracyclic compounds show similar behavior in comparison to other bifunctional derivatives. Their overall rate constants were greatly enhanced in comparison to classical psoralens. However, their high efficiency of covalent binding is counterbalanced by low affinity for noncovalent interaction with DNA.

Synthesis and photobiological properties of 4-hydroxymethyl-4'-methylpsoralen derivatives.

The synthesis and the photobiological activity of two new hydroxymethyl derivatives of psoralen namely 4-hydroxymethyl-4'-methyl- and 4-hydroxymethyl-4'-methyl-8-methoxypsoralen are described. Both compounds exhibited efficient photobinding to DNA and RNA. The DNA-photobinding process was investigated using different nucleic acid structures such as double-helical DNA, ribosomal RNA, bacterial DNA and DNA organized in the nucleosomal arrangement. The test derivatives were able to induce cross-links to a similar extent as 8-methoxypsoralen (8-MOP), used as a reference photochemotherapeutic drug. In contrast to 8-MOP, they produced relatively high levels of 1O2. Most photobiological effects (DNA synthesis inhibition, T2 phage sensitization, inhibition of tumor transmitting capacity) showed a good correlation with the extent of covalent photoaddition. On the other hand, the new 4-hydroxymethylpsoralens were unable to induce skin erythema, in striking contrast with 8-MOP. Thus, neither cross-linking of the nucleic acid nor 1O2 production were coupled with skin phototoxicity in this class of compounds. The new derivatives appear to represent an important beginning to development of new active photochemotherapeutic agents devoid of undesired phototoxic side effects.

Benzo- and tetrahydrobenzo-psoralen congeners: DNA binding and photobiological properties.

Four new benzo- and tetrahydrobenzo-psoralens have been examined in their reversible interaction toward DNA and in their DNA-photobinding properties. These compounds were also examined for their ability to produce singlet oxygen and in vivo skin photosensitization reaction. Fluorescence and equilibrium dialysis measurements show that the complexation ability of benzoderivatives is remarkably high. Binding is less effective in the case of the tetrahydrocongeners. All compounds photoreact quite effectively to DNA. The photoadducts were obtained by enzymatic hydrolysis of drug-modified DNA and were characterized by high performance liquid chromatographic elution techniques. The 3,4 position represents the unique photoreactive site for benzopsoralens. Denaturation-renaturation experiments confirm that the benzoderivatives are purely monofunctional, while the tetrahydrocongeners form interstrand cross-links, even though to a remarkably lesser extent than 8-methoxypsoralen (8-MOP). The new compounds, in the presence of long-wavelength ultraviolet radiation, are very moderately effective in forming reactive oxygen species; they are ineffective in promoting oxidation of tyrosine and 3-(3,4-dihydroxyphenyl)alanine to dopachrome and melanin. Skin photosensitizing experiments on guinea pigs indicate that benzo- and tetrahydrobenzopsoralen derivatives are almost devoid of any phototoxic effects. Thus, this class of compounds appears to be interesting for the development of new, less phototoxic chemotherapeutic agents that interact with DNA better than 8-MOP.

Photobiological activity of 3,4'-dimethyl-8-methoxypsoralen, a linear furocoumarin with unusual DNA-binding properties.

The furocoumarin derivative 3,4'-dimethyl-8-methoxypsoralen (DMe-8-MOP) exhibits remarkable antiproliferative activity, but is devoid of skin phototoxicity. To gain insight into this peculiar behaviour we investigated non-covalent and covalent binding of DMe-8-MOP to calf thymus DNA, along with DNA-synthesis inhibition and mutagenic activity. The non-covalent interaction of DMe-8-MOP with the nucleic acid is quite poor as shown by equilibrium dialysis, spectroscopic, chiroptical and hydrodynamic techniques. However, it exhibits relevant photobinding ability to DNA using both isolated nucleic acid samples and cellular systems. Unlike the large majority of congeners, DMe-8-MOP undergoes predominantly photochemical monoaddition to the double helical polynucleotide. Upon examination of the products obtained by enzymatic hydrolysis of DMe-8-MOP photomodified DNA, the formation of an unusual furan side adduct is proposed, which could account for the peculiar photochemical and photobiological properties of the 3,4'-dimethyl furocoumarin derivative.

New anthracenedione derivatives: interaction with DNA and biological effects.

Two anthracenedione derivatives [1 - (omega - diethylaminopropylamido) - 4 - hydroxy - 9,10 - anthracenedione hydrochloride (I) and 1 - (omega - diethylaminopropylamido) - 2 - methoxy - 4 - hydroxy - 9, 10 - anthracenedione hydrochloride (II)], having an electron-rich planar chromophore and an amino-substituted side chain, have been synthesized. Their binding ability to DNA was investigated by means of spectroscopic, equilibrium dialysis and fluorescence measurements. Their inhibition efficiency on nucleic acid synthesis was also evaluated both in mouse and human cells. Our results indicate that, in comparison with adriamycin, compound I shows a slightly weaker complexation ability to DNA, while compound II interacts with DNA at a substantially lower level. These data match quite well with the biological response on the inhibition of DNA and RNA synthesis exhibited by the above mentioned compounds; in fact compound I is slightly less efficient than adriamycin and about ten times more efficient than compound II. The close relationship between the results of physicochemical and biological studies is discussed.

Pyrrolocoumarin derivatives: DNA-binding properties.

The spectroscopic and DNA-binding properties of a number of pyrrolocoumarin derivatives, including linear tricyclic, angular tricyclic, linear tetracyclic and angular tetracyclic compounds were investigated. The compounds we examined form non-covalent complexes with duplex DNA, probably of the intercalation type. The binding constants are comparable with the constants found for the furocoumarin analogues. Although for some of the compounds the photoreactivity with DNA is comparable with that of 8-MOP, pyrrolocoumarins behave as monofunctional reagents. This fact is explained in terms of an increased delocalization of the 4',5' double bond in the pyrrole moiety. Denaturation-renaturation experiments and HPLC analysis of the photoadducts confirm that pyrrolocoumarins are essentially monofunctional DNA-photobinding agents.

Synthesis and photobiological properties of acetylpsoralen derivatives.

In an investigation to find monofunctional reactants for DNA which can act as new agents in the photochemotherapy of psoriasis, we have synthesized and studied some methylpsoralen derivatives which contain an acetyl group at one of the two reactive sites of the furocoumarin skeleton (at the 3 or 5' positions). The compounds do not react easily with DNA; their photobiological properties (e.g. the lack of an ability to inhibit DNA synthesis in Ehrlich ascites tumour cells, to induce T2 phage sensitization and to induce erythema in guinea-pig skin) are exactly in line with this behaviour. Some interesting features are shown by 4,8-dimethyl-5'-acetylpsoralen: it is capable of producing a very large amount of singlet oxygen--an order of magnitude higher than the other compounds and 8-methoxypsoralen (used as reference). In spite of this property, 4,8-dimethyl-5'-acetylpsoralen is non-phototoxic to the skin, and its other photobiological properties appear to be in line with its lack of interaction with DNA rather than its enhanced singlet oxygen production.

Synthesis and photobiological activity of new methylpsoralen derivatives.

The synthesis and the photobiological activity of two new derivatives of psoralen (3,4'-dimethylpsoralen and 3,4',8-trimethylpsoralen) has been described. They are congeners of the monofunctional linear furocoumarin 3,4'-dimethyl-8-methoxypsoralen. Both compounds bind very efficiently to DNA, the extent of this process being modulated by the nature of substituents at position 8. The number of photolesions is linearly related to adenine-thymine content of the nucleic acid which indicates lack of specificity for particular sequences of the nucleic acid. The structural arrangement of DNA (single stranded, double stranded, nucleosomes and chromatin) plays an additional role in affecting the photobinding process. Unlike their 8-methoxy congener the new derivatives cross-link DNA to a substantial extent. Their photobiological properties, including erythema formation, reflect very closely those of 8-methoxypsoralen (8-MOP). The conclusion can be drawn that 3,4'-dimethyl-8-MOP represents a unique derivative in its family.

Thienocoumarin derivatives: interaction with nucleic acids and synthetic polydeoxyribonucleotides.

This paper reports the photobiological properties of two new thienocoumarins, 4,6,9-trimethyl-2H-thieno[3,2-g]-1-benzopyran-2-one (compound I) and the 6,9-dimethyl-4-methoxymethyl-2H-thieno[3,2-g]-1-benzopyran-2-one (compound II). Cell growth inhibition studies have revealed significant antiproliferative potency on human tumor cell lines. The photoaddition process of these tritium-labeled derivatives was investigated using various nucleic acid structures (calf thymus DNA, bacterial DNA, and synthetic polydeoxyribonucleotides). The results obtained show that both compounds photobind to DNA to a higher extent than 8-MOP, taken as the reference drug. The capacity to form interstrand crosslinks into DNA helix was also evaluated. Interestingly, notwithstanding the lack of cutaneous phototoxicity, II revealed a good ability to induce diadduct formation.

Biological properties of benzodifuran derivatives.

The antiviral activity and the effect on DNA synthesis of two benzodifuran compounds were studied. DNA and some RNA viruses were significantly inhibited by concentrations ranging from 15 to 30 nM/ml. The inhibition of DNA synthesis in host cells was obtained with concentrations higher than those inhibiting virus replication. A favourable ratio between antiviral activity and inhibition of DNA synthesis of the host cells is present in these compounds. This activity is substantially due to the ability of the compounds to complex with DNA.

Interactions between DNA and benzo- and tetrahydrobenzofurocoumarins: thermodynamic and molecular modeling studies.

The non-covalent interaction of a series of new water-soluble benzo- and tetrahydrobenzofurocoumarins with salmon testes DNA has been studied using flow linear dichroism, circular dichroism, contact fluorescence energy transfer and ethidium bromide displacement assay. The new derivatives are characterised by having an alkyl amino side chain protonated at physiological pH; this fact strongly enhances the solubility in aqueous media and the affinity for the macromolecule. The results show significant difference in the affinity and the mode of binding among the examined compounds depending on the nature of the fourth condensed ring and the position of the alkylamino side chain. Benzofurocoumarins derivatives bind DNA by undergoing intercalation inside the duplex macromolecule, whereas tetrahydrobenzofurocoumarins derivatives show a substantial tilt relative to the base planes. Molecular modeling studies have been performed to characterise in detail the intercalation mechanism of these benzofurocoumarins to DNA.

Preparation and antiproliferative activity of 1H-pyrrolo [2,3-f]quinolinium and isoquinolinium iodides.

2-Carbomethoxy-N-methyl-1H-pyrrolo[2,3-f]quinolinium and isoquinolinium iodides were prepared. Their in vitro ability to form complexes with DNA is enhanced in respect to parent compounds. This, however, does not appear to be agreement with their ability to inhibit cellular DNA sunthesis.

1H-pyrrolo[2,3-f]quinoline and isoquinoline derivatives: synthesis and antiproliferative activity.

Fischer indol synthesis is reported for the preparation of some 2-substituted 1H-pyrrolo[2,3-f]quinoline and isoquinoline derivatives having a structural correlation with naturally occurring compound ellipticine. The prepared compounds proved capable of forming in vitro molecular complexes with native double-stranded DNA by intercalation between two base pairs and showed a relatively good activity in inhibiting the DNA synthesis in Ehrlich ascites tumor cells.

Synthesis and characterization of new methylpsoralens as potential photochemotherapeutic agents.

Three new psoralens with methyl groups on carbons involved in their reactive double bonds (compounds 9-11 in Scheme 1) were synthesized from the corresponding 7-hydroxycoumarins by cyclization of acetonyl derivatives of the latter in an alkaline medium. In preliminary tests, the new methyl-substituted psoralens exhibited considerable interaction in the dark with DNA, good photoreactivity against the macromolecule, and also interesting antiproliferative activity.

Some new methyl-8-methoxypsoralens: synthesis, photobinding to DNA, photobiological properties and molecular modelling.

The tricyclic structure of known natural photochemotherapeutic drugs such as 8-methoxypsoralen and 5-methoxypsoralen is often taken as a model in the search of new photosensitizer agents with less phototoxic and mutagenic effects. This paper describes the synthesis, characterization, photobinding to DNA, photobiological properties and computational chemistry of some 8-methoxypsoralen derivatives bearing two or three methyl groups at the key positions of the two photoactive double bonds. Results showed that photoreactivity and photobiological behaviour depend on the pattern of methyl substitutions. Antiproliferative activity in cell lines shows good correlation with DNA interaction data.

Synthesis and biological activity of linear and angular 4-methoxymethylthienocoumarins and 4-acetoxymethylthienocoumarins.

This paper reports the synthesis of 4-methoxymethyl and 4-acetoxymethyl-6,9-dimethyl-2H-thieno[3,2-g]-1-benzopyran-2-one as well as 4-methoxymethyl- and 4-acetoxymethyl-6,9-dimethyl-2H-thieno[2,3-h]-1- benzopyran-2-one. The synthesized derivatives were tested on human cells in UVA irradiation conditions. Skin phototoxicity and cross-link formation in DNA were also studied. Results indicate that the new thienocoumarins have good antiproliferative activity, greater than that of the well-known photochemotherapeutic drug 8-methoxypsoralen, but they are practically devoid of skin photosensitization effects.

Photobiological studies of new cyclopentene-psoralens.

Psoralen analogues bearing a cyclopentane ring fused to either the 4',5' double bond (compound 4) or the 3,4 double bond (compound 7) of the tricyclic furocoumarin structure were prepared. AM1 theoretical calculations performed for these compounds indicated that the electronic properties of their reactive double bonds were very similar to those of psoralen and its derivative 8-methoxypsoralen (8-MOP), though the overall molecular geometries were clearly different, particularly as regards the change in molecular curvature produced by the introduction of the cyclopentane ring. Compound 4 showed a capacity similar to that of 8-MOP to inhibit the growth of human cervix adenocarcinoma cells (HeLa) and to induce mutagenic effects, but it was definitely less phototoxic to skin than 8-MOP. Its ability to photoadd to DNA and to cross-link DNA strands was also demonstrated. Instead, compound 7 was practically devoid of biological activity and no interaction with the macromolecule could be detected. These differences in behaviour between 4 and 7 are probably due to the molecular curvature resulting from the introduction of the cyclopentane ring.