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G Zagotto

Publications and source records attributed to G Zagotto.

17 recordsLinked to original sources
PubMed2003

High-performance liquid chromatographic assay for the determination of Aloe Emodin in mouse plasma.

An isocratic high-performance liquid chromatography (HPLC) method was developed and validated to determine Aloe Emodin (AE) in mouse plasma. The analysis required 0.3 ml of plasma and involves extraction with dichloromethane. The HPLC separation was carried out on Symmetry Shield RP18, a mobile phase of methanol-water-acetic acid (65:35:0.2) and fluorescence detection at lambda(ex)=410 nm and lambda(em)=510 nm. The retention time of AE was 11.7 min. The assay was linear from 10 to 1,000 ng/ml (r2 > or = 0.999), showed intra- and inter-day precision within 7.8 and 4.7%, and accuracy of 87.3-105.7%. Detection limit (LOD) and quantification limit (LOQ) were 4.5 and 5 ng/ml, respectively. The method was applied to determine for the first time the pharmacokinetic of AE in mice.

Animals↗
PubMed2001

Quantitation of camptothecin and related compounds.

Camptothecin and congeners represent a clinically very useful class of anticancer agents. Proper identification and quantitation of the original compounds and their metabolites in biological fluids is fundamental to assess drug metabolism and distribution in animals and in man. In this paper we will review the recent literature available on the methods used for separation and quantitative determination of the camptothecin family of drugs. Complications arise from the fact that they are chemically labile, and the pharmacologically active lactone structure can undergo ring opening at physiological conditions. In addition, a number of metabolic changes usually occur, producing a variety of active or inactive metabolites. Hence, the conditions of extraction, pre-treatment and quantitative analysis are to be carefully calibrated in order to provide meaningful results.

Camptothecin↗
PubMed2001

Anthracyclines: recent developments in their separation and quantitation.

Anthracyclines are among the most widely used anticancer agents. Notwithstanding the large efforts to develop new drugs with a better pharmaceutical profile, daunorubicin, doxorubicin, epirubicin and idarubicin are still the most used in clinical practice. Many efforts are now ongoing to reduce the side effects by using pharmaceutical formulations able to release the drug in the most appropriate way and monitoring the quantity of anthracyclines and their metabolites in the body fluids or tissues frequently and in every patient to maintain the drug concentration within the expected range. This review describes the most recent developments in the separation and quantitation of the above clinically useful drugs, together with their principal metabolites. Some less widely used derivatives will also be considered.

Antibiotics, Antineoplastic↗
PubMed2000

New 1,4-anthracene-9,10-dione derivatives as potential anticancer agents.

The amino-substituted anthracene-9,10-dione (9,10-anthraquinone) derivatives represent one of the most important classes of potential anticancer agents. To better understand the basic rules governing DNA sequence specificity, we have recently synthesized a new class of D- and L-aminoacyl-anthraquinone derivatives. We have tested these new compounds as cytotoxic agents, and we have correlated their activity with the configuration of the chiral aminoacyl moiety. Molecular modeling studies have been performed to compare the test drugs in terms of steric overlapping.

Anthraquinones↗
PubMed1999

Binding of bis-substituted 2-aza-anthracenedione regioisomers to DNA: effects of the relative positioning of the side chains.

The DNA-binding properties of a series of 2-aza-anthracenedione (benz[g]isoquinoline-5,10-dione) derivatives bearing two 3-dimethylaminopropylamino side chains at different (6,9, 7,9 and 8,9) positions of the planar ring system have been investigated. The affinity for the nucleic acid is dramatically affected by the substitution pattern, the 6,9-regioisomer being substantially more effective than the 7,9- or the 8,9-congeners. This cannot be ascribed to different binding mechanisms, as all compounds are shown to intercalate into the double helix. Instead, the geometry of intercalation into DNA and the site specificity are extensively affected by the substitution pattern. The site preference is CA (or AC) for the 6,9-regioisomer, whereas it is TA (or AT) for the 8,9-congener, the 7,9-analogue lying in between. Molecular modeling studies are in agreement with the experimental results. Although the 6,9-regioisomer was remarkably cytotoxic, it stimulated topoisomerase II-mediated cleavage of DNA very poorly. Hence, a different mechanism of DNA damage is probably operating in 2-aza-anthracenediones as the main cell-killing event. Changes in affinity for DNA, intercalation geometry and sequence specificity can explain the different cytotoxic responses exhibited by the test drugs.

Animals↗
PubMed1998

Mapping drug interactions at the covalent topoisomerase II-DNA complex by bisantrene/amsacrine congeners.

To identify structural determinants for the sequence-specific recognition of covalent topoisomerase II-DNA complexes by anti-cancer drugs, we investigated a number of bisantrene congeners, including a 10-azabioisoster, bearing one or two 4, 5-dihydro-1H-imidazol-2-yl hydrazone side chains at positions 1, 4, or 9 of the anthracene ring system. The studied bisantrene/amsacrine (m-AMSA) hybrid and bisantrene isomers were able to poison DNA topoisomerase II with an intermediate activity between those of bisantrene and m-AMSA. Moving the side chain from the central to a lateral ring (from C-9 to C-1/C-4) only slightly modified the drug DNA affinity, whereas it dramatically affected local base preferences of poison-stimulated DNA cleavage. In contrast, switching the planar aromatic systems of bisantrene and m-AMSA did not substantially alter the sequence specificity of drug action. A computer-assisted steric and electrostatic alignment analysis of the test compounds was in agreement with the experimental data, since a common pharmacophore was shared by bisantrene, m-AMSA, and 9-substituted analogs, whereas the 1-substituted isomer showed a radically changed pharmacophoric structure. Thus, the relative space occupancy and electron distribution of putative DNA binding (aromatic rings) and enzyme binding (side chains) moieties are fundamental in directing the specific action of topoisomerase II poisons and in determining the poison pharmacophore.

Amsacrine↗
PubMed1998

DNA-binding preferences of bisantrene analogues: relevance to the sequence specificity of drug-mediated topoisomerase II poisoning.

To elucidate structure-activity relationships for drugs that are able to poison or inhibit topoisomerase II, we investigated the thermodynamics and stereochemistry of the DNA binding of a number of anthracene derivatives bearing one or two 4, 5-dihydro-1H-imidazol-2-yl-hydrazone side chains (characteristic of bisantrene) at different positions of the planar aromatic system. An aza-bioisostere, which can be considered a bisantrene-amsacrine hybrid, was also tested. The affinity for nucleic acids in different sequence contexts was evaluated by spectroscopic techniques, using various experimental conditions. DNA-melting and DNase I footprinting experiments were also performed. The location and number of the otherwise identical side chains dramatically affected the affinity of the test compounds for the nucleic acid. In addition, the new compounds exhibited different DNA sequence preferences, depending on the locations of the dihydroimidazolyl-hydrazone groups, which indicates a major role for the side-chain position in generating specific contacts with the nucleic acid. Molecular modeling studies of the intercalative binding of the 1- or 9-substituted isomers to DNA fully supported the experimental data, because a substantially more favorable recognition of A-T steps, compared with G-C steps, was found for the 9-substituted derivative, whereas a much closer energy balance was found for the 1-substituted isomer. These results compare well with the alteration of base specificity found for the topoisomerase II-mediated DNA cleavage stimulated by the isomeric drugs. Therefore, DNA-binding specificity appears to represent an important determinant for the recognition of the topoisomerase-DNA cleavable complex by the drug, at least for poisons belonging to the amsacrine-bisantrene family.

Animals↗
PubMed1997

Irreversible and reversible topoisomerase II DNA cleavage stimulated by clerocidin: sequence specificity and structural drug determinants.

In contrast to other topoisomerase II poisons, the microbial terpenoid clerocidin was shown to stimulate irreversible topoisomerase II-mediated DNA cleavage. To establish the structural determinants for drug activity, in this study we have investigated intensity patterns and sequence specificity of clerocidin-stimulated DNA cleavage using 5'-end 32P-labeled DNA fragments. At a majority of the sites, clerocidin-stimulated cleavage did not revert upon NaCl addition; nevertheless, at some sites, cleavage completely reverted. Statistical analyses showed that drug-preferred bases were different in the two cases: guanine and cytosine were highly preferred at position -1 at irreversible and reversible sites, respectively. These results demonstrated that cleavage irreversibility was site selective and required a guanine at the 3' end of the cut. Further experiments revealed that some irreversible sites showed an abnormal electrophoretic mobility in sequencing gels with respect to cleaved bands generated by 4-(9-acridinylamino)methanesulfon-m-anisidide, suggesting a chemical alteration of the DNA strand. Interestingly, the ability to stimulate irreversible cleavage progressively decreased over time when clerocidin was stored in ethanol. Under these conditions, nuclear magnetic resonance measurements demonstrated that the drug underwent structural modifications that involved the C-12-C-15 side chain. Thus, the results indicate that a specific moiety of clerocidin may react with the DNA (guanine at -1) in the ternary complex, resulting in cleavage irreversibility and in altered DNA mobility in sequencing gels.

Anti-Bacterial Agents↗
PubMed1997

Preferred interaction of D-peptidyl-anthraquinones with double-stranded B-DNA.

The quest for more specific drugs in antitumor chemotherapy led us to the design of anthraquinone-peptide conjugates capable of selective recognition of the nucleic acid. We present here the DNA binding characteristics, sequence specificity and geometry of interaction of a pair of enantiomers containing the lysine-glycine dipeptide in the side chains. The D enantiomer binds right handed double stranded DNA more efficiently than the L form under all conditions tested. The source of higher binding affinity is not electrostatic in nature and rests in the more favorable hydrophobic contacts of the D-lysyl side chains in the drug-DNA complex. Both derivatives exhibit preference for alternating GC base sequences and intercalate into DNA in a threading mode as suggested by chiroptical and theoretical studies. The D enantiomer, being a peptidyl derivative that contains a non-natural amino acid, has the considerable advantage of being less susceptible to enzymatic hydrolysis and could therefore represent a lead compound for further development.

Anthraquinones↗
PubMed1997

Amido analogs of mitoxantrone: physico-chemical properties, molecular modeling, cellular effects and antineoplastic potential.

To assess the effects of amido substitution in the side-chains of the anticancer drug mitoxantrone (MX) two analogs were synthesized, having hydroxyethylaminoacetyl- and hydroxyethylaminopropionyl- substituents at the nitrogens located at positions 1, 4 of the anthracenedione ring system. The novel derivatives exhibit DNA-affinity and redox properties similar to the parent drug. However, unlike MX, they are not able to stimulate DNA cleavage, as shown by alkaline elution experiments. Molecular modeling studies using ab initio quantum mechanical methods show that, while the stereochemistry of the drug molecule is not appreciably affected when an amide group replaces the aromatic amino function, the reverse is true for the electrostatic properties. Indeed, overlapping of electron density of MX with its analogs is very poor. Moreover, a reversal in the direction of MX dipole moment occurs in the amido congeners. This may explain the lack of recognition of the cleavable topoisomerase II-DNA complex and loss of cleavage stimulation. However, the new derivatives exhibit pharmacological activity comparable to that found for MX, as they are remarkably cytotoxic and are active in vivo against P388 murine leukemia. Hence, amido substitution may lead to a different mechanism of cytotoxicity, not related to classical protein or free radical-mediated DNA damage, which points to a novel type of antineoplastic pharmacophore.

Animals↗
PubMed1996

Peptidyl anthraquinones as potential antineoplastic drugs: synthesis, DNA binding, redox cycling, and biological activity.

A series of new compounds containing a 9,10-anthracenedione moiety and one or two peptide chains at position 1 and/or 4 have been synthesized. The amino acid residues introduced are glycine (Gly), lysine (Lys), and tryptophan (Trp), the latter two in both the L- and D-configurations. The peptidyl anthraquinones maintain the ability of intercalating efficiently into DNA, even though the orientation within the base-pair pocket may change somewhat with reference to the parent drugs mitoxantrone (MX) and ametantrone (AM). The interaction constants of the mono-, di-, and triglycyl derivatives are well comparable to those found for AM but 5-10 times lower than the value reported for MX. On the other hand, the glycyl-lysyl compounds bind DNA to the same extent as (L-isomer) or even better than (D-isomer) MX. As for the parent drugs without peptidyl chains, the new compounds prefer alternating CG binding sites, although to different extents. The bis-Gly-Lys derivatives are the least sensitive to base composition, which may be due to extensive aspecific charged interactions with the polynucleotide backbone. As far as redox properties are concerned, all peptidyl anthraquinones show a reduction potential very close to that of AM and 60-80 mV less negative than that of MX; hence, they can produce free-radical-damaging species to an extent similar to the parent drugs. The biological activity has been tested in human tumor and murine leukemia cell lines. Most of the test anthraquinones exhibit cytotoxic properties close to those of AM and considerably lower than those of MX. Stimulation of topoisomerase-mediated DNA cleavage is moderately present in representatives of the glycylanthraquinone family, whereas inhibition of the background cleavage occurs when Lys is present in the peptide chain. For most of the test anthraquinones, the toxicity data are in line with the DNA affinity scale and the topoisomerase II stimulation activity. However, in the lysyl derivatives, for which lack of cytotoxicity cannot be related to poor binding to DNA, the steric and electronic properties of the side-chain substituent must impair an effective recognition of the cleavable complex.

Animals↗
PubMed1994

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.

Animals↗
PubMed1993

Relevance of DNA binding to the mechanism of anti-herpesvirus activity of benzhydrazone.

Benzhydrazone (1H-benz(f)indene-1,3(2H)-dione bis (amidino-hydrazone) (BH) is a synthetic compound with selective anti-herpesvirus activity. Its selectivity seems to stem from the inhibition of viral protein glycosylation and several hypotheses have been formulated to explain such an effect. Data presented here demonstrate that DNA binding is a prominent feature of BH. Interaction is taking place with a relatively high affinity constant and is more efficient for GC-rich viral sequences. Experiments with the cloned DNA fragments from a BH-resistant virus strain indicate that BH-DNA complex formation is drastically reduced as compared to BH-sensitive virus. The occurrence of the resistant phenotype in HEp-2 cells but not in Vero cells could be explained by differences in BH cytotoxicity. Changes in drug uptake and accumulation by cells following infection, in addition to GC preference, may also account for the degree of antiviral selectivity shown by BH.

Animals↗
PubMed1993

On the mechanism of action of quinolone drugs.

Antibacterial quinolones are thought to inhibit DNA gyrase by trapping the enzyme as a complex with the DNA substrate. The precise molecular details of drug-DNA and drug-enzyme interactions remain controversial. Here, a model is proposed that accounts for the influence of magnesium ions on quinolone-DNA binding.

4-Quinolones↗
PubMed1993

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.

Animals↗
PubMed1992

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.

Animals↗