Natural compounds in the human diet and their ability to bind mutagens prevents DNA-mutagen intercalation

Physiological functions, pharmacological aspects and nutritional importance of green tomato- a future food

Green tomatoes contain significant levels of steroidal glycoalkoids (SGA) such as α-tomatine and green pigment chlorophyll. Tomatine is an admixture of two glycoalkoids; alpha tomatine and dehydrotomatine reported various health beneficial biological activities. Moreover, a hydrolyzed product of tomatine also contributes to age-related atrophy, and muscle weakness and helps the elderly recover from illness and injuries related to age. However, there is a lack of evidence regarding the absorption of tomatine in the human body concerning proposed biological activity, which should be an area of interest in the future. Once, the absorption study is established compounds concentrated in green tomatoes are potentially involved as protective compounds for several diseases and also used for functional food. To facilitate the use of green tomatoes in food processing, this comprehensive review provides data on the nutritional value of green tomatoes, with emphasis on the evolution of the physiological chemistry, analytical, medicinal, and pharmacological effects of the α-tomatine and chlorophyll in an experimental model. The broad aim of this review is to evaluate the health benefits of green tomatoes in addition to their nutritional value and to study the several features of the role of α-tomatine and chlorophyll in human health.

Spectroscopy studies of interaction hypericin with an anti-cancer therapy drug doxorubicin

The presented study was designed to estimate the ability of hypericin to interact with the anticancer drug doxorubicin. The hetero-association of hypericin and doxorubicin was investigated with absorption and fluorescence spectroscopy methods in aqueous solution of DMSO in two-component mixtures: doxorubicin-hypericin and three component mixtures: DNA-doxorubicin-hypericin. The data indicate that hypericin forms complexes with doxorubicin and that the association constants are on the order of 300,000 M^-1 in a buffer with 30% DMSO content. The absorption spectra of the hypericin - doxorubicin complexes were examined as well. Owing to its ability to interact with flat aromatic compounds, hypericin may potentially be used as an interceptor molecule to detoxification of patients after chemotherapy.

Study of the Potential Hepatoprotective Effect of Myo-Inositol and Its Influence on Zebrafish Development

Inositol is a natural substance found widely in plants. It is used in therapies for many medical cases. The aim of this study was to determine the toxicity of myo-inositol (MI) and to investigate its potential hepatoprotective character. In the first part of the study, zebrafish embryos were incubated with 5, 10, 20, 40, 60, 80, and 100 mg/mL MI. Endpoints such as survivability, hatching rate, malformation, and mobility were evaluated. Our results demonstrated that the high doses of MI lead to increased mortality and malformations and reduce the hatching rate in comparison to the control group. Moreover, low doses of this compound do not produce a negative effect on zebrafish and even have the ability to increase the hatching rate and mobility. In the second part of the study, the hepatoprotective effect of MI was tested. Zebrafish larvae from the line Tg (fabp10a:DsRed) were incubated for 24 h with 1% and 2% ethanol (EtOH), 5 mg/mL of MI with 1% EtOH, and 5 mg/mL of MI with 2% EtOH. No significant differences between the groups with EtOH and the group treated with EtOH with MI were observed. Our results suggest that MI has no positive benefits on hepatocytes of zebrafish larvae.

Withaferin A Acts as a Novel Regulator of Liver X Receptor-α in HCC

Withaferin A, a steroidal lactone derived from the Withania somnifera plant has been known for its anti-cancerous effects on various types of cancer cells. However, its effect on the hallmarks of cancer such as proliferation, migration, invasion, and angiogenesis is still poorly understood. The antitumor property of Withaferin A and its molecular mechanism of action on hepatocellular carcinoma (HCC) cells is not yet completely established. In this study, we aimed to elucidate the novel molecular function of Withaferin A on HCC cells and its effect on various gene expression. Our results clearly showed that Withaferin A treatment to HCC cells inhibited proliferation, migration, invasion, and anchorage-independent growth. Further, we explored the Withaferin A target genes by blotting human angiogenesis, and cytokine arrays using conditioned media of Withaferin A treated QGY-7703 cells. We found that many of Nuclear factor kappa B (NF-κB), angiogenesis and inflammation associated proteins secretion is downregulated upon Withaferin A treatment. Interestingly, all these genes expression is also negatively regulated by nuclear receptor Liver X receptor-α (LXR-α). Here, we explored a novel mechanism that Withaferin-A activated LXR-α inhibits NF-κB transcriptional activity and suppressed the proliferation, migration, invasion, and anchorage-independent growth of these HCC cells. All these data strongly confirmed that Withaferin A is a potent anticancer compound and suppresses various angiogenesis and inflammatory markers which are associated with the development and progression of HCC. This beneficial and potential therapeutic property of Withaferin A will be very useful for the treatment of HCC.

Biological reduction of aflatoxin B1 in yogurt by probiotic strains of Lactobacillus acidophilus and Lactobacillus rhamnosus

The present study was conducted to investigate the ability of two probiotic strains, L. acidophilus PTCC 1643 and L. rhamnosus PTCC 1637, to bind aflatoxin B₁ (AFB₁, 20 ng/ml) in comparison with yogurt starter cultures, at equal bacterial count (~ 10⁹ LogCFU/ml) during a 21-day storage period at 4 °C. All assessed treatments exhibited high percentages of AFB₁-binding, ranged from 64.56 to 96.58%. However, the ability of probiotic bacteria was statistically higher than yogurt starter cultures. Aflatoxin binding ability of the selected lactic acid bacteria was dependent on both time and bacteria species. The highest and the lowest percentages of AFB_1-removal was observed at 11th day of cold storage by L. rhamnosus (96.58 ± 3.97%) and at the first day of storage for yogurt starter cultures (64.56 ± 5.32%), respectively. The stability of bacterial cells-AFB₁ complex was remarkable, since only 0.84-26.75% of bounded AFB₁ was released from bacterial cells after 3 times washing during the storage period.

Cationic porphyrins as destabilizer of a G-quadruplex located at the promoter of human MYH7 β gene

G-quadruplex (GQ) architecture is adopted by guanine rich sequences, present throughout the eukaryotic genome including promoter locations and telomeric ends. The in vivo presence indicates their involvement and role in various biological processes. Various small ligands have been developed to interact and stabilize/destabilize G-quadruplex structures. Cationic porphyrins are among the most studied ligands, reported to bind and stabilize G-quadruplexes. Herein, we report the recognition and destabilization of a parallel G-quadruplex by porphyrins (TMPyP3 and TMPyP4). This G-quadruplex forming 23-nt G-rich sequence is in the promoter region of Human Myosin Heavy Chain β gene (MYH7β). Presence of various putative regulatory sequence elements (TATA Box, CCAAT, SP-1) located in the vicinity of this quadruplex motif, highlight its regulatory implications. Biophysical methods as Circular Dichroism Spectroscopy, UV-Absorption Spectroscopy, UV-Thermal Denaturation and Fluorescence Spectroscopy (steady as well as Time Resolved) have been used for studying the interaction and binding parameters. It is proposed that porphyrins have a destabilizing effect on the G-quadruplexes with parallel topology and a stronger binding specifically via intercalation mode is needed to cause destabilization. The study deals with better understanding and insights of DNA-Drug interactions in biological systems.Communicated by Ramaswamy H. Sarma.

Hetero-association models of non-covalent molecular complexation

The present review discusses the current state-of-the-art in building models enabling the description of non-covalent equilibrium complexation of different types of molecules in solution, which results in the formation of supramolecular structures different in length and composition (hetero-association or supramolecular multicomponent co-polymerisation). The description is focused on standard physical and chemical quantities such as experimental observables and equilibrium parameters of interaction (equilibrium constants and concentrations). The major partial cases of the hetero-association models, such as finite and indefinite isodesmic and cooperative complexations, and Benesi-Hildebrand and Langmuir adsorption models are considered. Future challenges in the development of the hetero-association models are provided.

Comparative study of binding interactions between porphyrin systems and aromatic compounds of biological importance by multiple spectroscopic techniques: A review

The specific spectroscopic and redox properties of porphyrins predestine them to fulfill the role of sensors during interacting with different biologically active substances. Monitoring of binding interactions in the systems porphyrin-biologically active compound is a key question not only in the field of physiological functions of living organisms, but also in environmental protection, notably in the light of the rapidly growing drug consumption and concurrently the production of drug effluents. Not always beneficial action of drugs on natural porphyrin systems induces to further studies, with commercially available porphyrins as the model systems. Therefore the binding process between several water-soluble porphyrins and a series of biologically active compounds (e.g. caffeine, guanine, theophylline, theobromine, xanthine, uric acid) has been studied in different aqueous solutions analyzing their absorption and steady-state fluorescence spectra, the porphyrin fluorescence lifetimes and their quantum yields. The magnitude of the binding and fluorescence quenching constants values for particular quenchers decreases in a series: uric acid > guanine > caffeine > theophylline > theobromine > xanthine. In all the systems studied there are characters of static quenching, as a consequence of the π-π-stacked non-covalent and non-fluorescent complexes formation between porphyrins and interacting compounds, accompanied simultaneously by the additional specific binding interactions. The porphyrin fluorescence quenching can be explain by the photoinduced intermolecular electron transfer from aromatic compound to the center of the porphyrin molecule, playing the role of the binding site. Presented results can be valuable for designing of new fluorescent porphyrin chemosensors or monitoring of drug traces in aqueous solutions. The obtained outcomes have also the toxicological and medical importance, providing insight into the interactions of the water-soluble porphyrins with biologically active substances.

Non-covalent interactions between thio-caffeine derivatives and water-soluble porphyrin in ethanol-water environment

To determine the binding interactions and ability to form the non-covalent systems, the association process between 5,10,15,20-tetrakis[4-(trimethylammonio)phenyl]-21H,23H-porphine tetra-p-tosylate (H₂TTMePP) and a series of five structurally diverse thio-caffeine analogues has been studied in ethanol and ethanol-water solutions, analyzing its absorption and steady-state fluorescence spectra. The porphyrin fluorescence lifetimes in the systems studied were established as well. During the titration with thio-caffeine compounds the slight bathochromic effect and considerable hypochromicity of the porphyrin Soret band maximum can be noted. The fluorescence quenching effect observed for interactions in H₂TTMePP - thio-caffeine derivative systems, as well as the order of binding and fluorescence quenching constants (of 10⁵-10³mol^-1) suggest the existence of the mechanism of static quenching due to the formation of non-covalent and non-fluorescent stacking complexes. In all the systems studied the phenomenon of the fractional accessibility of the fluorophore for the quencher was observed as well. Additionally, the specific binding interactions, due to the changes in reaction environment polarity, can be observed. It was found that thio-caffeine compounds can quench the porphyrin fluorescence according to the structure of thio-substituent in caffeine molecule. The obtained results can be potentially useful from scientific, therapeutic or environmental points of view.

Investigation of the binding affinity in vitamin B12-Bovine serum albumin system using various spectroscopic methods

The binding affinity between vitamin B12 (VitB12) and bovine serum albumin (BSA) has been investigated in aqueous solution at pH=7.4, employing UV-vis absorption and steady-state, synchronous and three-dimensional fluorescence spectra techniques. Representative effects noted for BSA intrinsic fluorescence resulting from the interactions with VitB12 confirm the formation of π-π stacked non-covalent and non-fluorescent complexes in the system VitB12-BSA. All the determined parameters, the binding, fluorescence quenching and bimolecular quenching rate constants (of the order of 10⁴Lmol^-1, 10³Lmol^-1 and 10¹¹Lmol^-1s^-1, respectively), as well as Förster resonance energy transfer parameters validate the mechanism of static quenching. The interaction with VitB12 induces folding of the polypeptide chains around Trp residues of BSA, resulting in a more hydrophobic surrounding. Presented outcomes suggest that the addition of VitB12 can lead to the more organized BSA conformation and its more folded tertiary structure, what could influence the physiological functions of bovine serum albumin, notably in case of its overuse or abnormal metabolism.

Analysis of the binding interaction in uric acid - Human hemoglobin system by spectroscopic techniques

The binding interaction between human hemoglobin and uric acid has been studied for the first time, by UV-vis absorption and steady-state, synchronous and three-dimensional fluorescence techniques. Characteristic effects observed for human hemoglobin intrinsic fluorescence during interaction with uric acid at neutral pH point at the formation of stacking non-covalent and non-fluorescent complexes. All the calculated parameters, the binding, fluorescence quenching and bimolecular quenching rate constants, as well as Förster resonance energy transfer parameters confirm the existence of static quenching. The results of synchronous fluorescence measurements indicate that the fluorescence quenching of human hemoglobin originates both from Trp and Tyr residues and that the addition of uric acid could significantly hinder the physiological functions of human hemoglobin.

Nano-encapsulated chlorophyllin significantly delays progression of lung cancer both in in vitro and in vivo models through activation of mitochondrial signaling cascades and drug-DNA interaction

Chlorophyllin (CHL), a sodium-copper-salt derived from chlorophyll, has been widely used as a food-dye, also reportedly having some anti-cancer effect. We tested if PLGA-loaded CHL (NCHL) could have additional protective abilities through its faster and targeted drug delivery in cancer cells. Physico-chemical characterization of NCHL was done through atomic-force microscopy and UV-spectroscopy. NCHL demonstrated greater ability of drug uptake and strong anti-cancer potentials in non-small cell lung cancer cells, A549, as revealed from data of% cell viability, generation of reactive-oxygen-species and expression of bax, bcl2, caspase3, p53 and cytochrome c proteins. Circular dichroic spectral data indicated strong binding of NCHL with calf-thymus-DNA, causing a conformational/structural change in DNA. Further, NCHL could cross the blood-brain-barrier in mice and showed greater efficacy in recovery process of tissue damage, reduction in chromosomal aberrations and% of micronuclei in co-mutagens (Sodiumarsenite+Benzo[a]Pyrene)-treated mice at a much reduced dose, indicating its use in therapeutic oncology.

Sensitive fluorescence assay of organophosphorus pesticides based on the fluorescence resonance energy transfer between CdTe quantum dots and porphyrin

A sensitive and selective quantum dot (QD)-based fluorescence resonance energy transfer (FRET) biosensor was successfully fabricated for the detection of organophosphorus pesticides (OPs).

Oxidative stress response in canine in vitro liver, kidney and intestinal models with seven potential dietary ingredients

In vitro cell culture systems are a useful tool to rapidly assess the potential safety or toxicity of chemical constituents of food. Here, we investigated oxidative stress and organ-specific antioxidant responses by 7 potential dietary ingredients using canine in vitro culture of hepatocytes, proximal tubule cells (CPTC), bone marrow-derived mesenchymal stem cells (BMSC) and enterocyte-like cells (ELC). Cellular production of free radical species by denatonium benzoate (DB), epigallocatechin gallate (EPI), eucalyptol (EUC), green tea catechin extract (GTE) and sodium copper chlorophyllin (SCC), tetrahydroisohumulone (TRA) as well as xylitol (XYL) were continuously measured for reactive oxygen/nitrogen species (ROS/RNS) and superoxide (SO) for up to 24h. DB and TRA showed strong prooxidant activities in hepatocytes and to a lesser degree in ELC. DB was a weak prooxidant in BMSC. In contrast DB and TRA were antioxidants in CPTC. EPI was prooxidant in hepatocytes and BMSC but showed prooxidant and antioxidant activity in CPTC. SCC in hepatocytes (12.5mg/mL) and CPTC (0.78mg/mL) showed strong prooxidant and antioxidant activity in a concentration-dependent manner. GTE was effective antioxidant only in ELC. EUC and XYL did not induce ROS/RNS in all 4 cell types. SO production by EPI and TRA increased in hepatocytes but decreased by SCC in hepatocytes and ELC. These results suggest that organ-specific responses to oxidative stress by these potential prooxidant compounds may implicate a mechanism of their toxicities.

Normalization of nano-sized TiO2-induced clastogenicity, genotoxicity and mutagenicity by chlorophyllin administration in mice brain, liver, and bone marrow cells

The intensive uses of titanium dioxide (TiO2) nanoparticles in sunscreens, toothpaste, sweats, medications, etc. making humans exposed to it daily by not little amounts and also increased its risks including genotoxicity. Thus, the present study was designed as one way to reduce nano-titanium-induced clastogenicity, genotoxicity, and mutagenicity in mice by co-administration of the free radical scavenger chlorophyllin (CHL). In addition, markers of oxidative stress were detected to shed more light on mechanism(s) underlying nano-sized TiO2 genotoxicity. Male mice were exposed to multiple injection into the abdominal cavity for five consecutive days with either CHL (40 mg/kg bw/day), or each of three dose levels of nano-sized TiO2 (500, 1000, or 2000 mg/kg bw/day) alone, or both simultaneously and sacrificed by cervical dislocation 24 h after the last treatment. After CHL co-administration, the observed dose-dependent genotoxicity of TiO2 nanoparticles indicated by the significant elevations in frequencies of both micronuclei and DNA damage induction was significantly decreased and returned to the negative control level. The observed induced mutations in p53 exons 5, 7, & 8 and 5 & 8 in the liver and brain, respectively, were declined in most cases. Moreover, CHL significantly decreased hepatic malondialdehyde level and significantly increased glutathione level and superoxide dismutase, catalase, and glutathione peroxidase activities that were significantly disrupted in animal groups treated with nano-TiO2 alone. In conclusion, the evidenced in vivo genotoxicity of nano-TiO2 in the present study was normalized after CHL co-administration which supports the previously suggested oxidative stress as the possible mechanism for titanium toxicity.

Spectroscopic study of associated systems formed between water-soluble cationic porphyrins or their copper (II) complexes and nucleic building blocks

The association process between two water soluble cationic porphyrins, 5,10,15,20-tetrakis[4-(trimethyl-ammonio)phenyl]-21H,23H-porphine tetra-p-tosylate (H2TTMePP) and 5,10,15,20-tetrakis(1-methyl-4-pyridyl)-21H,23H-porphine tetra-p-tosylate (H2TMePyP), as well as their Cu (II) complexes, with five series of nucleic agents has been studied using UV-VIS spectroscopy in aqueous solutions. During the titration with nucleic compounds the bathochromic effect of porphyrins absorption spectra can be observed as well as the hypochromicity of the Soret maximum. The association constants were calculated using a curve-fitting procedure (KAC of the order of magnitude of 103–105 mol−1). It has been shown that the interactions of H2TTMePP with nucleic agents are much stronger than interactions of H2TMePyP, which is most likely related to the kind and the size of the porphyrin substituent groups partaking in the process of stacking. The strength of the observed associated systems increases generally in a series: nucleic base

Heterocyclic Aromatic Amines Heterocomplexation with Biologically Active Aromatic Compounds and Its Possible Role in Chemoprevention

Food-borne heterocyclic aromatic amines (HCAs) are known mutagens and carcinogens present especially in Western population diet, which contains large amount of meat and its products. HCAs are capable of interacting with DNA directly through the formation of covalent adducts, however this process requires biological activation in liver, mainly by cytochrome P450 enzymes. This process may produce mutations and in consequence may contribute to the development of cancer. However, there are many studies showing that several biologically active aromatic compounds (BACs) may protect against genotoxic effects of HCAs. Direct interactions and noncovalent heterocomplexes formation may be one of the most important mechanisms of such protection. This work describes several BACs present in human diet, which are capable of molecular complexes formation with HCAs and protect cells as well as whole organisms against HCAs action.

Modulation of acridine mutagen ICR191 intercalation to DNA by methylxanthines--analysis with mathematical models

Caffeine (CAF) and other methylxanthines (MTX) may interact directly with several aromatic, intercalating ligands through mixed stacking aggregation. Formation of such stacking hetero-complexes may decrease their free form concentration and, in consequence, diminish their biological activity, which is often related to their direct interaction with DNA. In this paper interactions of acridine mutagen (ICR191) with DNA in the presence of three MTX: caffeine (CAF), pentoxifylline (PTX) and theophylline (TH) are investigated. Several mathematical models are used to calculate all association constant values and every component concentration in each analyzed mixture. Model McGhee-von Hippel is used to analyze ligand-DNA interaction, and model Zdunek et al.--to analyze ligand-MTX interactions. Finally, two distinct mathematical models are employed to analyze three-component mixture containing ligand, MTX and DNA molecules. The first model describes possible interactions of ligand with DNA and MTX, and rejects direct MTX interactions with DNA. The second model describes all interactions mentioned above and, additionally, allows MTX to interact directly with DNA. Results obtained using these models are similar. However, correspondence of theoretical results to experimental data is better for the first model than the second one. In this paper possible interactions of ICR191 with eukaryotic cell chromatin are also analyzed, showing that CAF reduces acridine mutagen potential to interact directly with cell chromatin. Additionally, it is demonstrated that MTX inhibit mutagenic activity of ICR191 in a dose-dependent manner. Furthermore, biological activity of ICR191-MTX mixtures corresponds with concentration of free mutagen form calculated using appropriate mathematical model.

Physicochemical Mechanisms of Synergistic Biological Action of Combinations of Aromatic Heterocyclic Compounds

The mechanisms of synergistic biological effects observed in the simultaneous use of aromatic heterocyclic compounds in combination are reviewed, and the specific biological role of heteroassociation of aromatic molecules is discussed.

Spectroscopic study of porphyrin-caffeine interactions

The association between water-soluble porphyrins: 4,4′,4″,4‴-(21 H,23 H-porphine-5,10,15,20-tetrayl)tetrakis-(benzoic acid) (H₂TCPP), 5,10,15,20-tetrakis(4-sulfonatophenyl)-21 H,23 H-porphine (H₂TPPS₄), 5,10,15,20-tetrakis[4-(trimethylammonio)phenyl]-21 H,23 H-porphine tetra-p-tosylate (H₂TTMePP), 5,10,15,20-tetrakis(1-methyl-4-pyridyl)-21 H,23 H-porphine tetra-p-tosylate (H₂TMePyP), the Cu(II) complexes of H₂TTMePP and H₂TMePyP, as well as chlorophyll a with caffeine (1,3,7-trimethylxanthine) has been studied analysing their absorption and emission spectra in aqueous (or acetone in case of chlorophyll a) solution. During the titration by caffeine the porphyrins absorption spectra undergo the evolution – the bathochromic effect can be observed as well as the hypochromicity of the Soret maximum. The association constants were calculated using curve-fitting procedure (K_AC of the order of magnitude of 10³ mol^-1). Whereas the emission spectra point at the presence of the fluorescence quenching effect testifying for the partial inactivation of the porphyrin molecule. The fluorescence quenching constants were calculated from Stern-Volmer plots. The results obtained show that caffeine can interact with water-soluble porphyrins and through formation of stacking complexes is able to quench their ability to emission.

Gene expression signature of DMBA-induced hamster buccal pouch carcinomas: modulation by chlorophyllin and ellagic acid

Chlorophyllin (CHL), a water-soluble, semi-synthetic derivative of chlorophyll and ellagic acid (EA), a naturally occurring polyphenolic compound in berries, grapes, and nuts have been reported to exert anticancer effects in various human cancer cell lines and in animal tumour models. The present study was undertaken to examine the mechanism underlying chemoprevention and changes in gene expression pattern induced by dietary supplementation of chlorophyllin and ellagic acid in the 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis model by whole genome profiling using pangenomic microarrays. In hamsters painted with DMBA, the expression of 1,700 genes was found to be altered significantly relative to control. Dietary supplementation of chlorophyllin and ellagic acid modulated the expression profiles of 104 and 37 genes respectively. Microarray analysis also revealed changes in the expression of TGFβ receptors, NF-κB, cyclin D1, and matrix metalloproteinases (MMPs) that may play a crucial role in the transformation of the normal buccal pouch to a malignant phenotype. This gene expression signature was altered on treatment with chlorophyllin and ellagic acid. Our study has also revealed patterns of gene expression signature specific for chlorophyllin and ellagic acid exposure. Thus dietary chlorophyllin and ellagic acid that can reverse gene expression signature associated with carcinogenesis are novel candidates for cancer prevention and therapy.

General analysis of competitive binding in drug-interceptor-DNA systems

A general model of competitive binding in drug-interceptor-DNA systems has been developed in order to quantify both the interceptor and protector mechanisms. The model involves full parameterization of the basic equations governing the mutual competition between drugs binding to DNA and incorporates as partial cases various similar models existing in the literature. The generality of the model results from strict accounting of the statistical effects of the binding of the drug and interceptor with DNA according to the McGhee-von Hippel formalism, and to the strict treatment of hetero-association between the drug and interceptor, which includes formation of all possible types of self- and hetero-complexes in solution. Indirect experimental evidence is provided for the importance of the protector mechanism in drug-caffeine-DNA systems, which is sometimes ignored in the literature because of the small magnitude of the CAF-DNA binding constant.

Quantification of the interceptor action of caffeine on the in vitro biological effect of the anti-tumour agent topotecan

Using published in vitro data on the dependence of the percentage of apoptosis induced by the anti-cancer drug topotecan in a leukaemia cell line on the concentration of added caffeine, and a general model of competitive binding in a system containing two aromatic drugs and DNA, it has been shown to be possible to quantify the relative change in the biological effect just using a set of component concentrations and equilibrium constants of the complexation of the drugs. It is also proposed that a general model of competitive binding and parameterization of that model may potentially be applied to any system of DNA-targeting aromatic drugs under in vitro conditions. The main reasons underpinning the proposal are the general feature of the complexation of aromatic drugs with DNA and their interaction in physiological media via hetero-association.