In vivo comprehensive metabolite profiling of esculetin and esculin derived from chicory in hyperuricemia rats using ultra-high-performance liquid chromatography coupled with quadrupole-orbitrap high-resolution mass spectrometry.

Chicory, renowned for its multifaceted benefits, houses two vital coumarins, esculetin and esculin, both instrumental in reducing uric acid. This study emphasizes the metabolic pathways of esculetin and esculin under both standard and hyperuricemia conditions. Hyperuricemia was induced in Sprague-Dawley rats using oxonic acid potassium salt (300 mg·kg-1 ) and a 10% fructose water regimen over 21 days. Leveraging the ultra-high-performance liquid chromatography-Q Exactive hybrid quadrupole-orbitrap high resolution mass spectrometry, we analyzed the fragmentation behaviors of esculetin and esculin in rat bio-samples. Post oral-intake of esculetin or esculin, a notable dip in serum uric acid levels was observed in hyperuricemia rats. The investigation unveiled 24 esculetin metabolites and 14 for esculin. The metabolic pathways of both compounds were hydrolysis, hydroxylation, hydrogenation, dehydroxylation, glucuronidation, sulfation, and methylation. Interestingly, certain metabolites presented variations between standard and hyperuricemia rats, indicating that elevated levels of uric acid may affect enzyme activity linked to these metabolic reactions. This is the first systematic study on comparison of metabolic profiles of esculetin and esculin in both normal and hyperuricemia states, which was helpful to enrich our understanding of the complicated structure-activity relationships between esculin and esculetin and shed light to their action mechanism.

Esculin and ferric citrate-incorporated sturgeon skin gelatine as an antioxidant film for food packaging to prevent Enterococcus faecalis contamination.

Herein, a sturgeon skin gelatine film combined with esculin and ferric citrate was developed as an edible food packaging material to prevent Enterococcus faecalis (E. faecalis) contamination. E. faecalis is able to hydrolyse esculin in the film, and then the hydrolysed product, esculetin, combines with ferric citrate to form a brown-black phenol iron complex. This phenomenon can be observed easily after 48 h of contamination under visible light, and it can be determined under 365 nm ultraviolet light with high sensitivity. With the addition of esculin and ferric citrate, the film showed better mechanical properties and water vapour permeability than those of the unmodified gelatine. When an increased amount of esculin was added, an increase in thermal stability, antioxidant activity, and antioxidant stability of the film was observed. These physicochemical characteristics are beneficial for developing a packaging material for food storage that mitigates foodborne illness caused by E. faecalis.

Long-range replica exchange molecular dynamics guided drug repurposing against tyrosine kinase PtkA of Mycobacterium tuberculosis.

Tuberculosis (TB) is a leading cause of death worldwide and its impact has intensified due to the emergence of multi drug-resistant (MDR) and extensively drug-resistant (XDR) TB strains. Protein phosphorylation plays a vital role in the virulence of Mycobacterium tuberculosis (M.tb) mediated by protein kinases. Protein tyrosine phosphatase A (MptpA) undergoes phosphorylation by a unique tyrosine-specific kinase, protein tyrosine kinase A (PtkA), identified in the M.tb genome. PtkA phosphorylates PtpA on the tyrosine residues at positions 128 and 129, thereby increasing PtpA activity and promoting pathogenicity of MptpA. In the present study, we performed an extensive investigation of the conformational behavior of the intrinsically disordered domain (IDD) of PtkA using replica exchange molecular dynamics simulations. Long-term molecular dynamics (MD) simulations were performed to elucidate the role of IDD on the catalytic activity of kinase core domain (KCD) of PtkA. This was followed by identification of the probable inhibitors of PtkA using drug repurposing to block the PtpA-PtkA interaction. The inhibitory role of IDD on KCD has already been established; however, various analyses conducted in the present study showed that IDDPtkA had a greater inhibitory effect on the catalytic activity of KCDPtkA in the presence of the drugs esculin and inosine pranobex. The binding of drugs to PtkA resulted in formation of stable complexes, indicating that these two drugs are potentially useful as inhibitors of M.tb.

Synergistic effects of binary ionic liquid-solvent systems on enzymatic esterification of esculin.

This work established a binary ionic liquid-solvent system for effective enzymatic esterification of naturally occurring phenolic glycosides (flavonoids); which could result in a dramatic enhancement of Novozym 435-catalyzed esterification of esculin, demonstrating a great synergetic effect. In essence, [OMIM][BF4]-toluene and [TOMA][Tf2N]-hexane binary systems both served >90 mol% of conversions of esculin after 96 h of reaction at 60 °C. Typically, binary [TOMA][Tf2N]-hexane system enabled Novozym 435 with extremely high catalytic efficiency (kcat/Km = 17.57 × 10-2 (Ms)-1), which was 55-fold higher than that Novozym 435 exhibited in t-butanol solvent (one of the best solvent systems for esterification reactions). It was also found that the superiormatching in property and structure between IL and solvent was the decisive factor for the outperformance of [TOMA][Tf2N]-hexane binary system, in which [TOMA] and hexane facilitate the solubilization of esculin and fatty acids and [Tf2N]- anions and hexane offer protective effects for lipase at elevated temperatures.

Preparation of Chitosan Okra Nanoparticles: Optimization and Evaluation as Mucoadhesive Drug Delivery System.

OBJECTIVE: To prepare chitosan-okra gum nanoparticles and their evaluation as mucoadhesive drug delivery system for intranasal delivery of esculin. METHOD: Esculin loaded chitosan-okra gum based nanoparticles were prepared using ionic gelation method. The preparation method was optimized using Box-Behnken experimental design employing okra gum concentration, chitosan concentration, pH and stirring speed as independent variables and particle size, encapsulation efficiency and zeta potential of the formulation were selected as dependent variables. The optimized formulation was characterized using FTIR, SEM and TEM. The nanoparticles were evaluated for their bioadhesive strength and in vitro drug release studies. The optimized intranasal formulation was administered to rats and the pharmacokinetic profile and biodistribution studies were carried out to calculate the targeting efficiency of the formulation in the brain. RESULTS: The nanoparticles were found to depict particle size in the range of 294.0 to 613.4 nm. The concentration of gums was found to significantly influence the particle size and encapsulation efficiency. The nanoparticles depicted bioadhesive strength of 32±2%. The in vitro drug release studies showed 96.4±4.2% release of esculin from nanoparticles in 4h. The drug targeting of NPs to brain was found to be nearly double that of esculin given as simple solution. CONCLUSION: The nanoparticles prepared using chitosan-okra gum were found to possess good mucoadhesive strength with and high brain targeting efficiency.

Colloidal characteristics and functionality of rationally designed esculin-loaded hydrogel microcapsules.

This work reports the development of different types of alginate hydrogel microparticles designed specifically for the esculin (ESC) payload. Negatively charged alginate (ALG) microspheres were prepared by the ionotropic gelation technique, and an oppositely charged polyelectrolyte (PE) shell as a compatible polycation (chitosan (CHIT) or gelatin (GEL)) or a synthetic PEs (poly(allylamine hydrochloride) (PAH) and poly(4-styrenesulfonate) (PSS)) were adsorbed using electrostatic complexation. Thorough characterization of microparticles was performed with advanced microscopic techniques (scanning electron, fluorescence and confocal), followed by stability studies, ESC encapsulation efficacy determination and in vitro release kinetics measurements. We provide an in-depth investigation of the relationships between the properties (thickness, viscosity, areal mass, zeta potential) of the outer shell and the retaining and release abilities of the fabricated microcarriers, using quartz crystal microbalance with dissipation monitoring technique (QCM-D), spectroscopic ellipsometry and streaming potential measurements, combined in a new approach that was not attempted before for micrometric particles. The PAH-PSS and GEL coatings provided sufficient protection against ESC release under simulated gastric conditions that followed a two-stage Corrigan-Gallagher model with a marginal release rate in the first (lag) stage. This seems to be an interesting outcome, since it is rather peculiar for a low-molecular weight hydrophilic compound encapsulated in a highly porous microhydrogel to be released in such a manner.

Antithrombotic potential of esculin 7, 3', 4', 5', 6'-O-pentasulfate (EPS) for its role in thrombus reduction using rat thrombosis model.

Currently available anticoagulants for prevention and treatment of thrombosis have several limitations, thus, small organic scaffolds that can dissolve clots in vivo in a dose dependent manner with lesser side effects are highly desirable. Here we report the synthesis of esculin pentasulfate (EPS) and assessment of its in vitro, in vivo and ex vivo anticoagulant and antithrombotic potential. Assessment of in vitro clotting times showed prolonged activated partial thromboplastin time (APTT), prothrombin time (PT) and thrombin time (TT) in the presence of EPS. EPS also showed remarkable reduction in thrombus formation when administered in occlusion induced thrombotic rats at a low dose (2.5 mg/kg). Further, assessment of clot rate with plasma isolated from EPS treated rats confirmed its anticoagulation potential. EPS at varying concentrations showed no significant cytotoxic effect on HEK293 cell line. Further, molecular docking analysis of EPS with known anticoagulant proteins [(antithrombin (ATIII) and heparin cofactor II (HCF II)] that require heparin revealed good binding affinity (-7.9 kcal/mol) with ATIII but not with HCF II. ATIII when incubated with EPS showed increased fluorescence intensity, with no change in secondary structure. Overall, our results clearly show the in vivo modulation of thrombus formation using a modified natural scaffold EPS.

Synthesis of Aesculetin and Aesculin Glycosides Using Engineered Escherichia coli Expressing Neisseria polysaccharea Amylosucrase.

Because glycosylation of aesculetin and its 6-glucoside, aesculin, enhances their biological activities and physicochemical properties, whole-cell biotransformation and enzymatic synthesis methodologies using Neisseria polysaccharea amylosucrase were compared to determine the optimal production method for glycoside derivatives. High-performance liquid chromatography analysis of reaction products revealed two glycosylated products (AGG1 and AGG2) when aesculin was used as an acceptor, and three products (AG1, AG2, and AG3) when using aesculetin. The whole-cell biotransformation production yields of the major transfer products for each acceptor (AGG1 and AG1) were 85% and 25%, respectively, compared with 68% and 14% for enzymatic synthesis. These results indicate that whole-cell biotransformation is more efficient than enzymatic synthesis for the production of glycoside derivatives.

Aesculin modulates bone metabolism by suppressing receptor activator of NF-κB ligand (RANKL)-induced osteoclastogenesis and transduction signals.

Aesculin (AES), a coumarin compound derived from Aesculus hippocasanum L, is reported to exert protective role against inflammatory diseases, gastric disease and cancer. However, direct effect of AES in bone metabolism is deficient. In this study, we examined the effects of AES on osteoclast (OC) differentiation in receptor activator of NF-κB ligand (RANKL)-induced RAW264.7 cells. AES inhibits the OC differentiation in both dose- and time-dependent manner within non-toxic concentrations, as analyzed by Tartrate Resistant Acid Phosphatase (TRAP) staining. The actin ring formation manifesting OC function is also decreased by AES. Moreover, expressions of osteoclastogenesis related genes Trap, Atp6v0d2, Cathepsin K and Mmp-9 are decreased upon AES treatment. Mechanistically, AES attenuates the activation of MAPKs and NF-κB activity upon RANKL induction, thus leading to the reduction of Nfatc1 mRNA expression. Moreover, AES inhibits Rank expression, and RANK overexpression markedly decreases AES's effect on OC differentiation and NF-κB activity. Consistently, AES protects against bone mass loss in the ovariectomized and dexamethasone treated rat osteoporosis model. Taken together, our data demonstrate that AES can modulate bone metabolism by suppressing osteoclastogenesis and related transduction signals. AES therefore could be a promising agent for the treatment of osteoporosis.

Glycosylation enables aesculin to activate Nrf2.

Since aesculin, 6,7-dihydroxycoumarin-6-O-ß-glucopyranoside, suppresses inflammation, we asked whether its anti-inflammatory activity is associated with the activation of nuclear factor-E2-related factor 2 (Nrf2), a key anti-inflammatory factor. Our results, however, show that aesculin marginally activated Nrf2. Since glycosylation can enhance the function of a compound, we then asked whether adding a glucose makes aesculin activate Nrf2. Our results show that the glycosylated aesculin, 3-O-ß-d-glycosyl aesculin, robustly activated Nrf2, inducing the expression of Nrf2-dependent genes, such as heme oxygenase-1, glutamate-cysteine ligase catalytic subunit, and NAD(P)H quinone oxidoreductase 1 in macrophages. Mechanistically, 3-O-ß-d-glycosyl aesculin suppressed ubiquitination of Nrf2, retarding degradation of Nrf2. Unlike aesculin, 3-O-ß-d-glycosyl aesculin significantly suppressed neutrophilic lung inflammation, a hallmark of acute lung injury (ALI), in mice, which was not recapitulated in Nrf2 knockout mice, suggesting that the anti-inflammatory function of the compound largely acts through Nrf2. In a mouse model of sepsis, a major cause of ALI, 3-O-ß-d-glycosyl aesculin significantly enhanced the survival of mice, compared with aesculin. Together, these results show that glycosylation could confer the ability to activate Nrf2 on aesculin, enhancing the anti-inflammatory function of aesculin. These results suggest that glycosylation can be a way to improve or alter the function of aesculin.

A new chromogenic medium for isolation of Bacteroides fragilis suitable for screening for strains with antimicrobial resistance.

There have been an increasing number of reports describing the acquisition of antimicrobial resistance by Bacteroides fragilis including the occurrence of strains with resistance to multiple antimicrobials that are relied upon for treatment of infections. The aim of this study was to design a chromogenic selective medium for isolation of B. fragilis that could be adapted for specific isolation of antimicrobial-resistant strains. Bacteroides chromogenic agar (BCA) was the result of this endeavour and allowed growth of Bacteroides spp. as black colonies and the efficient inhibition of almost all other genera tested. The medium also allowed some differentiation of B. fragilis from other members of the B. fragilis group. When compared with an adaptation of Bacteroides bile-esculin agar (BBE) for the isolation of B. fragilis from 100 stool samples, 30 isolates of B. fragilis were recovered on BCA compared with 19 isolates recovered on BBE (P = 0.022). When supplemented with meropenem (4 µg/ml) or metronidazole (2 µg/ml), BCA could be used to select for the growth of B. fragilis isolates with resistance to these agents. We conclude that BCA is a useful research tool for surveillance studies to assess the prevalence of B. fragilis and, in particular, the occurrence of antimicrobial-resistant strains.

Esculin and its oligomer fractions inhibit adhesion and migration of U87 glioblastoma cells and in vitro angiogenesis.

Cancer metastasis is the major cause of cancer-related death. Chemoprevention is defined as the use of natural or synthetic substances to prevent cancer formation or cancer progress. In the present study, we investigate the antitumor activity of esculin and its oligomer fractions in U87 glioblastoma cells. We showed that esculin and its oligomers reduced U87 cell growth in a dose dependent manner. They also inhibited cell adhesion to collagen IV and vitronectin by interfering with the function of their respective receptors α2ß1 and αvß5 integrins. Furthermore, the tested samples were able to reduce migration of U87 cells towards another extracellular matrix fibronectin. Moreover, esculin and its oligomer fractions inhibited in vitro angiogenesis of endothelial cells (HMEC-1). In summary, our data provide the first evidence that esculin and its oligomer fractions are able to reduce adhesion, migration of glioblastoma cells and in vitro angiogenesis. Esculin and its oligomers may thus exert multi-target functions against cancer cells.

HPLC Determination of Esculin and Esculetin in Rat Plasma for Pharmacokinetic Studies.

An optimized, sensitive and validated reversed-phase high-performance liquid chromatography (RP-HPLC) method with UV detection is described for simultaneous determination of esculin and its aglycone, esculetin, in rat plasma. After addition of internal standard (chrysin), plasma samples were pretreated by solid-phase extraction and introduced into the HPLC system. Analytes were separated on a RP C18 column with a mobile phase of 0.075% acetic acid in water (solvent A) and 90% acetonitrile in solvent A (solvent B) using gradient elution at a flow rate of 1.0 mL/min. The wavelength for UV detection was set at 338 nm. Calibration curves for esculin and esculetin were constructed over a range of 10-1,000 ng/mL. The developed method was found to be specific, precise and accurate. The method was successfully applied to study the pharmacokinetics of esculin and esculetin in rats. After oral administration of 120 mg/kg, the mean Cmax values were 340.3 and 316.5 ng/mL and the AUClast values were 377.3 and 1276.5 h ng/mL for esculin and esculetin, respectively. The bioavailability of esculin was calculated to be 0.62%.

Oligomerization of esculin improves its antibacterial activity and modulates antibiotic resistance.

In this particular study, the antibacterial activity of esculin and oligomer fractions was assessed. MIC values of esculin and its oligomer fractions as well as of some antibiotics against Gram-positive and Gram-negative strains and against Escherichia coli multiresistant variants were determined by the standard broth microdilution method. Both esculin and oligoesculin fractions exhibited antibacterial effect against reference strains; Staphylococcus aureus, Enterococcus faecalis, Salmonella enteritidis and Salmonella typhimurium. It appears that E3 oligomer fraction had the greatest antibacterial activity against these reference strains. Besides, as E2 and E3 revealed the best antibacterial effect against multiresistant variants of E. coli, we decided to test the effect of each, combined to the antibiotic against which the variants were resistant. In the interaction study, E2 and E3 oligoesculin fractions were found to be effective in reducing the resistance of E. coli 6574 to ofloxacin and the resistance of E. coli 6228 to amoxicillin. Only E3 oligoesculin fraction showed a synergetic interaction with amoxicillin and tetracyclin against E. coli 6708, but no interaction was found either with E2 or E3 fractions against E. coli 6234. Our study allowed us to conclude that oligomerization of esculin increases its antibacterial potential, according to the degree of polymerization.

A prodrug approach to the use of coumarins as potential therapeutics for superficial mycoses.

Superficial mycoses are fungal infections of the outer layers of the skin, hair and nails that affect 20-25% of the world's population, with increasing incidence. Treatment of superficial mycoses, predominantly caused by dermatophytes, is by topical and/or oral regimens. New therapeutic options with improved efficacy and/or safety profiles are desirable. There is renewed interest in natural product-based antimicrobials as alternatives to conventional treatments, including the treatment of superficial mycoses. We investigated the potential of coumarins as dermatophyte-specific antifungal agents and describe for the first time their potential utility as topical antifungals for superficial mycoses using a prodrug approach. Here we demonstrate that an inactive coumarin glycone, esculin, is hydrolysed to the antifungal coumarin aglycone, esculetin by dermatophytes. Esculin is hydrolysed to esculetin ß-glucosidases. We demonstrate that ß-glucosidases are produced by dermatophytes as well as members of the dermal microbiota, and that this activity is sufficient to hydrolyse esculin to esculetin with concomitant antifungal activity. A ß-glucosidase inhibitor (conduritol B epoxide), inhibited antifungal activity by preventing esculin hydrolysis. Esculin demonstrates good aqueous solubility (<6 g/l) and could be readily formulated and delivered topically as an inactive prodrug in a water-based gel or cream. This work demonstrates proof-of-principle for a therapeutic application of glycosylated coumarins as inactive prodrugs that could be converted to an active antifungal in situ. It is anticipated that this approach will be applicable to other coumarin glycones.

Spirostanol saponins and esculin from Rusci rhizoma reduce the thrombin-induced hyperpermeability of endothelial cells.

Rusci rhizoma extracts are traditionally used against chronic venous disorders (CVD). To determine the effect of its secondary plant metabolites on the endothelium, phenolic compounds and saponins from Butcher's broom were isolated from a methanolic extract, and their activity on the thrombin-induced hyperpermeability of human microvascular endothelial cells (HMEC-1) was investigated in vitro. In addition to the six known spirostanol saponins deglucoruscin (5), 22-O-methyl-deglucoruscoside (6), deglucoruscoside (7), ruscin (8), ruscogenin-1-O-(α-l-rhamnopyranosyl-(1→2)-ß-d-galactopyranoside (9) and 1-O-sulpho-ruscogenin (10), three new spirostanol derivatives were isolated and identified: 3'-O-acetyl-4'-O-sulphodeglucoruscin (1), 4'-O-(2-hydroxy-3-methylpentanoyl)-deglucoruscin (2) and 4'-O-acetyl-deglucoruscin (3). Furthermore, the coumarin esculin (4), which is also prominently present in other medicinal plants used in the treatment of CVD, was isolated for the first time from Rusci rhizoma. Five of the isolated steroid derivatives (2, 5, 8, 9 and 10) and esculin (4) were tested for their ability to reduce the thrombin-induced hyperpermeability of endothelial cells in vitro, and the results were compared to those of the aglycone neoruscogenin (11). The latter compound showed a slight but concentration-dependent reduction in hyperpermeability to 71.8% at 100µM. The highest activities were observed for the spirostanol saponins 5 and 8 and for esculin (4) at 10µM, and these compounds resulted in a reduction of the thrombin-induced hyperpermeability to 41.9%, 42.6% and 53.3%, respectively. For 2, 5 and 8, the highest concentration tested (100µM) resulted in a drastic increase of the thrombin effect. The effect of esculin observed at a concentration of 10µM was diminished at 100µM. These in vitro data provide insight into the pharmacological mechanism by which the genuine spirostanol saponins and esculin can contribute to the efficacy of Butcher's broom against chronic venous disorders.

Evaluation of mutagenic and antimutagenic activities of oligorutin and oligoesculin.

Rutin and esculin have been polymerised by laccase. Five fractions with M(w)¯ between 2127.42 and 8331.85g/mol for oligorutins, and between 688.12 and 6973g/mol for oligoesculins, were obtained. Fourier transformed infrared analysis showed that oligorutins were formed through C-C, C-O and CO linkages, while oligoesculins were obtained through C-C linkages. Monomers, their oligomers and their metabolites exhibited no mutagenic effect. Oligorutins and oligoesculins were more efficient in reducing the mutagenicity of methyl methanesulphonate, by, respectively, 69% and 64.8% in the presence of Salmonella typhimurium TA104, and 79.7% and 68.9% in the presence of S. typhimurium TA102, than were their monomers. The same oligomers revealed greater significant inhibitory effect of 2-aminoanthracene mutagenicity (respectively 82.4% and 79.3% in the presence of S. typhimurium TA104, and 89.2% and 82.9% in the presence of S. typhimurium TA102), than their monomers. Our results strongly suggest the enhancement of the tested monomer antimutagenicity after polymerisation.

Simultaneous determination of esculin and its metabolite esculetin in rat plasma by LC-ESI-MS/MS and its application in pharmacokinetic study.

A new liquid chromatography-tandem mass spectrometry (LC-MS/MS) method operated in the negative electrospray ionization (ESI) switching mode has been developed and validated for the simultaneous determination of esculin and its metabolite esculetin in rat plasma. After addition of internal standards scopoletin, the plasma sample was pretreated by solid-phase extraction (SPE), and separated on a reversed phase C(18) column with a mobile phase of 0.01% formic acid in water (solvent A) and methanol (solvent B) using isocratic elution (A:B=20:80, v/v). The detection of target compounds was done in multiple reaction monitoring (MRM) mode. The MRM detection was operated in the negative ESI mode using the transitions of m/z 339.1 ([M-H](-))→176.7 for esculetin, m/z 176.9 ([M-H](-))→133.0 and m/z 191.0 ([M-H](-))→175.9 for scopoletin. The standard curves, which ranged from 25 to 3200 ng/mL for esculin with the lowest limit of quantification (LLOQ) of 0.25 ng/mL and from 1.25 to 160 ng/mL for esculetin with the LLOQ of 1.25 ng/mL, were fitted to a 1/x weighted quadratic regression model. The method also afforded satisfactory results in terms of the sensitivity, specificity, precision (intra- and inter-day, RSD<8.73%), accuracy, recovery as well as the stability of the analyte under various conditions. The method was successfully applied to study the pharmacokinetics of esculin and its metabolite esculetin in rat plasma after oral administration of esculin at a dose of 100mg/kg.

Polyphenol fatty acid esters as serine protease inhibitors: a quantum-chemical QSAR analysis.

We investigated the ability of polyphenol fatty acid esters to inhibit the activity of serine proteases trypsin, thrombin, elastase and urokinase. Potent protease inhibition in micromolar range was displayed by rutin and rutin derivatives esterified with medium and long chain, mono- and polyunsaturated fatty acids (1e-m), followed by phloridzin and esculin esters with medium and long fatty acid chain length (2a-d, 3a-d), while unmodified compounds showed only little or no effect. QSAR study of the compounds tested provided the most significant parameters for individual inhibition activities, i.e. number of hydrogen bond donors for urokinase, molecular volume for thrombin, and solvation energy for elastase. According to the statistical analysis, the action of elastase inhibitors is opposed to those of urokinase and thrombin. Cluster analysis showed two groups of compounds: original polyphenols together with rutin esters with short fatty acid chain length and rutin esters with long fatty acid chain length.

Evaluation of the interaction of coumarins with biomembrane models studied by differential scanning calorimetry and Langmuir-Blodgett techniques.

Three coumarins, scopoletin (1), esculetin (2), and esculin (3), were investigated by differential scanning calorimetry and Langmuir-Blodgett techniques to gain information about the interaction of these compounds with cellular membranes. Phospholipids assembled as multilamellar vesicles or monolayers (at the air-water interface) were used as biomembrane models. Differential scanning calorimetry was employed to study the interaction of these coumarins with multilamellar vesicles and to evaluate their absorption by multilamellar vesicles. These experiments indicated that 1-3 interact in this manner to different extents. The Langmuir-Blodgett technique was used to study the effect of these coumarins on the organization of phospholipids assembled as a monolayer. The data obtained were in agreement with those obtained in the calorimetric experiments.