Novel trypanocidal thiophen-chalcone cruzain inhibitors: structure- and ligand-based studies.

Background: Chagas disease is a neglected tropical disease that affects millions of people worldwide and for which no effective treatment is available. Materials & methods: 17 chalcones were synthesized, for which the inhibition of cruzain and trypanocidal activity were investigated. Results: Chalcone C8 showed the highest cruzain inhibitory (IC50 = 0.536 µm) and trypanocidal activity (IC50 = 0.990 µm). Molecular docking studies showed interactions involving Asp161 and the thiophen group interacting with the S2 subsite. Furthermore, quantitative structure-activity relationship (q2 = 0.786; r2 = 0.953) and density functional theory studies were carried out, and a correlation between the lowest unoccupied molecular orbital surface and trypanocidal activity was observed. Conclusion: These results demonstrate that these chalcones are worthwhile hits to be further optimized in Chagas disease drug discovery programs.

Aldehyde biphenyl chalcones induce immunogenic apoptotic-like cell death and are promising new safe compounds against a wide range of hematologic cancers.

Aim: Investigate the apoptotic mechanisms of two new aldehyde biphenyl chalcones on leukemia cells. Materials & methods: From a series of 71 new chalcones, we selected the two most cytotoxic. Results: JA3 and JA7 were cytotoxic not only against hematological malignancies but also against solid tumor and cancer stem cells, yet with no toxicity to normal cells. Moreover, they induced immunogenic apoptotic-like cell death independently of promyelocytic leukemia protein, with extensive mitochondrial damages downstream of endoplasmic reticulum stress. Preventing endoplasmic reticulum stress and the upregulation of proapoptotic machinery inhibited JA3- and JA7-induced cell death. Likewise, blocking receptor Fas protected cells from killing. They increased the antileukemic effect of cytarabine and vincristine and killed leukemic cells collected from patients with different acute leukemia subtypes. Conclusion:JA3 and JA7 represent new promising prototypes for the development of new chemotherapeutics.

A new and efficient carboxymethyl-hexanoyl chitosan/dodecyl sulfate nanocarrier for a pyrazoline with antileukemic activity.

We describe herein a chitosan nanocarrier for drug delivery applications obtained through the self-assembly of carboxymethyl-hexanoyl chitosan and dodecyl sulfate (CHC-SDS). Nanocapsules with spherical morphology were obtained in phosphate buffer at pH 7.4. These CHC-SDS nanocapsules showed no toxicity toward Jurkat cells (acute lymphoblastic leukemia) and were used to encapsulate a new pyrazoline (H3TM04) with antileukemia activity. The samples were characterized by dynamic light scattering (DLS) and Laser Doppler Micro-Electrophoresis. The encapsulation efficiency was higher than 96% (293.6 µg mL-1) and the H3TM04-loaded nanocapsules (CHC-SDS-H) had a negative surface charge (-29.8 ±â€¯0.7 mV) and hydrodynamic radius of around 84 nm. For the first time, CHC-SDS-H were formed and the antitumoral cancer activity was proved. The in vitro assays showed the controlled release of H3TM04 from the CHC-SDS-H nanocapsules in phosphate buffer pH 7.4. The H3TM04 release data were described by the power law model, indicating that H3TM04 delivery occurred via an erosion mechanism. The cytotoxicity assays with Jurkat and K-562 cells (acute myeloid leukemia) demonstrated that the CHC-SDS-H nanocapsule decreases the half maximal inhibitory concentration (IC50). The study showed that CHC-SDS nanocapsules represent a promising nanocarrier for pyrazoline derivates that could be applied in leukemia therapy.

A novel thiosemicarbazone as a promising effective and selective compound for acute leukemia.

Acute leukemias are a heterogeneous group of aggressive malignant neoplasms associated with severe morbidities due to the nonselectivity of current chemotherapeutic drugs to nonmalignant cells. The investigation of novel natural and synthetic structures that might be used for the development of new drugs with greater efficiency and selectivity to leukemic cells is mandatory. In this context, thiosemicarbazones have been well described in the literature by their several biological properties and their reaction is known as versatile, low-cost, and highly chemoselective. With this perspective, this study aimed to investigate the cytotoxic effect and the main death mechanisms of a novel thiosemicarbazone (LAP17) on acute leukemia cell lines K562 and Jurkat. The results show that the strong cytotoxic effect of LAP17 to leukemic cells is due to apoptosis induction, which resulted in caspase-3 activation and DNA fragmentation. Intrinsic apoptosis seems to be related to the inversion of Bax/Bcl-2 expression, ΔΨm loss, and AIF release, whereas extrinsic apoptosis was initiated by FasR. Gene-expression profiling of HL-60 cells treated with LAP17 by the microarray technique revealed a significant enrichment of gene sets related to cell cycle arrest at G2/M. Accordingly, K562 and Jurkat cells treated with LAP17 revealed a clear arrest at G2/M phase. Taking into consideration that LAP17 was not cytotoxic to nonhematological cells (peripheral blood mononuclear cell and erythrocytes), these results suggest that LAP17 is a promising new compound that might be used as a prototype for the development of new antileukemic agents.

Insulin stimulus-secretion coupling is triggered by a novel thiazolidinedione/sulfonylurea hybrid in rat pancreatic islets.

New compounds with promising antidiabetic activity were synthesized. For the first time, a portion of the glibenclamide molecule was bound to a part of the core structure of thiazolidinedione to evaluate insulin secretagogue activity. Following studies in our laboratory, 4-{2-[2-(3,4-dichlorophenyl)-4-oxo-1,3-thiazolidin-3-yl]ethyl}benzene-1-sulfonamide (DTEBS) was selected to evaluate glycemia using the glucose tolerance test and insulin secretagogue activity by E.L.I.S.A. The mechanism of action of this compound was studied by 45 Ca2+ influx and whole-cell patch-clamp in rat pancreatic isolated islets. Furthermore, AGE formation in vitro was investigated. We herein show that this novel hybrid compound (DTEBS) exhibits an insulinogenic index and a profile of serum insulin secretion able to maintain glucose homeostasis. Its mechanism of action is mediated by ATP-sensitive potassium channels (KATP) and L-type voltage-dependent calcium channels (VDCC) and by activating protein kinase C and A (PKC and PKA). In addition, the stimulatory action of the compound on calcium influx and insulin secretion indicates that the potentiation of voltage-sensitive K+ currents (Kv) is due to the repolarization phase of the action potential after secretagogue excitation-secretion in pancreatic islets. Furthermore, under these experimental conditions, the compound did not induce toxicity and the in vitro late response of the compound to protein glycation reinforces its use to prevent complications of diabetes. DTEBS exerts an insulin secretagogue effect by triggering KATP, VDCC, and Kv ionic currents, possibly via PKC and PKA pathway signal transduction, in beta-cells. Furthermore, DTEBS may hold potential for delaying the late complications of diabetes.

Mechanism of action of camphoryl-benzene sulfonamide derivative on glucose uptake in adipose tissue.

The aim of the present study was to investigate the mechanism of action of a sulfonamide derivative on glucose uptake in adipose tissue, as well as to characterize the effects of this compound on intestinal disaccharidases and advanced glycation end-products (AGEs) formation. Camphoryl-benzene sulfonamide (CS) was able to stimulate glucose uptake in isolated adipocytes, adipose tissue, and in soleus muscle. The stimulatory effect of the compound (10 µM) on glucose uptake on adipose tissue was blocked by diazoxide, wortmannin, U73122, colchicine, and N-ethylmaleimide. On the other hand, the effects of CS were not blocked by glibenclamide, an inhibitor of the K+ -ATP channel, or even by the inhibitor of protein p38 MAPK, SB 203580. In vivo, this compound reduced intestinal disaccharidase activity, while, in vitro, CS reduced the formation of AGEs at 7, 14, and 28 days of incubation. The stimulatory effect of CS on glucose uptake requires the activation of the K+ -ATP channel, translocation, and fusion of GLUT4 vesicles to the plasma membrane on adipocytes for glucose homeostasis. In addition, the inhibition of disaccharidase activity contributes to the glucose homeostasis in a short-term as well as the remarkable reduction in AGE formation indicates that the CS may prevent of complications of late diabetes.

Mechanisms underlying the antiproliferative effects of a series of quinoxaline-derived chalcones.

The present study aimed to characterize the effects of quinoxaline-derived chalcones, designed on the basis of the selective PI3Kγ inhibitor AS605240, in oral cancer cells. Three lead compounds, namely N9, N17 and N23, were selected from a series of 20 quinoxaline-derived chalcones, based on an initial screening using human and rat squamous cell carcinoma lineages, representing compounds with at least one methoxy radical at the A-ring. The selected chalcones, mainly N9 and N17, displayed marked antiproliferative effects, via apoptosis and autophagy induction, with an increase of sub-G1 population and Akt inhibition. The three chalcones displayed marked in vitro antitumor effects in different protocols with standard chemotherapy drugs, with acceptable toxicity on normal cells. There was no growth retrieval, after exposure to chalcone N9 alone, in a long-term assay to determine the cumulative population doubling (CPD) of human oral cancer cells. A PCR array evaluating 168 genes related to cancer and inflammation, demonstrated striking actions for N9, which altered the expression of 74 genes. Altogether, our results point out quinoxalinic chalcones, mainly N9, as potential strategies for oral cancer treatment.

Solid lipid nanoparticles improve octyl gallate antimetastatic activity and ameliorate its renal and hepatic toxic effects.

Metastasis is the main cause of cancer-related death and requires the development of effective treatments with reduced toxicity and effective anticancer activity. Gallic acid derivatives have shown significant biological properties including antitumoral activity as shown in a previous study with octyl gallate (G8) in vitro. Thus, the aim of this work was to evaluate the antimetastatic effect of free and solid lipid nanoparticle-loaded G8 in mice in a lung metastasis model. Animals inoculated with melanoma cells presented metastasis in lungs, which was significantly inhibited by treatment with G8 and solid lipid nanoparticle-loaded G8, named G8-NVM. However, G8-treated mice showed an increase in several toxicological parameters, which were almost completely circumvented by G8-NVM treatment. This study supports the need for pharmacological studies on new potential medicinal plants to treat cancer and can provide new perspectives on using nanotechnology to improve biological activities while decreasing the chemotherapy toxicological effects of anticancer drugs.

Toxicological Evaluation of Anti-Scrapie Trimethoxychalcones and Oxadiazoles.

An altered form of the cellular prion protein, the PrPScor PrPRes, is implicated in the occurrence of the still untreatable transmissible spongiform encephalopathies. We have previously synthesized and characterized aromatic compounds that inhibit protease-resistant prion protein (PrPRes) accumulation in scrapie-infected cells. These compounds belong to different chemical classes, including acylhydrazones, chalcones and oxadiazoles. Some of the active compounds were non-toxic to neuroblastoma cells in culture and seem to possess drugable properties, since they are in agreement with the Lipinski´s rule of 5 and present desirable pharmacokinetic profiles as predicted in silico. Before the evaluation of the in vivo efficacy of the aromatic compounds in scrapie-infected mice, safety assessment in healthy mice is needed. Here we used Swiss mice to evaluate the acute toxicity profile of the six most promising anti-prionic compounds, the 2,4,5-trimethoxychalcones (J1, J8, J20 and J35) and the 1,3,4-oxadiazoles (Y13 and Y17). One single oral administration (300 mg/kg) of J1, J8, J20, J35, Y13 and Y17 or repeated intraperitoneal administration (10 mg/kg, 3 times a week, for 4 weeks) of J1, J8 and J35, did not elicit toxicity in mice. We strongly believe that the investigated trimethoxychalcones and oxadiazoles are interesting compounds to be further analyzed in vivo against prion diseases.

SB225002 Induces Cell Death and Cell Cycle Arrest in Acute Lymphoblastic Leukemia Cells through the Activation of GLIPR1.

Acute Lymphoblastic Leukemia (ALL) is the most frequent childhood malignancy. In the effort to find new anti-leukemic agents, we evaluated the small drug SB225002 (N-(2-hydroxy-4-nitrophenyl)-N'-(2-bromophenyl)urea). Although initially described as a selective antagonist of CXCR2, later studies have identified other cellular targets for SB225002, with potential medicinal use in cancer. We found that SB225002 has a significant pro-apoptotic effect against both B- and T-ALL cell lines. Cell cycle analysis demonstrated that treatment with SB225002 induces G2-M cell cycle arrest. Transcriptional profiling revealed that SB225002-mediated apoptosis triggered a transcriptional program typical of tubulin binding agents. Network analysis revealed the activation of genes linked to the JUN and p53 pathways and inhibition of genes linked to the TNF pathway. Early cellular effects activated by SB225002 included the up-regulation of GLIPR1, a p53-target gene shown to have pro-apoptotic activities in prostate and bladder cancer. Silencing of GLIPR1 in B- and T-ALL cell lines resulted in increased resistance to SB225002. Although SB225002 promoted ROS increase in ALL cells, antioxidant N-Acetyl Cysteine pre-treatment only modestly attenuated cell death, implying that the pro-apoptotic effects of SB225002 are not exclusively mediated by ROS. Moreover, GLIPR1 silencing resulted in increased ROS levels both in untreated and SB225002-treated cells. In conclusion, SB225002 induces cell cycle arrest and apoptosis in different B- and T-ALL cell lines. Inhibition of tubulin function with concurrent activation of the p53 pathway, in particular, its downstream target GLIPR1, seems to underlie the anti-leukemic effect of SB225002.

N-(1'-naphthyl)-3,4,5-trimethoxybenzohydrazide as microtubule destabilizer: Synthesis, cytotoxicity, inhibition of cell migration and in vivo activity against acute lymphoblastic leukemia.

Tubulin-interacting agents, like vinca alkaloid and taxanes, play a fundamental role in cancer chemotherapy, making cellular microtubules (MT), one of the few validated anticancer targets. Cancer resistance to classical MT inhibitors has motivated the development of novel molecules with increased efficacy and lower toxicity. Aiming at designing structurally-simple inhibitors of MT assembly, we synthesized a series of thirty-one 3,4,5-trimethoxy-hydrazones and twenty-five derivatives or analogs. Docking simulations suggested that a representative N-acylhydrazone could adopt an appropriate stereochemistry inside the colchicine-binding domain of tubulin. Several of these compounds showed anti-leukemia effects in the nanomolar concentration range. Interference with MT polymerization was validated by the compounds' ability to inhibit MT assembly at the biochemical and cellular level. Selective toxicity investigations done with the most potent compound, a 3,4,5-trimethoxy-hydrazone with a 1-naphthyl group, showed remarkably selective toxicity against leukemia cells in comparison with stimulated normal lymphocytes, and no acute toxicity in vivo. Finally, this molecule was as active as vincristine in a murine model of human acute lymphoblastic leukemia at a weekly dose of 1 mg/kg.

In vitro and in vivo effects of free and chalcones-loaded nanoemulsions: insights and challenges in targeted cancer chemotherapies.

Several obstacles are encountered in conventional chemotherapy, such as drug toxicity and poor stability. Nanotechnology is envisioned as a strategy to overcome these effects and to improve anticancer therapy. Nanoemulsions comprise submicron emulsions composed of biocompatible lipids, and present a large surface area revealing interesting physical properties. Chalcones are flavonoid precursors, and have been studied as cytotoxic drugs for leukemia cells that induce cell death by different apoptosis pathways. In this study, we encapsulated chalcones in a nanoemulsion and compared their effect with the respective free compounds in leukemia and in non-tumoral cell lines, as well as in an in vivo model. Free and loaded-nanoemulsion chalcones induced a similar anti-leukemic effect. Free chalcones induced higher toxicity in VERO cells than chalcones-loaded nanoemulsions. Similar results were observed in vivo. Free chalcones induced a reduction in weight gain and liver injuries, evidenced by oxidative stress, as well as an inflammatory response. Considering the high toxicity and the side effects induced generally by all cancer chemotherapies, nanotechnology provides some options for improving patients' life quality and/or increasing survival rates.

New structure-activity relationships of chalcone inhibitors of breast cancer resistance protein: polyspecificity toward inhibition and critical substitutions against cytotoxicity.

Adenosine triphosphate-binding cassette subfamily G member 2 (ABCG2) plays a major role in cancer cell multidrug resistance, which contributes to low efficacy of chemotherapy. Chalcones were recently found to be potent and specific inhibitors, but unfortunately display a significant cytotoxicity. A cellular screening against ABCG2-mediated mitoxantrone efflux was performed here by flow cytometry on 54 chalcone derivatives from three different series with a wide panel of substituents. The identified leads, with submicromolar IC50 (half maximal inhibitory concentration) values, showed that the previously identified 2'-OH-4',6'-dimethoxyphenyl, as A-ring, could be efficiently replaced by a 2'-naphthyl group, or a 3',4'-methylenedioxyphenyl with lower affinity. Such a structural variability indicates 3polyspecificity of the multidrug transporter for inhibitors. At least two methoxyl groups were necessary on B-ring for optimal inhibition, but substitution at positions 3, 4, and 5 induced cytotoxicity. The presence of a large O-benzyl substituent at position 4 and a 2'-naphthyl as A-ring markedly decreased the cytotoxicity, giving a high therapeutic ratio, which constitutes a critical requirement for future in-vivo assays in animal models.

Cytotoxic 3,4,5-trimethoxychalcones as mitotic arresters and cell migration inhibitors.

Based on classical colchicine site ligands and a computational model of the colchicine binding site on beta tubulin, two classes of chalcone derivatives were designed, synthesized and evaluated for inhibition of tubulin assembly and toxicity in human cancer cell lines. Docking studies suggested that the chalcone scaffold could fit the colchicine site on tubulin in an orientation similar to that of the natural product. In particular, a 3,4,5-trimethoxyphenyl ring adjacent to the carbonyl group appeared to benefit the ligand-tubulin interaction, occupying the same subcavity as the corresponding moiety in colchicine. Consistent with modeling predictions, several 3,4,5-trimethoxychalcones showed improved cytotoxicity to murine acute lymphoblastic leukemia cells compared with a previously described parent compound, and inhibited tubulin assembly in vitro as potently as colchicine. The most potent chalcones inhibited the growth of human leukemia cell lines at nanomolar concentrations, caused microtubule destabilization and mitotic arrest in human cervical cancer cells, and inhibited human breast cancer cell migration in scratch wound and Boyden chamber assays.

Activity of novel quinoxaline-derived chalcones on in vitro glioma cell proliferation.

Gliomas are the most common and devastating tumors of the central nervous system (CNS). Many pieces of evidence point out the relevance of natural compounds for cancer therapy and prevention, including chalcones. In the present study, eight synthetic quinoxaline-derived chalcones, structurally based on the selective PI3Kγ inhibitor AS605240, were evaluated for anti-proliferative activity and viability inhibition using glioma cell lines from human and rat origin (U-138 MG and C6, respectively), at different time-periods of incubation and concentrations. The results revealed that four chalcones (compounds 1, 6, 7 and 8), which present methoxy groups at A-ring, displayed higher efficacies and potencies, being able to inhibit either cell proliferation or viability, in a time- and concentration-dependent manner, with an efficacy that was greater than that seen for the positive control compound AS605240. Flow cytometry analysis demonstrated that incubation of C6 cells with compound 6 led to G1 phase arrest, likely indicating an interference with apoptosis. Furthermore, compound 6 was able to visibly inhibit AKT activation, allied to the stimulation of ERK MAP-kinase. The chalcones tested herein, especially those displaying a methoxy substituent, might well represent promising molecules for the adjuvant treatment of glioma progression.

Octyl and dodecyl gallates induce oxidative stress and apoptosis in a melanoma cell line.

This study investigated the mechanism of cytotoxicity of octyl (G8) and dodecyl (G12) gallates in a murine melanoma cell line (B16F10). For this purpose, several methods to measure cell viability were used to determine if the cytotoxicity induced by these gallates corresponds to a general or an organelle-specific effect. Furthermore, the mechanisms related to apoptosis were examined, by studying the caspase-3 activity, oxidative stress, mitochondrial potential and the expression of anti- or proapoptotic proteins. When comparing the various methods of assessing cell viability, the tested gallates showed a higher cytotoxicity in the assay that indicates lysosomal activity, compared with the assays that indicate mitochondrial and ribosomal activities. Both gallates promoted the release of lactate dehydrogenase into the medium, indicating an effect on cell membrane integrity. The gallates also promoted cellular oxidative stress, mitochondrial depolarization and an increase in caspase-3 activity. Furthermore, the gallates induced an increase in proapoptotic (Bax) and a decrease in antiapoptotic (Bcl-2) proteins expression. Our results indicate that the apoptotic cell death induced by G8 and G12 in B16F10 cells involves lipid membrane damages, lysosomal and mitochondrial dysfunction, which was accompanied by alterations in apoptotic proteins expression and seems to be triggered by cellular oxidative stress.

4-[(1,3-Dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-2-yl)meth-yl]-N'-[(E)-4-nitro-benzyl-idene]benzene-sulfono-hydrazide dimethyl sulfoxide monosolvate.

The mol-ecular structure of the title compound, C(26)H(18)N(4)O(6)S·C(2)H(6)OS, shows an E conformation of the hydrazone double bond. The presence of a methyl-ene group between the benzo[de]isoquinoline and benzene-sulfonyl moieties allows the 4-nitro-phenyl ring and the benzo[de]isoquinoline system to be parallel with respect to each other, so that the mol-ecule adopts a U-shaped spatial conformation. The dihedral angle between mean planes of these aromatic groups is 4.4 (1)°. This special arrangement enables neighboring mol-ecules to be inter-calated, forming slipped π-π inter-actions [centroid-centroid distance = 3.535 (2) Å] between the 4-nitro-phenyl and benzo[de]isoquinoline groups and point-to-face C-H⋯π inter-actions between the benzo[de]isoquinoline and benzene-sulfonyl aromatic systems. In addition, the crystal packing also features an inter-molecular N-H⋯O inter-action involving the amine group and the dimethyl sulfoxide solvent mol-ecule.

The effects of the selective and non-peptide CXCR2 receptor antagonist SB225002 on acute and long-lasting models of nociception in mice.

This study evaluated the antinociceptive effects of the selective and non-peptide CXCR2 antagonist SB225002 in mouse models of pain. As assessed in different tests of spontaneous nociception, intraperitoneal (i.p.) administration of SB225002 caused consistent and dose-related reduction of acetic acid-induced abdominal constrictions, whereas it did not significantly affect the nociception evoked by formalin, capsaicin, glutamate or phorbol ester acetate (PMA). Systemic treatment with SB225002 strikingly reduced the spontaneous nociception induced by 8-bromo-cAMP (8-Br-cAMP), or mechanical hypernociception induced by prostaglandin E(2) (PGE(2)), epinephrine, or the keratinocyte-derived chemokine (KC). In the carrageenan model, SB225002 markedly reduced mechanical hypernociception when administered by i.p., intrathecal (i.t.) or intracerebroventricular (i.c.v.) routes, or even when co-administered with carrageenan into the mouse paw, indicating peripheral and central sites of action for SB225002. In addition, i.p. treatment with SB225002 significantly attenuated the increase in MPO activity or the elevation of IL-1beta, TNFalpha or KC levels following carrageenan injection. In the persistent models of pain evoked by complete Freund's adjuvant (CFA) or by the partial ligation of the sciatic nerve (PLSN), the repeated administration of SB225002 displayed prominent and long-lasting antinociceptive effects. Notably, SB225002 did not evoke unspecific central effects, as evaluated in the open-field and rota-rod tests, or even in the latency responses for thermal stimuli. Our data confirm the previous notion on the critical role exerted by chemokines in pain, indicating that selective CXCR2 antagonists, such as SB225002, might well represent interesting and innovative alternatives for the management of both acute and chronic pain.

Gallic acid ester derivatives induce apoptosis and cell adhesion inhibition in melanoma cells: The relationship between free radical generation, glutathione depletion and cell death.

Malignant melanoma is a lethal disease, and the incidence and mortality associated with it are increasing worldwide. It has a significant tendency to develop both metastasis and resistance to chemotherapy. The tumor cells show abnormal redox regulation, and although the molecular mechanisms involved are not well characterized, they seem to be related to oxidative stress. In a previous study, we showed the antitumoral properties of gallic acid ester derivatives in leukemia cells. Here, we show the effect of octyl, decyl, dodecyl and tetradecyl gallates on B16F10 cells, a melanoma cell line. All compounds induced cytotoxic effects, and the IC(50) values obtained were between 7microM and 17microM after 48h of incubation. Cell death occurred through apoptosis, as demonstrated by the genomic DNA fragmentation pattern. The gallates were able to induce significant production of free radicals, deplete both glutathione and ATP, activate NF-kappaB and promote the inhibition of cell adhesion under the experimental conditions. The glutathione depletion induced by these compounds was related to the inhibition of gamma-glutamylcysteine synthase activity. These results suggest that gallates induce tumoral cell death through apoptosis as a consequence of oxidative stress, though they use different mechanisms to do so. These findings are important since melanoma cells are resistant to death because of their high level of antioxidant defense, adhesion capability and propensity to metastasize.

Evaluation of anti-herpetic and antioxidant activities, and cytotoxic and genotoxic effects of synthetic alkyl-esters of gallic acid.

The n-alkyl esters of gallic acid (CAS 13857-8) have a diverse range of uses as antioxidants in food, cosmetics and pharmaceutical industries. Pharmaceutical studies performed with these compounds have found that they have many therapeutic potentialities including anti-cancer, antiviral and antimicrobial properties. However, more interest has been devoted to their antioxidant activity due to the ability to scavenge and reduce reactive oxygen species (ROS) formation. In this study, gallic acid and 14 different alkyl gallates were tested. The cytotoxicity and anti-herpetic (HSV-1, KOS and 29-R strains) activity were studied by using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) colorimetric assay and the cell viability by using the Trypan blue dye exclusion method. The genotoxicity was studied by the Comet assay and the antioxidant activity by using the DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging and microsomal lipid peroxidation-inhibiting activities. The results showed that all the tested compounds have anti-herpetic activity at non cytotoxic concentrations with selectivity indices (SI = CC50/EC50) varying from 0.89 to 18.34, depending on the used HSV-1 strain. It was observed that all tested alkyl gallates showed some degree of genotoxicity, at the tested concentrations, except cetyl gallate, at 256.60 micromol/L (p <0.05, t-Student test), probably induced by ROS released by infected cells and/or by the alkyl gallates that were not antioxidants, at the tested concentrations, in which they demonstrated anti-herpetic activity. The hydroxyl groups can induce DNA damage due interactions with some metal ions, which are naturally present in the culture medium supplemented with fetal bovine serum, probably explaining the genotoxicity detected. However, the obtained results showed considerable antioxidant activity at smaller concentrations, when compared to quercetin which is considered as a reference drug due to its already described antioxidant potential: DPPH radical scavenging activity with IC50 values varying from 17 to 31 micromol/L; and microsomal lipid peroxidation-inhibiting activity with IC50 values varying from 21 to 59 micromol/L. It was observed that the presence of hydroxyl groups in these molecules is important for their pharmacological profile, but the length of the lateral carbonic chain does not have considerable influence.