Effects of protocatechuic acid, S-methylmethanethiosulfonate or 5-hydroxy-4-(2-phenyl-(E)ethenyl)-2(5H)-furanone(KYN-54) on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced pulmonary carcinogenesis in mice

Therapeutic Perspective of Vitamin C and Its Derivatives

l-Ascorbic acid (ASA), vitamin C, is a ubiquitous carbohydrate-like compound that has an essential role in a number of cellular processes, such as collagen synthesis, cellular oxidation, and various hydroxylation reactions. ASA is a biomolecule of critical importance for protection of cellular components against oxidative damage caused by toxic free radicals and other reactive oxygen species (ROS) that are involved in the development of various types of chronic diseases. Vitamin C has a switchover role from being an antioxidant in physiological conditions to a prooxidant under pathologic conditions. Moreover, some l-ascorbic acid derivatives exhibit strong and selective antitumor and antiviral activity. This review emphasizes the advances on diverse and potent biological profiles of l-ascorbic acid and its derivatives, and their perspective in the development of new bioactive chemical entities in the future. The work is primarily addressed at antioxidant, anticancer, and antiviral potencies of l-ascorbic acid and compounds containing its butenolide structural motif.

Novel pathways and therapies in experimental diabetic atherosclerosis

Diabetic subjects are at a greater risk of developing major vascular complications due to abnormalities pertinent to the diabetic milieu. Current treatment options achieve significant improvements in glucose levels and blood pressure control, but do not necessarily prevent or retard diabetes-mediated macrovascular disease. In this review, we highlight several pathways that are increasingly being appreciated as playing a significant role in diabetic vascular injury. We focus particularly on the advanced glycation end product/receptor for advanced glycation end product (AGE/RAGE) axis and its interplay with the nuclear protein HMGB1. We discuss evidence implicating a significant role for the renin-angiotensin system, urotensin II and PPAR, as well as the importance of proinflammatory mediators and oxidative stress in cardiovascular complications. The specific targeting of these pathways may lead to novel therapies to reduce the burden of diabetic vascular complications.

Structural identification of mouse fecal metabolites of theaflavin 3,3'-digallate using liquid chromatography tandem mass spectrometry

Black tea consumption has been associated with many health benefits including the prevention of cancer and heart disease. Theaflavins are the major bioactive polyphenols present in black tea. Unfortunately, limited information is available on their biotransformation. In the present study, we investigated the metabolic fate of theaflavin 3,3'-digallate (TFDG), one of the most abundant and bioactive theaflavins, in mouse fecal samples using liquid chromatography/electrospray ionization tandem mass spectrometry by analyzing the MS(n) (n=1-3) spectra. Four metabolites theaflavin, theaflavin 3-gallate, theaflavin 3'-gallate, and gallic acid were identified as the major mouse fecal metabolites of TFDG. Glucuronidated and sulfated, instead of methylated metabolites of theaflavin 3-gallate, theaflavin 3'-gallate, and TFDG were detected and identified as the minor mouse fecal metabolites of TFDG. Our results indicate that TFDG can be degraded in mice. Further studies on the formation of those metabolites in TFDG-treated mice in germ-free conditions are warranted. To our knowledge, this is the first report on the biotransformation of TFDG in mice.

NNK-Induced Lung Tumors: A Review of Animal Model

The incidence of lung adenocarcinoma has been remarkably increasing in recent years due to the introduction of filter cigarettes and secondary-hand smoking because the people are more exposed to higher amounts of nitrogen oxides, especially 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone(NNK), which is widely applied in animal model of lung tumors. In NNK-induced lung tumors, genetic mutation, chromosome instability, gene methylation, and activation of oncogenes have been found so as to disrupt the expression profiles of some proteins or enzymes in various cellular signal pathways. Transgenic animal with specific alteration of lung cancer-related molecules have also been introduced to clarify the molecular mechanisms of NNK in the pathogenesis and development of lung tumors. Based on these animal models, many antioxidant ingredients and antitumor chemotherapeutic agents have been proved to suppress the NNK-induced lung carcinogenesis. In the future, it is necessary to delineate the most potent biomarkers of NNK-induced lung tumorigenesis, and to develop efficient methods to fight against NNK-associated lung cancer using animal models.

Gas-Phase Structure, Rotational Barrier, and Vibrational Properties of Methyl Methanethiosulfonate, CH3SO2SCH3: An Experimental and Computational Study

The molecular structure of methyl methanethiosulfonate, CH3SO2SCH3, has been determined in the gas phase from electron-diffraction data supplemented by ab initio (HF, MP2) and density functional theory (DFT) calculations using 6-31G(d), 6-311++G(d,p), and 6-311G(3df,3pd) basis sets. Both experimental and theoretical data indicate that although both anti and gauche conformers are possible by rotating about the S-S bond, the preferred conformation is gauche. The barrier to internal rotation in the CSSC skeleton has been calculated using the RHF/6-31G(d), MP2/6-31G(d), and B3LYP/6-31G(d) methods as well as MP2 with a 6-31G(3df) basis set on sulfur and 6-31G(d) on C, H, and O. A 6-fold decomposition of the rotational barrier has been performed in terms of a Fourier-type expansion, enabling us to analyze the nature of the potential function, showing that the coefficients V1 and V2 are the dominant terms; V1 is associated with nonbonding interactions, and V2 is associated with hyperconjugative interactions. A natural bond orbital analysis showed that the lone pair --> sigma* hyperconjugative interactions favor the gauche conformation. Furthermore, the infrared spectra for the liquid and solid phases and the Raman spectrum for the liquid have been recorded, and the observed bands have been assigned to the vibrational normal modes. The experimental vibrational data, along with calculated theoretical force constants, were used to define a scaled quantum mechanical force field for the target system that enabled us to estimate the measured frequencies with a final root-mean-square deviation of 6 cm-1.

Effect of naturally occurring plant phenolics on the induction of drug metabolizing enzymes by o-toluidine

Plant phenolics modify the metabolic activation of several carcinogens, including aromatic amines. In this study, we have evaluated the effects of three structurally diversified plant phenolics, protocatechuic acid (PCA), tannic acid (TA) and ellagic acid (EA) on cytochrome p450-dependent enzymes and glutathione S-transferase (GST) activities after oral administration alone or in combination with o-toluidine in rat liver and kidney. Protocatechuic and ellagic acids significantly decreased the activities of ethoxy- (EROD), methoxy- (MROD) and penthoxyresorufin (PROD) dealkylases in liver. In kidney, all phenolics inhibited only the activity of PROD. Enzyme modulation in liver correlated with CA metabolism measured in plasma. Treatment of rats with ellagic acid 1 h before o-toluidine administration diminished the activities of all hepatic alkoxyresorufine dealkylases induced by o-toluidine but increased renal EROD. In contrast to EA, protocatechuic and tannic acids increased the activities of p450-dependent enzymes in liver. All phenolics administered in combination with o-toluidine increased the activity of GST, which was reduced after the treatment with o-toluidine alone. In addition, CA metabolism in plasma resulting from oral treatment with CA was measured. The formation of CA metabolites was reduced by PCA and EA, and the metabolism of CA induced by o-toluidine was depressed by administration of all three phenolics. Our results indicate that plant phenolics, especially EA, may modulate the genotoxic effects of o-toluidine by modifying pathways leading to the formation of its reactive metabolite. Moreover, as the result of CYP1A modification these compounds may affect the metabolism of CA.

In vitro cytotoxicity of protocatechuic acid to cultured human cells from oral tissue: involvement in oxidative stress

Data on the biologic activity of protocatechuic acid are contradictory; some studies have shown that it acts as an antioxidant and suppresses chemical-induced carcinogenesis and others that it induces oxidative stress and promotes tumour formation. The anticarcinogenicity of protocatechuic acid was postulated to be related, in part, to its specific suppression of neoplastic hyperproliferation. To determine whether protocatechuic acid was preferentially antiproliferative to malignant cells, non-malignant and carcinoma cells were exposed for 24 hr to protocatechuic acid (2.5 to 25 mM) and viability was assessed with the neutral red assay. The cell lines were derived from tissues of the human oral cavity, the initial site of exposure upon ingestion of dietary protocatechuic acid, and included normal GN61 gingival fibroblasts, immortalized, non-tumorigenic S-G gingival epithelial cells, and malignant HSG1 cells derived from the salivary gland, HSC-2 cells from the floor of the oral cavity, and CAL27 cells from the tongue. Selective toxicity of protocatechuic acid to malignant cells was not observed. Furthermore, using a total cellular protein determination to quantitate cell growth, no differences in comparative sensitivities of S-G epithelial cells and HSG1 carcinoma cells were noted in a 3 day continuous exposure to 2.5 to 12.5 mM protocatechuic acid and in recovery from a 24 hr exposure to 3 to 15 mM protocatechuic acid. The S-G and HSG1 cells were then used to study the effects of elevated concentrations of protocatechuic acid on oxidative stress. For both cell types, protocatechuic acid induced oxidative stress, presumably through its bioactivation by a tyrosinase pathway. A brief exposure to 25 mM protocatechuic acid lowered the levels of intracellular glutathione and potentiated Fe2+-induced lipid peroxidation of the cells. As determined with the neutral red assay, S-G and HSG1 cells exposed briefly to a non-toxic level (0.5 mM) of the glutathione depleter, 1,3-bis(2-chloroethyl)-N-nitrosourea, were hypersensitive to a subsequent challenge with 10 mM protocatechuic acid and preexposure of the S-G and HSG1 cells to a nontoxic level of protocatechuic acid (2.5 mM) enhanced their sensitivity to a subsequent exposure to tert-butyl hydroperoxide. These findings were consistent with protocatechuic acid, at high levels (> or = 10 mM), acting as an inducer of oxidative stress.