Modulation of cytochrome P4501A1 activity by ascorbigen in murine hepatoma cells

Indole scaffolds as a promising class of the aryl hydrocarbon receptor ligands

The aryl hydrocarbon receptor (AhR), deemed initially as a xenobiotic sensor, plays multiple physiological roles and is involved in various pathophysiological processes and many diseases' etiology. Therefore, the therapeutic and chemopreventive targeting of AhR is a fundamental issue. To date, thousands of structurally diverse ligands of AhR have been identified. The bottleneck in targeting the AhR is that it is a Janus-faced player with beneficial vs. harmful effects in the ligand-specific context. A distinct structural class of the AhR ligands is those with indole-based scaffolds. The present review summarizes the knowledge on the existing indole-derived AhR ligands, comprising natural and dietary compounds, synthetic compounds including clinically used drugs, endogenous intermediary metabolites, and catabolites produced by human microbiota. The examples of novel, indole ring containing, rational design based AhR ligands are presented. The molecular, in vitro, and in vivo effects are described.

Modulation of rat hepatic and kidney phase II enzymes by cabbage juices: comparison with the effects of indole-3-carbinol and phenethyl isothiocyanate

The effect of raw cabbage and sauerkraut juices on the expression and activity of phase II enzymes, glutathione S-transferase (GST) and NAD(P)H:quinone oxidoreductase 1 (NQO1), in the rat liver and kidney was compared with that of two commercially available products of glucosinolate degradation: indole-3-carbinol (I3C) and phenethyl isothiocyanate (PEITC). Male Wistar rats were treated by oral administration with cabbage juices, I3C or PEITC for 4, 10 and 30 d. The results showed that juices, particularly sauerkraut juice as with I3C and PEITC, significantly increased GST and NQO1 activities in the rat liver. The only exception was the 30 d time point of feeding with raw cabbage juice. Cabbage juices, I3C and PEITC affected the hepatic GST μ to the greatest extent and GST α to a lesser extent. The results of the present study also showed that the treatment of rats with juices and compounds tested caused the translocation of the NF-E2-related transcription factor (Nrf2) active subunit from the cytosol to the nucleus, providing an argument for the involvement of this transcription factor in the induction of GST and NQO1. In contrast to the liver, cabbage juices affected only the renal GST θ, while treatment with I3C and PEITC significantly increased the activity of NQO1. Thus, the results of the present study indicate that induction of the key detoxifying enzymes by cabbage juices, particularly sauerkraut, may be responsible for their chemopreventive activity demonstrated by epidemiological studies and in animal models. However, the final effects might be organ or tissue dependent.

Chemical evaluation and sensory quality of sauerkrauts obtained by natural and induced fermentations at different NaCl levels from Brassica oleracea Var. capitata Cv. Bronco grown in eastern Spain. Effect of storage

The aim of the present work was to optimize fermentation conditions of white cabbage ( Brassica oleracea L. var. capitata cv. Bronco) grown in winter in eastern Spain. The influence of two salt concentrations (0.5 and 1.5% NaCl) in combination with spontaneous or induced cabbage fermentation on the content of ascorbigen (ABG) and vitamin C as well as on the sensory quality of sauerkraut was investigated. The effect of storage at 4 degrees C for 1-3 months was also studied. ABG content increased from 14 micromol/100 g of dm in raw cabbage to 63-137 micromol/100 g of dm during fermentation, whereas vitamin C decreased from 354 to 236-277 mg/100 g of dm, and the variations depended on the fermentation conditions. Sauerkrauts obtained by Leuconostoc mesenteroides at 0.5% NaCl showed the highest ABG content and a large amount of vitamin C. Refrigeration for 1-3 months led to a reduction of ABG and vitamin C levels, but L. mesenteroides sauerkrauts presented considerable amounts of both compounds at the end of the storage period (74-82 micromol/100 g of dm and 33-44 mg/100 g of dm, respectively), higher than those found with Lactobacillus plantarum and the mixed starter culture before storage. Experimental sauerkrauts presented better organoleptic properties than the commercial products, and no differences in overall acceptability were found among natural fermentations and those performed with starter cultures. These results suggest than low-salted sauerkraut produced with L. mesenteroides provided highly beneficial antioxidant and anticarcinogenic compounds and low sodium content, which is in accordance with the general trend in industrialized countries of reducing the salt level of foods to prevent cardiovascular diseases.

Covalent interaction of ascorbic acid with natural products

While ascorbic acid (vitamin C) is mostly known as a cofactor for proline hydroxylase and as a biological antioxidant, it also forms covalent bonds with natural products which we here refer to as 'ascorbylation'. A number of natural products containing an ascorbate moiety has been isolated and characterized from a variety of biological sources, ranging from marine algae to flowering plants. Most of these compounds are formed either as a result of nucleophilic substitution or addition by ascorbate, e.g. the ascorbigens from Brassica species are ascorbylated indole derivatives. Some ascorbylated tannins appear to be formed from electrophilic addition to dehydroascorbic acid. There are also examples of annulations of ascorbate with dietary polyphenols, e.g. epigallocatechin gallate (EGCG) and resveratrol derivatives. Herein is a survey of 33 ascorbylated natural products and their reported biological activities.

Pharmacological and biological screening of ascorbigen: protection against glucose-induced endothelial cell toxicity

Cruciferous vegetables contain significant amounts of ascorbigen and related substances with known molecular structures. This study tested the hypothesis that ascorbigen demonstrates antioxidant properties and protects human umbilical cord endothelial cells against hyperglycemic toxicity in vitro. It was observed that ascorbigen, in micromolar concentrations, protected against endothelial cell death from glucose toxicity. Additionally, ascorbigen at 3.0 mm shifted the concentration response curve of l-phenylephrine to the right, with a reduction in the maximal contractile effects of the agonist. This action was not related to alpha-adrenoceptor blockade. Ascorbigen also relaxed the vascular tone induced by l-phenylephrine, which is not mediated by an endothelial cell nitric oxide-dependent mechanism. On the guinea-pig ileum, the spasmogenic effects of carbachol, histamine and serotonin were reduced in the presence of 3 mM ascorbigen. Spasm of the gut induced by the acetylcholinesterase inhibitor, physostigmine, was antagonized by ascorbigen with an IC50 of 286 microM. This natural product also has a weak antiparasitic activity. The cytoprotective effects of ascorbigen may be highly relevant in the optimum physiological regulation of the function and the therapeutic value of this substance in disease settings needs to be further investigated.

Glucosinolate derivatives in stored fermented cabbage

The research focused on the glucosinolate (GLS) breakdown products formed during the fermentation of cabbage. A relationship between the contents of degradation products in fermented cabbage and native GLS in raw cabbage was investigated. The effect of fermented cabbage storage on the contents of individual compounds was also assayed. Ascorbigen formed from one of the degradation products of glucobrassicin (indole GLS) was found to be a dominating compound in fermented cabbage. Irrespective of the time of fermented cabbage storage, the content of ascorbigen reached approximately 14 micromol/100 g. Neither the content of isothiocyanates, the major degradation products of aliphatic GLS, nor that of cyanides exceeded 2.5 microM. Storage of cabbage caused periodical increases and decreases in the contents of cyanides and consequent declines in the contents of isothiocyanates. The highest relative contents (expressed as a percentage of the native GLS content) of degradation products--ranging from >70 to 96%--were reported for the products of glucoraphanin degradation, whereas the lowest-- <5% --were reported for the products of sinigrin degradation.

N-methoxyindole-3-carbinol is a more efficient inducer of cytochrome P-450 1A1 in cultured cells than indol-3-carbinol

The well-documented reduction of cancer risk by high dietary cruciferous vegetable intake may in part be caused by modulation of cytochrome P-450 (CYP) expression and activity by indoles. The purpose of the present experiments was to study the mechanism of CYP 1A1 induction by N-methoxyindole-3-carbinol (NI3C) in cultured cells and to compare the CYP-inducing potential of NI3C and indole-3-carbinol (I3C) administered to rats. NI3C induced 7-ethoxyresorufin-O-deethylase (EROD) activity in Hepa-1c1c7 cells in a concentration-dependent manner with 10-fold higher efficiency than I3C. Inasmuch as NI3C induced binding of the aryl hydrocarbon receptor (AhR) to the dioxin-responsive element and induced expression of endogenous CYP 1A1 mRNA and an AhR-responsive chloramphenicol acetyl transferase construct, we conclude that NI3C can activate the AhR. Besides the induction of CYP 1A1, we observed an inhibition of EROD activity, with a concentration causing 50% inhibition of 6 microM. Oral administration of NI3C at 570 mumol/kg body wt to male Wistar rats increased the hepatic CYP 1A1 and 1A2 protein levels, as well as the EROD and 7-methoxyresorufin O-demethylase activities at 8 and 24 hours after administration, but the responses were less pronounced than after administration of I3C at 570 mumol/kg body wt. Furthermore, NI3C did not induce hepatic 7-pentoxyresorufin O-depentylase activity, as I3C did. Ascorbigen, another indolylic compound formed during degradation of glucobrassicin in the presence of ascorbic acid, was tested in the same animal model, and ascorbigen only weakly induced hepatic CYP 1A1 and 1A2, but not CYP 2B1/2. In conclusion, NI3C is a more efficient inducer of CYP 1A1 in cultured cells than I3C but is less active when administered to rodents.

Determination of ascorbigens in autolysates of various Brassica species using supercritical fluid chromatography

A new method of analysis based on normal phase supercritical fluid chromatography (SFC) has been developed for investigation of ascorbigens [2-C-(indol-3-ylmethyl)-beta-L-xylo-3-hexulofuranosonic acid gamma-lactone derivatives]. This method has been adapted to preparative isolation and quantitative determinations of individual ascorbigens comprising ascorbigen, neoascorbigen, and 4-methoxyascorbigen. The structures of these compounds have been revealed from 1D ((1)H, (13)C) and 2D (COSY, HMQC, HMBC) NMR experiments. The developed SFC method had an acceptable linearity for the ascorbigens with correlation coefficients (R(2)) > 0.9995 (n = 10) in the range of 0.13-4.9 nmol injected, detection limits were below 13 pmol, retention time stabilities were excellent, and relative response factors have been determined. The SFC method has been used for determination of ascorbigens produced during autolysis of indol-3-ylmethylglucosinolates in various Brassica vegetables and rapeseed seedlings. Generally, 30-60% of the indol-3-ylmethylglucosinolates in the plants were transformed into ascorbigens, with the concentration in autolysates varying from 0.51 +/- 0.002 to 3.72 +/- 0.21 micromol/g of dry weight (DW) for ascorbigen, from 0.05 +/- 0.01 to 2.42 +/- 0.23 micromol/g of DW for neoascorbigen, and from 0.03 +/- 0.002 to 0.84 +/- 0.07 micromol/g of DW for 4-methoxyascorbigen.