["Silymarin"--an extract from the milk thistle (Silybum marianum)--is it a drug or nutritional supplement?]. / "Silymarin"--extrakt z ostropestrce mariánského (Silybum marianum)--lék nebo potravní doplnek?

Thanks to the new knowledge, there is an increase of interest in plant extracts in the developed countries, but their classification is, however, problematic. It is necessary to clearly define the borderline between a drug or a defined content of an individual active principle, and a nutritional supplement, which is freely on sale. The extract from the seeds of S. marianum of (ESM) shows biological effects corresponding to nutritional supplements, and it is therefore more logical to class ESM with this group and to investigate the pharmacological effects in its chemically defined components.

Human hepatocyte--a model for toxicological studies. Functional and biochemical characterization.

Isolated human hepatocytes (HH) are an accepted model for in vitro experiments for testing liver function and xenobiotic metabolism. Preferred over more traditional animal hepatocyte model used in toxicological studies, it is the model of choice when substances undergoing biotransformation in man are investigated. The aim of this study was to optimize isolation and culture conditions for HH primary culture with regard to cell yield, viability, and metabolic activity, and to evaluate the suitability of donor samples for toxicology experiments. Cell viability, total cytochrome P450 (CYP) content, CYP3A4, CYP1A2 activity, and finally mixed ethoxycoumarin-O-deethylase (ECOD) activity were parameters measured in order to characterize the isolated HH. The quality of the primary cultures, stable and functional for a seven-day period following 24 hour stabilization, was assessed by lactate dehydrogenase (LDH) leakage and response to the model toxin tert-butylhydroperoxide (tBH) and to silybinin, a model cytoprotective substance. Based on HH obtained from livers of five multiorgan donors (average age 44.8 years, three males and two females), the individual variability of donors needs to be considered in evaluating cultures focussing on clinical liver tests. Greater sensitivity to toxins and silybinin was found in the hepatocyte culture from one donor with higher aminotransferase activity. In another case, higher serum bilirubin appeared to be linked to higher ECOD activity. Our conclusion is that values of clinical liver tests ought to suggest a healthy organ thus eliminating previous hepatocyte damage, the crucial factor of primary culture stability and functioning.

[The human hepatocyte: I. A model for studying metabolism and toxicity of xenobiotics]. / Lidský hepatocyt: I. Model pro studium metabolizmu a toxicity xenobiotik.

Isolated human hepatocytes have become one of the most attractive experimental approaches to the study of the specific metabolic functions of the human liver, interactions between liver cells and infectious agents, and metabolism and pharmacotoxicity of drugs. Particularly the primary cell culture model provides an in vitro system for investigating specific mechanisms in a precisely controlled conditions. In the present paper the legislative and ethical problems concerning availability of human liver samples, techniques developed for isolation, preservation and cultivation of hepatocytes are discussed. In addition, a comparison of human and rat hepatocyte models in the study of the metabolism and cytotoxicity of taxol is reviewed.

Effect of silymarin on serum cholesterol levels in rats.

Previously we have shown that perorally administered silymarin, a mixture of flavonolignans extracted from the seeds of Silybum marianum, possesses a hypocholesterolemic effect in rats fed high cholesterol diet enriched with fat. The aim of this paper was to complete the data concerning peroral and parenteral administration of silymarin. The rats fed standard laboratory diet did not respond to peroral administration of silymarin by decrease of serum cholesterol, but the mild increase in HDL cholesterol was found. Parenterally injected silymarin failed to reduce serum cholesterol both in rats fed high cholesterol diet and standard laboratory diet. The results suggest that silymarin could act either due to the fat-mediated improved bioavailability and/or by inhibiting of resorption of dietary cholesterol.

Silymarin inhibits the development of diet-induced hypercholesterolemia in rats.

To study the ability of silymarin, a standardized mixture of antioxidant flavonolignans from the medicinal plant Silybum marianum, and of silybin, the main flavonolignan of silymarin, to inhibit the development of diet-induced hypercholesterolemia the rats were fed high cholesterol diet (HCD). Silymarin or silybin were given as dietary supplements, and their influences on serum cholesterol levels were compared to those of probucol, an antioxidant hypocholesterolemic drug. Anticholesterolemic effect of silymarin was parallel to that of probucol, and dose-dependent at dietary drug concentrations of 0.1-0.5-1.0% (w/w). However, in contradistinction to probucol, silymarin caused an increase in high density lipoprotein (HDL)-cholesterol and a decrease in liver cholesterol content, changes considered to be of benefit. In addition to its anticholesterolemic effect silymarin partially prevented the HCD-induced decrease in liver reduced glutathione, an endogenous antioxidant. Silybin was not so effective as silymarin suggesting that either other constituent(s) of silymarin may be responsible for its anticholesterolemic effect or the bioavailability of silybin alone might be lower than that of silybin as a compound of silymarin.

Sanguinarine and chelerythrine as inhibitors of aromatic amino acid decarboxylase.

Quaternary benzo[c]phenanthridine alkaloids sanguinarine, chelerythrine and their dihydroderivatives were tested as inhibitors of aromatic amino acid decarboxylase (EC 4.1, 1.28, AAD) from rat liver. Sanguinarine and chelerythrine exhibited strong inhibition of AAD with Ki 1.2 x 10(-4) M and 5.8 x 10(-4) M, respectively, while no inhibitory effect was observed for their dihydroderivatives. The inhibition was found to be irreversible. The enzyme-inhibitor interaction apparently stabilized AAD against thermal inactivation. Pyridoxal-5'-phosphate partially decreased but did not reverse the inhibition. Dithiothreitol prevented the inhibitory effect of sanguinarine and chelerythrine which indicates that the interaction with thiol groups essential for AAD activity is included in the inhibition mechanism.

Benzo[c]phenanthridine alkaloids sanguinarine and chelerythrine: biological activities and dental care applications.

This article reviews chemical, pharmacological, and toxicological research relating to two principal benzo[c]phenanthridine alkaloids, namely sanguinarine and chelerythrine, in the period 1980-1994. The medical applications of these alkaloids in relation to their biological activities are discussed.

Biochemical evaluation of colchicine and related analogs.

Transformation of ten colchicinoids by isolated rat liver microsomes resulted in the mixture of C-2, C-3, and C-10 O-demethylated metabolites. Colchicinoids administered i.p. to rats (2.5 mumol/kg) increased serum and liver activities of alkaline phosphatase and decreased liver microsomal demethylase activity as well as cytochrome P-450 content. The changes of acid phosphatase level were less pronounced. The aspartate and alanine aminotransferase activities were significantly increased only in colchicine treated rats. No relations between enzyme activity changes and colchicinoid hydrophobicities quantified by partition coefficients (log P) were found. However, the enzyme activity changes were related to the type of substitution at C-3, C-7, and C-10 of colchicinoids. Particularly, O-demethylation at C-3 resulted into the fall of alkaline phosphatase response. On the other hand, the microsomal demethylation and cytochrome P-450 content were related to the modification of the nitrogen substituent at C-7.

The in vitro and in vivo biotransformation of N-deacetyl-N-formylcolchicine.

The major pathway of metabolic transformation of N-deacetyl-N-formylcolchicine is the oxidative cytochrome P450 dependent O-demethylation of substituents in the aromatic ring A and tropolone ring C. It was found that O-demethylation (both, in vitro and in vivo) takes place predominantly in the aromatic ring, especially at position 2.

The effect of N-deacetylcolchiceine on serum lipoproteins in rats.

N-Deacetylcolchiceine (DAC) administered i.p. to rats decreased the level of serum cholesterol and apoB. It was accompanied by the fall of HDL-C due to the decrease of both HDL subfractions HDLa and HDLb, and by a rather weaker decrease of LDL-C. The levels of serum and lipoprotein triacylglycerols were not significantly affected. The "clearing reaction" to heparin in DAC rats differed from controls with regard to plasma cholesterol resulting in its accumulation in HDLa and LDL simultaneously with an increased activity of post-heparin lipoprotein lipase. These results suggest that the DAC accelerates the lipoprotein cholesterol metabolism.

Electrochemical and thermal studies of some quaternary benzo(c) phenanthridine alkaloids.

The conditions of the electrochemical reduction and oxidation as well as those of thermal demethylation of quaternary benzo(c)-phenanthridine alkaloids namely chelerythrine (1), sanguinarine (2), and fagaronine (3) were studied. Differences in their electrochemical and thermal behavior are correlated with the results obtained from biotransformation studies with liver microsomal fraction.

Ketoconazole-resistant mutants of Microsporum gypseum. I. Isolation of mutants, biochemical methods.

The ketoconazole-resistant mutants were isolated from four strains of the dermatophyte Microsporum gypseum. The frequency of spontaneous mutants ranged within 10(-8) to 10(-9) (per spore and nucleus). The method was established for obtaining the spontaneous mutants manifested as the faster growing sectors. By means of mutagenic effect of UV radiation, the frequency of mutants increased by one order. The method used for determination of ergosterol the biosynthesis of which could be associated with the mechanism of resistance to ketoconazole is described and evaluated.

Ketoconazole-resistant mutants of Microsporum gypseum. II. Characteristics of mutants.

The presented study deals with the properties of two wild strains of dermatophyte Microsporum gypseum and of eleven mutants resistant to ketoconazole. The growth rate of spontaneous mutants is greater than that of the wild strain, the group of UV-induced mutants manifests in general lower growth rate. The resistance level varies in the interval 1.1-1.6 (spontaneous mutants), resp. 2.7-5.5 (UV-induced mutants). The phenomenon of cross-resistance to other imidazole drugs (miconazole, clotrimazole) has been observed in mutants. There is further given the characteristic of ergosterol synthesis influence by the three used antifungal drugs. The data obtained are discussed from the point of view of possible biochemical processes resulting in the formation of resistance to ketoconazole.

Separation and Quantification of Some Alkaloids from Fumaria parviflora by Capillary Isotachophoresis1.

The isotachophoretic separation of some isoquinoline alkaloids in acid-base partially purified extracts from Bulgarian FUMARIA PARVIFLORA was studied. The electrolyte system for model mixtures of alkaloids (-)-stylopine, (-)-canadine, coptisine, berberine, protopine, cryptopine, chelidonine, bulbocapnine, papaverine, parfumine and for the plant extracts contained the leading ion K (+) (0.01 M), counter ion CH (3)COO (-), pH (L) 5.5, and the terminating ion H (+) (acetic acid 0.01 M). In the plant extracts, protopine and parfumine were quantitatively determined during F. PARVIFLORA growth and development in the term May-June 1984.