Identification of benzo[c]phenanthridine metabolites in human hepatocytes by liquid chromatography with electrospray ion-trap and quadrupole time-of-flight mass spectrometry

Identification of Sanguinarine Metabolites in Rats Using UPLC-Q-TOF-MS/MS

Sanguinarine (SAN), as the main active component of a traditional Chinese veterinary medicine, has been widely used in the animal husbandry and breeding industry. However, the metabolites of SA are still uncertain. Therefore, this research aimed to investigate the metabolites of SA based on rats in vivo. The blood, feces, and urine of rats were collected after the oral administration of 40 mg/kg SAN. Ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS/MS) was employed to identify the metabolites of SAN. The elemental composition of sanguinarine metabolites was inferred by analyzing their exact molecular weight, and the structures of the metabolites were predicted based on their fragment ions and cleavage pathways. A total of 12 metabolites were identified, including three metabolites in the plasma, four in the urine, and nine in the feces. According to the possible metabolic pathways deduced in this study, SAN was mainly metabolized through reduction, oxidation, demethylation, hydroxylation, and glucuronidation. This present research has summarized the metabolism of SAN in rats, which is helpful for further studying the metabolic mechanism of SAN in vivo and in vitro.

Safety and efficacy of a feed additive consisting of Macleaya cordata (Willd.) R. Br. extract and leaves (Sangrovit® extra) for all poultry species (excluding laying and breeding birds) (Phytobiotics Futterzusatzstoffe GmbH)

Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of Macleaya cordata (Willd.) R. Br. extract and leaves (Sangrovit® Extra) when used as a zootechnical feed additive (functional group: other zootechnical additives) for all poultry species (excluding laying and breeding birds). The additive is standardised to contain a concentration of the sum of the four alkaloids sanguinarine, chelerythrine, protopine and allocryptopine of 1.25%, with 0.5% sanguinarine. Owing to the presence of the DNA intercalators sanguinarine and chelerythrine, a concern for genotoxicity was identified. The EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) had no safety concerns when the additive is used at the recommended level of 150 mg/kg complete feed (corresponding to 0.750 mg sanguinarine/kg complete feed) for chickens for fattening and other poultry species for fattening. No conclusion can be drawn for poultry reared for laying/breeding. The use of Sangrovit® Extra in poultry species for fattening at the maximum recommended level was considered of low concern for consumers. The additive was shown to be irritant to the eyes but not irritant to skin or a skin sensitiser. The FEEDAP Panel could not exclude the potential of the additive to be a respiratory sensitiser. When handling the additive, exposure of unprotected users to sanguinarine and chelerythrine may occur. Therefore, to reduce the risk, the exposure of users should be reduced. The use of Sangrovit® Extra as a feed additive under the proposed conditions of use was considered safe for the environment. The additive Sangrovit® Extra had the potential to be efficacious in improving performance of chickens for fattening at 45 mg/kg complete feed. This conclusion was extended to chickens reared for laying/breeding and extrapolated to all poultry species for fattening or reared for laying/breeding.

Sex differences in the pharmacokinetics and tissue residues of Macleaya cordata extracts in rats

Macleaya cordata extracts (MCE) are listed as feed additives in animal production by the European Food Authority. The core components of MCE are mainly sanguinarine (SA) and chelerythrine (CHE). This study aims to investigate sex differences in the pharmacokinetics and tissue residues of MCE in rats.Male and female rates were intragastrically administered MCE (1.25 mg·kg^-1 body weight and 12.5 mg·kg^-1 body weight dose for 28 days). SA and CHE concentrations were determined using high-performance liquid chromatography/tandem mass spectrometry.The peak plasma concentration (C_max) and area under the curve (AUC) of both CHE and SA were higher in female than in male rats (12.5 mg·kg^-1 body weight group), whereas their half-life (T_1/2) and apparent volume of distribution (V_d) was lower (p < 0.05). Tissue rfesidue analysis indicated that SA and CHE were more distributed in male than in female rats and were highly distributed in the cecum and liver. SA and CHE were completely eliminated from the liver, kidney, lung, heart, spleen, leg muscle, and cecum after 120 h, indicating they did not accumulate in rats for a long time.Overall, we found that the pharmacokinetics and tissue residues of SA and CHE of male and female rats showed sex differences.

Visible-Light-Promoted Biomimetic Reductive Functionalization of Quaternary Benzophenanthridine Alkaloids

Reduction of an iminium C═N double bond is the most important phase I metabolism process associated with the cytotoxic property of quaternary benzophenanthridine alkaloids (QBAs). Inspired by the light-mediated reduction of QBAs with nicotinamide adenine dinucleotide, a visible-light-promoted reductive functionalization reaction of QBAs is reported in this study. C4-Alkyl-1,4-dihydropyridines (DHPs) enable the direct reductive alkylation of QBA independently, serving as both single-electron-transfer reductant reagents under irradiation with 455 nm blue light in the absence of photocatalysts and additional additives. Our protocol can be further applied to the semisynthesis of natural 6-substituted dihydrobenzophenanthridine derivatives such as O-acetyl maclekarpine E.

Metabolism and Tissue Distribution of Chelerythrine and Effects of Macleaya Cordata Extracts on Liver NAD(P)H Quinone Oxidoreductase

Background:Macleaya cordata (Willd.) (Papaveraceae) is listed as a feed additive in animal production by the European Food Authority.

Methods: The metabolites of chelerythrine in rats were measured in vitro and in vivo by rapid and accurate high-performance liquid chromatography/quadrupole-time-of-flight mass spectrometry (HPLC/QqTOF-MS). The structures of CHE metabolites were elucidated by comparing their changes in accurate molecular masses and fragment ions with those of parent ion or metabolite. The metabolic enzymes that were involved in chelerythrine reduction were investigated using an inhibition method. The tissue distribution of chelerythrine and the effects on NQO1 following intragastric administration with M. cordata extracts in rats were examined.

Results: A total of twelve metabolites of chelerythrine were characterized by this approach in rat liver S9 and in vivo. The reduction of the iminium bond of chelerythrine and subsequent O-demethylation was the main metabolic pathway of chelerythrine in rat liver S9 while the reduction of the iminium bond of chelerythrine was the main metabolic pathway of chelerythrine in rats in vivo. After the rats were given intragastric administration, the low concentration residues of sanguinarine and chelerythrine in different rat tissues were found at 48 h after the last dose, suggesting that both compounds could be widely distributed in tissues. The results also indicated that XO, NQO1, NQO2, and carbonyl reductase are involved in chelerythrine reduction. Macleaya cordata extracts treated female and male rats, respectively, showed different responses, inhibiting NQO1 activity in males, but inducing NQO1 activity in females. Chelerythrine had a weak impact on NQO1 activity, but sanguinarine inhibited NQO1 activity

Conclusion: Through studying the effects of cytosolic reductase inhibitors on chelerythrine reduction and the impact of chelerythrine and sanguinarine on the activity of NQO1 in vitro and in vivo, we clarified the potential drug interaction of Macleaya cordata extract in clinical application, so as to provide theoretical guidance for clinically safe medication. In addition, it provided a reference basis for the metabolic mechanism of chelerythrinein rats.

Pharmacokinetics of Chelerythrine and Its Metabolite after Oral and Intramuscular Administrations in Pigs

The objective of this study was to investigate the single- and multiple-dose pharmacokinetics of chelerythrine (CHE) and its metabolite, dihydrochelerythrine (DHCHE), after oral and IM administrations in pigs.Six crossbreed (Landrace × Large White) female pigs (7 to 8 weeks old; 24.1 ± 2.6 kg bw) administered oral and IM CHE at a dose of 0.1 mg/kg orally and intramuscularly in a cross-over design. Multiple oral administration was performed at 0.1 mg/kg a time, three times a day at 8-h intervals for three consecutive days. Blood samples were collected from the anterior vena cava and placed into heparinized centrifuge tubes before dosing (time 0 h) and at different times after oral oral and IM administrations. Pretreatment plasma was analyzed by high-performance liquid chromatography tandem mass spectrometry.After IM administration, CHE and DHCHE rapidly reached peak concentrations (C_max, 69.79 ± 15.41 and 3.47 ± 1.23 ng/ml) at 0.42 ± 0.13 and 0.33 ± 0.13 h, respectively. After single oral administration, CHE and DHCHE rapidly increased to reach C_max of 5.04 ± 1.00 and 1.21 ± 0.35 ng/ml at 1.83 ± 0.26 and 1.67 ± 0.26 h, respectively. The half-life (T_1/2) was 2.03 ± 0.26 and 2.56 ± 1.00 h for CHE and DHCHE, respectively. After multiple oral administration, the average steady-state concentrations (C_ss) of CHE and DHCHE were 2.51 ± 0.40 and 0.6 ± 0.06 ng/ml, respectively.CHE is metabolized rapidly after a single oral administration, multiple daily doses and long-term use of CHE are recommended.

Redox properties of individual quercetin moieties

Quercetin is one of the most prominent and widely studied flavonoids. Its oxidation has been previously investigated only indirectly by comparative analyses of structurally analogous compounds, e.g. dihydroquercetin (taxifolin). To provide direct evidence about the mechanism of quercetin oxidation, we employed selective alkylation procedures for the step-by-step blocking of individual redox active sites, i.e. the catechol, resorcinol and enol C-3 hydroxyls, as represented by newly prepared quercetin derivatives 1-3. Based on the structure-activity relationship (SAR), electrochemical, and computational (density functional theory) studies, we can clearly confirm that quercetin is oxidized in the following steps: the catechol moiety is oxidized first, forming the benzofuranone derivative via intramolecular rearrangement mechanism; therefore the quercetin C-3 hydroxy group cannot be involved in further oxidation reactions or other biochemical processes. The benzofuranone is oxidized subsequently, followed by oxidation of the resorcinol motif to complete the electrochemical cascade of reactions. Derivatization of individual quercetin hydroxyls has a significant effect on its redox behavior, and, importantly, on its antiradical and stability properties, as shown in DPPH/ABTS radical scavenging assays and UV-Vis spectrophotometry, respectively. The SAR data reported here are instrumental for future studies on the oxidation of biologically or technologically important flavonoids and other polyphenols or polyhydroxy substituted aromatics. This is the first complete and direct study mapping redox properties of individual moieties in quercetin structure.

Structurally Simple Phenanthridine Analogues Based on Nitidine and Their Antitumor Activities

A series of novel structurally simple analogues based on nitidine was designed and synthesized in search of potent anticancer agents. The antitumor activity against human cancer cell lines (HepG2, A549, NCI-H460, and CNE1) was performed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay in vitro. The results showed that some of them had good anticancer activities, especially derivatives with a [(dimethylamino)ethyl]amino side chain in the C-6 position. Planar conjugated compounds 15a, 15b, and 15c, with IC₅₀ values of 1.20 μM, 1.87 μM, and 1.19 μM against CNE1 cells, respectively, were more active than nitidine chloride. Compound 15b and compound 15c with IC₅₀ values of 1.19 μM and 1.37 μM against HepG2 cells and A549 cells demonstrated superior activities to nitidine. Besides, compound 5e which had a phenanthridinone core displayed extraordinary cytotoxicity against all test cells, particularly against CNE1 cells with the IC₅₀ value of 1.13 μM.

Alkaloids Reactivity: DFT Analysis of Selective Demethylation Reactions

All possible demethylation reactions of a diverse family of quaternary alkaloids by means of DFT calculations are here described. We aim to develop a rational model that allows the explanation of the high selectivity observed experimentally and predicts the occurrence of new alkaloid derivatives. To this end, we have performed a detailed analysis of the initial reagents and products. In addition, as a proof of concept, an experimentally unknown demethylation reaction of coralyne has been carried out, thus verifying the reliability of the theoretical model presented here.

Pharmacokinetics of sanguinarine, chelerythrine, and their metabolites in broiler chickens following oral and intravenous administration

Sanguinarine (SA) and chelerythrine (CHE) are the main active components of the phytogenic livestock feed additive, Sangrovit®. However, little information is available on the pharmacokinetics of Sangrovit® in poultry. The goal of this work was to study the pharmacokinetics of SA, CHE, and their metabolites, dihydrosanguinarine (DHSA) and dihydrochelerythrine (DHCHE), in 10 healthy female broiler chickens following oral (p.o.) administration of Sangrovit® and intravenous (i.v.) administration of a mixture of SA and CHE. The plasma samples were processed using two different simple protein precipitation methods because the parent drugs and metabolites are stable under different pH conditions. The absorption and metabolism of SA following p.o. administration were fast, with half-life (t_1/2 ) values of 1.05 ± 0.18 hr and 0.83 ± 0.10 hr for SA and DHSA, respectively. The maximum concentration (C_max ) of DHSA (2.49 ± 1.4 μg/L) was higher that of SA (1.89 ± 0.8 μg/L). The area under the concentration vs. time curve (AUC) values for SA and DHSA were 9.92 ± 5.4 and 6.08 ± 3.49 ng/ml hr, respectively. Following i.v. administration, the clearance (CL) of SA was 6.79 ± 0.63 (L·h^-1 ·kg^-1 ) with a t_1/2 of 0.34 ± 0.13 hr. The AUC values for DHSA and DHCHE were 7.48 ± 1.05 and 0.52 ± 0.09 (ng/ml hr), respectively. These data suggested that Sangrovit® had low absorption and bioavailability in broiler chickens. The work reported here provides useful information on the pharmacokinetic behavior of Sangrovit® after p.o. and i.v. administration in broiler chickens, which is important for the evaluation of its use in poultry.

Effects of 2-aryl-1-cyano-1,2,3,4-tetrohydroisoquinolines on apoptosis induction mechanism in NB4 and MKN-45 cells

Our previous study found that 2-aryl-1-cyano-1,2,3,4-tetrahydroisoquinolines (CATHIQs) have excellent anti-cancer activity and obvious apoptosis induction phenomenon. As our continuing research, this study further explored their underlying molecular mechanism of apoptosis induction in cancer cells. Flow cytometry analysis showed that the NB4 cells treated by 1-cyano-2-(2-fluorophenyl)-1,2,3,4-tetrahydroisoquinoline or the MKN-45 cells treated by 1-cyano-2-(4-trifluoromethylphenyl)-1,2,3,4-tetrahydroisoquinoline for 48 h were at early stage of apoptosis, and the cell cycle arrest was only slightly affected. Apoptosis rates of the cells significantly increase with the treatment concentration of the compounds. The compounds could significantly decrease the activities of SOD, raise the MDA level and promote the LDH leakage, suggesting that the excessive formation of ROS should be involved in the cell apoptosis. Western blot analysis showed that the compounds improved both Bax/Bcl-2 ratio and cleavages of procaspase-3, promoted efflux of cytochrome c to cytosol and phosphorylation of p38 and JNK, and attenuated phosphorylations of Akt and ERK. Together, inhibitions of PI3K/Akt and ERK and activation of p38 mediated the compounds-induced apoptosis through modulating the mitochondrial pathway and/or ROS production.

Sanguinarine is reduced by NADH through a covalent adduct

Sanguinarine is a benzo[c]phenanthridine alkaloid with interesting cytotoxic properties, such as induction of oxidative DNA damage and very rapid apoptosis, which is not mediated by p53-dependent signaling. It has been previously documented that sanguinarine is reduced with NADH even in absence of any enzymes while being converted to its dihydro form. We found that the dark blue fluorescent species, observed during sanguinarine reduction with NADH and misinterpreted by Matkar et al. (Arch. Biochem. Biophys. 2008, 477, 43-52) as an anionic form of the alkaloid, is a covalent adduct formed by the interaction of NADH and sanguinarine. The covalent adduct is then converted slowly to the products, dihydrosanguinarine and NAD⁺, in the second step of reduction. The product of the reduction, dihydrosanguinarine, was continually re-oxidized by the atmospheric oxygen back to sanguinarine, resulting in further reacting with NADH and eventually depleting all NADH molecules. The ability of sanguinarine to diminish the pool of NADH and NADPH is further considered when explaining the sanguinarine-induced apoptosis in living cells.

Carcinogenic potential of sanguinarine, a phytochemical used in 'therapeutic' black salve and mouthwash

Black salves are escharotic skin cancer therapies in clinical use since the mid 19th century. Sanguinaria canadensis, a major ingredient of black salve formulations, contains a number of bioactive phytochemicals including the alkaloid sanguinarine. Despite its prolonged history of clinical use, conflicting experimental results have prevented the carcinogenic potential of sanguinarine from being definitively determined. Sanguinarine has a molecular structure similar to known polyaromatic hydrocarbon carcinogens and is a DNA intercalator. Sanguinarine also generates oxidative and endoplasmic reticulum stress resulting in the unfolded protein response and the formation of 8-hydroxyguanine genetic lesions. Sanguinarine has been the subject of contradictory in vitro and in vivo genotoxicity and murine carcinogenesis test results that have delayed its carcinogenic classification. Despite this, epidemiological studies have linked mouthwash that contains sanguinarine with the development of oral leukoplakia. Sanguinarine is also proposed as an aetiological agent in gallbladder carcinoma. This literature review investigates the carcinogenic potential of sanguinarine. Reasons for contradictory genotoxicity and carcinogenesis results are explored, knowledge gaps identified and a strategy for determining the carcinogenic potential of sanguinarine especialy relating to black salve are discussed. As patients continue to apply black salve, especially to skin regions suffering from field cancerization and skin malignancies, an understanding of the genotoxic and carcinogenic potential of sanguinarine is of urgent clinical relevance.

Antibacterial efficacy and pharmacokinetic evaluation of sanguinarine in common carp (Cyprinus carpio) following a single intraperitoneal administration

Sanguinarine (SA), with antimicrobial and antiparasitic activities against fish pathogens, exhibits great potential commercial use in aquaculture. However, little information on pharmacokinetics of SA restricts further application in aquaculture. In this study, pharmacokinetics of SA in common carp (Cyprinus carpio) following a single intraperitoneal administration [10 mg kg(-1) BW (body weight)] was evaluated by high-performance liquid chromatography (HPLC). The peak concentration (Cmax ) of SA in kidney was 11.8 μg g(-1) , which was higher than in other tissues and plasma. The terminal half-life in fish tissue and plasma was as follows: 42.3 h (kidney) > 37.2 h (liver) > 20.1 h (gill) > 18.8 h (muscle) > 10.9 h (spleen) > 10.0 h (plasma). Additionally, we determined the bacterial loads in tissues of common carp infected with Aeromonas hydrophila after i.p. administration of SA at 0, 5, 10 and 20 mg kg(-1) BW. The results showed that i.p. administration of SA at 10 mg kg(-1) BW significantly enhanced antibacterial efficacy against A. hydrophila, where the antibacterial ratio in the gill, kidney, spleen and liver on day 5 was 95.13%, 93.33%, 90.09% and 92.82%, respectively. Overall, these results suggested the potential of SA to treat A. hydrophila infection in common carp farming industry.

Cytotoxicity evaluation of large cyanobacterial strain set using selected human and murine in vitro cell models

The production of cytotoxic molecules interfering with mammalian cells is extensively reported in cyanobacteria. These compounds may have a use in pharmacological applications; however, their potential toxicity needs to be considered. We performed cytotoxicity tests of crude cyanobacterial extracts in six cell models in order to address the frequency of cyanobacterial cytotoxicity to human cells and the level of specificity to a particular cell line. A set of more than 100 cyanobacterial crude extracts isolated from soil habitats (mainly genera Nostoc and Tolypothrix) was tested by MTT test for in vitro toxicity on the hepatic and non-hepatic human cell lines HepG2 and HeLa, and three cell systems of rodent origin: Yac-1, Sp-2 and Balb/c 3T3 fibroblasts. Furthermore, a subset of the extracts was assessed for cytotoxicity against primary cultures of human hepatocytes as a model for evaluating potential hepatotoxicity. Roughly one third of cyanobacterial extracts caused cytotoxic effects (i.e. viability<75%) on human cell lines. Despite the sensitivity differences, high correlation coefficients among the inhibition values were obtained for particular cell systems. This suggests a prevailing general cytotoxic effect of extracts and their constituents. The non-transformed immortalized fibroblasts (Balb/c 3T3) and hepatic cancer line HepG2 exhibited good correlations with primary cultures of human hepatocytes. The presence of cytotoxic fractions in strongly cytotoxic extracts was confirmed by an activity-guided HPLC fractionation, and it was demonstrated that cyanobacterial cytotoxicity is caused by a mixture of components with similar hydrophobic/hydrophilic properties. The data presented here could be used in further research into in vitro testing based on human models for the toxicological monitoring of complex cyanobacterial samples.

Simultaneous quantitative determination of sanguinarine, chelerythrine, dihydrosanguinarine and dihydrochelerythrine in chicken by HPLC-MS/MS method and its applications to drug residue and pharmacokinetic study

A specific and reliable HPLC-MS/MS method was developed and validated for simultaneously determination of sanguinarine, chelerythrine and their metabolites (dihydrosanguinarine and dihydrochelerythrine) in chicken tissue for the first time. This is important because these compounds are related to the use of a naturally occurring and novel feed additive with many benefits, but the levels of these compounds must be strictly controlled. The compounds were extracted by acetonitrile and 1% HCl-methanol solution successively and then separated on a C18 column. A triple-quadrupole mass spectrometer equipped with an electrospray ionization (ESI) source was used for detection. Quantification was performed using multiple reaction monitoring with positive mode. The method was validated in terms of specificity, linearity, precision, accuracy and stability. The calibration curves were linear over the concentration range of 0.5-100.0ng/g for sanguinarine, 0.5-100.0ng/g for chelerythrine, 0.2-100.0ng/g for dihydrosanguinarine and 0.1-100ng/g for dihydrochelerythrine, respectively. All of the recovery rates of the four analytes were over 85%. The RSD of intra-day and inter-day precision was less than 5.0%, and the relative error was all within 12.0%. This validated method has been successfully applied to assess the drug residue and metabolite residue characteristics of sanguinarine and chelerythrine in chicken tissue after oral administration of the extracts of Macleaya cordata (Willd.) R. Br, and to investigate the pharmacokinetic parameters of sanguinarine and dihydrosanguinarine in chicken plasma.

Pseudocyanides of sanguinarine and chelerythrine and their series of structurally simple analogues as new anticancer lead compounds: Cytotoxic activity, structure-activity relationship and apoptosis induction

6-Cyano dihydrosanguinarine (CNS) and 6-cyano dihydrochelerythrine (CNC) are respectively artificial derivatives of sanguinarine and chelerythrine, two anticancer quaternary benzo[c]phenanthridine alkaloids (QBAs) while 1-cyano-2-aryl-1,2,3,4-tetrahydroisoquinolines (CATHIQs) are a class of structurally simple analogues of CNS or CNC. This study investigated the inhibition activity of CNS, CNC and CATHIQs on cancer cells, apoptosis induction as well as their preliminary SAR. The results showed that CNS and 18 out of CATHIQs showed IC50 values of 0.53 and 0.62-2.24μM against NB4 and 1.53 and 2.99-11.17μM against MKN-45 cells, respectively, superior to a standard anticancer drug cis-platinum with IC50 of 2.39 and 11.36μM. CNC showed a higher activity against NB4 cells (IC50=1.85μM) and a moderate activity against MKN-45 cells (IC50=12.72μM). Among all CATHIQs, 2 and 17 gave the highest activity against NB4 cells and MKN-45 cells (IC50=0.62 and 2.99μM), respectively. DAPI staining, AO/EB staining and ultrastructure analysis of cells demonstrated that CATHIQs were able to induce apoptosis of the cells in a concentration-dependent manner. SAR showed that substitution patterns on the N-aromatic ring significantly influenced the activity of CATHIQs. The general trend was that the introduction of electron-withdrawing substituents like halogen atom, nitro, trifluoromethyl led to a significant improvement of the activity, while the presence of electron-donating groups like methyl, methoxyl caused a reduction of the activity. In most cases, the 2' site was the most favorable substitution position for the improvement of the activity. Thus, the present results strongly suggested that QBA-type pseudocyanides may serve as potential alternatives of anticancer QBAs while CATHIQs should be a class of promising lead compounds for the development of new QBA-like-type anticancer drugs. CNS exhibited the highest cytotoxicities with IC50 values of 0.53μM on NB4 cells and 1.53μM on MKN-45 cells.

Reductive metabolism of the sanguinarine iminium bond by rat liver preparations

BACKGROUND

Sanguinarine (SA) is a quaternary benzo[c]phenanthridine alkaloid that is mainly present in the Papaveraceae family. SA has been extensively studied because of its antimicrobial, anti-inflammatory, antitumor, antihypertensive, antiproliferative and antiplatelet activities. Metabolic studies demonstrated that SA bioavailability is apparently low, and the main pathway of SA metabolism is iminium bond reduction resulting in dihydrosanguinarine (DHSA) formation. Nevertheless, the metabolic enzymes involved in SA reduction are still not known in detail. Thus, the aim of this study was to investigate the rat liver microsomes and cytosol-induced SA iminium bond reduction, and to examine the effects of cytosol reductase inhibitors on the reductive activity.

METHODS

DHSA formation was quantified by HPLC. The possible enzymes responsible for DHSA formation were examined using selective individual metabolic enzyme inhibitors.

RESULTS

When SA was incubated with liver microsomes and cytosol in the absence of NAD(P)H, DHSA, the iminium bond reductive metabolite was formed. The reductase activity of the liver microsomes and cytosol was also enhanced significantly in the presence of NADH. The amount of DHSA formed in the liver cytosol was 4.6-fold higher than in the liver microsomes in the presence of NADH. The reductase activity in the liver cytosol was inhibited by the addition of flavin mononucleotide and/or riboflavin. Inhibition studies indicated that menadione, dicoumarol, quercetin and 7-hydroxycoumarin inhibited rat liver cytosol-mediated DHSA formation in the absence of NADH. However, only menadione and quercetin inhibited rat liver cytosol-mediated DHSA formation in the presence of NADH.

CONCLUSIONS

These results suggest that the SA iminium bond reduction proceeds via two routes in the liver cytosol. One route is direct non-enzymatic reduction by NAD(P)H, and the other is enzymatic reduction by possible carbonyl and/or quinone reductases in the liver cytosol.

Identification of in vitro metabolites of a new anticoccidial drug nitromezuril using HepG2 cells, rat S9 and primary hepatocytes by liquid chromatography/tandem mass spectrometry

RATIONALE

Nitromezuril is a novel triazine compound possessing remarkable anticoccidial activity that could have possible future use in the prevention of coccidiosis; however, its metabolic characteristics have still not been revealed.

METHODS

In the present study, the in vitro metabolism of nitromezuril in HepG2 cells, rat S9 and primary hepatocytes was investigated using high-performance liquid chromatography with electrospray ionization tandem mass spectrometry. The structures of metabolites and their product ions were easily and reliably characterized based on the accurate MS(2) spectra and known structure of nitromezuril.

RESULTS

As expected, three metabolites (M1-M3) were detected in a HepG2 cells system, one metabolite was respectively detected and identified as M1 in rat S9 and M2 in rat primary hepatocytes. M1 and M2 were confirmed respectively based on comparing their retention times, full scan, product ion scan with available authentic standards and M3 was tentatively identified as hydroxyl compound of M2.

CONCLUSIONS

Pathways of nitromezuril were reported for the first time and no obvious species difference was shown. The proposed metabolic pathways of nitromezuril can be expected to play a key role in pharmacodynamics and food safety evaluations.

NQO1 involves in the imine bond reduction of sanguinarine and recombinant adeno-associated virus mediated NQO1 overexpression decreases sanguinarine-induced cytotoxicity in rat BRL cells

Although sanguinarine (SANG) can be transformed to dihydrosanguinarine (DHSA) in human and animals, the enzyme involved in the imine bond reduction of SANG is still unknown. In this study, we found that rat

NAD(P)H

quinone oxidoreductase 1 expressed by prokaryotic system can transform SANG to DHSA in an NADPH dependent manner. We also found out that there was more DHSA in rAAV-NQO1 infected than rAAV-CYP1A1 and rAAV-control infected BRL cells. SANG decreased rat BRL cell proliferation and augmented cell apoptosis in a time and dose dependent manner. However, the influence of DHSA to BRL cells is not significant difference than SANG. SANG-induced apoptosis was correlated with the up-regulation of Bax/Bcl2 ratio and the down-regulation of Bcl2. SANG can also dose dependently down regulate NQO1 expression, but CYP1A1 expression was a little up regulated. Since CYP1A1 involving in SANG oxidative reactions and NQO1 involving in the transform of SANG to DHSA, we hypothesized that up regulation of NQO1 could reduce SANG cytotoxicity and up regulation of CYP1A1 could increase SANG cytotoxitity. Our further study showed that recombinant adeno-associated virus (rAAV) mediated overexpression of NQO1 significantly increased cell proliferation and decreased Bax/Bcl2 ratio, apoptosis, and cytotoxicity, whereas rAAV mediated CYP1A1 overexpression had opposite effects. These data illustrated that NQO1 involved in the imine bond reduction of sanguinarine and this was a less toxic metabolizing pathway than CYP1A1-metabolizing pathway.

Identification of sanguinarine metabolites in pig liver preparations by accurate mass measurements using electrospray ionization hybrid ion trap/time-of-flight mass spectrometry

RATIONALE

Sanguinarine (SA) is currently used in veterinary medicine for animal husbandry as a natural component of feed additive Sangrovit. To date, SA metabolism in food-producing animals has not yet been reported. Therefore, the purpose of the present study was to investigate the metabolism of SA in pig liver microsomes and cytosol.

METHODS

The SA incubations mixtures of microsomes and cytosol were processed by trichloroacetic acid (TCA) and acetonitrile. Then, the samples were analyzed using a sensitive and reliable method based on liquid chromatography combined with hybrid ion trap/time-of-flight mass spectrometry (LC-IT/TOFMS). The structural elucidations of these metabolites were performed by comparing the changes in the accurate molecular masses and product ions generated from precursor ions with those of the parent drug.

RESULTS

Seven metabolites were identified in pig liver preparations. Dihydrosanguinarine (DHSA, m/z 334) was the main metabolite formed in liver microsomes and the only one in cytosol. One oxidative metabolite and two O-demethylenated metabolites of SA (m/z 320) were found in the TCA-treated microsomal samples. However, SA pseudobase and two additional O-demethylenated metabolites of DHSA (m/z 322) were found only in the acetonitrile-treated microsomal samples.

CONCLUSIONS

It was demonstrated that different metabolites of SA were identified depending on the acidic or neural extraction conditions. A metabolic pathway of SA in pig was tentatively proposed based on these characterized metabolites and early reports.

Liquid chromatography coupled with time-of-flight and ion trap mass spectrometry for qualitative analysis of herbal medicines

With the expansion of herbal medicine (HM) market, the issue on how to apply up-to-date analytical tools on qualitative analysis of HMs to assure their quality, safety and efficacy has been arousing great attention. Due to its inherent characteristics of accurate mass measurements and multiple stages analysis, the integrated strategy of liquid chromatography (LC) coupled with time-of-flight mass spectrometry (TOF-MS) and ion trap mass spectrometry (IT-MS) is well-suited to be performed as qualitative analysis tool in this field. The purpose of this review is to provide an overview on the potential of this integrated strategy, including the review of general features of LC-IT-MS and LC-TOF-MS, the advantages of their combination, the common procedures for structure elucidation, the potential of LC-hybrid-IT-TOF/MS and also the summary and discussion of the applications of the integrated strategy for HM qualitative analysis (2006-2011). The advantages and future developments of LC coupled with IT and TOF-MS are highlighted.