Residue behavior and risk assessment of afidopyropen and its metabolite M440I007 in tea.

Afidopyropen, a novel insecticide, is highly effective against piercing insects such as the tea leafhopper. The residual levels of afidopyropen and M440I007 in tea cultivation, processing, and brewing were studied. During tea cultivation, afidopyropen dissipated faster in fresh tea shoots in the rainy season (T1/2 of 1.2-2.5 d) than that in the dry season (T1/2 of 3.1-4.4 d); afidopyropen was metabolized into M440I007, the level of which peaked in 1 d, and degraded rapidly (over 90 %) afterward 3 d. The green tea processing steps had little effect on decreasing the afidopyropen residue (PF of 0.90-1.18). Low infusion rates of afidopyropen (16.7 %-17.7 %) and M440I007 (4.1 %-6.2 %) were observed from dry green tea to infusion; furthermore, the risk of ingesting afidopyropen from drinking tea was low, with the risk quotient values < 0.0001. This study can offer guidance on the rational application of afidopyropen in tea plants.

Dioscorea bulbifera L.-induced hepatotoxicity and involvement of metabolic activation of furanoterpenoids.

The rhizome of Dioscorea bulbifera L. (DBL) is a popular traditional herb in the treatment of goiters, breast lumps, and tumors. Unfortunately, DBL can give rise to severe hepatotoxicity. More than 100 cases of liver injury, due to the usage of DBL in China, have been reported in the past half-century. The main toxic components of DBL are furanoditerpenoids diosbulbin B (DSB) as well as 8-epidiosbulbin E (EEA). This toxic effect requires metabolic oxidation of the furan ring mediated by cytochrome P450 enzymes, and the P450 3A subfamily is the main enzyme responsible for the reported hepatotoxicity. cis-Enedial intermediates resulting from furan ring oxidation can react with nucleophilic sites of macromolecules, such as protein and DNA, which may trigger the toxicities. This review illustrates the liver injury induced by DBL including metabolic activation of DSB and EEA, the essential components responsible for DBL-induced hepatotoxicity, along with biochemical mechanisms of their toxic actions. It will facilitate the development of approaches to prevent and intervene in liver injury induced by DBL for its safe use in clinical practice.

In Vitro DNA Adduction Resulting from Metabolic Activation of Diosbulbin B and 8-Epidiosbulbin E Acetate.

Diosbulbin B (DBB) and 8-epidiosbulbin E acetate (EEA), belonging to furan-containing diterpenoid lactones, are the primary components of Dioscorea bulbifera L. (DB), a traditional Chinese medicine herb. Our earlier studies indicated that consumption of DBB or EEA induced acute hepatotoxicities. Both DBB and EEA were bioactivated by P450 3A4 to generate the corresponding cis-enedial reactive metabolites which are associated with the hepatotoxicities. It has been proposed that the electrophilic intermediates attack cellular nucleophiles such as protein or DNA, thought to be a mechanism of triggering toxicities. The purposes of our present study were to define the interaction of the electrophilic reactive metabolites originating from DBB and EEA with 2'-deoxyguanosine (dGuo), 2'-deoxycytidine (dCyd), and 2'-deoxyadenosine (dAdo) and to characterize DNA adducts arising from the reactive metabolites of DBB and EEA. The reactive metabolites of DBB and EEA were found to covalently bind to the exocyclic and endocyclic nitrogens of dCyd, dGuo, and dAdo to generate oxadiazabicyclo[3.3.0]octaimine adducts. The reactive metabolites of DBB and EEA also attacked dGuo, dAdo, and dCyd of calf thymus DNA. The DNA adducts possibly contribute to the toxicologies of DBB and EEA.

Comparative transcriptome analysis of oil palm flowers reveals an EAR-motif-containing R2R3-MYB that modulates phenylpropene biosynthesis.

BACKGROUND: Oil palm is the most productive oil crop and the efficiency of pollination has a direct impact on the yield of oil. Pollination by wind can occur but maximal pollination is mediated by the weevil E. kamerunicus. These weevils complete their life cycle by feeding on male flowers. Attraction of weevils to oil palm flowers is due to the emission of methylchavicol by both male and female flowers. In search for male flowers, the weevils visit female flowers by accident due to methylchavicol fragrance and deposit pollen. Given the importance of methylchavicol emission on pollination, we performed comparative transcriptome analysis of oil palm flowers and leaves to identify candidate genes involved in methylchavicol production in flowers. RESULTS: RNA sequencing (RNA-Seq) of male open flowers, female open flowers and leaves was performed using Illumina HiSeq 2000 platform. Analysis of the transcriptome data revealed that the transcripts of methylchavicol biosynthesis genes were strongly up-regulated whereas transcripts encoding genes involved in lignin production such as, caffeic acid O-methyltransferase (COMT) and Ferulate-5-hydroxylase (F5H) were found to be suppressed in oil palm flowers. Among the transcripts encoding transcription factors, an EAR-motif-containing R2R3-MYB transcription factor (EgMYB4) was found to be enriched in oil palm flowers. We determined that EgMYB4 can suppress the expression of a monolignol pathway gene, EgCOMT, in vivo by binding to the AC elements present in the promoter region. EgMYB4 was further functionally characterized in sweet basil which also produces phenylpropenes like oil palm. Transgenic sweet basil plants showed significant reduction in lignin content but produced more phenylpropenes. CONCLUSIONS: Our results suggest that EgMYB4 possibly restrains lignin biosynthesis in oil palm flowers thus allowing enhanced carbon flux into the phenylpropene pathway. This study augments our understanding of the diverse roles that EAR-motif-containing MYBs play to fine tune the metabolic flux along the various branches of core phenylpropanoid pathway. This will aid in metabolic engineering of plant aromatic compounds.

Bromodomain and extraterminal (BET) proteins regulate biliary-driven liver regeneration.

BACKGROUND & AIMS: During liver regeneration, hepatocytes are derived from pre-existing hepatocytes. However, if hepatocyte proliferation is compromised, biliary epithelial cells (BECs) become the source of new hepatocytes. We recently reported on a zebrafish liver regeneration model in which BECs extensively contribute to hepatocytes. Using this model, we performed a targeted chemical screen to identify important factors that regulate BEC-driven liver regeneration, the mechanisms of which remain largely unknown. METHODS: Using Tg(fabp10a:CFP-NTR) zebrafish, we examined the effects of 44 selected compounds on BEC-driven liver regeneration. Liver size was assessed by fabp10a:DsRed expression; liver marker expression was analyzed by immunostaining, in situ hybridization and quantitative PCR. Proliferation and apoptosis were also examined. Moreover, we used a mouse liver injury model, choline-deficient, ethionine-supplemented (CDE) diet. RESULTS: We identified 10 compounds that affected regenerating liver size. Among them, only bromodomain and extraterminal domain (BET) inhibitors, JQ1 and iBET151, blocked both Prox1 and Hnf4a induction in BECs. BET inhibition during hepatocyte ablation blocked BEC dedifferentiation into hepatoblast-like cells (HB-LCs). Intriguingly, after JQ1 washout, liver regeneration resumed, indicating temporal, but not permanent, perturbation of liver regeneration by BET inhibition. BET inhibition after hepatocyte ablation suppressed the proliferation of newly generated hepatocytes and delayed hepatocyte maturation. Importantly, Myca overexpression, in part, rescued the proliferation defect. Furthermore, oval cell numbers in mice fed CDE diet were greatly reduced upon JQ1 administration, supporting the zebrafish findings. CONCLUSIONS: BET proteins regulate BEC-driven liver regeneration at multiple steps: BEC dedifferentiation, HB-LC proliferation, the proliferation of newly generated hepatocytes, and hepatocyte maturation.

Protection of Angelica sinensis (Oliv) Diels against hepatotoxicity induced by Dioscorea bulbifera L. and its mechanism.

Dioscorea bulbifera L., a traditionally used medicinal plant in China, is reported to induce hepatotoxicity. The present study is designed to investigate the protection of an ethanol extract of Angelica sinensis (Oliv) Diels (AE) against an ethyl acetate fraction of D. bulbifera (EF)-induced liver injury and its engaged mechanism. High performance liquid chromatography (HPLC) analysis showed that the amount of diosbulbin B in EF was 16.03% and ferulic acid in AE was 0.18%. EF (350 mg/kg) increased serum alanine/aspartate aminotransferase (ALT/AST), alkaline phosphatase (ALP) activities and total bilirubin (TB) amount, while AE inhibited such an increase. Liver histological evaluation showed that AE prevented development of severe hepatic lesions induced by EF. Further results showed that EF decreased the expression of Bcl-2 and induced the cleaved activation of caspase-9 and -3, and all those effects were reversed by AE. AE also reversed EF-induced decreased expression of the inhibitor of kappa B (IκB), superoxide dismutase (SOD), and glutathione peroxidase (GPx). Taken together, our results demonstrate that AE can prevent EF-induced hepatotoxicity via preventing apoptosis, meanwhile IκB, SOD, and GPx may be involved in such protection.

Cytochrome p450-mediated metabolic activation of diosbulbin B.

Diosbulbin B (DIOB), a furan-containing diterpenoid lactone, is the most abundant component of Dioscorea bulbifera L. (DB), a traditional Chinese medicine herb. Administration of purified DIOB or DB extracts has been reported to cause liver injury in animals. The mechanisms of DIOB-induced hepatotoxicity remain unknown. The major objective of this study was to identify reactive metabolites of DIOB. A DIOB-derived cis-enedial was trapped by N-acetyl lysine (NAL) and glutathione (GSH) or N-acetyl cysteine (NAC) in rat and human liver microsomal incubation systems after exposure to DIOB. Four metabolites (M1-M4) associated with GSH were detected by liquid chromatography coupled to tandem mass spectrometry. Apparently, M1 was derived from both NAL and GSH. M2 and M3 resulted from the reaction of GSH without the involvement of NAL. Two molecules of GSH participated in the formation of M4. M2 and M3 were also detected in bile and urine of rats given DIOB. M5, a DIOB-derived NAC/NAL conjugate, was detected in microsomal incubations with DIOB fortified with NAC and NAL as trapping agents. Biomimetic M1-M5 were prepared by oxidation of DIOB with Oxone for metabolite identification. Microsomal incubation study demonstrated that ketoconazole inhibited the production of the enedial in a concentration-dependent manner, and CYP3A4 was found to be the enzyme responsible for the metabolic activation of DIOB. The metabolism study facilitates the understanding of the role of bioactivation of DIOB in its hepatotoxicity.

Aristolochic acid-induced upper tract urothelial carcinoma in Taiwan: clinical characteristics and outcomes.

Aristolochic acid (AA), a component of all Aristolochia-based herbal medicines, is a potent nephrotoxin and human carcinogen associated with upper urinary tract urothelial carcinoma (UUC). To investigate the clinical and pathological characteristics of AA-induced UUC, this study included 152 UUC patients, 93 of whom had been exposed to AA based on the presence of aristolactam-DNA adducts in the renal cortex. Gene sequencing was used to identify tumors with A:T-to-T:A transversions in TP53, a mutational signature associated with AA. Cases with both aristolactam-DNA adducts and A:T-to-T:A transversions in TP53 were defined as AA-UUC, whereas patients lacking both of these biomarkers were classified as non-AA-UUC. Cases with either biomarker were classified as possible-AA-UUC. Forty (26%), 60 (40%), and 52 (34%) patients were classified as AA-UUC, possible-AA-UUC and non-AA-UUC, respectively. AA-UUC patients were younger (median ages: 64, 68, 68 years, respectively; p=0.189), predominately female (65%, 42%, 35%, respectively; p=0.011), had more end-stage renal disease (28%, 10%, 12%, respectively; p=0.055), and were infrequent smokers (5%, 22%, 33%, respectively; p=0.07) compared to possible-AA-UUC and non-AA-UUC patients. All 14 patients who developed contralateral UUC had aristolactam-DNA adducts; ten of these also had signature mutations. The contralateral UUC-free survival period was shorter in AA-UUC compared to possible- or non-AA-UUC (p=0.019 and 0.002, respectively), whereas no differences among groups were observed for bladder cancer recurrence. In conclusion, AA-UUC patients tend to be younger and female, and have more advanced renal disease. Notably, AA exposure was associated with an increased risk for developing synchronous bilateral and metachronous contralateral UUC.

The preclinical profile of asenapine: clinical relevance for the treatment of schizophrenia and bipolar mania.

INTRODUCTION: Asenapine is a novel antipsychotic drug approved for the treatment of acute schizophrenia, manic, or mixed episodes associated with bipolar I disorder, as a maintenance treatment of schizophrenia and as an adjunctive therapy with lithium or valproate for the acute treatment of manic or mixed episodes associated with bipolar I disorder in adults. AREAS COVERED: This review focuses on the preclinical profile of asenapine. It analyzes the pharmacological, neurochemical, behavioral, and molecular mechanisms of asenapine and their contribution to the beneficial therapeutic advantages of the drug as reported in published preclinical and clinical studies, product labels, and poster presentations. EXPERT OPINION: Asenapine exhibits a broad pharmacological profile that targets a wide range of neurotransmitter receptors with variable affinities. The drug preferentially increases dopamine, norepinephrine, and acetylcholine levels in cortical and limbic brain areas. It also potentiates cortical glutamatergic neurotransmission, and is active in behavioral animal models predictive of antipsychotic, antidepressant, and pro-cognitive activities. Chronic administration of asenapine alters the abundance of dopamine, serotonin, glutamate, adrenergic, and cholinergic receptor subtypes in different brain regions. These action mechanisms of asenapine might contribute to its unique psychopharmacological properties in the improved treatment of schizophrenia and other psychotic disorders.

Integrating carbon-halogen bond formation into medicinal plant metabolism.

Halogenation, which was once considered a rare occurrence in nature, has now been observed in many natural product biosynthetic pathways. However, only a small fraction of halogenated compounds have been isolated from terrestrial plants. Given the impact that halogenation can have on the biological activity of natural products, we reasoned that the introduction of halides into medicinal plant metabolism would provide the opportunity to rationally bioengineer a broad variety of novel plant products with altered, and perhaps improved, pharmacological properties. Here we report that chlorination biosynthetic machinery from soil bacteria can be successfully introduced into the medicinal plant Catharanthus roseus (Madagascar periwinkle). These prokaryotic halogenases function within the context of the plant cell to generate chlorinated tryptophan, which is then shuttled into monoterpene indole alkaloid metabolism to yield chlorinated alkaloids. A new functional group-a halide-is thereby introduced into the complex metabolism of C. roseus, and is incorporated in a predictable and regioselective manner onto the plant alkaloid products. Medicinal plants, despite their genetic and developmental complexity, therefore seem to be a viable platform for synthetic biology efforts.

Structure and formation of the fluorescent compound of Lignum nephriticum.

The intense blue fluorescence of the infusion of Lignum nephriticum (Eysenhardtia polystachya), first observed in the sixteenth century, is due to a novel four-ring tetrahydromethanobenzofuro[2,3-d]oxacine which is not present in the plant but is the end product of an unusual, very efficient iterative spontaneous oxidation of at least one of the tree's flavonoids.

Approach to the biosynthesis of atisine-type diterpenoid alkaloids.

To determine the biosynthesis pathway of the atisine-type diterpenoid alkaloids spiramines A/B and C/D, feeding experiments in in vitro cultured plantlets and enzymatic transformations in cell-free extracts were performed in combination with LCMS and tandem MS analyses. L-[2-(13)C,(15)N]Serine was used in the feeding experiments and enzymatic transformations, and the diterpene spiraminol was identified as a biosynthetic precursor of spiramine alkaloids. The LCMS and tandem MS spectra of the extracts from these experiments indicated that L-[2-(13)C,(15)N]serine was incorporated into spiramines A/B and C/D. The labeled reaction products show that l-serine is the one possible nitrogen source involved in the biosynthesis of atisine-type DAs.

Imaging induction of cytoprotective enzymes in intact human cells: coumberone, a metabolic reporter for human AKR1C enzymes reveals activation by panaxytriol, an active component of red ginseng.

We here present an optical method for monitoring the activity of the inducible aldo-keto reductases AKR1C2 and AKR1C3 in living human cells. The induction of these enzymes is regulated by the antioxidant response element (ARE), as demonstrated in recent literature, which in turn is dependent on the transcription factor Nrf2. The activation of ARE leads to the transcription of a coalition of cytoprotective enzymes and thus represents an important target for the development of new therapies in the area of neurodegenerative diseases and cancer. Through the use of Coumberone, a metabolic fluorogenic probe, and isoform-selective inhibitors, the upregulation of cellular stress markers AKR1C2 and AKR1C3 can be quantitatively measured in the presence of ARE activator compounds, via either a fluorimetric assay or fluorescence microscopy imaging of intact cells. The method has both high sensitivity and broad dynamic range, as demonstrated by induction studies in three cell lines with dramatically different metabolic capabilities (transfected monkey kidney COS-1 cells, human neuroblastoma IMR-32 cells, and human liver HepG2 cells). We applied the new method to examine a number of neurotrophic natural products (spirotenuipesine A, spirotenuipesine B, scabronine G-methylester, and panaxytriol), and discovered that panaxytriol, an active component of red ginseng extracts, is a potent ARE inducer. The upregulation of AKR1C enzymes, induced by chemically homogeneous panaxytriol, was partially dependent on PKC and PI3K kinases as demonstrated by the application of selective inhibitors. This cellular mechanism may account for panaxytriol's neurotrophic, neuroprotective, and anticancer properties. The protective effects of ARE inducers against tumorgenesis and neurodegeneration fuel the growing interest in this area of research and the method described here will greatly enable these endeavors.

An improved beta-lactamase reporter assay: multiplexing with a cytotoxicity readout for enhanced accuracy of hit identification.

A problem inherent to the use of cellular assays for drug discovery is their sensitivity to cytotoxic compounds, which can result in false hits from certain compound screens. To alleviate the need to follow-up hits from a reporter assay with a separate cytotoxicity assay, the authors have developed a multiplexed assay that combines the readout of a beta-lactamase reporter with that of a homogeneous cytotoxicity indicator. Important aspects to the development of the multiplexed format are addressed, including results that demonstrate that the IC(50) values of 40 select compounds in a beta-lactamase reporter assay for nuclear factor kappa B and SIE pathway antagonists are not affected by the addition of the cytotoxicity indicator. To demonstrate the improvement in hit confirmation, the multiplexed assay was used to perform a small-library screen (7728 compounds) for serotonin 5HT1A receptor antagonists. Hits identified from analysis of the beta-lactamase reporter data alone were compared to those hits determined when the reporter and cytotoxicity data generated from the multiplexed assay were combined. Confirmation rates were determined from compound follow-up using dose-response analysis of the potential antagonist hits identified by the initial screen. In this representative screen, the multiplexed assay approach yielded a 19% reduction in the number of compounds flagged for follow-up, with a 37% decrease in the number of false hits, demonstrating that multiplexing a beta-lactamase reporter assay with a cytotoxicity readout is a highly effective strategy for reducing false hit rates in cell-based compound screening assays.

Development of a process for the production of the anticancer lead compound pleurotin by fermentation of Hohenbuehelia atrocaerulea.

Pleurotin is a naphthoquinone antibiotic originally isolated from Pleurotus griseus. Two pleurotin producing strains of Hohenbuehelia atrocaerulea have been identified, which, on solid substrate fermentation for 2 months yield 1-2 mg/l of the antibiotic. Described here is the lengthy developmental process which resulted in a production protocol being developed which reliably yields pleurotin from liquid fermentation at >300 mg/l. Critical to obtaining this increase in titer was inclusion in the media of an aqueous extract of alder wood.

[The metabolic transformation of (-)-securinine].

AIM: To study the in vitro and in vivo metabolism of (-)-securinine. METHODS: The metabolic transformation of (-)-securinine was studied by using phenobarbital-induced rat liver microsomal incubate containing the NADPH-generating system in vitro and the constitution of the system was optimized. A reversed phase HPLC method was established to analyze the parent drug and its metabolites. The major metabolites were isolated and purified by liquid-liquid extraction, preparative TLC and HPLC, and their structures were elucidated as 6-hydroxyl securinine, 6-carbonyl securinine, 5 beta-hydroxyl securinine and 5 alpha-hydroxyl securinine by 1HNMR, 13CNMR and MS spectral analysis. An HPLC method was developed to analyze securinine and its metabolites in biofluids (bile, urine) of rat. The bile, urine and their enzymatic hydrolyzed samples of the rat i.p. administrated with (-)-securinine were determined by using this method. RESULTS: Four main metabolites of (-)-securinine in rat hepatic microsome incubation were obtained and their structures were elucidated. Metabolites from in vitro study were confirmed in biofluids (bile, urine) which were collected from rats given securinine i.p. It was suggested that 6-hydroxyl securinine was excreted in conjugated form as well by analyzing enzymatic hydrolyzed bile. CONCLUSION: The main metabolic pathway of (-)-securinine in vitro and in vivo is basically elucidated.

[Study on the chiral separation of securinine by high-performance capillary electrophoresis and its stereoselective metabolism in rat].

AIM: To establish a high-performance capillary electrophoresis (HPCE) chiral separation method for d-securinine and l-securinine, and use this method to investigate the stereoselective metabolism process of d- and l-securinine in Wistar rats. METHODS: The electrophoretic condition and parameters were investigated and the optimized conditions were as following: the electrophoretic medium was 40 mmol.L-1 Tris-H3PO4 buffer (pH adjusted to 6.0 with H3PO4) containing 32 mmol.L-1 HP-beta-CD as chiral selector. Determination was carried out with a UV detector at 254 nm. The separations were performed at 16 degrees C with a positive voltage of 15 kV. Samples were injected into the capillary by pressure for 6 s. The biological samples (urine, bile, plasma and feces) of rats were alkalized and extracted with ethyl acetate. RESULTS: The experimental results showed that the concentration of HP-beta-CD, the concentration of the running buffer and the pH value of the buffer were the main important factors which effected the resolution. d-Securinine and l-securinine were separated at baseline level under the determination conditions. The determination was not interfered by endogenous components and metabolites. After i.p. administration, the rats excreted more d-securinine than l-securinine through bile, urine and feces. The metabolism process in rats was stereoselective. CONCLUSION: This method is simple, reliable and suitable for studying the stereoselective metabolism of securinine in rats.

Occurrence of the insecticidal 16,17-didehydro-16(E)-stemofoline in Stemona collinsae.

The occurrence of two alkaloids, 16,17-didehydro-16(E)-stemofoline and its isomer at C-4, 16,17-didehydro-4(E)-16(E)-stemofoline, were found together with a known insecticidal compound, stemofoline, in Stemona collinsae. The 16,17-didehydro-16(E)-stemofoline displayed higher insecticidal and antifeedant activities against the diamondback moth larvae than stemofoline.