Rapid screening and characterization of metabolites from a marine-derived actinomycete by high-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry

Development and validation of an LC-MS/MS method for the determination of AZD7648 in rat plasma: Application to a pharmacokinetic study

AZD7648 is a potent DNA-PK inhibitor that is being developed for the treatment of ovarian cancer. The study aimed to develop a simple and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to determine the concentration of AZD7648 in rat. AZD7648 was extracted from plasma by acetonitrile-mediated protein precipitation. The quantification was performed on a Thermo Vantage TSQ mass spectrometer with ibrutinib as an internal standard. A Waters Acquity UPLC BEH C18 column combined with 0.1% aqueous formic acid and acetonitrile was employed for chromatographic separation. The precursor-to-product ion transitions were m/z 421.2 > 337.2 and m/z 441.2 > 138.1 for AZD7648 and internal standard, respectively. This method was successfully validated according to the US Food and Drug Administration guidance. The calibration curve was linear over the concentration range of 0.5-1,000 ng/ml with correlation coefficient >0.999. The precision expressed as the coefficient of variation was <8.09%, while the accuracy expressed as relative error ranged from -10.00 to 9.08%. The mean recovery was >94.49%. AZD7648 was stable in rat plasma after storage under certain conditions. The validated method was demonstrated to be selective, sensitive and reliable, and has been successfully applied to the pharmacokinetic study of AZD7648 in rat plasma after oral and intravenous administration (1 mg/kg).

Actinomycins from Soil-Inhabiting Streptomyces as Sources of Antibacterial Pigments for Silk Dyeing

Actinobacteria produce a broad spectrum of bioactive substances that are used in the pharmaceutical, agricultural, and biotechnology industries. This study investigates the production of bioactive substances in Streptomyces, isolated from soil under five tropical plants, focusing on their potential as natural antibacterial dyes for silk fabrics. Out of 194 isolates, 44 produced pigments on broken rice as a solid substrate culture. Eight antibacterial pigmented isolates from under Magnolia baillonii (TBRC 15924, TBRC 15927, TBRC 15931), Magnolia rajaniana (TBRC 15925, TBRC 15926, TBRC 15928, TBRC 15930), and Cinnamomum parthenoxylon (TBRC 15929) were studied in more detail. TBRC 15927 was the only isolate where all the crude extracts inhibited the growth of the test organisms, Staphylococcus epidermidis TISTR 518 and S. aureus DMST 4745. The bioactive compounds present in TBRC 15927 were identified through LC-MS/MS analysis as belonging to the actinomycin group, actinomycin D (or X1), X2, and X0β. Also, the ethyl acetate crude extract exhibited non-toxicity at an IC50 value of 0.029 ± 0.008 µg/mL on the mouse fibroblast L-929 assay. From the 16S rRNA gene sequence analysis, TBRC 15927 had 100% identity with Streptomyces gramineus JR-43T. Raw silk dyed with the positive antimicrobial TBRC 15927 extract (8.35 mg/mL) had significant (>99.99%) antibacterial properties. Streptomyces gramineus TBRC 15927 is the first actinomycin-producing strain reported to grow on broken rice and shows promise for antibacterial silk dyeing.

Endophytic actinobacteria from wild medicinal plants are a natural source of insecticide to control the African cotton leafworm (Spodoptera littoralis)

Insecticide resistance in agricultural pests has prompted the need to discover novel compounds with new modes of action. We investigated the potency of secondary metabolites from seventy endophytic actinobacteria against laboratory and field strains of Spodoptera littoralis (fourth instar), comparable to the bioinsecticide spinetoram (Radiant SC 12%). Endophytes from Artemisia herba-alba and A. judaica were highly effective. Chemical profiling of the most potent metabolite of the strain Streptomyces sp. ES2 was investigated using LC-QTOF-MS-MS technique, and the activity was validated through molecular docking studies. Metabolic extracts from actinobacteria belonging to Streptomyces, Nocardioides, and Pseudonocardia showed immediate and latent death to the Spodoptera littoralis fourth instar larvae. The metabolite from strain ES2 has shown the most promising and significant histopathological and inhibitory effects on the fourth instar larvae. ES2 metabolite caused lesions in the body wall cuticle, indicating a different mode of action than that of Radiant. Chemical profiling of ES2 showed the presence of cyromazine (molt inhibitor), 4-nitrophenol, and diazinon as key constituents. In conclusion, these findings suggest that secondary metabolites from endophytic actinobacteria inhabiting wild medicinal plants can be a sustainable source for promising natural biocontrol agents. This is the first illustration of the insecticidal activity of Artemisia spp. microbiome, and natural cyromazine synthesis by actinobacteria.

A simple and sensitive LC-MS/MS method for the determination of polyphyllin VII in rat plasma and its application to pharmacokinetic study

Polyphyllin VII is an isoprene saponin extracted from Rhizoma paridis, and it can effectively suppress tumor initiation, growth, and metastasis. In this study, we aim to develop and validate an LC-MS/MS method for the quantification of polyphyllin VII in rat plasma using digoxin as the internal standard (IS). The plasma samples were precipitated with methanol, and the samples were separated on an ACQUITY BEH C₁₈ column (2.1 × 50 mm, 1.7 μm). The mobile phase consisted of 0.1% formic acid solution and acetonitrile. The detection was performed in the multiple reactions monitoring mode, with the precursor-to-product transitions of m/z 1075.4 > 883.3 for polyphyllin VII and m/z 779.4 > 649.6 for the IS. The method showed excellent linearity over the concentration range of 0.5-1000 ng/ml, with a correlation coefficient of 0.9996 (r = 0.9996). The lower limit of quantification was 0.5 ng/ml. The inter- and intra-day accuracy (relative error) ranged from -4.8 to 5.9%, and precision (relative standard deviation) was < 9.0%. The assay showed high extraction recovery, ranging from 90.6 to 95.6%. Polyphyllin VII was demonstrated to be stable under the storage conditions. The validated LC-MS/MS method was successfully applied to the pharmacokinetic study of polyphyllin VII in rats after oral, intraperitoneal, and intravenous administrations. The pharmacokinetic results indicated that polyphyllin VII showed low oral (5.86%) bioavailability and moderate (38.81%) intraperitoneal bioavailability.

Characterization of the metabolite of cabozantinib generated from liver microsomes and hepatocytes by ultra-high performance liquid chromatography coupled to quadrupole/orbitrap high resolution mass spectrometry

Cabozantinib is a potent inhibitor of tyrosine kinase receptor that plays key role in tumor pathogenesis. Cabozantinib has been approved by U. S. Food and Drug Administration for the treatment of cancer. The present work was aimed to explore the in vitro metabolism of cabozantinib using liver microsomes and hepatocytes from animal species and humans through ultra-high performance liquid chromatography coupled to quadrupole/orbitrap high resolution mass spectrometer. The metabolites were characterized by their elemental compositions, MS and MS/MS spectra. As a result, a total of 26 metabolites were identified, and 15 metabolites were newly reported. Among these metabolites, M12 (oxidative defluorination), M19 and M22 (demethylation), M21 (hydroxylation) and M26 (N-oxygenation) were the major metabolites in all species. Our data revealed that cabozantinib was metabolized via the following pathways: oxidative defluorination, hydroxylation, amide hydrolysis, O-dealkylation, N-oxygenation, demethylation and glucuronidation. Human recombinant cytochrome P450 (CYP) enzyme analysis revealed that metabolism of cabozantinib was mainly catalyzed by CYP3A4, while other CYP enzymes played negligible role. The current study provided valuable metabolic data of cabozantinib from different animal species and humans, which would aid in safety and efficacy assessment.

In Vitro Metabolism Study of Seongsanamide A in Human Liver Microsomes Using Non-Targeted Metabolomics and Feature-Based Molecular Networking

Seongsanamide A is a bicyclic peptide with an isodityrosine residue discovered in Bacillus safensis KCTC 12796BP which exhibits anti-allergic activity in vitro and in vivo without significant cytotoxicity. The purpose of this study was to elucidate the in vitro metabolic pathway and potential for drug interactions of seongsanamide A in human liver microsomes using non-targeted metabolomics and feature-based molecular networking (FBMN) techniques. We identified four metabolites, and their structures were elucidated by interpretation of high-resolution tandem mass spectra. The primary metabolic pathway associated with seongsanamide A metabolism was hydroxylation and oxidative hydrolysis. A reaction phenotyping study was also performed using recombinant cytochrome P450 isoforms. CYP3A4 and CYP3A5 were identified as the major metabolic enzymes responsible for metabolite formation. Seongsanamide A did not inhibit the cytochrome P450 isoforms commonly involved in drug metabolism (IC₅₀ > 10 µM). These results will contribute to further understanding the metabolism and drug interaction potential of various bicyclic peptides.

Detection and structural characterization of the metabolites of dihydroresveratrol in rats by liquid chromatography coupled to high-resolution tandem mass spectrometry

RATIONALE

Dihydroresveratrol has been demonstrated to possess a wide spectrum of bioactivities, such as anti-oxidant and anti-inflammatory effects. The aim of the present study was to investigate the metabolic profiles of dihydroresveratrol in rats.

METHODS

The in vitro metabolism was elucidated by incubating dihydroresveratrol with rat hepatocytes for 2 h at 37°C. For in vivo metabolism, dihydroresveratrol was orally administered to rats at a single dose of 50 mg/kg and the resulting biliary and urinary samples were collected. All the samples were analyzed by liquid chromatography combined with electrospray ionization high-resolution mass spectrometry. The structures of the metabolites were proposed based on their accurate masses and their MS/MS product ions.

RESULTS

A total of 16 metabolites including three phase I metabolites and 13 phase II metabolites were detected and structurally proposed. Among these metabolites, M6 and M14 were unambiguously identified as 3'-hydroxylresveratrol and resveratrol, respectively, using reference standards. Dihydroresveratrol was mainly metabolized into resveratrol (M14) and a glucuronide conjugate (M12), which were excreted into urine and bile as the major metabolites.

CONCLUSIONS

The metabolic pathways of dihydroresveratrol involved hydroxylation, dehydrogenation, glucuronidation, glutathione (GSH) conjugation and methylation. The present study provided useful information with regard to the metabolic profiles of dihydroresveratrol in rats.

Micromonospora species from rarely-exploited Egyptian habitats: chemical profile, antimicrobial, and antitumor activities through antioxidant property

The development of new anticancer agents with a selective action mechanism has become a significant scientific challenge, especially as cancers remain the world's leading cause of death. Actinobacteria and its bioactive compounds have recently become a promising perspective alternative to cancer therapy. In this study, some extracted metabolites of Micromonospora exhibited potent antimicrobial with microbial inhibition zone ≥ 7 mm, and cytotoxic activities against MCF-7 and HepG2 cell lines with promising activities ≥ 85%. Additionally, treatment of DENA/CCl4 rats with the strain Micromonospora sp1 has induced a substantial amelioration of the liver functions, enhancing liver architecture near normal and antioxidant properties through elevation of antioxidant enzyme levels. So that these preliminary results can provide metabolites from Micromonospora sp1 as an anti-liver cancer therapy. Finally, we introduced the chemical profiling of Micromonospora sp1 metabolic extract by LC-QTOF-MS-MS technique, where eight compounds with reported antioxidant property anti-liver cancer activity were targeted, validated as iNOS inhibitor through molecular docking studies. The findings in this study can be a significant step towards studying natural bioactive products produced by Micromonospora spp. as agents for anti-liver cancer. KEY POINTS: • Metabolites of Micromonospora strain from unexploited Egyptian habitats were investigated with LC/MS library-based chemical profile and molecular docking studies as iNOS inhibitors. • Some Micromonospora strains exhibited potent antimicrobial with microbial inhibition zone ≥ 7 mm, and cytotoxic activities against MCF-7 and HepG2 cell lines with promising activities ≥ 85%. • Micromonospora extract exhibited anti-liver cancer activity in vivo through the antioxidant property by inhibiting the liver cancer biomarkers (LDH and AFP) and enhancing other biochemical parameters.

High-resolution mass spectrometry-based approach for the identification and profiling of the metabolites of taletrectinib formed in liver microsomes

Taletrectinib is a potent, orally active, and selective ROS1/NTRK kinase inhibitor. The aim of this study was to study the metabolism of taletrectinib in rat, dog, and human liver microsomes. The biotransformation of taletrectinib was carried out using rat, dog, and human liver microsomes supplemented with nicotinamide adenine dinucleotide phosphate tetrasodium salt (NADPH) and uridine diphosphate glucuronic acid (UDPGA). The microsomal incubations were conducted at 37°C for 60 min. The formed metabolites were identified by ultrahigh performance liquid chromatography coupled to high-resolution tandem mass spectrometry (UHPLC-HRMS) using electrospray ionization in the positive ion mode. They were identified by accurate masses and MS/MS spectra and based on their fragmentation pathways. With UHPLC-HRMS, a total of 10 metabolites including one glucuronide conjugate (M7) were structurally identified. M9 and M10 were unambiguously identified as taletrectinib alcohol and taletrectinib ketone, respectively, using reference standards. The phase I metabolic pathways of taletrectinib involved N-dealkylation, O-dealkylation, oxidative deamination, and oxygenation; the phase II metabolic pathways referred to glucuronidation. The current study investigated the in vitro metabolic fate of taletrectinib in animals and human species, which would bring us considerable benefits for the subsequent studies focusing on the pharmacological effect and toxicity of this drug.

Identification of the stable and reactive metabolites of tetrahydropiperine using ultrahigh-performance liquid chromatography combined with diode-array detection and high-resolution mass spectrometry

RATIONALE

Tetrahydropiperine is one of the natural arylpentanamide compounds isolated from Piper nigrum L., which has been demonstrated to have insecticidal activity. The aim of this study was to investigate the metabolic profiles of tetrahydropiperine in mouse, rat, dog, monkey and human hepatocytes.

METHODS

The in vitro metabolism of tetrahydropiperine was elucidated via incubation with hepatocytes for 2 h at 37°C. The samples were analyzed using ultrahigh-performance liquid chromatography combined with diode-array detection and high-resolution tandem mass spectrometry operated in positive electrospray ionization mode. The structures of the metabolites were characterized using their retention times and their tandem mass spectrometric product ions.

RESULTS

A total of 20 metabolites were detected and their structures were proposed. These metabolites were formed mainly through the following pathways: (1) 1,3-benzodioxole ring opening to form a catechol derivative (M12), which was prone to glucuronidation (M6 and M8), methylation (M17) and glutathione (GSH)-derived conjugation through an ortho-quinone intermediate (M4) or via an aldehyde intermediate (M7); (2) dehydrogenation to form a piperanine (M15), which was subsequently subject to hydroxylation (M2 and M5) and GSH conjugation (M10 and M11) via Michael addition; (3) hydroxylation (M13, M14, M16, M18 and M19); and (4) direct GSH conjugation through an aldehyde intermediate (M3).

CONCLUSIONS

The major metabolic pathways of tetrahydropiperine were hydroxylation, dehydrogenation, methylation, GSH conjugation and glucuronidation. Tetrahydropiperine was bioactivated through ortho-quinone, Michael receptor and aldehyde intermediates.

Pharmacokinetics and bioavailability of ipatasertib in dog plasma using LC/MS/MS

A rapid, sensitive, and reliable liquid chromatography-tandem mass spectrometric method was developed to quantify ipatasertib in dog plasma. The dog plasma sample was deproteinated by using acetonitrile with ulixertinib as an internal standard followed by separation on a Spursil C₁₈ -EP column with a gradient mobile phase comprising 2 mM ammonium acetate containing 0.1% formic acid and acetonitrile. Positive ion electrospray was used, and multiple reaction monitoring transitions were m/z 458.2 > 387.2 for ipatasertib and m/z 433.1 > 262.1 for the internal standard. The developed method was validated with a linear range of 0.3-1500 ng/mL, and with correlation coefficient greater than 0.9989. The lower limit of quantification was 0.3 ng/mL. The intra- and inter-day precision ranged from 3.58 to 14.32%, whereas the intra- and inter-day accuracy was in the range of -2.50-13.25%. No carry-over and matrix effects were observed under the current conditions. The extraction recovery was demonstrated to be greater than 85.43%. Ipatasertib was stable during the storage, processing, and determination. The validated assay was further successfully applied to a pharmacokinetic study of ipatasertib in dogs after oral and intravenous administrations. The bioavailability of ipatasertib was determined to be 19.3%.

A novel LC-MS/MS method for the determination of ziritaxestat in rat plasma and its pharmacokinetic study

Ziritaxestat is a first-in-class autotoxin inhibitor. The purpose of this study was to develop a liquid chromatography/electrospray ionization tandem mass spectrometric (LC-MS/MS) method for the determination of ziritaxestat in rat plasma. The plasma sample was deproteinated using acetonitrile and then separated on an Acquity BEH C₁₈ column with water containing 0.1% formic acid and acetonitrile as mobile phase, which was delivered at 0.4 ml/min. Ziritaxestat and the internal standard (crizotinib) were quantitatively monitored with precursor-to-product transitions of m/z 589.3 > 262.2 and m/z 450.1 > 260.2, respectively. The total running time was 2.5 min. The method showed excellent linearity over the concentration range 0.5-2000 ng/ml, with correlation coefficient >0.9987. The extraction recovery was >82.09% and the matrix effect was not significant. Inter- and intra-day precisions (RSD) were <11.20% and accuracies were in the range of -8.50-7.45%. Ziritaxestat was demonstrated to be stable in rat plasma under the tested conditions. The validated LC-MS/MS method was successfully applied to study the pharmacokinetic profiles of ziritaxestat in rat plasma after intravenous and oral administration. Pharmacokinetic results demonstrated that ziritaxestat displayed a short half-life (~3 h) and low bioavailability (20.52%).

Metabolic profiles and pharmacokinetics of goitrin in rats through liquid chromatography combined with electrospray ionization-tandem mass spectrometry

Several chemical and biological studies have revealed R,S-goitrin as the main bioactive constituent of Isatis indigotica Fort., responsible for antiviral antiendotoxin activity; however, few pharmacokinetic studies have been conducted. To comprehend the kinetics of R,S-goitrin and promote its curative application, a rapid and sensitive UHPLC-MS/MS method was developed. The selected reaction monitoring transitions were m/z 130.0 → 70.0 for R,S-goitrin and m/z 181.1 → 124.0 for the internal standard in a positive-ion mode. The established UHPLC-MS/MS method achieved good linearity for R,S-goitrin at 10-2000 ng/mL. The intra- and interday accuracy levels were within ±9.7%, whereas the intraday and interday precision levels were <11.3%. The extraction recovery, stability and matrix effect were within acceptable limits. The validated method was successfully applied for the pharmacokinetic analysis of R,S-goitrin in rats after oral administration. Moreover, a total of six metabolites were structurally identified through UHPLC-Q/TOF-MS. The proposed metabolic pathways of R,S-goitrin in rats involve demethylation, acetylation, glutathionylation and oxygenation.

Metabolic profiles of neratinib in rat by using ultra-high-performance liquid chromatography coupled with diode array detector and Q-Exactive Orbitrap tandem mass spectrometry

Neratinib is a tyrosine kinase inhibitor that has been approved by the US Food and Drug Administration for the treatment of breast cancer. However, its metabolism remains unknown. This study was carried out to investigate the in vitro and in vivo metabolism of neratinib using an UHPLC-DAD-Q Exactive Orbitrap-MS instrument with dd-MS2 on-line data acquisition mode. The post-acquisition data was processed using MetWorks software. Under the current conditions, a total of 12 metabolites were detected and structurally identified based on their accurate masses, fragment ions and chromatographic retention times. Among these metabolites, M3, M10 and M12 were unambiguously identified using chemically synthesized reference standards. M6 and M7 (GSH conjugates) were the major metabolites. The metabolic pathways of neratinib were proposed accordingly. Our findings suggested that neratinib was mainly metabolized via O-dealkylation (M3), oxygenation (M8), N-demethylation (M10), N-oxygenation (M12), GSH conjugation (M1, M2, M4, M5, M6 and M7) and N-acetylcysteine conjugation (M9 and M11). The α,β-unsaturated ketone was the major metabolic site and GSH conjugation was the predominant metabolic pathway. In conclusion, this study provided valuable metabolic data and would benefit the assessment of the contributions to the overall activity or toxicity from the key metabolites.

Preparation and structural determination of four metabolites of senkyunolide I in rats using ultra performance liquid chromatography/quadrupole-time-of-flight tandem mass and nuclear magnetic resonance spectra

Background

Senkyunolide I (SEI) is one of the most important bioactive phthalides of Ligusticum chuanxiong Hort. (Umbelliferae), a Traditional Chinese Medicine. Our previous studies suggested that it might be developed as a potential treatment for migraine.

Methods

In this paper, we aimed to isolate and characterize the main metabolites of SEI after gavage feeding in rats. Their structures were identified precisely on the basis of nuclear magnetic resonance (NMR) spectroscopy and UPLC/Q-TOF-MS spectrometry. We also established the main metabolic pathways of SEI in rats.

Results

Four metabolites (M1-M4) were isolated, for the first time, from bile samples of rats by preparative high-performance liquid chromatography. Their structures were determined as SEI-6S-O-β-D-glucuronide (M1), SEI-7S-O-β-D-glucuronide (M2), SEI-7S-S-glutathione (M3) and SEI-7R-S-glutathione (M4) on the basis of the molecular mass of the analytes, using ultra performance liquid chromatography/quadrupole-time-of-flight mass spectrometry and 1D and 2D NMR.

Conclusions

The results demonstrated that glucuronide and glutathione conjugation were the major pathways of SEI metabolism in vivo, and the configuration at the 7th-position could be inverted during glutathione conjugation.

Characterization of picroside II metabolites in rats by ultra-high-performance liquid chromatography combined with electrospray ionization quadrupole time-of-flight tandem mass spectrometry

Picroside II, a bioactive compound isolated from Picrorhiza scrophulariiflora Pennell, has been reported to have hepatoprotective, neuroprotective, and antioxidant effects. However, the detailed in vivo biotransformation of this compound has been rarely reported. This study aimed to investigate the metabolic profiles of picroside II in rats by using ultra-high-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry. Metabolite structures were elucidated based on accurate mass measurements of deprotonated molecules and their fragmentation patterns. Thirteen metabolites were structurally identified, and the detailed metabolic pathways were proposed. The findings revealed that after oral administration, picroside II mainly undergoes four metabolic pathways. In the first pathway, picroside II is deglycosylated to generate aglycone, which is isomerized to a dialdehyde-type intermediate. A series of metabolic reactions, including glucuronidation, subsequently occurs. In the second pathway, picroside II is subjected to ester bond hydrolysis to form vanillic acid, which is further subjected to sulfate conjugation, glycine conjugation, glucuronidation, and demethylation. In the third pathway, picroside II is directly conjugated with glucuronic acid to yield a predominant metabolite (M01) in plasma. In the fourth pathway, picroside II is directly conjugated with sulfate. These findings provide insights into the in vivo disposition of picroside II and are useful to understand the mechanism of effectiveness and toxicity of this compound as well as P. scrophulariiflora-related preparations.

Structure Elucidation of the Metabolites of 2', 3', 5'-Tri-O-Acetyl-N6-(3-Hydroxyphenyl) Adenosine in Rat Urine by HPLC-DAD, ESI-MS and Off-Line Microprobe NMR

2', 3', 5'-Tri-O-acetyl-N6-(3-hydroxyphenyl) adenosine (also known as WS070117) is a new adenosine analog that displays anti-hyperlipidemic activity both in vitro and in vivo experiments as shown in many preliminary studies. Due to its new structure, little is known about the metabolism of WS070117. Hence, the in vivo metabolites of WS070117 in rat urine following oral administration were investigated. Identification of the metabolites was conducted using the combination of high-performance liquid chromatography (HPLC) coupled with diode array detector (DAD), ion trap electrospray ionization-mass spectrometry (ESI-MS), and off-line microprobe nuclear magnetic resonance (NMR) measurements. Seven metabolites were obtained as pure compounds at the sub-milligram to milligram levels. Results of structure elucidation unambiguously revealed that the phase I metabolite, N6-(3-hydroxyphenyl) adenosine (M8), was a hydrolysate of WS070117 by hydrolysis on the three ester groups. N6-(3-hydr-oxyphenyl) adenine (M7), also one of the phase I metabolites, was the derivative of M8 by the loss of ribofuranose. In addition to two phase I metabolites, there were five phase II metabolites of WS070117 found in rat urine. 8-hydroxy-N6-(3-hydroxy-phenyl) adenosine (M6) was the product of M7 by hydrolysis at position 8. The other four were elucidated to be N6-(3-O-β-D-glucuronyphenyl) adenine (M2), N8-hydroxy-N6-(3-O-sulfophenyl) adenine (M3), N6-(3-O-β-D-glucuronyphenyl) adenosine (M4), and N6-(3-O- sulfophenyl) adenosine (M5). Phase II metabolic pathways were proven to consist of hydroxylation, glucuronidation and sulfation. This study provides new and valuable information on the metabolism of WS070117, and also demonstrates the HPLC/MS/off-line microprobe NMR approach as a robust means for rapid identification of metabolites.

Metabolic pathway monitoring of phenalinolactone biosynthesis from Streptomyces sp. Tü6071 by liquid chromatography/mass spectrometry coupling

RATIONALE

A rapid and precise analytical method for the investigation of natural products is required for pathway monitoring of the biosynthesis of secondary metabolites. Phenalinolactones, used in antibiotic research, are produced by Streptomyces sp. Tü6071. For the analysis of those compounds, prior to mass spectrometric analysis, an efficient separation technique is required.

METHODS

For the identification of phenalinolactones from liquid cultures of Streptomyces sp. Tü6071, a new method comprising the combination of solid-phase extraction (SPE) prior to liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) was established. MS/MS product ion scans were applied for phenalinolactone detection and structure elucidation, performed in negative mode and optimized for sensitivity and specificity. For the discovery of new intermediates, a MS/MS precursor ion scan was applied.

RESULTS

Analysis of the extracts revealed that the Oasis® MAX cartridge, containing a quaternary amine functionality, is the most efficient SPE material for purification of phenalinolactones, since it allowed sufficient enrichment and detection of intermediates from the biosynthetic pathway by LC/ESI-MS/MS. Using the precursor ion scan technique, two new secondary metabolites, PL IM1 with m/z 672.6 and PL IM2 with m/z 433.3, have been detected. The structures of the new intermediates are postulated and arranged into the biosynthetic pathway of phenalinolactones.

CONCLUSIONS

A precise analytical method was established for the identification of phenalinolactones by combining purification from Streptomyces using SPE prior to LC/ESI-MS/MS. By optimising LC/ESI-MS/MS settings, this method has been successfully applied for pathway monitoring of secondary metabolites. Application of a precursor ion scan allowed for the identification of unknown intermediates in biosynthetic pathways.

MALDI-TOF mass spectrometry, an efficient technique for in situ detection and characterization of actinomycins

An extensive study of actinomycins was performed using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS). Actinomycins represent a well-known family of peptidolactone chromopeptides with potent cytostatic and antibiotic properties. Using five well-characterized streptomycete strains, we introduced MALDI-TOF MS as an efficient technique for rapid in situ detection of actinomycins in surface extracts of cells picked from agar plates. By this procedure, actinomycin complexes can be investigated with high sensitivity and accuracy in a minimum of time. These studies were complemented by mass spectrometric investigation of actinomycins obtained from culture filtrate extracts and purified by high-performance liquid chromatography to detect yet unknown actinomycin species. By feeding experiments, C-demethyl-actinomycins from Streptomyces chrysomallus and Streptomyces parvulus as well as hemi-actinomycins from Streptomyces antibioticus lacking one of the two pentapeptide lactone rings were isolated and characterized as novel variants for structure-activity relationship studies. Structural characterization of the investigated actinomycins was performed by post source decay MALDI-TOF MS. The specific features of the fragmentation patterns of the protonated and cationized forms of selected actinomycins were investigated in detail.

Identification of 20(S)-protopanaxatriol metabolites in rats by ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry and nuclear magnetic resonance spectroscopy

20(S)-Protopanaxatriol (PPT), one of the aglycones of ginsenosides, has been shown to exert cardioprotective effects against myocardial ischemic injury. However, studies on PPT metabolism have rarely been reported. This study is the first to investigate the in vivo metabolism of PPT following oral administration by ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UPLC-Q/TOF-MS) and nuclear magnetic resonance (NMR) spectroscopy. The structures of the metabolites were identified based on the characteristics of their MS data, MS(2) data, and chromatographic retention times. A total of 22 metabolites, including 17 phase I and 5 phase II metabolites, were found and tentatively identified by comparing their mass spectrometry profiles with those of PPT. Two new monooxygenation metabolites, (20S,24S)-epoxy-dammarane-3,6,12,25-tetraol and (20S,24R)-epoxy-dammarane-3,6,12,25-tetraol, were chemicallly synthesized and unambiguously characterized according to the NMR spectroscopic data. The metabolic pathways of PPT were proposed accordingly for the first time. Results revealed that oxidation of (1) double bonds at Δ((24,25)) to form 24,25-epoxides, followed by rearrangement to yield 20,24-oxide forms; and (2) vinyl-methyl at C-26/27 to form corresponding carboxylic acid were the predominant metabolic pathways. Phase II metabolic pathways were proven for the first time to consist of glucuronidation and cysteine conjugation. This study provides valuable and new information on the metabolism of PPT, which is indispensable for understanding the safety and efficacy of PPT, as well as its corresponding ginsenosides.

Critical evaluation of screening techniques for emerging environmental contaminants based on accurate mass measurements with time-of-flight mass spectrometry

Emerging contaminants from wastewater effluent samples were analysed, using posttarget and nontarget analysis techniques. The samples were analysed with an ultra performance liquid chromatograph-time-of-flight mass spectrometer (UPLC-TOF-MS), and the resulting data were processed with commercial deconvolution software. The method works well for posttarget analysis with prior information about the retention times of the compounds of interest. With positive polarity, 63 of 66 compounds and with negative polarity, 18 of 20 compounds were correctly identified in a spiked sample, while two compounds of a total of 88 fell out of the mass range. Furthermore, a four-stage process for identification was developed for the posttarget analysis lacking the retention time data. In the process, the number of candidate compounds was reduced by using the accurate mass of selected compounds in two steps (stages 1 and 2), structure-property relationships (stage 3) and isotope patterns of the analytes (stage 4). The process developed was validated by analysing wastewater samples spiked with 88 compounds. This procedure can be used to gain a preliminary indication of the presence of certain analytes in the samples. Nontarget analysis was tested by applying a theoretical mass spectra library for a wastewater sample spiked with six pharmaceuticals. The results showed a high number of false identifications. In addition, manual processing of the data was considered laborious and ineffective. Finally, the posttarget analysis was applied to a real wastewater sample. The analysis revealed the presence of six compounds that were afterwards confirmed with standard compounds as being correct. Three psycholeptics (nordiazepam, oxazepam and temazepam) could be tentatively identified, using the identification process developed. Posttarget analysis with UPLC-TOF-MS proved to be a promising method for analysing wastewater samples, while we concluded that the software for nontarget analysis will need improvement before it can be used in environmental analytical work with LC-TOF-MS systems.

Identification of metabolites of geniposide in rat urine using ultra-performance liquid chromatography combined with electrospray ionization quadrupole time-of-flight tandem mass spectrometry

Geniposide, an iridoid glycoside, is an important and characteristic compound in the fruits of Gardenia jasminoides Ellis, a commonly used medicinal herb in Chinese traditional and folk medicine for the treatment of inflammation and jaundice. However, few studies have been carried out on the metabolism of geniposide. In this study, we have established a rapid and sensitive method using ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UPLC/ESI-QTOF-MS) for analysis of the metabolic profile of geniposide in rat urine after oral administration. A total of ten metabolites were detected and identified by comparing their fragmentation patterns with that of geniposide using Metabolynx™ and MassFragment™ software tools. The results revealed that the principal metabolism pathways of geniposide in rat occurred after deglycosylation of the irdoid glycoside take place and this is followed by glucuronidation and the pyran-ring cleavages. The major metabolite, the glucuronic acid conjugate of genipin as observed in vivo, was further confirmed by the in vitro enzymatic study. The results of this work have demonstrated the feasibility of the UPLC/ESI-QTOF-MS approach for rapid and reliable characterization of metabolites from iridoid compounds.