Drug Metabolism and Bioanalysis Letters Formerly: Drug Metabolism Letters - Volume 15, Issue 1, 2022

Background: Herbal products are derived from different natural sources, mainly used as a source of food material and medicine in the health sectors since ancient times. Herbal products have gained popularity in modern medicine due to their beneficial health properties and pharmacological activities. Flavonoids are an important class of secondary metabolites found to be present in medicinal plants and their derived products. Flavonoids have been known for their anti-allergic, anti-bacterial, anti-diabetic, anti-inflammatory, anti-viral, anti-proliferative, anti-mutagenic, antithrombotic, anti-carcinogenic, anti-oxidant and hepatoprotective activities in the medicine. Nicotiflorin is a flavonoidal class phytochemical, found in medicinal plants, including Traditional Chinese medicine. Methods: Scientific data on the medicinal importance and pharmacological activities of nicotiflorin have been collected and analyzed in the present work in order to know the therapeutic importance of nicotiflorin in medicine. Scientific data have been collected from Google, Google Scholar, Science Direct, PubMed and Scopus and analyzed in the present work. Analytical techniques data of separation, isolation and identification of nicotiflorin have also been collected and presented in the current work. Further biological importance of flavonoidal class phytochemicals was also discussed in the present work to understand the biological importance of nicotiflorin in medicine as it belongs to the flavonoid class. Results: Scientific data analysis revealed the therapeutic importance and pharmacological activities of nicotiflorin. Nicotiflorin has significant biological potential against coronavirus, ischemia, renal impairment, hepatic complication, memory dysfunction and myocardial infarction. The biological potential of nicotiflorin against α-glucosidase and α-amylase enzymes, multiple myeloma cells and insulin secretion has also been discussed in the present work. Analytical data revealed the significance of modern analytical tools in medicine for the isolation, separation and quantification of nicotiflorin. Conclusion: Scientific data analysis of different research works revealed the biological importance and therapeutic potential of nicotiflorin in medicine.

Background and Objective: Compound X is a drug candidate for the treatment of neurodegenerative diseases. Its brain distribution was evaluated as part of the lead identification and optimization activities undertaken in early drug discovery. Methods: The brain distribution of compound X was studied in genetic transporter knockout rodent models, in vivo models with a chemical inhibitor, and in vitro transporter cell systems. Results: Compound X was found to be a substrate for human Breast Cancer-Resistance Protein (BCRP) in vitro (efflux ratio 8.1) and rodent Bcrp in vivo (Kp, uuKO/Kp, uuWT = 0.15/0.057 = 2.7, p< 0.05) but not a substrate for human P-glycoprotein (P-gp) in vitro (efflux ratio 1.0) nor rodent P-gp in vivo (Kp, uuKO/Kp, uuWT = 0.056/ 0.051 = 1.1, p> 0.05). When both transporters were knocked out in vivo, Kp, uu increased to 0.51±0.02. A similar pattern observed across compounds with related chemistry corroborating the structure-activity relationship. Conclusion: While in vitro assays showed compound X to be a substrate for human BCRP and not P-gp, in vivo studies indicated a synergistic effect between rodent efflux transporters. However, this only accounted for ~50% of restricted BBB-transport, suggesting involvement of other efflux transporters. Considering Kp, uu as a key criterion for assessing the technical quality of CNS candidates before progression into clinical development, it is important to identify relevant screening assays for a better understanding of low Kp, uu and brain distribution in pre-clinical models for translation to humans.

Background: In this study, we focused primarily on three anti-malarial drugs, namely chloroquine, mefloquine, and proguanil, and these were tested against two malarial targets DHFR and GST. The species Plasmodium falciparum, Plasmodium malariae, Plasmodium ovale, Plasmodium vivax were used for the study. Objective: The purpose of this study was to determine the sequence and structural similarity of the proteins DHFR and GST among four Plasmodium species as well as to discover the in silico interactions with the aforementioned drug candidates. Methods: Bioinformatics databases, such as PDB, UniProt, DrugBank, PubChem, and tools, and software like Phyre 2.0, Clustal O (1.2.4), AutoDock 4, AutoDock Vina, and Discovery Studio Visualizer were used to determine the evolutionary significance of the Plasmodium species. Result: The variations showed a difference in the binding patterns of drugs with our target proteins. Our finding reveals the Plasmodium spp divergence or convergence as well as the structural and sequential similarity or dissimilarity features. Conclusion: Our result suggests that due to the deviation in the sequences and structures, variations in protein-drug binding patterns have emerged.

Objective: The study aims to explore the human in vivo metabolism of SEP-227900 (4H-furo[3, 2-b] pyrrole-carboxylic acid, m.w 151.03), a D-amino-acid oxidase (DAAO) inhibitor, by using plasma and urine samples from first-in-human study. Methods: The human plasma and urine samples were from a single dose cohort that consisted of 9 healthy male volunteers each received an 80- mg dose of SEP-227900 orally. The pooled pre-dose urine and the pooled 0-24 h urine sample were created across 9 subjects by equal volume. Plasma samples were pooled by equal volume across 9 subjects to obtain 0-12 h plasma for metabolite searching, and also pooled by timepoints across 9 subjects to obtain 0.5, 5, and 12-h plasma for semi-quantitation. The plasma was de-proteinized by acetonitrile (1:3 v/v plasma-acetonitrile), then the supernatant was dried down, reconstituted, and injected for LC-HRMS/UV analysis. The urine sample was just simply centrifuged before analysis. LC-HRMS/UV was utilized to search predictable and unknown metabolites and estimate their relative abundances. Accurate mass measurement by Orbitrap-MS and MS/MS was used for metabolite identification. Chromatographic separation was achieved on a MACMOD AQ C8 column (250 × 4.6 mm, 5-μm) with a gradient mobile phase (A: 10 mM NH4Ac; B: acetonitrile; flowrate: 0.700 ml/min) for a total run-time of 65 min. The definite position in the molecule for the glucuronidation metabolism was characterized by the detected migration phenomenon, methylation with diazomethane (CH2N2), and NMR. Results: Unchanged parent drug and four metabolite peaks were detected in humans: M1 was a mono-oxidative metabolite of SEP-227900; M2 was a glucuronide conjugate of SEP-227900; M3 was a glycine conjugate of SEP-227900; M4 was a glycine conjugate of M1. The specific position of the oxidation in M1 solely based on the mass spectral (MS and MS/MS) data was not identified. However, for the major metabolite M2, the acyl glucuronidation was unambiguously determined through multiple pieces of experimental evidence such as the observation of a migration pattern, mono-methylation by diazomethane, and NMR measurement. This determination is of significance related to the safety evaluation of investigational new drug development. The glycine conjugate of SEP-227900, i.e., M3, was found to be the most abundant metabolite in human urine (approximately 3-fold higher level than the glucuronide level). All together (mainly glycine-conjugate and glucuronide), it resulted in greater than 80% of the dosed amount in urine excretion (a separate measurement showed 23% of the dosed amount in urine excretion as the glucuronide). Conclusion: Four metabolites were found in humans: SEP-227900-glycine conjugate, SEP- 227900-glucuronide, mono-oxidative metabolite, and its consequent glycine conjugate. The glucuronide metabolite was identified as acyl glucuronide. Greater than 80% of the dosed amount of SEP-227900 was excreted in the urine, mainly in the forms of glycine- and glucuronide- conjugates.

Background: Genetic polymorphism of cytochrome P450 (CYP) contributes to variability in drug metabolism, clearance, and response. This study aimed to investigate the functional and molecular basis for altered ligand binding and catalysis in CYP2D6*14A and CYP2D6*14B, two unique alleles common in the Asian population. Methods: CYP proteins expressed in Escherichia coli were studied using the substrate 3-cyano-7- ethoxycoumarin (CEC) and inhibitor probes (quinidine, fluoxetine, paroxetine, terbinafine) in the enzyme assay. Computer modelling was additionally used to create three-dimensional structures of the CYP2D6*14 variants. Results: Kinetics data indicated significantly reduced intrinsic clearance in CYP2D6*14 variants, suggesting that P34S, G169R, R296C, and S486T substitutions worked cooperatively to alter the conformation of the active site that negatively impacted the deethylase activity of CYP2D6. For the inhibition studies, IC50 values decreased in quinidine, paroxetine, and terbinafine but increased in fluoxetine, suggesting a varied ligand-specific susceptibility to inhibition. Molecular docking further demonstrated the role of P34S and R296C in altering access channel dimensions, thereby affecting ligand access and binding and subsequently resulting in varied inhibition potencies. Conclusion: In summary, the differential selectivity of CYP2D6*14 variants for the ligands (substrate and inhibitor) was governed by the alteration of the active site and access channel architecture induced by the natural mutations found in the alleles.

Aim: The main aim of the current study was to obtain forward dosimetry assessments of pyrrolizidine alkaloid senkirkine plasma and liver concentrations by setting up a human physiologically based pharmacokinetic (PBPK) model based on the limited information available. Background: The risks associated with plant-derived pyrrolizidine alkaloids as natural toxins have been assessed. Objective: The pyrrolizidine alkaloid senkirkine was investigated because it was analyzed in a European transcriptomics study of natural hepatotoxins and in a study of the alkaloidal constituents of traditional Japanese food plants Petasites japonicus. The in silico human plasma and liver concentrations of senkirkine were modeled using doses reported for acute-term toxicity in humans. Methods: Using a simplified PBPK model established using rat pharmacokinetic data, forward dosimetry was conducted. Since in vitro rat and human intrinsic hepatic clearances were similar; an allometric scaling approach was applied to rat parameters to create a human PBPK model. Results: After oral administration of 1.0 mg/kg in rats in vivo, water-soluble senkirkine was absorbed and cleared from plasma to two orders of magnitude below the maximum concentration in 8 h. Human in silico senkirkine plasma concentration curves were generated after virtual daily oral administrations of 3.0 mg/kg senkirkine (the dose involved in an acute fatal hepatotoxicity case). A high concentration of senkirkine in the culture medium caused in vitro hepatotoxicity as evidenced by lactate dehydrogenase leakage from human hepatocyte-like HepaRG cells. Conclusion: Higher virtual concentrations of senkirkine in human liver and plasma than those in rat plasma were estimated using the current rat and human PBPK models. Current simulations suggest that if P. japonicus (a water-soluble pyrrolizidine alkaloid-producing plant) is ingested daily as food, hepatotoxic senkirkine could be continuously present in human plasma and liver.