Phase I Metabolism of Pterostilbene, a Dietary Resveratrol Derivative: Metabolite Identification, Species Differences, Isozyme Contribution, and Further Bioactivation

Advances in antitumor effects of pterostilbene and its derivatives

Pterostilbene (PT) is a naturally occurring small molecule stilbenoid that has garnered significant attention due to its potential therapeutic effects in tumor diseases. In this review, we conducted a comprehensive analysis of the antitumor effects of PT and its derivatives on various cancer types, including colon, breast, liver, lung, and pancreatic cancers in recent 20 years. We have succinctly summarized the PT derivatives that exhibit superior anti-tumor efficacy compared to PT. Additionally, we reviewed the potential structure-activity relationship (SAR) rules and clinical application methods to establish a foundation for chemical modification and clinical utilization of stilbene compounds.

Pterostilbene in the treatment of inflammatory and oncological diseases

Pterostilbene (PTS), a naturally occurring analog of resveratrol (RSV), has garnered significant attention due to its potential therapeutic effects in treating inflammatory and oncological diseases. This comprehensive review elucidates the pharmacological properties, mechanisms of action, and therapeutic potential of PTS. Various studies indicate that PTS exhibits anti-inflammatory, antioxidant, and antitumour properties, potentially making it a promising candidate for clinical applications. Its influence on regulatory pathways like NF-κB and PI3K/Akt underscores its diverse strategies in addressing diseases. Additionally, PTS showcases a favorable pharmacokinetic profile with better oral bioavailability compared to other stilbenoids, thus enhancing its therapeutic potential. Given these findings, there is an increased interest in incorporating PTS into treatment regimens for inflammatory and cancer-related conditions. However, more extensive clinical trials are imperative to establish its safety and efficacy in diverse patient populations.

Resveratrol Derivatives Inhibit Transthyretin Fibrillization: Structural Insights into the Interactions between Resveratrol Derivatives and Transthyretin

Hereditary ATTR amyloidosis is a disease caused by the deposition of amyloid fibrils formed by mutated transthyretin (TTR), a protein that binds to thyroid hormone in the serum, in the organs. The development of a small molecule that binds to and stabilizes TTR is a promising strategy for the treatment of ATTR amyloidosis. In the present study, we demonstrated that the resveratrol derivatives including pterostilbene available as a dietary supplement inhibit the fibrillization of V30M-TTR to the same extent as the approved drug tafamidis. Furthermore, based on a thermodynamic and X-ray crystallographic analysis, the binding of the resveratrol derivative to TTR was shown to be enthalpy-driven, with the binding enthalpy being acquired by hydrogen bonding to S117. Moreover, direct observation of hydrogen atoms by neutron crystallography provided details of the hydrogen bond network by S117 and emphasized the importance of the CH···π interaction by L110 in the ligand binding.

Overexpression of Glutathione S-Transferases in Human Diseases: Drug Targets and Therapeutic Implications

Glutathione S-transferases (GSTs) are a major class of phase II metabolic enzymes. Besides their essential role in detoxification, GSTs also exert diverse biological activities in the occurrence and development of various diseases. In the past few decades, much research interest has been paid to exploring the mechanisms of GST overexpression in tumor drug resistance. Correspondingly, many GST inhibitors have been developed and applied, solely or in combination with chemotherapeutic drugs, for the treatment of multi-drug resistant tumors. Moreover, novel roles of GSTs in other diseases, such as pulmonary fibrosis and neurodegenerative diseases, have been recognized in recent years, although the exact regulatory mechanisms remain to be elucidated. This review, firstly summarizes the roles of GSTs and their overexpression in the above-mentioned diseases with emphasis on the modulation of cell signaling pathways and protein functions. Secondly, specific GST inhibitors currently in pre-clinical development and in clinical stages are inventoried. Lastly, applications of GST inhibitors in targeting cell signaling pathways and intracellular biological processes are discussed, and the potential for disease treatment is prospected. Taken together, this review is expected to provide new insights into the interconnection between GST overexpression and human diseases, which may assist future drug discovery targeting GSTs.

Synthesis, In Vitro, and In Vivo Investigations of Pterostilbene-Tethered Analogues as Anti-Breast Cancer Candidates

Pterostilbene has been found to be an active scaffold with anti-breast cancer (BC) action. In this study, fourteen pterostilbene-tethered analogues (2A-2N) were prepared and screened in vitro against MDA-MB-231 and MCF-7 cells. Meanwhile, their structures were characterized using ¹H-NMR, ¹³C-NMR, and HRMS (ESI) spectroscopy techniques. Among them, analogue 2L displayed the most potent anti-proliferation effect on MDA-MB-231 (IC₅₀ = 10.39 μM) and MCF-7 cells (IC₅₀ = 11.73 μM). Furthermore, the meaningful structure-activity relationships suggested that the introduction of a saturated six-membered nitrogen heterocyclic ring into the side chain favored anti-BC capacity. Biological observations indicated that 2L could cause the typical morphological changes in apoptosis, namely an increase in reactive oxygen species level and a loss of mitochondrial membrane potential in BC cells. Importantly, 2L could induce mitochondrial-mediated apoptosis by regulating the expression of caspase-related proteins. Consistent with the results of our in vitro study, 2L apparently inhibited tumor growth in MDA-MB-231 xenograft mice without obvious toxicity. These findings revealed that 2L is expected to be a promising anti-BC lead compound that merits further investigations.

Mechanistic Study of Icaritin-Induced Inactivation of Cytochrome P450 2C9

Icaritin (ICT) is a prenylflavonoid derivative that has been approved by National Medical Products Administration for the treatment of hepatocellular carcinoma. This study aims to evaluate the potential inhibitory effect of ICT against cytochrome P450 (CYP) enzymes and to elucidate the inactivation mechanisms. Results showed that ICT inactivated CYP2C9 in a time-, concentration-, and NADPH-dependent manner with Ki = 1.896 μM, Kinact = 0.02298 minutes-1, and Kinact/Ki = 12 minutes-1 mM-1, whereas the activities of other CYP isozymes was minimally affected. Additionally, the presence of CYP2C9 competitive inhibitor, sulfaphenazole, superoxide dismutase/catalase system, and GSH all protected CYP2C9 from ICT-induced activity loss. Moreover, the activity loss was neither recovered by washing the ICT-CYP2C9 preincubation mixture nor the addition of potassium ferricyanide. These results, collectively, implied the underlying inactivation mechanism involved the covalent binding of ICT to the apoprotein and/or the prosthetic heme of CYP2C9. Furthermore, an ICT-quinone methide (QM)-derived GSH adduct was identified, and human glutathione S-transferases (GST) isozymes GSTA1-1, GSTM1-1, and GSTP1-1 were shown to be substantially involved in the detoxification of ICT-QM. Interestingly, our systematic molecular modeling work predicted that ICT-QM was covalently bound to C216, a cysteine residue located in the F-G loop downstream of substrate recognition site (SRS) 2 in CYP2C9. The sequential molecular dynamics simulation confirmed the binding to C216 induced a conformational change in the active catalytic center of CYP2C9. Lastly, the potential risks of clinical drug-drug interactions triggered by ICT as a perpetrator were extrapolated. In summary, this work confirmed that ICT was an inactivator of CYP2C9. SIGNIFICANCE STATEMENT: This study is the first to report the time-dependent inhibition of CYP2C9 by icaritin (ICT) and the intrinsic molecular mechanism behind it. Experimental data indicated that the inactivation was via irreversible covalent binding of ICT-quinone methide to CYP2C9, while molecular modeling analysis provided additional evidence by predicting C216 as the key binding site which influenced the structural confirmation of CYP2C9's catalytic center. These findings suggest the potential of drug-drug interactions when ICT is co-administered with CYP2C9 substrates clinically.

In Vivo Metabolite Profiling of DMU-212 in ApcMin/+ Mice Using UHPLC-Q/Orbitrap/LTQ MS

3,4,5,4'-Trans-tetramethoxystilbene (Synonyms: DMU-212) is a resveratrol analogue with stronger antiproliferative activity and more bioavailability. However, the metabolite characterization of this component remains insufficient. An efficient strategy was proposed for the comprehensive in vivo metabolite profiling of DMU-212 after oral administration in ApcMin/+ mice based on the effectiveness of the medicine. Ultra-high performance liquid chromatography-quadrupole/orbitrap/linear ion trap mass spectrometry (UHPLC-Q/Orbitrap/LTQ MS) in the AcquireXTM intelligent data acquisition mode, combining the exact mass and structural information, was established for the profiling and identification of the metabolites of DMU-212 in vivo, and the possible metabolic pathways were subsequently proposed after the oral dose of 240mg/kg for 3 weeks in the colorectal adenoma (CRA) spontaneous model ApcMin/+ mice. A total of 63 metabolites of DMU-212 were tentatively identified, including 48, 48, 34 and 28 metabolites in the ApcMin/+ mice's intestinal contents, liver, serum, and colorectal tissues, respectively. The metabolic pathways, including demethylation, oxidation, desaturation, methylation, acetylation, glucuronide and cysteine conjugation were involved in the metabolism. Additionally, further verification of the representative active metabolites was employed using molecular docking analysis. This study provides important information for the further investigation of the active constituents of DMU-212 and its action mechanisms for CRA prevention.

The Research Progress of Extraction, Purification and Analysis Methods of Phenolic Compounds from Blueberry: A Comprehensive Review

Blueberry is the source of a variety of bioactive substances, including phenolic compounds, such as anthocyanins, pterostilbene, phenolic acids, etc. Several studies have revealed that polyphenols in blueberry have important bioactivities in maintaining health, such as antioxidant and anti-tumor activities, immune regulation, the prevention of chronic diseases, etc. Therefore, these phenolic compounds in blueberries have been widely used in the field of healthcare, and the extraction, isolation, and purification of phenolic compounds are the prerequisites for their utilization. It is imperative to systematically review the research progress and prospects of phenolic compounds present in blueberries. Herein, the latest progress in the extraction, purification, and analysis of phenolic compounds from blueberries is reviewed, which can in turn provide a foundation for further research and usage of blueberries.