Bioactivation of the phytoestrogen diosmetin by CYP1 cytochromes P450

Natural products for the treatment of age-related macular degeneration

BACKGROUND

Age-related macular degeneration (AMD) is a chronic retinal disease that significantly influences the vision of the elderly.

PURPOSE

There is no effective treatment and prevention method. The pathogenic process behind AMD is complex, including oxidative stress, inflammation, and neovascularization. It has been demonstrated that several natural products can be used to manage AMD, but systematic summaries are lacking.

STUDY DESIGN AND METHODS

PubMed, Web of Science, and ClinicalTrials.gov were searched using the keywords "Biological Products" AND "Macular Degeneration" for studies published within the last decade until May 2023 to summarize the latest findings on the prevention and treatment of age-related macular degeneration through the herbal medicines and functional foods.

RESULTS

The eligible studies were screened, and the relevant information about the therapeutic action and mechanism of natural products used to treat AMD was extracted. Our findings demonstrate that natural substances, including retinol, phenols, and other natural products, prevent the development of new blood vessels and protect the retina from oxidative stress in cells and animal models. However, they have barely been examined in clinical studies.

CONCLUSION

Natural products could be highly prospective candidate drugs used to treat AMD, and further preclinical and clinical research is required to validate it to control the disease.

Diosmetin: A dietary flavone as modulator of signaling pathways in cancer progression

Flavonoids, constituting the most extensive category of polyphenols, founds in a variety of plants and comprise over 9000 compounds. Diosmetin, O-methylated flavone (3',5,7-trihydroxy-4'-methoxyflavone) of flavonoid aglycone diosmin have witnessed a significant surge in recent years. Many studies showed that flavonoids induced cytotoxicity in different organ specific cancer types. Thus, current review evaluates the anticancer potential of diosmetin and shed light on its mechanism of action such as cell cycle regulation, apoptosis via both intrinsic and extrinsic pathway, autophagy and tumour progression and metastasis. It also provides comprehensive analysis of different cancer targets and their role in breast, colon, hepatic, gliomas, leukemia, lung, prostate and skin cancer. Combination studies of diosmetin to improve drug sensitivity and reduce toxicity towards normal cells has been also discussed. Besides, in vitro studies, present review also discuss the anticancer potential of diosmetin on xenograft mice model. Different natural sources of diosmetin, limitations, pharmacokinetic analysis and toxicity study also summarized in current review. The emphasis on enhancing solubility and permeability for clinical utility has been thoroughly highlighted with particular attention given to the utilization of nano formulations to overcome existing barriers. At last, in-depth analysis of current challenges and a forward-looking perspective deliberated to address the existing gaps and position it as a promising lead compound for clinical applications in cancer treatment. This discussion is boosted by diosmetin's potential anticancer properties on different cancers, makes valuable candidates in the ongoing quest for effective therapeutic interventions against cancer.

CYP1-Activation and Anticancer Properties of Synthetic Methoxylated Resveratrol Analogues

Naturally occurring stilbenoids, such as the (E)-stilbenoid resveratrol and the (Z)-stilbenoid combretastatin A4, have been considered as promising lead compounds for the development of anticancer drugs. The antitumour properties of stilbenoids are known to be modulated by cytochrome P450 enzymes CYP1A1 and CYP1B1, which contribute to extrahepatic phase I xenobiotic and drug metabolism. Thirty-four methyl ether analogues of resveratrol were synthesised, and their anticancer properties were assessed, using the MTT cell proliferation assay on a panel of human breast cell lines. Breast tumour cell lines that express CYP1 were significantly more strongly affected by the resveratrol analogues than the cell lines that did not have CYP1 activity. Metabolism studies using isolated CYP1 enzymes provided further evidence that (E)-stilbenoids can be substrates for these enzymes. Structures of metabolic products were confirmed by comparison with synthetic standards and LC-MS co-elution studies. The most promising stilbenoid was (E)-4,3',4',5'-tetramethoxystilbene (DMU212). The compound itself showed low to moderate cytotoxicity, but upon CYP1-catalysed dealkylation, some highly cytotoxic metabolites were formed. Thus, DMU212 selectively affects proliferation of cells that express CYP1 enzymes.

3D-QSAR assisted identification of selective CYP1B1 inhibitors: an effective bioisosteric replacement/molecular docking/electrostatic complementarity analysis

Cytochrome P450-1B1 is a majorly overexpressed drug-metabolizing enzyme in tumors and is responsible for inactivation and subsequent resistance to a variety of anti-cancer drugs, i.e., docetaxel, tamoxifen, and cisplatin. In the present study, a 3D quantitative structure-activity relationship (3D-QSAR) model has been constructed for the identification, design, and optimization of novel CYP1B1 inhibitors. The model has been built using a set of 148 selective CYP1B1 inhibitors. The developed model was evaluated based on certain statistical parameters including q2 and r2 which showed the acceptable predictive and descriptive capability of the generated model. The developed 3D-QSAR model assisted in understanding the key molecular fields which were firmly related to the selective CYP1B1 inhibition. A theoretic approach for the generation of new lead compounds with optimized CYP1B1 receptor affinity has been performed utilizing bioisosteric replacement analysis. These generated molecules were subjected to a developed 3D-QSAR model to predict the inhibitory activity potentials. Furthermore, these compounds were scrutinized through the activity atlas model, molecular docking, electrostatic complementarity, molecular dynamics, and waterswap analysis. The final hits might act as selective CYP1B1 inhibitors which could address the issue of resistance. This 3D-QSAR includes several chemically diverse selective CYP1B1 receptor ligands and well accounts for the individual ligand's inhibition affinities. These features of the developed 3D-QSAR model will ensure future prospective applications of the model to speed up the identification of new potent and selective CYP1B1 receptor ligands.

A Cross-Talk about Radioresistance in Lung Cancer-How to Improve Radiosensitivity According to Chinese Medicine and Medicaments That Commonly Occur in Pharmacies

Lung cancer is one of the most common cancers in the population and is characterized by non-specific symptoms that delay the diagnosis and reduce the effectiveness of oncological treatment. Due to the difficult placement of the tumor, one of the main methods of lung cancer treatment is radiotherapy, which damages the DNA of cancer cells, inducing their apoptosis. However, resistance to ionizing radiation may develop during radiotherapy cycles, leading to an increase in the number of DNA points of control that protect cells from apoptosis. Cancer stem cells are essential for radioresistance, and due to their ability to undergo epithelial-mesenchymal transition, they modify the phenotype, bypassing the genotoxic effect of radiotherapy. It is therefore necessary to search for new methods that could improve the cytotoxic effect of cells through new mechanisms of action. Chinese medicine, with several thousand years of tradition, offers a wide range of possibilities in the search for compounds that could be used in conventional medicine. This review introduces the potential candidates that may present a radiosensitizing effect on lung cancer cells, breaking their radioresistance. Additionally, it includes candidates taken from conventional medicine-drugs commonly available in pharmacies, which may also be significant candidates.

Crosstalk between xanthine oxidase (XO) inhibiting and cancer chemotherapeutic properties of comestible flavonoids- a comprehensive update

Gout is an inflammatory disease caused by metabolic disorder or genetic inheritance. People throughout the world are strongly dependent on ethnomedicine for the treatment of gout and some receive satisfactory curative treatment. The natural remedies as well as established drugs derived from natural sources or synthetically made exert their action by mechanisms that are closely associated with anticancer treatment mechanisms regarding inhibition of xanthine oxidase, feedback inhibition of de novo purine synthesis, depolymerization and disappearance of microtubule, inhibition of NF-ĸB activation, induction of TRAIL, promotion of apoptosis, and caspase activation and proteasome inhibition. Some anti-gout and anticancer novel compounds interact with same receptors for their action, e.g., colchicine and colchicine analogues. Dietary flavonoids, i.e., chrysin, kaempferol, quercetin, fisetin, pelargonidin, apigenin, luteolin, myricetin, isorhamnetin, phloretinetc etc. have comparable IC₅₀ values with established anti-gout drug and effective against both cancer and gout. Moreover, a noticeable number of newer anticancer compounds have already been isolated from plants that have been using by local traditional healers and herbal practitioners to treat gout. Therefore, the anti-gout plants might have greater potentiality to become selective candidates for screening of newer anticancer leads.

Anti-Inflammatory and Chondroprotective Effects Induced by Phenolic Compounds from Onion Waste Extracts in ATDC-5 Chondrogenic Cell Line

Osteoarthritis is a prevalent degenerative condition that is closely related to the destruction and inflammation of cartilage. The high prevalence of this pathology exhorts researchers to search for novel therapeutic approaches. Vegetable-fruit wastes have emerged as a promising origin of anti-inflammatory and antioxidant compounds that, in some cases, may also exert chondroprotective effects. This study aims to decipher the potential of onion waste products in the inhibition of molecular events involved in osteoarthritis. Onion extracts showed a high content of phenolic compounds and antioxidant properties. Cytocompatibility was demonstrated in the chondrogenic cell line ATDC-5, exerting viability percentages higher than 90% and a slight increase in the S phase cycle cell. The induction of inflammation mediated by the lipopolysaccharide and onion extracts' treatment substantially inhibited molecular markers related to inflammation and cartilage degradation, highlighting the promising application of onion extracts in biomedical approaches. The in silico analyses suggested that the results could be attributed to protocatechuic, ellagic, and vanillic acids' greater cell membrane permeability. Our work provides distinctive information about the possible application of waste onion extracts as functional components with anti-inflammatory and chondroprotective characteristics in osteoarthritis.

Investigation into the in vivo mechanism of diosmetin in patients with breast cancer and COVID-19 using bioinformatics

Patients with breast cancer are prone to SARS-CoV-2 infection [the causative virus of coronavirus disease (COVID-19)] due to their lack of immunity. In the current study, we examined the mechanism of action of Diosmetin, a flavonoid with anti-inflammatory properties, in patients with BRCA infected with SARS-CoV-2.We used bioinformatics technology to analyze the binding ability, biological function, and other biological characteristics of Diosmetinin vivo and examine the core target and potential mechanism of action of Diosmetin in patients with patients with breast cancer infected with SARS-CoV-2. A prognostic model of SARS-COV-2–infected breast cancer patients was constructed, and the core genes were screened out, revealing the correlation between these core genes and clinicopathological characteristics, survival rate, and high-risk and low-risk populations. The docking results revealed that Diosmetin binds well to the core genes of patients with breast cancer with COVID-19. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses suggested that Diosmetin inhibited inflammation, enhanced immune function, and regulated the cellular microenvironment in patients with BRCA/COVID-19. For the first time, we reveal the molecular functions and potential targets of Diosmetin in patients with breast cancer infected with SARS-CoV-2, improving the reliability of the new drug and laying the foundation for further research and development.

EPA Modulates KLK Genes via miR-378: A Potential Therapy in Prostate Cancer

It is known that miRNA-378a-3p (miR-378) could be induced by eicosapentaenoic acid (EPA), an omega-3 fatty acid. Herein, we first demonstrated how miR-378 exerts anti-prostate cancer (PCa) actions by influencing multiple target genes, including KLK2, KLK4, KLK6, and KLK14, which are implicated in PCa development, cell proliferation, and cell survival. Furthermore, these genes also correlate with androgen and mTOR signaling transduction, and are considered pivotal pathways for the onset and progression of PCa. In total, four PCa cell lines and eight pairing tissues (tumor vs. normal) from clinical PCa patients were included in the current study. The results showed high significance after EPA induced tumor cells containing higher expression levels of miR-378, and led the PCa cells having low cell viabilities, and they progressed to apoptosis when compared with normal prostate cells (p < 0.001). The findings indicated that EPA might become a potential therapy for PCa, especially because it is derived from the components of natural fish oil; it may prove to be a great help for solving the problem of castration-resistant prostate cancer (CRPC).

Diosmetin inhibits cell growth and proliferation by regulating the cell cycle and lipid metabolism pathway in hepatocellular carcinoma

Diosmetin (DSM), a newly discovered natural flavonoid, found in citrus plants and olive leaves, has been reported to inhibit the progression of cancer when used as a food supplement. This study aimed to investigate DSM's anti-hepatocellular carcinoma (HCC) properties and possible molecular mechanisms. Hep3B and HCCLM3 cells were selected to evaluate the anti-HCC properties of DSM in vitro. RNA sequencing (RNA-seq) was used to identify the possible molecular targets and pathways. Gas chromatography-mass spectrometry (GC-MS) was used to evaluate the effect of DSM treatment on the primary metabolites of HCCLM3 cells. Tumor xenograft was performed in nude mice to examine the anti-HCC properties of DSM in vivo. The results showed that DSM inhibited the proliferation and migration of HCC cells in vitro in a dose-dependent manner. RNA-seq identified 4459 differentially expressed genes (DEGs) that were highly enriched in the cell cycle pathway. In addition, DSM regulated cell growth by arresting the cell cycle in the G1 phase by decreasing the expression of BCL2, CDK1, and CCND1. Furthermore, metabolomics analysis revealed that DSM interfered with the lipid metabolism pathway of HCC cells by significantly inhibiting the synthesis of metabolites, such as acetic acid, decanoic acid, glycerol, and L-proline. Subcutaneous tumor formation experiments revealed that DSM significantly reduced the tumor volume and weight when compared to the control. Immunohistochemical analysis further revealed that DSM treatment significantly decreased the expression of the proliferative marker KI67. Our findings demonstrated that DSM exhibited antitumor effects on HCC cells by inhibiting cell proliferation via cell cycle arrest and interfering with lipid metabolism.

Pharmacology of Diosmin, a Citrus Flavone Glycoside: An Updated Review

Flavonoids are phytochemicals that are well known for their beneficial pharmacological properties. Diosmin is a flavone glycoside derived from hesperidin, a flavanone abundantly found in citrus fruits. Daflon is an oral phlebotonic flavonoid combination containing diosmin and hesperidin (9:1) that is commonly used for the management of blood vessel disorders. After oral administration, diosmin is converted to diosmetin, which is subsequently absorbed and esterified into glucuronide conjugates that are excreted in the urine. Pharmacological effects of diosmin have been investigated in several in vitro and in vivo studies, and it was found to possess anti-inflammatory, antioxidant, antidiabetic, antihyperlipidemic, and antifibrotic effects in different disease models. Diosmin also demonstrated multiple desirable properties in several clinical studies. Moreover, toxicological studies showed that diosmin has a favorable safety profile. Accordingly, diosmin is a potential effective and safe treatment for many diseases. However, diosmin exhibits inhibitory effects on different metabolic enzymes. This encourages the investigation of its potential therapeutic effect and safety in different diseases in clinical trials, while taking potential interactions into consideration.

Metabolic Activation of the Toxic Natural Products From Herbal and Dietary Supplements Leading to Toxicities

Currently, herbal and dietary supplements have been widely applied to prevent and treat various diseases. However, the potential toxicities and adverse reactions of herbal and dietary supplements have been increasingly reported, and have gradually attracted widespread attention from clinical pharmacists and physicians. Metabolic activation of specific natural products from herbal and dietary supplements is mediated by hepatic cytochrome P450 or intestinal bacteria, and generates chemical reactive/toxic metabolites that bind to cellular reduced glutathione or macromolecules, and form reactive metabolites-glutathione/protein/DNA adducts, and these protein/DNA adducts can result in toxicities. The present review focuses on the relation between metabolic activation and toxicities of natural products, and provides updated, comprehensive and critical comment on the toxic mechanisms of reactive metabolites. The key inductive role of metabolic activation in toxicity is highlighted, and frequently toxic functional groups of toxic natural products were summarized. The biotransformation of drug cytochrome P450 or intestinal bacteria involved in metabolic activation were clarified, the reactive metabolites-protein adducts were selected as biomarkers for predicting toxicity. And finally, further perspectives between metabolic activation and toxicities of natural products from herbal and dietary supplements are discussed, to provide a reference for the reasonable and safe usage of herbal and dietary supplements.

Extensive metabolism of flavonoids relevant to their potential efficacy on Alzheimer's disease

Alzheimer's disease (AD) is an age-related neurodegenerative disorder, the incidence of which is climbing with ever-growing aged population, but no cure is hitherto available. The epidemiological studies unveiled that chronic intake of flavonoids was negatively associated with AD risk. Flavonoids, a family of natural polyphenols widely distributed in human daily diets, were readily conjugated by phase II drug metabolizing enzymes after absorption in vivo, and glucuronidation could occur in 1 min following intravenous administration. Recently, as many as 191 metabolites were obtained after intragastric administration of a single flavonoid, indicating that other bioactive metabolites, besides conjugates, might be formed and account for the contradiction between efficacy of flavonoids in human or animal models and low systematic exposure of flavonoid glycosides or aglycones. In this review, metabolism of complete 68 flavonoid monomers potential for AD treatment, grouped in flavonoid O-glycosides, flavonoid aglycones, flavonoid C-glycosides, flavonoid dimers, flavonolignans and prenylated flavonoids according to their common structural elements, respectively, has been systematically retrospected, summarized and discussed, including their unequivocally identified metabolites, metabolic interconversions, metabolic locations, metabolic sites (regio- or stereo-selectivity), primarily involved metabolic enzymes or intestinal bacteria, and interspecies correlations or differences in metabolism, and their bioactive metabolites and the underlying mechanism to reverse AD pathology were also reviewed, providing whole perspective about advances on extensive metabolism of diverse potent flavonoids in vivo and in vitro up to date and aiming at elucidation of mechanism of actions of flavonoids on AD or other central nervous system (CNS) disorders.

The Activation of Procarcinogens by CYP1A1/1B1 and Related Chemo-Preventive Agents: A Review

CYP1A1 and CYP1B1 are extrahepatic P450 family members involved in the metabolism of procarcinogens, such as PAHs, heterocyclic amines and halogen-containing organic compounds. CYP1A1/1B1 also participate in the metabolism of endogenous 17-β-estradiol, producing estradiol hydroquinones, which are the intermediates of carcinogenic semiquinones and quinones. CYP1A1 and CYP1B1 proteins share approximately half amino acid sequence identity but differ in crystal structures. As a result, CYP1A1 and CYP1B1 have different substrate specificity to chemical procarcinogens. This review will introduce the general molecular biology knowledge of CYP1A1/1B1 and the metabolic processes of procarcinogens regulated by these two enzymes. Over the last four decades, a variety of natural products and synthetic compounds which interact with CYP1A1/1B1 have been identified as effective chemo-preventive agents against chemical carcinogenesis. These compounds are mainly classified as indirect or direct CYP1A1/1B1 inhibitors based on their distinct mechanisms. Indirect CYP1A1/1B1 inhibitors generally impede the transcription and translation of CYP1A1/1B1 genes or interfere with the translocation of aryl hydrocarbon receptor (AHR) from the cytosolic domain to the nucleus. On the other hand, direct inhibitors inhibit the catalytic activities of CYP1A1/1B1. Based on the structural features, the indirect inhibitors can be categorized into the following groups: flavonoids, alkaloids and synthetic aromatics, whereas the direct inhibitors can be categorized into flavonoids, coumarins, stilbenes, sulfur containing isothiocyanates and synthetic aromatics. This review will summarize the in vitro and in vivo activities of these chemo-preventive agents, their working mechanisms, and related SARs. This will provide a better understanding of the molecular mechanism of CYP1 mediated carcinogenesis and will also give great implications for the discovery of novel chemo-preventive agents in the near future.

Preference for O-demethylation reactions in the oxidation of 2'-, 3'-, and 4'-methoxyflavones by human cytochrome P450 enzymes

2'-, 3'-, and 4'-Methoxyflavones (MeFs) were incubated with nine forms of recombinant human cytochrome P450 (P450 or CYP) enzymes in the presence of an NADPH-generating system and the products formed were analyzed with LC-MS/MS methods.CYP1B1.1 and 1B1.3 were highly active in demethylating 4'MeF to form 4'-hydroxyflavone (rate of 5.0 nmol/min/nmol P450) and further to 3',4'-dihydroxyflavone (rates of 2.1 and 0.66 nmol/min/nmol P450, respectively). 3'MeF was found to be oxidized by P450s to m/z 239 (M-14) products (presumably 3'-hydroxyflavone) and then to 3',4'-dihydroxyflavone. P450s also catalyzed oxidation of 2'MeF to m/z 239 (M-14) and m/z 255 (M-14, M-14 + 16) products, presumably mono- and di-hydroxylated products, respectively.At least two types of ring oxidation products having m/z 269 fragments were formed, although at slower rates than the formation of mono- and di-hydroxylated products, on incubation of these MeFs with P450s; one type was products oxidized at the C-ring, having m/z 121 fragments, and the other one was the products oxidized at the A-ring (having m/z 137 fragments).Molecular docking analysis indicated the preference of interaction of O-methoxy moiety of methoxyflavones in the active site of CYP1A2.These results suggest that 2'-, 3'-, and 4'-methoxyflavones are principally demethylated by human P450s to form mono- and di-hydroxyflavones and that direct oxidation occurs in these MeFs to form mono-hydroxylated products, oxidized at the A- or B-ring of MeF.

Citrus Flavones: An Update on Sources, Biological Functions, and Health Promoting Properties

Citrus spp. are among the most widespread plants cultivated worldwide and every year millions of tons of fruit, juices, or processed compounds are produced and consumed, representing one of the main sources of nutrients in human diet. Among these, the flavonoids play a key role in providing a wide range of health beneficial effects. Apigenin, diosmetin, luteolin, acacetin, chrysoeriol, and their respective glycosides, that occur in concentrations up to 60 mg/L, are the most common flavones found in Citrus fruits and juices. The unique characteristics of their basic skeleton and the nature and position of the substituents have attracted and stimulated vigorous investigations as a consequence of an enormous biological potential, that manifests itself as (among other properties) antioxidant, anti-inflammatory, antiviral, antimicrobial, and anticancer activities. This review analyzes the biochemical, pharmacological, and biological properties of Citrus flavones, emphasizing their occurrence in Citrus spp. fruits and juices, on their bioavailability, and their ability to modulate signal cascades and key metabolic enzymes both in vitro and in vivo. Electronic databases including PubMed, Scopus, Web of Science, and SciFinder were used to investigate recent published articles on Citrus spp. in terms of components and bioactivity potentials.

Screening of flavonoid aglycons' metabolism mediated by the human liver cytochromes P450

Biological effects of flavonoids have been extensively studied in the last 80 years. As flavonoids represent a rather large group of compounds, data on metabolic biotransformations of these compounds is relatively limited to those well studied. The objective of this study was to screen the metabolism of 30 selected flavonoid aglycons mediated by the most relevant metabolic enzymes, human liver cytochromes P450. For this purpose, in vitro experiments with human liver microsomes and recombinant enzymes were conducted. To evaluate flavonoid's metabolism and structure of the products, high-performance liquid chromatography coupled with high-resolution mass spectrometry was used. Out of 30 flavonoids, 15 were susceptible to oxidative metabolism mediated by cytochromes P450. Dominant reactions were aromatic hydroxylation and O-demethylation, or a combination of these reactions. The dominant enzyme responsible for the observed metabolic reactions is CYP1A2, whereas other human liver cytochromes P450, namely, CYP2C19, CYP2D6, CYP2E1 and CYP3A4, contribute to flavonoid metabolism to a lesser degree. These results, to some extent, contribute to the understanding of the metabolism of constituents found in antioxidant dietary supplements and their possible interactions with other xenobiotics, i.e., medicinal products.

Potential of Teucrium chamaedrys L. to modulate apoptosis and biotransformation in colorectal carcinoma cells

ETHNOPHARMACOLOGICAL RELEVANCE

Teucrum chamaedrys L. is one of the known medicinal plants, useful for treatment of various health problems, especially digestive. In this study, we investigated methanol, ethyl-acetate and acetone extracts of T. chamaedrys in respect to their anticancer properties in SW480 colorectal cancer cells.

MATERIALS AND METHODS

Cytotoxicity and proapoptotic potential were assessed by MTT cell viability assay and AO/EB double staining. Molecular mechanisms of induced apoptosis were determined by monitoring Fas receptor protein expression through immunofluorescence, Caspase 8 and 9 activity, as well as concentrations of O₂^.- spectrophotometrically. Additionally, mRNA expression of biotransformation enzymes (CYP1A1, CYP1B1, GSTP1) and membrane transporters (MRP1 and MRP2) involved in drug resistance were investigated by qPCR method. Qualitative analysis of individual phenolic compounds was performed by reversed phase HPLC-MS analysis.

RESULTS

Methanol extract shows the best cytotoxicity and selectivity compared to ethyl-acetate and acetone extracts, mainly causing apoptosis of SW480 cells, without affecting normal HaCaT keratinocytes. The increased expression of Fas receptor protein and caspase 8 activity indicate that the death receptor-mediated pathway plays a crucial role in the observed apoptosis. The increased caspase 9 activity and O₂^.- concentration suggest that mitochondria are also involved in the apoptosis. T. chamaedrys methanol extract inhibits mRNA expression of CYP1A1, CYP1B1, GSTP1, MRP1 and MRP2 in SW480 cells.

CONCLUSIONS

Induction of apoptosis and inhibition of CYP1A1, CYP1B1, GSTP1, MRP1 and MRP2 mRNA expression implies that T. chamaedrys can serve as a valuable source of bioactive compounds as dietary supplements or selective anticancer agents, with the ability to induce apoptosis and modulate drug resistance in colorectal cancer cells.

Anti-Proliferation and Pro-Apoptotic Effects of Diosmetin via Modulating Cell Cycle Arrest and Mitochondria-Mediated Intrinsic Apoptotic Pathway in MDA-MB-231 Cells

Background

Breast cancer is one of the most malignant tumors worldwide. The natural flavonoid diosmetin has been reported to exhibit various pharmacological activities, including anti-cancer effects. This study aimed to investigate the anti-breast cancer effects of diosmetin on MDA-MB-231 cells and to explore the underlying molecular mechanisms of cell apoptosis.

Material/Methods

The MDA-MB-231 cells were incubated with diosmetin for 24 h. Then, cell viability and lactate dehydrogenase (LDH) leakage were detected using CCK-8 and LDH assay kits, respectively. Inverted fluorescence microscopy and flow cytometry were used to measure the mitochondrial membrane potential (MMP) and intracellular reactive oxygen species (ROS). Cell apoptosis and cell cycle were determined by flow cytometry. The expressions of apoptosis and cell cycle-related genes were determined by Western blotting and qRT-PCR.

Results

The results revealed that diosmetin exerts significant cytotoxic effects on MDA-MB-231 cells, as indicated by decreased cell viability, increased intracellular ROS accumulation and LDH release, as well as cell cycle arrest in G0/G1 phase, inducing mitochondrial dysfunction and apoptosis. Moreover, diosmetin treatment significantly downregulated the expression levels of Bcl-2 and Cyclin D1, and upregulated that of p53, Bax, caspase 3, cleaved caspase 9, and cleaved caspase 3.

Conclusions

These findings demonstrate that diosmetin has anti-proliferative and pro-apoptotic activities against MDA-MB-231 cells via cell cycle arrest and the mitochondria-mediated intrinsic apoptotic pathway. Our results extend the understanding of the anti-tumor mechanism of diosmetin and suggest that it may be of use as an active natural agent for the prevention or treatment of human breast cancer.

Profiling and comparison of the metabolites of diosmetin and diosmin in rat urine, plasma and feces using UHPLC-LTQ-Orbitrap MSn

Diosmin (diosmetin-7-O-rutinoside) and its aglycone diosmetin, natural bioflavonoids distributing in a variety of citrus fruits and Chinese herbal medicines, possessed positive effects against hepatic, renal, lung, gastric, cerebral and cardiac injury. However, the in vivo metabolic profiles of diosmin and diosmetin in urine, plasma and feces still remain ambiguous. In this study, metabolites of diosmin and diosmetin were identified using an UHPLC-LTQ-Orbitrap MSⁿ strategy coupled with multiple metabolite templates, extracted ion chromatograms (EICs) and diagnostic product ions (DPIs). As a result, 46 diosmetin metabolites and 64 diosmin metabolites were respectively identified in rat biological samples. Methylation, demethylation, hydroxylation, glycosylation, glucuronidation, diglucuronidation and sulfation were common metabolic pathways of diosmetin and diosmin, while demethoxylation, decarbonylation, dihydroxylation and dehydroxylation were particular metabolic pathways of diosmin comparing with that of diosmetin. Diosmetin was not detected in all the biological samples, suggesting that it was quickly transformed into other metabolites in vivo. Diosmin and diosmetin-7-O-glucoside identified in urine and feces as well as their subsequent metabolites accounted for a substantial part of all the diosmin metabolic products. Metabolic profiles of diosmetin and diosmin indicated that they were primarily excreted through the urine route possibly originating from the dominant role of their phase II metabolism in vivo. Our results have provided a better understanding of the similarities and differences in pharmacodynamics and pharmacokinetics of diosmetin and diosmin in the future.

Oxidation of Flavone, 5-Hydroxyflavone, and 5,7-Dihydroxyflavone to Mono-, Di-, and Tri-Hydroxyflavones by Human Cytochrome P450 Enzymes

Biologically active plant flavonoids, including 5,7-dihydroxyflavone (57diOHF, chrysin), 4',5,7-trihydroxyflavone (4'57triOHF, apigenin), and 5,6,7-trihydroxyflavone (567triOHF, baicalein), have important pharmacological and toxicological significance, e.g., antiallergic, anti-inflammatory, antioxidative, antimicrobial, and antitumorgenic properties. In order to better understand the metabolism of these flavonoids in humans, we examined the oxidation of flavone, 5-hydroxyflavone (5OHF), and 57diOHF to various products by human cytochrome P450 (P450 or CYP) and liver microsomal enzymes. Individual human P450s and liver microsomes oxidized flavone to 6-hydroxyflavone, small amounts of 5OHF, and 11 other monohydroxylated products at different rates and also produced several dihydroxylated products (including 57diOHF and 7,8-dihydroxyflavone) from flavone. We also found that 5OHF was oxidized by several P450 enzymes and human liver microsomes to 57diOHF and further to 567triOHF, but the turnover rates in these reactions were low. Interestingly, both CYP1B1.1 and 1B1.3 converted 57diOHF to 567triOHF at turnover rates (on the basis of P450 contents) of >3.0 min^-1, and CYP1A1 and 1A2 produced 567triOHF at rates of 0.51 and 0.72 min^-1, respectively. CYP2A13 and 2A6 catalyzed the oxidation of 57diOHF to 4'57triOHF at rates of 0.7 and 0.1 min^-1, respectively. Our present results show that different P450s have individual roles in oxidizing these phytochemical flavonoids and that these reactions may cause changes in their biological and toxicological properties in mammals.

The synthesis of 4,6-diaryl-2-pyridones and their bioactivation in CYP1 expressing breast cancer cells

As part of a programme to develop anticancer prodrugs which are activated by cytochrome P450 (CYP)1B1, a library of 4,6-diaryl-2-pyridones was synthesised in yields of 6-60% from the corresponding chalcones. A number of these derivatives showed promising antiproliferative activities in human breast cancer cell lines which express CYP1B1 and CYP1A1, while showing little toxicity towards a non-tumour breast cell line with no CYP expression. Metabolism studies provided evidence supporting the involvement of CYP1 enzymes in the bioactivation of these compounds.

Estrogenic properties of coumarins and meroterpene from the fruits of Cullen corylifolium: Experimental and computational studies

Coumarins and meroterpene from the fruits of Cullen corylifolium were evaluated for their ability to bind and activate human estrogen receptor α (hERα) by a combination of in vitro studies and molecular dynamics simulations. The recombinant hERα ligand binding domain (hERα-LBD) was produced in BL21 (DE3)pLysS and the fluorescence polarization (FP) assay was performed to determine the binding affinities of coumarins and meroterpene with receptor protein. These compounds displayed distinct binding potency toward hERα-LBD, generally increased with their increasing molecular length and Connolly solvent-excluded volume (CSEV). In an estrogen response element-luciferase (ERE-Luc) reporter gene assay, coumarins and meroterpene acted as agonists of human estrogen receptor α. Subsequently, molecular docking was conducted to elucidate the molecular mechanism behind their agonistic activities. Coumarins and meroterpene adopted an agonist conformation within the cavity of hERα-LBD. The hydrophobic and hydrogen-bonding interactions were dominant forces to stabilize their binding. The structure-activity relationship analysis suggested that the presence of hydroxyl groups and prenyl group were crucial for possessing estrogenic activities. Comparison of the calculated binding energies with the determined binding affinities yielded a good correlation (R² = 0.9727). In conclusion, molecular modeling techniques can potentially be applied for in silico screening of selective estrogen receptor modulators (SERMs) from undescribed compounds.

Diosmetin suppresses human prostate cancer cell proliferation through the induction of apoptosis and cell cycle arrest

Diosmetin, a plant flavonoid, has been shown to exert promising effects on prostate cancer cells as an anti‑proliferative and anticancer agent. In this study, using western blot analysis for protein expression and flow cytometry for cell cycle analysis, we determined that the treatment of the LNCaP and PC‑3 prostate cancer cells with diosmetin resulted in a marked decrease in cyclin D1, Cdk2 and Cdk4 expression levels (these proteins remain active in the G0‑G1 phases of the cell cycle). These changes were accompanied by a decrease in c-Myc and Bcl-2 expression, and by an increase in Bax, p27Kip1 and FOXO3a protein expression, which suggests the potential modulatory effects of diosmetin on protein transcription. The treatment of prostate cancer cells with diosmetin set in motion an apoptotic machinery by inhibiting X-linked inhibitor of apoptosis (XIAP) and increasing cleaved PARP and cleaved caspase-3 expression levels. On the whole, the findings of this study provide an in-depth analysis of the molecular mechanisms responsible for the regulatory effects of diosmetin on key molecules that perturb the cell cycle to inhibit cell growth, and suggest that diosmetin may prove to be an effective anticancer agent for use in the treatment of prostate cancer in the future.

Tangeretin inhibits the proliferation of human breast cancer cells via CYP1A1/CYP1B1 enzyme induction and CYP1A1/CYP1B1-mediated metabolism to the product 4' hydroxy tangeretin

Tangeretin is a polymethoxylated flavone with multifaceted anticancer activity. In the present study, the metabolism of tangeretin was evaluated in the CYP1 expressing human breast cancer cell lines MCF7 and MDA-MB-468 and in the normal breast cell line MCF10A. Tangeretin was converted to 4' OH tangeretin by recombinant CYP1 enzymes and by CYP1 enzymes expressed in MCF7 and MDA-MB-468 cells. This metabolite was absent in MCF10A cells that did not express CYP1 enzymes. Tangeretin exhibited submicromolar IC50 (0.25 ± 0.15 μM) in MDA-MB-468 cells, whereas it was less active in MCF7 cells (39.3 ± 1.5 μM) and completely inactive in MCF10A cells (>100 μM). In MDA-MB-468 cells that were coincubated with the CYP1 inhibitor acacetin, an approximately 70-fold increase was noted in the IC50 (18 ± 1.6 μM) of tangeretin. In the presence of the CYP1 inhibitor acacetin, the conversion of tangeretin to 4' OH tangeretin was significantly reduced in MDA-MB-468 cells (2.55 ± 0.19 μM vs. 6.33 ± 0.12 μM). The mechanism of antiproliferative action involved cell cycle arrest at the G1 phase for MCF7 and MDA-MB-468 cells. Tangeretin was further shown to induce CYP1 enzyme activity and CYP1A1/CYP1B1 protein expression in MCF7 and MDA-MB-468 cells. These results suggest that tangeretin inhibits the proliferation of breast cancer cells via CYP1A1/CYP1B1-mediated metabolism to the product 4' hydroxy tangeretin.

Cytoprotective effects of diosmetin against hydrogen peroxide-induced L02 cell oxidative damage via activation of the Nrf2-ARE signaling pathway

Oxidative stress is considered a crucial mediator in the pathogenesis of various liver diseases. The flavone diosmetin has been reported to exhibit antioxidant activities; however, the hepatoprotective effects of diosmetin against oxidative stress, and the underlying molecular mechanisms, remain unknown. The present study aimed to investigate the potential hepatoprotective effects of diosmetin on hydrogen peroxide (H2O2)‑induced oxidative damage in L02 cells and attempted to evaluate the role of the nuclear factor erythroid 2‑related factor 2 (Nrf2)/antioxidant response element pathway in this process. L02 cells were divided into groups: Control (DMSO, diosmetin), H2O2, Trolox or tertiary butylhydroquinone and diosmetin (different doses). Protective effects in L02 cells were determined by CCK‑8, cell apoptosis and lactate dehydrogenase leakage assays. Flow cytometry and inverted fluorescence microscope were used to measure the intracellular reactive oxygen species (ROS) and mitochondrial membrane potential (MMP). Protein expression levels were of Nrf2, heme oxygenase‑1 (HO‑1) and NAD(P)H quinone oxidoreductase‑1 (NQO1) were determined by western blotting and mRNA levels were determined by reverse transcription‑quantitative polymerase chain reaction. The results revealed that H2O2 induced notable injury to L02 cells, as demonstrated by decreased cell viability, increased lactate dehydrogenase release, apoptotic rate and intracellular ROS production, and by the loss of MMP. Conversely, diosmetin (20‑40 µM) significantly reversed the damaging effects of H2O2, which indicated that diosmetin may exhibit potent hepatoprotective potential against H2O2‑induced oxidative damage. Furthermore, pretreatment with diosmetin elevated mRNA and protein expression levels of Nrf2, HO‑1 and NQO1. The present study is the first, to the best of our knowledge, to demonstrate that activation of the Nrf2/NQO1‑HO‑1 signaling pathway maybe involved in the cytoprotective effects of diosmetin against oxidative stress. Therefore, diosmetin may be considered a promising therapeutic agent for the treatment of various liver diseases associated with oxidative stress.

Identification of karanjin isolated from the Indian beech tree as a potent CYP1 enzyme inhibitor with cellular efficacy via screening of a natural product repository

CYP1A1 is thought to mediate carcinogenesis in oral, lung and epithelial cancers. In order to identify a CYP1A1 inhibitor from an edible plant, 394 natural products in the IIIM's natural product repository were screened, at 10 μM concentration, using CYP1A1-Sacchrosomes™ (i.e. microsomal enzyme isolated from recombinant baker's yeast). Twenty-seven natural products were identified that inhibited 40-97% of CYP1A1's 7-ethoxyresorufin-O-deethylase activity. The IC50 values of the 'hits', belonging to different chemical scaffolds, were determined. Their selectivity was studied against a panel of 8 CYP-Sacchrosomes™. In order to assess cellular efficacy, the 'hits' were screened for their capability to inhibit CYP enzymes expressed within live recombinant human embryonic kidney (HEK293) cells from plasmids encoding specific CYP genes (1A2, 1B1, 2C9, 2C19, 2D6, 3A4). Isopimpinellin (IN-475; IC50, 20 nM) and karanjin (IN-195; IC50, 30 nM) showed the most potent inhibition of CYP1A1 in human cells. Isopimpinellin is found in celery, parsnip, fruits and in the rind and pulp of limes whereas different parts of the Indian beech tree, which contain karanjin, have been used in traditional medicine. Both isopimpinellin and karanjin negate the cellular toxicity of CYP1A1-mediated benzo[a]pyrene. Molecular docking and molecular dynamic simulations with CYP isoforms rationalize the observed trends in the potency and selectivity of isopimpinellin and karanjin.

Nobiletin bioactivation in MDA-MB-468 breast cancer cells by cytochrome P450 CYP1 enzymes

Nobiletin is a fully methoxylated flavone that has demonstrated anticancer activity via multiple modes of action. In the present study, the metabolism and further antiproliferative activity of nobiletin was evaluated in the CYP1 expressing human breast cancer cell line MDA-MB-468 and the normal breast cell line MCF10A. Nobiletin was metabolized in MDA-MB-468 cells to a single-demethylated derivative assigned NP1. This metabolite was absent in MCF10A cells that did not express CYP1 enzymes. Nobiletin exhibited submicromolar IC50 (0.1 ± 0.04 μM) in MDA-MB-468 cells, whereas it was considerably less active in MCF10A cells (40 μM). In MDA-MB-468 cells that were coincubated with the CYP1 inhibitor acacetin, an approximately 300-fold increase was noted in the IC50 (30 ± 2.4 μM) of nobiletin. In the presence of the CYP1 inhibitor acacetin, the conversion of nobiletin to NP1 was significantly reduced in MDA-MB-468 cells. Furthermore, a significant increase was noted in the population of the cells at the G1 phase, following treatment with nobiletin (10 μM) for 24 h compared with the control cells treated with DMSO (0.1%) alone (55.9 ± 0.14 vs. 45.6 ± 1.96), whereas the cell cycle of MCF10A cells was not significantly altered under the same treatment conditions. Taken collectively, the results suggest that nobiletin is selectively bioactivated in MDA-MB-468 breast cancer cells via metabolism by the cytochrome P450 CYP1 family of enzymes.

Cytochrome P450 CYP1 metabolism of hydroxylated flavones and flavonols: Selective bioactivation of luteolin in breast cancer cells

Natural flavonoids with methoxy substitutions are metabolized by CYP1 enzymes to yield the corresponding demethylated products. The present study aimed to characterize the metabolism and further antiproliferative activity of the hydroxylated flavonoids apigenin, luteolin, scutellarein, kaempferol and quercetin in CYP1 recombinant enzymes and in the CYP1 expressing cell lines MCF7 and MDA-MB-468, respectively. Apigenin was converted to luteolin and scutellarein, whereas kaempferol was metabolized only to quercetin by recombinant CYP1 enzymes. Luteolin metabolism yielded 6 hydroxyluteolin only by recombinant CYP1B1, whereas CYP1A1 and CYP1A2 were not capable of metabolizing this compound. Molecular modeling demonstrated that CYP1B1 favored the A ring orientation of apigenin and luteolin to the heme group compared with CYP1A1. The IC50 of the compounds luteolin, scutellarein and 6 hydroxyluteolin was significantly lower in MDA-MB-468, MCF7 and MCF10A cells compared with that of apigenin. Similarly, the IC50 of quercetin in MDA-MB-468 cells was significantly lower compared with that of kaempferol. The most potent compound was luteolin in MDA-MB-468 cells (IC50 = 2 ± 0.3 μM). In the presence of the CYP1-inhibitors α-napthoflavone and/or acacetin, luteolin activation was lessened. Taken collectively, the data demonstrate that the metabolism of hydroxylated flavonoids by cytochrome P450 CYP1 enzymes, notably CYP1A1 and CYP1B1, can enhance their antiproliferative activity in breast cancer cells. In addition, this antiproliferative activity is attributed to the combined action of the parent compound and the corresponding CYP1 metabolites.

Spectroscopic and structural studies of the diosmin monohydrate and anhydrous diosmin

Diosmin, a flavone glycoside frequently used in therapy of various veins diseases in monohydrate form, exhibits poor solubility in water and low bioavailability. Due to the fact that the anhydrous forms of drugs generally have better bioavailability than the corresponding hydrates, the aim of this study was to analyze the conversion of diosmin monohydrate (DSNM) to anhydrous diosmin (DSNA) that occurs upon heating. The mechanism of this transformation was examined as well as advanced structural studies of each form were performed using 13C CP/MAS SSNMR, DSC, FT-IR and PXRD techniques. Spectroscopic findings were supported by CASTEP-DFT calculations of NMR and IR parameters. The pathway of reversible transformation was specified as follows: DSNM upon heating for 24h at temperature up to 110°C losses non-crystalline water and converts into metastable form (DSNM*) that turns into DSNA during heating at temperature 140°C for next 24h. Under room temperature DSNA spontaneously absorbs moisture from air and turns into a DSNM within 72h. The detailed analysis of CP kinetic parameters (T1ρI) revealed presence of metastable, intermediate form of diosmin (DSNM*) and allowed its characterization. The results are essential for further studies comparing dissolution and bioavailability of DSNM and DSNA. The study provided an understanding of the conversion pathway of the diosmin monohydrate into its anhydrate form when it is exposed to increased temperature.

Radiosensitizing effect of diosmetin on radioresistant lung cancer cells via Akt signaling pathway

Radiotherapy is a powerful tool in the treatment of cancer that has the advantage of preserving normal tissues. However, tumor radioresistance currently remains a major impediment to effective RT. Thus, exploring effective radiation sensitizers is urgently needed. In this study, we have shown that diosmetin, the aglycone of the lavonoid glycoside from olive leaves, citrus fruits and some medicinal herbs, has a promising effect on radiotherapy sensitization. In our results, DIO could induce G1 phase arrest and thus enhance the radiosensitivity of radioresistant A549/IR lung cancer cells. Furthermore, DIO also restrains the IR-induced DNA damage repair by inhibiting the activated Akt signaling pathway. The combination of Akt inhibition (DIO, LY294002 or MK-2206) and radiation potently blocked A549/IR cancer cell proliferation. In summary, these observations suggest that the natural compound DIO could act as a potential drug for the treatment of radioresistant lung cancer cells.

Diosmetin induces apoptosis by upregulating p53 via the TGF-β signal pathway in HepG2 hepatoma cells

Diosmetin (Dio) is a major active component of flavonoid compounds. A previous study demonstrated that Dio exhibited anticancer activity and induced apoptosis in HepG2 human hepatoma cells via cytochrome P450, family 1-catalyzed metabolism. The present study observed that cell proliferation of HepG2 cells was inhibited by Dio treatment and tumor protein p53 was significantly increased following Dio treatment. Following addition of recombinant transforming growth factor-β (TGF-β) protein to Dio-treated HepG2 cells, cell growth inhibition and cell apoptosis was partially reversed. These findings suggest a novel function for the TGF-β/TGF-β receptor signaling pathway and that it may be a key target of Dio-induced cell apoptosis in HepG2 cells.

Effect of diosmetin on airway remodeling in a murine model of chronic asthma

Bronchial asthma, one of the most common allergic diseases, is characterized by airway hyperresponsiveness (AHR), inflammation, and remodeling. The anti-oxidant flavone aglycone diosmetin ameliorates the inflammation in pancreatitis, but little is known about its impact on asthma. In this study, the effects of diosmetin on chronic asthma were investigated with an emphasis on the modulation of airway remodeling in BALB/c mice challenged with ovalbumin (OVA). It was found that diosmetin significantly relieved inflammatory cell infiltration, goblet cell hyperplasia, and collagen deposition in the lungs of asthmatic mice and notably reduced AHR in these animals. The OVA-induced increases in total cell and eosinophil counts in bronchoalveolar lavage fluid were reversed, and the level of OVA-specific immunoglobulin E in serum was attenuated by diosmetin administration, implying an anti-Th2 activity of diosmetin. Furthermore, diosmetin remarkably suppressed the expression of smooth muscle actin alpha chain, indicating a potent anti-proliferative effect of diosmetin on airway smooth muscle cells (ASMCs). Matrix metallopeptidase-9, transforming growth factor-β1, and vascular endothelial growth factor levels were also alleviated by diosmetin, suggesting that the remission of airway remodeling might be attributed to the decline of these proteins. Taken together, our findings provided a novel profile of diosmetin with anti-remodeling therapeutic benefits, highlighting a new potential of diosmetin in remitting the ASMC proliferation in chronic asthma.

Flavonoid diosmetin increases ATP levels in kidney cells and relieves ATP depleting effect of ochratoxin A

Diosmetin (DIOS) is a flavone aglycone commonly occurring in citrus species and olive leaves, in addition it is one of the active ingredients of some medications. Based on both in vitro and in vivo studies several beneficial effects are attributed to DIOS but the biochemical background of its action seems to be complex and it has not been completely explored yet. Previous investigations suggest that most of the flavonoid aglycones have negative effect on ATP synthesis in a dose dependent manner. In our study 17 flavonoids were tested and interestingly DIOS caused a significant elevation of intracellular ATP levels after 6- and 12-h incubation in MDCK kidney cells. In order to understand the mechanism of action, intracellular ATP and protein levels, ATP/ADP ratio, cell viability and ROS levels were determined after DIOS treatment. In addition, impacts of different enzyme inhibitors and effect of DIOS on isolated rat liver mitochondria were also tested. Finally, the influence of DIOS on the ATP depleting effect of the mycotoxin, ochratoxin A was also investigated. Our major conclusions are the followings: DIOS increases intracellular ATP levels both in kidney and in liver cells. Inhibition of glycolysis or citric acid cycle does not decrease the observed effect. DIOS-induced elevation of ATP levels is completely abolished by the inhibition of ATP synthase. DIOS is able to completely reverse the ATP-depleting effect of the mycotoxin, ochratoxin A. Most probably the DIOS-induced impact on ATP system does not originate from the antioxidant property of DIOS. Based on our findings DIOS may be promising agent to positively influence ATP depletion caused by some metabolic poisons.

Identification of small molecule activators of BMP signaling

Bone Morphogenetic Proteins (BMPs) are morphogens that play a major role in regulating development and homeostasis. Although BMPs are used for the treatment of bone and kidney disorders, their clinical use is limited due to the supra-physiological doses required for therapeutic efficacy causing severe side effects. Because recombinant BMPs are expensive to produce, small molecule activators of BMP signaling would be a cost-effective alternative with the added benefit of being potentially more easily deliverable. Here, we report our efforts to identify small molecule activators of BMP signaling. We have developed a cell-based assay to monitor BMP signaling by stably transfecting a BMP-responsive human cervical carcinoma cell line (C33A) with a reporter construct in which the expression of luciferase is driven by a multimerized BMP-responsive element from the Id1 promoter. A BMP-responsive clone C33A-2D2 was used to screen a bioactive library containing ∼5,600 small molecules. We identified four small molecules of the family of flavonoids all of which induced luciferase activity in a dose-dependent manner and ventralized zebrafish embryos. Two of the identified compounds induced Smad1, 5 phosphorylation (P-Smad), Id1 and Id2 expression in a dose-dependent manner demonstrating that our assays identified small molecule activators of BMP signaling.

Pharmacokinetic study of luteolin, apigenin, chrysoeriol and diosmetin after oral administration of Flos Chrysanthemi extract in rats

Flos Chrysanthemi (the flower of Chrysanthemum morifolium Ramat.) is widely used in China as a food and traditional Chinese medicine for many diseases. Luteolin and apigenin are two main bioactive components in Flos Chrysanthemi, and chrysoeriol and diosmetin are two methylated metabolites of luteolin in vivo by cathechol-O-methyltransferase (COMT). However, there was lack of pharmacokinetic information of chrysoeriol and diosmetin after oral administration of Flos Chrysanthemi extract (FCE). The present study aimed to develop an HPLC-UV method for simultaneous determination of rat plasma concentration of luteolin, apigenin, chrysoeriol and diosmetin and utilize it in pharmacokinetic study of the four compounds after orally giving FCE to rats. The method was successfully validated and applied to the pharmacokinetic study when oral administration of FCE to rats with or without co-giving a COMT inhibitor, entacapone. Chrysoeriol and diosmetin were detected in rat plasma after oral administration of FCE and their concentrations were significantly decreased after co-giving entacapone. Furthermore, AUC of luteolin was significantly increased by entacapone, while that of chrysoeriol was decreased by entacapone, which revealed COMT might play an important role in the disposition of luteolin in rats after dosing of FCE. In conclusion, a sensitive, accurate and reproducible HPLC-UV method for simultaneous determination of luteolin, apigenin, chrysoeriol and diosmetin in rat plasma were developed, pharmacokinetics of chrysoeriol and diosmetin combined with luteolin and apigenin were characterized after oral administration of FCE to rats, which gave us more information on pharmacokinetics and potential pharmacological effects of FCE in vivo.

Bioactivation of the citrus flavonoid nobiletin by CYP1 enzymes in MCF7 breast adenocarcinoma cells

Recent studies have demonstrated cytochrome P450 CYP1-mediated metabolism and CYP1-enzyme induction by naturally occurring flavonoids in cancer cell line models. The arising metabolites often exhibit higher activity than the parent compound. In the present study we investigated the CYP1-mediated metabolism of the citrus polymethoxyflavone nobiletin by recombinant CYP1 enzymes and MCF7 breast adenocarcinoma cells. Incubation of nobiletin in MCF7 cells produced one main metabolite (NM1) resulting from O-demethylation in either A or B rings of the flavone moiety. Among the three CYP1 isoforms, CYP1A1 exhibited the highest rate of metabolism of nobiletin in recombinant CYP microsomal enzymes. The intracellular CYP1-mediated bioconversion of the flavone was reduced in the presence of the CYP1A1 and CYP1B1-selective inhibitors α-napthoflavone and acacetin. In addition nobiletin induced CYP1 enzyme activity, CYP1A1 protein and CYP1B1 mRNA levels in MCF7 cells at a concentration dependent manner. MTT assays in MCF7 cells further revealed that nobiletin exhibited significantly lower IC50 (44 μM) compared to cells treated with nobiletin and CYP1A1 inhibitor (69 μM). FACS analysis demonstrated cell a cycle block at G1 phase that was attenuated in the presence of CYP1A1 inhibitor. Taken together the data suggests that the dietary flavonoid nobiletin induces its own metabolism and in turn enhances its cytostatic effect in MCF7 breast adenocarcinoma cells, via CYP1A1 and CYP1B1 upregulation.

Cytochrome P450 1A1-mediated anticancer drug discovery: in silico findings

INTRODUCTION

Target-specific drugs may offer fewer side/adverse effects in comparison with other anticancer agents and thus save normal healthy cells to a greater extent. The selective overexpression of cytochrome P450 1A1 (CYP1A1) in tumor cells induces the metabolism of benzothiazole and aminoflavone compounds to their reactive species, which are responsible for DNA adduct formation and cell death. This review encompasses the novelty of CYP1A1 as an anticancer drug target and explores the possible in silico strategies that would be applicable in the discovery and development of future antitumor compounds.

AREAS COVERED

This review highlights the various ligand-based and target-based in silico methodologies that were efficiently used in exploration of CYP1A1 as a novel antitumor target. These methodologies include electronic structure analysis, CoMFA studies, homology modeling, molecular docking, molecular dynamics analysis, pharmacophore mapping and quantitative structure activity relationship (QSAR) studies. It also focuses on the various approaches used in the development of the lysyl amide prodrug of 5F-203 (NSC710305) and dimethanesulfonate salt of 5-aminoflavone (NSC710464) as clinical candidates from their less potent analogues.

EXPERT OPINION

Selective overexpression of CYP1A1 in cancer cells offers tumor-specific drug design to ameliorate the current adverse effects associated with existing antitumor agents. Medicinal chemistry and in vitro driven approaches, in combination with knowledge-based drug design and by using the currently available tools of in silico methodologies, would certainly make it possible to design and develop novel anticancer compounds targeting CYP1A1.

Inhibition of cytochrome P450 2C8-mediated drug metabolism by the flavonoid diosmetin

The aim of this study was to assess the effects of diosmetin and hesperetin, two flavonoids present in various medicinal products, on CYP2C8 activity of human liver microsomes using paclitaxel oxidation to 6α-hydroxy-paclitaxel as a probe reaction. Diosmetin and hesperetin inhibited 6α-hydroxy-paclitaxel production in a concentration-dependent manner, diosmetin being about 16-fold more potent than hesperetin (mean IC(50) values 4.25 ± 0.02 and 68.5 ± 3.3 µM for diosmetin and hesperetin, respectively). Due to the low inhibitory potency of hesperetin, we characterized the mechanism of diosmetin-induced inhibition only. This flavonoid proved to be a reversible, dead-end, full inhibitor of CYP2C8, its mean inhibition constant (K(i)) being 3.13 ± 0.11 µM. Kinetic analysis showed that diosmetin caused mixed-type inhibition, since it significantly decreased the V(max) (maximum velocity) and increased the K(m) value (substrate concentration yielding 50% of V(max)) of the reaction. The results of kinetic analyses were consistent with those of molecular docking simulation, which showed that the putative binding site of diosmetin coincided with the CYP2C8 substrate binding site. The demonstration that diosmetin inhibits CYP2C8 at concentrations similar to those observed after in vivo administration (in the low micromolar range) is of potential clinical relevance, since it may cause pharmacokinetic interactions with co-administered drugs metabolized by this CYP.