The chemopreventive effect of 5-demethylnobiletin, a unique citrus flavonoid, on colitis-driven colorectal carcinogenesis in mice is associated with its colonic metabolites

Unlocking the potential of flavonoids: Natural solutions in the fight against colon cancer

Colorectal cancer (CRC) is a major cause of cancer-related deaths worldwide, underscoring the importance of understanding the diverse molecular and genetic underpinnings of CRC to improve its diagnosis, prognosis, and treatment. This review delves into the adenoma-carcinoma-metastasis model, emphasizing the "APC-KRAS-TP53" signature events in CRC development. CRC is categorized into four consensus molecular subtypes, each characterized by unique genetic alterations and responses to therapy, illustrating its complexity and heterogeneity. Furthermore, we explore the role of chronic inflammation and the gut microbiome in CRC progression, emphasizing the potential of targeting these factors for prevention and treatment. This review discusses the impact of dietary carcinogens and lifestyle factors and the critical role of early detection in improving outcomes, and also examines conventional chemotherapy options for CRC and associated challenges. There is significant focus on the therapeutic potential of flavonoids for CRC management, discussing various types of flavonoids, their sources, and mechanisms of action, including their antioxidant properties, modulation of cell signaling pathways, and effects on cell cycle and apoptosis. This article presents evidence of the synergistic effects of flavonoids with conventional cancer therapies and their role in modulating the gut microbiome and immune response, thereby offering new avenues for CRC treatment. We conclude by emphasizing the importance of a multidisciplinary approach to CRC research and treatment, incorporating insights from genetic, molecular, and lifestyle factors. Further research is needed on the preventive and therapeutic potential of natural compounds, such as flavonoids, in CRC, underscoring the need for personalized and targeted treatment strategies.

Rapid and comprehensive metabolites identification of 5-demethylnobiletin in rats using UPLC/Triple-TOF-MS/MS based on multiple mass defect filter and their neuroprotection against ferroptosis

5-Demethylnobiletin (5-deNOB) is a hydroxylated polymethoxyflavone (PMF) from Citrus plants known for its neurotrophic, anti-tumor, and antioxidant bioactivities. An ultra-high performance liquid chromatography coupled with triple-time of flight tandem mass spectrometry (UPLC/Triple-TOF-MS/MS) analysis combining with multiple mass defect filter (MMDF) and MetabolitePilot™ was employed to detect and characterize the metabolites of 5-deNOB in rats. A total of 130 metabolites were identified in rats, with 100, 25, 34, and 52 metabolites found in urine, plasma, bile, and feces, respectively. The major metabolic pathways involved demethylation, hydroxylation, dehydroxylation, glucuronidation, and methylation. In a bioassay of evaluating neuroprotection against ferroptosis in PC12 cells, most of the metabolites exhibited superior activity compared to 5-deNOB. These results provide valuable insights into the in vivo pharmacodynamic properties of 5-deNOB and offer potential active small molecules for neuroprotective therapy. Furthermore, the findings demonstrate the effectiveness of UPLC/Triple-TOF-MS/MS combined with MMDF and MetabolitePilot™ for rapid discovery and identification of the in vivo metabolites of natural products.

Integrated multi-omics analysis reveals the positive leverage of citrus flavonoids on hindgut microbiota and host homeostasis by modulating sphingolipid metabolism in mid-lactation dairy cows consuming a high-starch diet

BACKGROUND

Modern dairy diets have shifted from being forage-based to grain and energy dense. However, feeding high-starch diets can lead to a metabolic disturbance that is linked to dysregulation of the gastrointestinal microbiome and systemic inflammatory response. Plant flavonoids have recently attracted extensive interest due to their anti-inflammatory effects in humans and ruminants. Here, multi-omics analysis was conducted to characterize the biological function and mechanisms of citrus flavonoids in modulating the hindgut microbiome of dairy cows fed a high-starch diet.

RESULTS

Citrus flavonoid extract (CFE) significantly lowered serum concentrations of lipopolysaccharide (LPS) proinflammatory cytokines (TNF-α and IL-6), acute phase proteins (LPS-binding protein and haptoglobin) in dairy cows fed a high-starch diet. Dietary CFE supplementation increased fecal butyrate production and decreased fecal LPS. In addition, dietary CFE influenced the overall hindgut microbiota's structure and composition. Notably, potentially beneficial bacteria, including Bacteroides, Bifidobacterium, Alistipes, and Akkermansia, were enriched in CFE and were found to be positively correlated with fecal metabolites and host metabolites. Fecal and serum untargeted metabolomics indicated that CFE supplementation mainly emphasized the metabolic feature "sphingolipid metabolism." Metabolites associated with the sphingolipid metabolism pathway were positively associated with increased microorganisms in dairy cows fed CFE, particularly Bacteroides. Serum lipidomics analysis showed that the total contents of ceramide and sphingomyelin were decreased by CFE addition. Some differentially abundant sphingolipid species were markedly associated with serum IL-6, TNF-α, LPS, and fecal Bacteroides. Metaproteomics revealed that dietary supplementation with CFE strongly impacted the overall fecal bacterial protein profile and function. In CFE cows, enzymes involved in carbon metabolism, sphingolipid metabolism, and valine, leucine, and isoleucine biosynthesis were upregulated.

CONCLUSIONS

Our research indicates the importance of bacterial sphingolipids in maintaining hindgut symbiosis and homeostasis. Dietary supplementation with CFE can decrease systemic inflammation by maintaining hindgut microbiota homeostasis and regulating sphingolipid metabolism in dairy cows fed a high-starch diet. Video Abstract.

Antioxidants from different citrus peels provide protection against cancer

Cancer is one of the leading causes of death. Despite significant advancements in the discovery of medications for the treatment of cancer, these drugs are hindered by applicability and efficacy issues and frequently exhibit major side effects that can further impair patients 'quality of life. Therefore, the development of therapeutically sound anti-cancer medicines derived from natural products has gained prominence in the field of functional foods. Some of these compounds have shown efficacy in the prevention and treatment of cancer as well as low toxicity. Additionally, many recent studies have explored the recycling of agro-industrial waste to create bioactive chemicals. Citrus peels are produced in vast quantities in the food processing sector; due to their abundance of flavonoids, they may be inexpensive sources of protection against several cancers. Citrus is a common type of fruit that contains a variety of nutrients. In particular, the antioxidant chemicals found in citrus peel have been identified as potential cancer-fighting agents. Antioxidant substances such as flavonoids prevent the development of cancer by inhibiting the metastatic cascade, decreasing the mobility of cancer cells in the circulatory system, promoting apoptosis, and suppressing angiogenesis. To explore the most effective uses of citrus peel-derived antioxidants, this review presents background information, an overview of the role of citrus antioxidants in cancer therapy, and a discussion of the key underlying molecular mechanisms.

Citrus peel polyphenols alleviate intestinal inflammation in mice with dextran sulfate sodium-induced acute colitis

Citrus peel polyphenols have possess the distinct anti-inflammatory activities. However, its underlying mechanism on ulcerative colitis have not been elucidated. The aim of this research was to investigate the anti-inflammatory effect and action mechanisms of citrus peel polyphenols. Total citrus peel polyphenols were concentrated using macroporous resins and separated into water-soluble citrus polyphenols and ester-soluble citrus peel polyphenols. These extracts were then gavaged to acute colitis mice induced by dextran sulfate sodium for 14 days using a dose of 300 mg/kg▪bw. High performance liquid chromatography results showed that the extracts contained flavanones, flavonoids, and phenolic acids. Compared to the dextran sulfate sodium group, total citrus peel polyphenols, water-soluble citrus polyphenols, and ester-soluble citrus peel polyphenols significantly ameliorated the severity of colitis symptoms. Additionally, citrus peel polyphenols reduced the activity of myeloperoxidase, lowered secretion of tumor necrosis factor-α and interleukin-6, and increased interleukin-10. Meanwhile, total citrus peel polyphenols, water-soluble citrus polyphenols, and ester-soluble citrus peel polyphenols effectively blocked the activation of the nuclear factor-kappa B. These results demonstrated that citrus peel polyphenols alleviated ulcerative colitis in mice by damping pro-inflammatory cytokine secretion and suppressing the nuclear factor-kappa B pathway activation.

Dietary 5-demethylnobiletin prevents antibiotic-associated dysbiosis of gut microbiota and damage to the colonic barrier

5-Demethylnobiletin (5DN) is an important ingredient of citrus extract that is rich in polymethoxyflavones (PMFs). In this study, we systemically investigated the preventive effects of 5DN on antibiotic-associated intestinal disturbances. Experimental mice were gavaged 0.2 mL per day of the antibiotic cocktail (12.5 g L^-1 cefuroxime and 10 g L^-1 levofloxacin) for 10 days, accompanied by dietary 0.05% 5DN for 10 and 20 days. The results showed that the combination of cefuroxime and levofloxacin caused swelling of the cecum and injury to the colon tissue. Meanwhile, the balance of intestinal oxidative stress and the barrier function of mice was also damaged by the antibiotics through upregulation of the relative mRNA levels of superoxide dismutase 3 (SOD3), quinine oxidoreductase 1 (NQO1) and glutathione peroxidase 1 (GPX1), and downregulation of the relative protein levels of tight junction proteins (TJs). Moreover, antibiotic exposure led to disorder of the gut microbiota, particularly increased harmful bacteria (Proteobacteria) and decreased beneficial bacteria (Bacteroideta). However, dietary 5DN could reduce antibiotic-associated intestinal damage, evidenced by the results that 5DN alleviated gut oxidative damage and attenuated intestinal barrier injury via increasing the expression of TJs including occludin and zonula occluden1 (ZO1). Additionally, dietary 5DN modulated the composition of the gut microbiota in antibiotic-treated mice by increasing the relative levels of beneficial bacteria, such as Dubosiella and Lactobacillus. Moreover, PMFs increased the contents of isobutyric acid and butyric acid, which were almost eliminated by antibiotic exposure. In conclusion, 5DN could alleviate antibiotic-related imbalance of intestinal oxidative stress, barrier function damage, intestinal flora disorders and the reduction of short-chain fatty acids (SCFAs), which lays a foundation for exploring safer and more effective ways to prevent or mitigate antibiotic-associated intestinal damage.

Spatial Distribution and Antioxidant Activity of Extracts from Citrus Fruits

Citrus fruits are recommended components of the human diet because of their enriched composition in bioactive compounds and health benefits. Among their notable components are phenols, with a special emphasis on flavonoids, limonoids, and carboxylic acids. In this research, we have carried out a spatial metabolomics analysis for the characterization of these bioactive families in three citrus fruits, namely, lemons, limes, and mandarins. Sampling was undertaken, for which the juices and three fruit tissues, namely, albedo, flavedo, and segments, were analyzed. This characterization allowed for the determination of 49 bioactive compounds in all the samples. The composition of the different extracts was correlated with the antioxidant capacity measured by the DPPH radical scavenging activity and β-carotene bleaching assays. Flavonoids, found in the albedo and flavedo at higher concentrations, were the main components responsible for DPPH radical scavenging activity. On the other hand, the combined action of flavonoids and limonoids contributed to explaining the antioxidant activity measured by the β-carotene bleaching assay. Generally, the antioxidant capacity of juices was lower than that estimated for extracts from citrus tissues.

Soluble Epoxide Hydrolase Contributes to Cell Senescence and ER Stress in Aging Mice Colon

Aging, which is characterized by enhanced cell senescence and functional decline of tissues, is a major risk factor for many chronic diseases. Accumulating evidence shows that age-related dysfunction in the colon leads to disorders in multiple organs and systemic inflammation. However, the detailed pathological mechanisms and endogenous regulators underlying colon aging are still largely unknown. Here, we report that the expression and activity of the soluble epoxide hydrolase (sEH) enzyme are increased in the colon of aged mice. Importantly, genetic knockout of sEH attenuated the age-related upregulation of senescent markers p21, p16, Tp53, and β-galactosidase in the colon. Moreover, sEH deficiency alleviated aging-associated endoplasmic reticulum (ER) stress in the colon by reducing both the upstream regulators Perk and Ire1 as well as the downstream pro-apoptotic effectors Chop and Gadd34. Furthermore, treatment with sEH-derived linoleic acid metabolites, dihydroxy-octadecenoic acids (DiHOMEs), decreased cell viability and increased ER stress in human colon CCD-18Co cells in vitro. Together, these results support that the sEH is a key regulator of the aging colon, which highlights its potential application as a therapeutic target for reducing or treating age-related diseases in the colon.

5-Demethylnobiletin mediates cell cycle arrest and apoptosis via the ERK1/2/AKT/STAT3 signaling pathways in glioblastoma cells

5-Demethylnobiletin is the active ingredient in citrus polymethoxyflavones that could inhibit the proliferation of several tumor cells. However, the anti-tumor effect of 5-Demethylnobiletin on glioblastoma and the underlying molecular mechanisms are remains unknown. In our study, 5-Demethylnobiletin markedly inhibited the viability, migration and invasion of glioblastoma U87-MG, A172 and U251 cells. Further research revealed that 5-Demethylnobiletin induces cell cycle arrest at the G0/G1 phase in glioblastoma cells by downregulating Cyclin D1 and CDK6 expression levels. Furthermore, 5-Demethylnobiletin significantly induced glioblastoma cells apoptosis by upregulating the protein levels of Bax and downregulating the protein level of Bcl-2, subsequently increasing the expression of cleaved caspase-3 and cleaved caspase-9. Mechanically, 5-Demethylnobiletin trigged G0/G1 phase arrest and apoptosis by inhibiting the ERK1/2, AKT and STAT3 signaling pathway. Furthermore, 5-Demethylnobiletin inhibition of U87-MG cell growth was reproducible in vivo model. Therefore, 5-Demethylnobiletin is a promising bioactive agent that might be used as glioblastoma treatment drug.

5-Demethylnobiletin: Insights into its pharmacological activity, mechanisms, pharmacokinetics and toxicity

BACKGROUND

5-Demethylnobiletin (5DN) is a polymethoxyflavone (PMF) primarily found in citrus fruits. It has various health-promoting properties and hence has attracted significant attention from scholars worldwide.

PURPOSE

This review is the first to systematically summarize the recent research progress of 5DN, including its pharmacological activity, mechanism of action, pharmacokinetics, and toxicological effects. In addition, the pharmacological mechanism of action of 5DN has been discussed from a molecular biological perspective, and data from in vivo and in vitro animal studies have been compiled to provide a more thorough understanding of 5DN as a potential lead drug.

METHODS

Data were extracted from SciFinder, PubMed, ScienceDirect and China National Knowledge Infrastructure (CNKI) from database inception to January 2022.

RESULTS

5DN has broad pharmacological activities. It exerts anti-inflammatory effects, promotes apoptosis and autophagy, and induces melanogenesis mainly by regulating the JAK2/STAT3, caspase-dependent apoptosis, ROS-AKT/mTOR, MAPK and PKA-CREB signaling pathways. 5DN can be used for treating diseases such as cancer, inflammation-related diseases, rheumatoid arthritis, and neurodegenerative diseases. To date, there have been only a few toxicological studies on 5DN, and both in vitro and in vivo on 5DN have not revealed significant toxic side effects. Pharmacokinetic studies have revealed that the metabolites of 5DN are mainly 5,3'-didemethylnobiletin (M1); 5,4'-didemethylnobiletin (M2) and 5,3',4'-tridemethylnobiletin (M3), in either, glucuronide-conjugated or monomeric form. The pharmacokinetic products of 5DN, especially M1, possess better activity than 5DN for the treatment of cancer.

CONCLUSION

The anticancer effects of 5DN and its metabolites warrant further investigation as potential drug candidates, especially through in vivo studies. In addition, the therapeutic effects of 5DN in neurodegenerative diseases should be examined in more experimental models, and the absorption and metabolism of 5DN should be further investigated in vivo.

5-Demethylnobiletin Inhibits Cell Proliferation, Downregulates ID1 Expression, Modulates the NF-κB/TNF-α Pathway and Exerts Antileukemic Effects in AML Cells

Acute myeloid leukemia (AML) is characterized by the dysregulation of hematopoietic cell proliferation, resulting in the accumulation of immature myeloid cells in bone marrow. 5-Demethylnobiletin (5-demethyl NOB), a citrus 5-hydroxylated polymethoxyflavone, has been reported to exhibit various bioactivities, such as antioxidant, anti-inflammatory and anticancer properties. In this study, we investigated the antileukemic effects of 5-demethyl NOB and its underlying molecular mechanisms in human AML cells. We found that 5-demethyl NOB (20−80 μM) significantly reduced human leukemia cell viability, and the following trend of effectiveness was observed: THP-1 ≈ U-937 > HEL > HL-60 > K562 cells. 5-Demethyl NOB (20 and 40 μM) modulated the cell cycle through the regulation of p21, cyclin E1 and cyclin A1 expression and induced S phase arrest. 5-Demethyl NOB also promoted leukemia cell apoptosis and differentiation. Microarray-based transcriptome, Gene Ontology (GO) and Gene Set Enrichment Analysis (GSEA) of differentially expressed genes (DEGs) analysis showed that the expression of inhibitor of differentiation/DNA binding 1 (ID1), a gene associated with the GO biological process (BP) cell population proliferation (GO: 0008283), was most strongly suppressed by 5-demethyl NOB (40 μM) in THP-1 cells. We further demonstrated that 5-demethyl NOB-induced ID1 reduction was associated with the inhibition of leukemia cell growth. Moreover, DEGs involved in the hallmark gene set NF-κB/TNF-α signaling pathway were markedly enriched and downregulated by 5-demethyl NOB. Finally, we demonstrated that 5-demethyl NOB (20 and 40 μM), combined with cytarabine, synergistically reduced THP-1 and U-937 cell viability. Our current findings support that 5-demethyl NOB dramatically suppresses leukemia cell proliferation and may serve as a potential phytochemical for human AML chemotherapy.

Mannose Attenuates Colitis-Associated Colorectal Tumorigenesis by Targeting Tumor-Associated Macrophages

Mannose has recently drawn extensive attention for its substantial anti-cancer activities, but the underlying mechanism remains largely unclear. The aim of this study was to investigate the effects of mannose on experimental colitis-associated colorectal tumorigenesis and underlying mechanisms. Data clearly showed that at plasma concentrations achieved after oral administration, mannose slightly affected malignancy of tumor cells or tumor promoter-induced transformation of pre-neoplastic cells, but substantially suppressed manifestation of the M2-like phenotype of tumor-associated macrophages (TAMs) in a cancer cell and macrophage co-culture model. Mechanistically, mannose might greatly impair the production of tumor cell-derived lactate which has a critical role in the functional polarization of TAMs. Importantly, oral administration of mannose protected mice against colitis-associated colorectal tumorigenesis by normalizing TAM polarization. Collectively, these findings highlight the importance of TAMs in colorectal tumorigenesis, and provide a rationale for introducing mannose supplementation to patients suffering from inflammatory bowel diseases.

Gastrointestinal biotransformation and tissue distribution of pterostilbene after long-term dietary administration in mice

The metabolic fate of dietary compounds is closely related to their biological functions. Pterostilbene (PT) is a methylated stilbene found in many plant foods. Herein, we investigated gastrointestinal biotransformation and tissue distribution of PT in mice fed with 0.05% PT (w/w) for 5 weeks. PT and its major metabolites i.e. PT sulfate (PT-S), pinostilbene, pinostilbene sulfate, hydroxylated PT and hydroxylated PT sulfate were identified and quantified in the mucosa and content of the digestive tissues, blood, urine and vital organs. The results showed PT underwent demethylation, hydroxylation and conjugation in the small intestine, while the conjugated metabolites were largely deconjugated in the colon. Anaerobic fermentation with mouse cecal bacteria demonstrated the microbiota mediated deconjugation and demethylation of PT-S and PT, respectively. In conclusion, oral consumption of PT led to extensive biotransformation in mouse gastrointestinal tract and the metabolites of PT might play important roles in the bioactivity of PT.

Bioactive Compounds of Citrus Fruits: A Review of Composition and Health Benefits of Carotenoids, Flavonoids, Limonoids, and Terpenes

The increased consumption of fruits, vegetables, and whole grains contributes to the reduced risk of many diseases related to metabolic syndrome, including neurodegenerative diseases, cardiovascular disease (CVD), diabetes, and cancer. Citrus, the genus Citrus L., is one of the most important fruit crops, rich in carotenoids, flavonoids, terpenes, limonoids, and many other bioactive compounds of nutritional and nutraceutical value. Moreover, polymethoxylated flavones (PMFs), a unique class of bioactive flavonoids, abundantly occur in citrus fruits. In addition, citrus essential oil, rich in limonoids and terpenes, is an economically important product due to its potent antioxidant, antimicrobial, and flavoring properties. Mechanistic, observational, and intervention studies have demonstrated the health benefits of citrus bioactives in minimizing the risk of metabolic syndrome. This review provides a comprehensive view of the composition of carotenoids, flavonoids, terpenes, and limonoids of citrus fruits and their associated health benefits.

Dietary 5-demethylnobiletin modulates xenobiotic-metabolizing enzymes and ameliorates colon carcinogenesis in benzo[a]pyrene-induced mice

The intake of common polycyclic aromatic hydrocarbons (PAHs), such as benzo[a]pyrene (BaP), is strongly correlated to the initiation of colon cancer. BaP is a well-known pro-carcinogen that is metabolically activated by xenobiotic-metabolizing enzymes. Studies indicate that polymethoxyflavones, including 5-demethylnobiletin (5-DMNB), exhibit anti-inflammatory and anti-carcinogenic properties. However, the effects of 5-DMNB on xenobiotic-metabolizing enzymes and BaP-induced carcinogenesis remain unclear. The combination of BaP and a promoting agent-dextran sulfate sodium (DSS)-has been demonstrated to induce tumors in mouse models. Thus, this study aimed to determine the protective effect of 5-DMNB on carcinogen biotransformation and BaP/DSS-induced colon carcinogenesis. Our results showed that 5-DMNB had a substantial inhibitory effect on CYP1B1 induced by BaP and upregulated the detoxification enzymes UDP-glucuronosyltransferases (UGTs) and glutathione S-transferases (GSTs). Furthermore, subsequent analyses confirmed that the dietary administration of 5-DMNB markedly ameliorated tumor formation in BaP/DSS-treated mice. Exposure to BaP/DSS also significantly elevated TNF-α levels, and the administration of 5-DMNB reversed this increase. Taken together, we determined that 5-DMNB attenuates BaP/DSS-induced colon cancer through the regulation of inflammation and xenobiotic-metabolizing enzymes. These results indicate that 5-DMNB has significant potential as a novel chemopreventive agent for preventing carcinogen activation and inflammation-associated carcinogenesis.

Dietary Tangeretin Alleviated Dextran Sulfate Sodium-Induced Colitis in Mice via Inhibiting Inflammatory Response, Restoring Intestinal Barrier Function, and Modulating Gut Microbiota

In this study, the preventive effect of tangeretin (TAN), a natural flavonoid derivative from citrus fruits, on the dextran sulfate sodium (DSS)-induced colitis in mice was evaluated. Our results showed that dietary TAN (0.04% and 0.08% w/w in the diet) significantly reduced the severity of colitis caused by DSS treatment in mice, evidenced by the increased colon length, the reduced disease activity index, and the attenuated colonic tissue damages. Moreover, dietary TAN inhibited the inflammatory response via down-regulating the overexpression of colonic inflammatory cytokines. Immunohistochemical analysis revealed that the intestinal barrier function was restored by TAN through enhancing claudin-1 and ZO-1 expressions. Additionally, dietary TAN modulated gut microbiota in colitic mice via enhancing gut microbiota diversity, ascending the level of beneficial bacteria, e.g., Lachnospiraceae and Lactobacillaceae, and descending the level of harmful bacteria, e.g., Enterobacteriaceae and Alistipes. Besides, dietary TAN promoted short-chain fatty acids production in DSS-treated mice. Altogether, these findings provided scientific evidence for the rational utilization of TAN as a preventive agent against colonic inflammation and related diseases.

Identification of 4'-Demethyltangeretin as a Major Urinary Metabolite of Tangeretin in Mice and Its Anti-inflammatory Activities

The present study showed that oral administration of tangeretin (TAN) in mice resulted in the production of 4'-demethyltangeretin (4DT) as a major urinary metabolite. The anti-inflammatory efficacy of TAN and 4DT was determined in RAW 264.7 macrophages stimulated by lipopolysaccharides (LPS). 4DT produced considerably stronger inhibition on the overproduction of prostaglandin E₂ and nitric oxide than TAN did at the same concentrations. Western blot and quantitative polymerase chain reaction analyses indicated that 4DT exerted more potent suppressive activity on the over-expression of interleukin-1β, inducible nitric oxide synthase, and cyclooxygenase-2 than TAN. Treatments with TAN and 4DT diminished LPS-stimulated nuclear factor κB (NFκB) translocation via suppressing the degradation of inhibitor κB (IκBα). Furthermore, both compounds attenuated mitogen-activated protein kinases (MAPKs) and Akt signaling upregulated by LPS. Overall, our findings showed that TAN and 4DT inhibited the LPS-stimulated inflammatory response in macrophages by suppressing Akt/MAPKs/NFκB proinflammatory pathways, while 4DT showed more potent activity than TAN, its parent compound.

The biological fate and bioefficacy of citrus flavonoids: bioavailability, biotransformation, and delivery systems

Citrus fruits are among the most popularly consumed fruits worldwide, including oranges, grapefruits, pomelos and lemons. Citrus flavonoids such as hesperidin, naringin and nobiletin have shown an array of health benefits in cell, animal and clinical studies, including antioxidative, anti-inflammatory, neuroprotective, anticancer, and anti-obesity activities. Citrus flavonoids have limited bioavailability after oral administration, leaving the major part unabsorbed and persisted in the colon. Recent studies have highlighted the important role of the gut microbiota and in vivo biotransformation on the bioactivity of citrus flavonoids. This article discusses the biological fate of citrus flavonoids from the viewpoint of their absorption, distribution, metabolism and excretion in vivo. Many delivery systems have been designed to enhance the oral bioavailability of citrus flavonoids, such as emulsions, self-emulsifying systems, nanoparticles and solid dispersions. The ultimate goal of these delivery systems is to enhance the bioefficacy of citrus flavonoids. Several studies have found that the increased bioavailability leads to enhanced bioefficacy of citrus flavonoids in specific animal models. Regarding the complex dynamics of citrus flavonoids and gut microbiota, the bioavailability-bioactivity relationship is an interesting but under-discussed area. Comprehensively understanding the biological fate and bioefficacy of citrus flavonoids would be helpful to develop functional foods with better health benefits.

Rhamnetin decelerates the elimination and enhances the antitumor effect of the molecular-targeting agent sorafenib in hepatocellular carcinoma cells via the miR-148a/PXR axis

The pregnane X receptor (PXR) mediates the resistance of sorafenib in hepatocellular carcinoma (HCC) by promoting the clearance or elimination of sorafenib via the drug resistance-related downstream genes of the PXR. Previously, we revealed that rhamnetin (a flavonoid functioning as an inhibitor of sirtuin (Sirt)1) could inhibit expression of the downstream gene of the PXR: multidrug resistance 1 (mdr-1). However, how rhamnetin regulates the PXR pathway in HCC cells is not known. Here, we demonstrated that rhamnetin decelerated elimination of the molecular-targeting agent sorafenib in HCC cells via the microRNA (miR)-148a/PXR axis. Rhamnetin treatment decreased expression of the drug resistance-related downstream genes of PXR (cyp3a4 [cytochrome P-450] or mdr-1 [multi-drug resistance 1]), which mediate the metabolism or elimination of sorafenib in HCC cells. Mechanistically, rhamnetin increased expression of miR-148a (which is tumor-suppressive) in a P53-dependent manner, leading to inhibition of PXR expression and decrease in expression of its downstream genes. Rhamnetin enhanced miRNA-148a transcription by repressing Sirt1 activation to enhance acetylation at residue-373 of P53. Rhamnetin treatment decelerated the metabolic clearance of sorafenib in HCC cells and enhanced the sensitivity of HCC cells to sorafenib. Our results suggest that rhamnetin could be a potential agent for overcoming sorafenib resistance in HCC treatment.

Identification of Xanthomicrol as a Major Metabolite of 5-Demethyltangeretin in Mouse Gastrointestinal Tract and Its Inhibitory Effects on Colon Cancer Cells

5-Demethyltangeretin (5DT) is a unique polymethoxyflavone mainly found in the peel of citrus, and has shown potent suppressive effects on multiple human cancer cells. Biotransformation plays a critical role in the biological activities of dietary bioactive components because their metabolites may exert significant bioactivities. In the present study, the metabolic fate of 5DT in mouse gastrointestinal (GI) tract after long-term oral intake and the anti-cancer effects of its major metabolite were determined. It was found that 5DT underwent extensive biotransformation after oral ingestion in mice. A major demethylated metabolite was produced via phase I metabolism, while conjugates (glucuronide and sulfate) were generated via phase II metabolism. Specifically, 4'-position on the B ring of 5DT was the major site for demethylation reaction, which led to the production of xanthomicrol (XAN) as a major metabolite. More importantly, the level of XAN in the colon was significantly higher than that of 5DT in 5DT-fed mice. Thus, we further determined the suppressive effects of XAN on human colon cancer HCT116 cells. We found that XAN effectively inhibited the proliferation of HCT116 cells by arresting cell cycle and inducing cellular apoptosis, which was further evidenced by upregulated p53 and p21 and downregulated cyclin D and CDK4/6 level. In conclusion, this study identified XAN as a major metabolite of 5DT in mouse GI tract, and demonstrated its suppressive effects on HCT116 colon cancer cells.