Application of Bioactive Quercetin in Oncotherapy: From Nutrition to Nanomedicine

Recent Advances in Liposomal Drug Delivery System of Quercetin for Cancer Targeting: A Mechanistic Approach

Quercetin (QT, 3,3',4',5,7-pentahydroxyflavone), is a natural flavonoid with nutritional value and acts as a potential free-radical scavenger (antioxidant). QT has also been explored for its anti-cancer as well as anti-proliferative activities against numerous cancerous cells. Moreover, QT exhibits significant pro-apoptotic activity against tumor cells and is well established to control the growth of different carcinoma cells at various phases of the cell cycle. Hence, it can reduce the burden of human solid cancer and metastasis. Both these activities have been established in a diverse class of human cell lines in-vitro as well as in animal models (in-vivo). Apart from the promising therapeutic activities of QT molecule, their applications have been limited due to some major concerns, including low oral bioavailability and poor aqueous solubility. Also, rapid gastrointestinal digestion of QT seems to be a key barrier for its clinical translations for oral drug delivery in conventional dosage form. Henceforth, to overcome these drawbacks, QT is loaded with liposomal systems, which exhibit promising outcomes in the upregulation of QT by the epithelial system and also improved its targeting at the site of action. Furthermore, Liposomes based Drug Delivery Systems (LDDS) have showed significant therapeutic activity with conjugated drug moiety and exhibit safety, biocompatibility, biodegradability, and mitigated toxicity despite having certain limitations associated with physiological and biological barriers. Herein, in this review, we have focused on the mechanism related with the chemotherapeutic activity of QT and also discussed the promising activity of QT-loaded LDDS as a potent chemotherapeutic agent for cancer therapy.

Participation of MicroRNAs in the Treatment of Cancer with Phytochemicals

Cancer is a global health concern and one of the main causes of disease-related death. Even with considerable progress in investigations on cancer therapy, effective anti-cancer agents and regimens have thus far been insufficient. There has been compelling evidence that natural phytochemicals and their derivatives have potent anti-cancer activities. Plant-based anti-cancer agents, such as etoposide, irinotecan, paclitaxel, and vincristine, are currently being applied in medical treatments for patients with cancer. Further, the efficacy of plenty of phytochemicals has been evaluated to discover a promising candidate for cancer therapy. For developing more effective cancer therapy, it is required to apprehend the molecular mechanism deployed by natural compounds. MicroRNAs (miRNAs) have been realized to play a pivotal role in regulating cellular signaling pathways, affecting the efficacy of therapeutic agents in cancer. This review presents a feature of phytochemicals with anti-cancer activity, focusing mainly on the relationship between phytochemicals and miRNAs, with insights into the role of miRNAs as the mediators and the regulators of anti-cancer effects of phytochemicals.

Improved oral delivery of quercetin with hyaluronic acid containing niosomes as a promising formulation

Quercetin, a substance from nature has various biological effects; while, some challenges like low solubility in water and absorption, and high first-pass metabolism hindered its clinical efficiencies. So, various strategies using novel nanocarriers have been designed to overcome these obstacles. This study aimed to fabricate the polymeric niosomes by incorporating hyaluronic acid to deliver quercetin. After preparation, quercetin entrapped niosomes were investigated in terms of size, zeta potential, quercetin entrapment, CTAB turbidimetric assay, AFM, TEM, differential scanning Calorimetry, X-Ray diffraction, DPPH antioxidant determination, and in vivo anti-inflammatory analysis. The analysis of the results exhibited that size of niosomes containing quercetin and hyaluronic acid was 231.07 ± 8.39 nm with a zeta potential of -34.00 ± 0.95 mV. Moreover, quercetin entrapment efficiency and loading were 94.67 ± 1.62% and 1.65 ± 0.37%, respectively. TEM and AFM showed that polymeric niosomes were spheres. The release data presented that the Higuchi model was the best-fitted model. DPPH antioxidant determination displayed that 80 µl of polymeric niosomes with 7.46 × 10^-8mol of quercetin had a remarkable antioxidant potency. According to the in vivo oedema evaluation, the potency of polymeric formulations was superior to the simple suspension of quercetin to control inflammation in rats by oral administration.

Antioxidant Activity and Hemocompatibility Study of Quercetin Loaded Plga Nanoparticles

Quercetin (QU) is an important flavonoid compound presenting lots of biological activities, but its application has been limited due to its low aqueous solubility and instability. In this study, conducted to improve these properties of the quercetin, quercetin-encapsulated PLGA nanoparticles were prepared, characterized, and evaluated for antioxidant and hemolytic activity. Nanoparticles were produced by single emulsion solvent evaporation method. Four different process parameters initial QU amount, PVA concentration, PVA volume, and initial PLGA amount were investigated to obtain the nanoparticles which have minimum particle size and maximum entrapment efficiency. Synthesized nanoparticles were evaluated for particle size, entrapment efficiency, and reaction yield. Additionally, antioxidant properties and in-vitro hemolytic activity of quercetin loaded nanoparticles with different particle size were also evaluated for the first time in the literature. The antioxidant activity results showed that nanoparticles have different antioxidant activity, depending on the amount of quercetin release from nanoparticles at different particle sizes. The hemolytic activity results show that all nanoparticles exhibited favorable compatibility to red blood cells and no significant hemolytic effect was observed.

Drug delivery based pharmacological enhancement and current insights of quercetin with therapeutic potential against oral diseases

The heavy burden of oral diseases such as oral cancers, dental caries, periodontitis, etc. and their consequence on the patient's quality of life demonstrated an urgent demand for developing effective therapeutics. Quercetin as a natural derived flavonoid, could be utilized in the therapeutic formulation of various diseases such as diabetes, breast cancer and asthma, owing to its prominent pharmacological values. In the last decade, the applications of quercetin as a natural compound in oral treatment have attracted increasing interest due to its multifunction including antioxidant, antibacterial, anti-inflammatory and antineoplastic activities. Besides, considering the low bioavailability of quercetin, great efforts have been made in its drug delivery systems to address the problem of limited application. Therefore, this review summarized the cutting-edge researches on versatile effects and enhanced bioavailability of quercetin resulting from innovative drug delivery systems, particularly focused on its potential against oral diseases. The application of quercetin would provide novel and promising therapeutic approach for clinical treatment, promoting the development of global dental public health.

Therapeutic Potential of Quercetin as an Antiatherosclerotic Agent in Atherosclerotic Cardiovascular Disease: A Review

Atherosclerotic cardiovascular disease (ASCVD) is one of the diseases with the highest morbidity and mortality globally. It causes a huge burden on families and caregivers and high costs for medicine and surgical interventions. Given expensive surgeries and failures of most conventional treatments, medical community tries to find a more cost-effective cure. Thus, attentions have been primarily focused on food or herbs. Quercetin (Qu) extracted from food, a flavonoid component, develops potentials of alternative or complementary medicine in atherosclerosis. Due to the wide range of health benefits, researchers have considered to apply Qu as a natural compound in therapy. This review is aimed to identify the antiatherosclerosis functions of Qu in treating ASCVD such as anti-inflammatory, antioxidant properties, effects on endothelium-dependent vasodilation, and blood lipid-lowering.

Therapeutic Potential of Quercetin: New Insights and Perspectives for Human Health

Quercetin (Que) and its derivatives are naturally occurring phytochemicals with promising bioactive effects. The antidiabetic, anti-inflammatory, antioxidant, antimicrobial, anti-Alzheimer's, antiarthritic, cardiovascular, and wound-healing effects of Que have been extensively investigated, as well as its anticancer activity against different cancer cell lines has been recently reported. Que and its derivatives are found predominantly in the Western diet, and people might benefit from their protective effect just by taking them via diets or as a food supplement. Bioavailability-related drug-delivery systems of Que have also been markedly exploited, and Que nanoparticles appear as a promising platform to enhance their bioavailability. The present review aims to provide a brief overview of the therapeutic effects, new insights, and upcoming perspectives of Que.

Antiproliferative effects of combinational therapy of Lycopodium clavatum and quercetin in colon cancer cells

Background Colorectal cancer (CRC) is the third most prevalent form of cancer and fourth leading cause of morbidity worldwide. Surgical resection remains the only curative approach for CRC, but recurrence following surgery is the main problem and ultimate cause of death. Lycopodium clavatum and quercetin have been found to exert its anticancer properties. The aim of the present study is to investigate whether quercetin or L. clavatum extract and combination of both have any profound role in reducing major inflammatory cytokines in Colo-320 cells. Methods L. clavatum and Quercetin alone or in combination was administered to colon cancer cells and various toxicity markers, gene expression analyses of apototic genes and gelatin zymmography were performed. Results Quercetin (50 μm) in combination with L. clavatum extract (10 μL) distinctly reduced cell growth and highlighted their potential effects in extirpation of colon cancer cells. Treatment with increased dose of L. clavatum extract in combination with quercetin reduced the colony size and proliferation potential when compared to the sole treatment of plant extracts. In the antimicrobial assays, it was observed that Lycopodium alone exhibited antimicrobial activity against Escherichia coli and Pseudomonas aeruginosa. Characterization of L. clavatum extract and quercetin was performed and confirmed the presence of flavonoids and alkaloids. Treatment with Lycopodium and quercetin combination induced significant down-regulation in activities of MMP2 and MMP9 tested by gelatin zymography. The combined treatment greatly affected the mRNA expression of p53, Bcl2, Bax, Caspase 3, Wnt 1, Cyclin D1, and Catalase genes in colon cancer cells. Conclusion The synergistic effect between Lycopodium and quercetin might bring forward the enhanced antitumorigenic properties of combinational therapy with natural products to successfully combat the cancer progression with minimal side effects and resistance to drugs.

Partitioned Extracts of Bauhinia championii Induce G0/G1 Phase Arrest and Apoptosis in Human Colon Cancer Cells

Bauhinia championii (Benth.) is one of the commonly used herbs in Taiwan. The stem of this plant has been used to treat epigastria pain and rheumatoid arthritis. However, the antitumor activities of this herb have never been reported. This study aims to investigate the mechanism of anticancer activity of the extracts from B. championii (BC). BC was fractionated with a series of organic solvents, including n-hexane (H), ethyl acetate (EA), 1-butanol (B), and water (W). We first investigated the effects of BC-H, BC-EA, BC-B and BC-W partitioned fraction on cell viability. In HCT 116 colon cancer cell lines, BC-EA showed the highest inhibition of cell viability and changed the morphology of cells. With dose- and time-dependent manners, BC-EA inhibited the proliferation of HCT 116 cells by inducing apoptosis and G₀/G₁ phase arrest of cell cycle. To determine the underlying mechanisms, down-regulated CDK2, Cyclin D, and Cyclin E and up-regulated p16, p21, and p53 may account for the cell cycle arrest, while the apoptotic effect of BC-EA may attribute to increased intracellular Ca2+, loss of mitochondria membrane potential (ΔΨm), increase of Bax, Bak, puma, and AIF, and decrease of Bcl-2. Furthermore, the inactivation of Ras signaling pathway by BC-EA also contributed to its apoptotic effect on HCT 116. Our study demonstrates that BC-EA not only inhibits cell growth but also induces apoptosis through inhibiting Ras signal pathway and increasing p53 expression levels. We suggest that BC-EA may be a new dietary supplement and a useful tool to search for therapeutic candidates against colon cancer.

Effect of Quercetin on PC12 Alzheimer's Disease Cell Model Induced by Aβ 25-35 and Its Mechanism Based on Sirtuin1/Nrf2/HO-1 Pathway

Objective

This study is aimed at studying the effect of quercetin on the Alzheimer disease cell model induced by Aβ_25-35 in PC12 cells and its mechanism of action.

Methods

The AD cell model was established by Aβ_25-35. Quercetin was used at different concentrations (0, 10, 20, 40, and 80 μmol/L). The morphology of cells was observed, and the effect on cell survival rate was detected by the MTT method. Cell proliferation was detected by the SRB method. The contents of LDH, SOD, MDA, GSH-Px, AChE, CAT, and T-AOC were detected by kits. The expression of sirtuin1/Nrf2/HO-1 was detected by RT-qPCR and Western blot.

Results

PC12 cells in the control group grew quickly and adhered well to the wall, most of which had extended long axons and easily grew into clusters. In the model group, cells were significantly damaged and the number of cells was significantly reduced. It was found that PC12 cells were swollen, rounded, protruding, and retracting, with reduced adherent function and floating phenomenon. Quercetin could increase the survival rate and proliferation rate of PC12 cells; reduce the levels of LDH, AChE, MDA, and HO-1 protein; and increase the levels of SOD, GSH-Px, CAT, T-AOC, sirtuin1, and Nrf2 protein.

Conclusion

Quercetin can increase the survival rate of PC12 injured by Aβ_25-35, promote cell proliferation, and antagonize the toxicity of Aβ; it also has certain neuroprotective effects. Therefore, quercetin is expected to become a drug for the treatment of AD.

Efficient synergistic combination effect of Quercetin with Curcumin on breast cancer cell apoptosis through their loading into Apo ferritin cavity

Combination of natural agents has received a great attention in cancer treatment because of synergistically increased apoptotic effect on cancer cell lines by triggering several apoptotic signaling pathways. However, the hydrophobic nature, poor bioavailability and low cellular uptake of most natural agents limit their therapeutic effectiveness. The purpose of this study was to design Apoferritin nanoparticles loaded with Quercetin and Curcumin (Que-Cur-HoS-Apo NPs) and to test their synergistic antitumor properties on a breast cancer cell line (MCF7). The physico-chemical characterization of the Que-Cur-HoS-Apo NPs by Size Exclusion Chromatography (FPLC) and Dynamic Light Scattering (DLS) confirmed the encapsulation of the compounds in the protein cage with narrow size distribution in the range 17.4 ± 1.2 nm. Cell viability study indicated that Que-Cur-HoS-Apo NPs were able to exert a more pronounced effect at lower dose on the MCF7 cell line when compared to the free combination of the drugs. The Que-Cur-HoS-Apo system allowed cellular uptake of natural agents thus triggering enhanced apoptosis. These effects were confirmed by Annexin-V/7-AAD Staining Assay and intracellular Reactive Oxygen Species (ROS) quantitative detection. These results suggest the potential of Que-Cur-HoS-Apo NPs as a promising anti-cancer agent in breast cancer therapy and pave the way to examine Que-Cur-HoS-Apo NPs effect in vivo.

Green graphene nanoplates for combined photo-chemo-thermal therapy of triple-negative breast cancer

Aim: Green graphene oxide (GO) nanoplates, which are reduced and stabilized by quercetin and guided by folate receptors (quercetin reduced and loaded GO nanoparticles-folic acid [FA]), were developed to mediate combined photo-chemo-thermal therapy of triple-negative breast cancer. Materials & methods: Modified Hummers method was used for the synthesis of GO followed by its reduction using quercetin, FA was then conjugated as a targeting ligand. A cytotoxicity assay, apoptosis assay and cellular uptake assay were performed in vitro in MDA-MB-231 cell line with and without irradiation of a near-infrared 808 nm laser. Results & conclusion: Quercetin reduced and loaded GO nanoparticles-FA showed significantly high cellular uptake (p < 0.001) and cytotoxic effects in MDA-MB-231 cells, which was even more prominent under the situation of near-infrared 808 nm laser irradiation, making it a potential option for treating triple-negative breast cancer.

Quercetin Inhibits Cell Survival and Metastatic Ability via the EMT-mediated Pathway in Oral Squamous Cell Carcinoma

This study aimed to investigate whether quercetin exerts anticancer effects on oral squamous cell carcinoma (OSCC) cell lines and to elucidate its mechanism of action. These anticancer effects in OSCC cells were assessed using an MTT assay, flow cytometry (to assess the cell cycle), wound-healing assay, invasion assay, Western blot analysis, gelatin zymography, and immunofluorescence. To investigate whether quercetin also inhibits transforming growth factor β1 (TGF-β1)-induced epithelial-mesenchymal transition (EMT) in human keratinocyte cells, HaCaT cells were treated with TGF-β1. Overall, our results strongly suggest that quercetin suppressed the viability of OSCC cells by inducing cell cycle arrest at the G2/M phase. However, quercetin did not affect cell viability of human keratinocytes such as HaCaT (immortal keratinocyte) and nHOK (primary normal human oral keratinocyte) cells. Additionally, quercetin suppresses cell migration through EMT and matrix metalloproteinase (MMP) in OSCC cells and decreases TGF-β1-induced EMT in HaCaT cells. In conclusion, this study is the first, to our knowledge, to demonstrate that quercetin can inhibit the survival and metastatic ability of OSCC cells via the EMT-mediated pathway, specifically Slug. Quercetin may thus provide a novel pharmacological approach for the treatment of OSCCs.

Contemporary Formulations for Drug Delivery of Anticancer Bioactive Compounds

BACKGROUND

The immense development in the field of anticancer research has led to an increase in the research of bioactive compounds with anticancer potential. It has been known that many bioactive natural compounds have low solubility (and low bioavailability) as their main drawback when it comes to the formulation and drug delivery to specific sites.

OBJECTIVE

As many attempts have been made to overcome this issue, this review gives a summary of the current accomplishments regarding the development of new Drug Delivery Systems (DDSs) represented by nanoparticles (NPs) and exosomes.

METHODS

We analyzed the published data concerning selected compounds that present the most prominent plant secondary metabolites with anticancer potential, specifically flavone (quercetin), isoflavone (genistein and curcumin) and stilbene (resveratrol) groups that have been formulated as NPs and exosomes. In addition, we summarized the patent literature published from 2015-2018 that address these formulations.

RESULTS

Although the exact mechanism of action for the selected natural compounds still remains unclear, the anticancer effect is evident and the main research efforts are directed to finding the most suitable delivery systems. Recent patents in this field serve as evidence that these newly designed natural compound delivery systems could be powerful new anticancer agents in the very near future if the noted difficulties are overcome.

CONCLUSION

The focus of recent research is not only to clarify the exact mechanisms of action and therapeutic effects, but also to answer the issue of suitable delivery systems that can transport sufficient doses of bioactive compounds to the desired target.

Medicinal plants: Adjunct treatment to tuberculosis chemotherapy to prevent hepatic damage

The effectiveness of herbs for the management of chemically induced hepatotoxicity has been discussed by many researchers. However, there is a paucity of compressive literature on the significance of hepatoprotective plants for the management of anti-TB drug induced toxicity. Anti-TB drugs have been reported to causes hepatic damage, due to which, many patients across the globe discontinued the treatment. Medicinal plants have multiple therapeutic effects. The assessment of biological activity of plants against Mycobacterium and its use for hepatic recovery provides an effective treatment approach. Traditionally used medicinal plants are the rich source of phytochemicals and secondary metabolites. These compounds can restore normal function, enzymatic activity and structure of hepatic cells against anti-TB drug induced hepatotoxicity. The present review covers comprehensive details on different hepatoprotective and antimycobacterial plants studied during past few decades so that potential adjuvants can be studied for Tuberculosis chemotherapy.

Dietary flavonoids: Nano delivery and nanoparticles for cancer therapy

Application of nanotechnologies to cancer therapy might increase solubility and/or bioavailability of bioactive compounds of natural or synthetic origin and offers other potential benefits in cancer therapy, including selective targeting. In the present review we aim to evaluate in vivo studies on the anticancer activity of nanoparticles (NPs) obtained from food-derived flavonoids. From a systematic search a total of 60 studies were identified. Most of the studies involved the flavanol epigallocatechin-3-O-gallate and the flavonol quercetin, in both delivery and co-delivery (with anti-cancer drugs) systems. Moreover, some studies investigated the effects of other flavonoids, such as anthocyanins aglycones anthocyanidins, flavanones, flavones and isoflavonoids. NPs inhibited tumor growth in both xenograft and chemical-induced animal models of cancerogenesis. Encapsulation improved bioavailability and/or reduced toxicity of both flavonoids and/or co-delivered drugs, such as doxorubicin, docetaxel, paclitaxel, honokiol and vincristine. Moreover, flavonoids have been successfully applied in molecular targeted nanosystems. Selectivity for cancer cells involves pH- and/or reactive oxygen species-mediated mechanisms. Furthermore, flavonoids are good candidates as drug delivery for anticancer drugs in green synthesis systems. In conclusion, although human studies are needed, NPs obtained from food-derived flavonoids have promising anticancer effects in vivo.

Phospholipid-polymer hybrid nanoparticle-mediated transfollicular delivery of quercetin: prospective implement for the treatment of androgenic alopecia

Objectives: The aim of the study was to deliver effective doses of quercetin (Que) to the lower region of hair follicles (HFs) using the transfollicular route through dipalmotylphosphatidylcholine (DPPC)-reinforced poly lactide-co- glycolide nanoparticles (DPPC-PLGA hybrid NPs) for the treatment of alopecia. Method: PLGA and DPPC-PLGA hybrid NPs were prepared by double-emulsification solvent evaporation method. NPs were characterized for size, shape, zeta potential entrapment and drug release. Drug-polymer interactions were determined by infrared spectroscopy (Fourier transform infrared spectroscopy, FTIR) and differential scanning calorimetry (DSC). Follicular uptake of fluorescent marker tagged NPs was assessed on isolated rat skin by fluorescent microscopy. Potential of hybrid NPs to induce hair regrowth was tested on testosterone-induced alopecia in rat models by visual inspection, hair follicular density measurement (no./mm), and histological skin tissue section studies. Key findings: Hybrid NPs had mean vesicles size 339 ± 1.6, zeta potential -32.6 ± 0.51, and entrapment efficiency 78 ± 5.5. Cumulative drug release after 12 h was found to be 47.27 ± 0.79%. FTIR and DSC confirmed that drug was independently dispersed in the amorphous form in the polymer. Data from fluorescence microscopy suggested that NPs were actively taken up by HFs. In-vivo studies on alopecia-induced rat models showed that hybrid NPs improved hair regrowth potential of Que and accumulation of NPs at HFs end region inhibit HFs cells apoptosis. Conclusion: This study concludes that phospholipid-polymer hybrid NPs could be the promising transfollicular delivery system for Que in the treatment of androgenic alopecia management.

Quercetin Inhibits the Production of IL-1β-Induced Inflammatory Cytokines and Chemokines in ARPE-19 Cells via the MAPK and NF-κB Signaling Pathways

Quercetin, a bioflavonoid derived from vegetables and fruits, exerts anti-inflammatory effects in various diseases. Our previous study revealed that quercetin could suppress the expression of matrix metalloprotease-9 (MMP-9) and intercellular adhesion molecule-1 (ICAM-1) to achieve anti-inflammatory effects in tumor necrosis factor-α (TNF-α)-stimulated human retinal pigment epithelial (ARPE-19) cells. The present study explored whether quercetin can inhibit the interleukin-1β (IL-1β)-induced production of inflammatory cytokines and chemokines in ARPE-19 cells. Prior to stimulation by IL-1β, ARPE-19 cells were pretreated with quercetin at various concentrations (2.5–20 µM). The results showed that quercetin could dose-dependently decrease the mRNA and protein levels of ICAM-1, IL-6, IL-8 and monocyte chemoattractant protein-1 (MCP-1). It also attenuated the adherence of the human monocytic leukemia cell line THP-1 to IL-1β-stimulated ARPE-19 cells. We also demonstrated that quercetin inhibited signaling pathways related to the inflammatory process, including phosphorylation of mitogen-activated protein kinases (MAPKs), inhibitor of nuclear factor κ-B kinase (IKK)α/β, c-Jun, cAMP response element-binding protein (CREB), activating transcription factor 2 (ATF2) and nuclear factor (NF)-κB p65, and blocked the translocation of NF-κB p65 into the nucleus. Furthermore, MAPK inhibitors including an extracellular signal-regulated kinase (ERK) 1/2 inhibitor (U0126), a p38 inhibitor (SB202190) and a c-Jun N-terminal kinase (JNK) inhibitor (SP600125) decreased the expression of soluble ICAM-1 (sICAM-1), but not ICAM-1. U0126 and SB202190 could inhibit the expression of IL-6, IL-8 and MCP-1, but SP600125 could not. An NF-κB inhibitor (Bay 11-7082) also reduced the expression of ICAM-1, sICAM-1, IL-6, IL-8 and MCP-1. Taken together, these results provide evidence that quercetin protects ARPE-19 cells from the IL-1β-stimulated increase in ICAM-1, sICAM-1, IL-6, IL-8 and MCP-1 production by blocking the activation of MAPK and NF-κB signaling pathways to ameliorate the inflammatory response.

Reversal of Multidrug Resistance in Cancer by Multi-Functional Flavonoids

Multidrug resistance (MDR) resulting from different defensive mechanisms in cancer is one of the major obstacles of clinical treatment. To circumvent MDR many reversal agents have been developed, but most of them fail in clinical trials due to severely adverse effects. Recently, certain natural products have been reported to overcome MDR, including flavonoids which are abundant in plants, foods, and herbs. The structure of flavonoids can be abbreviated as C6-C3-C6 (C for carbon), and further categorized into flavonoids, iso-flavonoids and neo-flavonoids, according to their structural backbones. Flavonoids possess multiple bioactivities, and a growing body of research has indicated that both flavonoids and iso-flavonoids can either kill or re-sensitize conventional chemotherapeutics to resistant cancer cells. Here, we summarize the research and discuss the underlying mechanisms, concluding that these flavonoids do not function as specific regulators of target proteins, but rather as multi-functional agents that negatively regulate the key factors contributing to MDR.

MicroRNA-Mediated Health-Promoting Effects of Phytochemicals

Phytochemicals are known to benefit human health by modulating various cellular processes, including cell proliferation, apoptosis, and inflammation. Due to the potential use of phytochemicals as therapeutic agents against human diseases such as cancer, studies are ongoing to elucidate the molecular mechanisms by which phytochemicals affect cellular functions. It has recently been shown that phytochemicals may regulate the expression of microRNAs (miRNAs). MiRNAs are responsible for the fine-tuning of gene expression by controlling the expression of their target mRNAs in both normal and pathological cells. This review summarizes the recent findings regarding phytochemicals that modulate miRNA expression and promote human health by exerting anticancer, photoprotective, and anti-hepatosteatosis effects. Identifying miRNAs modulated by phytochemicals and understanding the regulatory mechanisms mediated by their target mRNAs will facilitate the efforts to maximize the therapeutic benefits of phytochemicals.

Size-Dependent Biological Effects of Quercetin Nanocrystals

Quercetin (QE) is an attractive natural compound for cancer prevention due to its beneficial anti-oxidative and anti-proliferative effects. However, QE is poorly soluble in water and slightly soluble in oil, which results in its low oral bioavailability and limits its application in the clinic. The aim of this study was to prepare QE nanocrystals (QE-NCs) with improved solubility and high drug loading, furthermore, the size-dependent anti-cancer effects of QE-NCs were studied. We prepared QE-NCs with three different particle sizes by wet milling, then, cell proliferation, migration and invasion were studied in A549 cells. The QE-NCs had antitumor effects in a dose- and size-dependent manner. Compared with the large particles, the small particles had a strong inhibitory impact on cell biological effects (p < 0.05 or p < 0.01). Moreover, Western blot assay indicated that QE-NCs may inhibit the migration and invasion of A549 cells by inhibiting the STAT3 signaling pathway, and the particle size may have an effect on this process. In this study, it was proven that NCs could dramatically enhance the anticancer efficacy of QE at the cellular level. In addition, particle size had a considerable influence on the dissolution behavior and antitumor effects of NCs.

Curcumin and quercetin synergistically inhibit cancer cell proliferation in multiple cancer cells and modulate Wnt/β-catenin signaling and apoptotic pathways in A375 cells

BACKGROUND

Traditional therapy using natural products, especially flavonoids and alkaloids have been in practice for a long time. Among flavonoids, curcumin, quercetin, berberine, and epigallocatechin have been studied in greater detail in terms of their anticancer and anti-inflammatory activities. Although many studies focused on the PI3K, MAP kinase and NF-κB pathways, a thorough investigation of modulation of players in the apoptotic and Wnt/β-catenin signaling pathway by curcumin and quercetin has not been done. Also, only few studies have been carried out on curcumin and quercetin co-treatment studies.

HYPOTHESIS/PURPOSE

We hypothesized that the combination of natural products will have synergistic effects and the antiproliferative effect will be attenuated via apoptotic as well as Wnt/β-catenin signaling pathways.

STUDY DESIGN AND METHODS

To test our hypothesis, we compared potency of natural anticancer agents in four cancer cell lines, A549, HCT116, MCF7, and A375 by MTT and colony proliferation assays and investigated mechanism of anticancer activities by analyzing players in apoptotic and Wnt/β-catenin signaling pathways in A375 cells treated with test agents individually or in combination.

RESULTS

Epicatechins, up to 100 μM concentration, did not inhibit cancer cell proliferation, while curcumin inhibited proliferation in A549 and HCT116 cancer cell lines with an IC₅₀ of 3 to 8.5 μM. Quercetin showed stronger inhibition of cell proliferation than berberine. Combination study with two most potent agents, curcumin and quercetin, in 4 cancer cell lines, suggested synergistic effect on cell proliferation with several fold decreases in IC₅₀. Further investigation of the mechanism of action of curcumin and quercetin in melanoma cells, A375, suggested that inhibition of cell proliferation occurred through down-regulation of Wnt/β-catenin signaling pathway proteins, DVL2, β-catenin, cyclin D1, Cox2, and Axin2. In addition, both curcumin and quercetin induced apoptosis by down-regulating BCL2 and inducing caspase 3/7 through PARP cleavage.

CONCLUSION

These results demonstrate that curcumin and quercetin inhibit cancer cell proliferation synergistically and Wnt/β-catenin signaling and apoptotic pathways are partly responsible for antiproliferative activities.

Lecithin-Stabilized Polymeric Micelles (LsbPMs) for Delivering Quercetin: Pharmacokinetic Studies and Therapeutic Effects of Quercetin Alone and in Combination with Doxorubicin

In this study, lecithin-stabilized polymeric micelles (L_sbPMs) were prepared to load quercetin (QUE) in order to improve its bioavailability and increase its antitumor activity. Its combination with doxorubicin (DOX) to minimize DOX-mediated cardiac toxicity and increase the antitumor activity of QUE-loaded L_sbPMs was also examined. L_sbPMs were prepared following a previously reported procedure. Results demonstrated that optimal QUE-loaded L_sbPMs contained quercetin, D-α-tocopheryl polyethylene glycol succinate, and lecithin at a weight ratio of 6:40:80. Drug-release studies showed that QUE released from L_sbPMs followed a controlled release pattern. A cytotoxicity assay revealed that QUE-loaded L_sbPMs had significant anticancer activities against MCF-7, SKBR-3, and MDA-MB-231 human breast cancer cells and CT26 mouse colon cancer cells. In animal studies, intravenous administration of QUE-loaded L_sbPMs resulted in efficient growth inhibition of CT26 colon cancer cells in a Balb/c mice model. In a pharmacokinetics study compared to free QUE, intravenous and oral administration of QUE-loaded L_sbPMs was found to have significantly increased the relative bioavailability to 158% and 360%, respectively, and the absolute bioavailability to 5.13%. The effect of QUE-loaded L_sbPMs in combination with DOX resulted in efficient growth inhibition of CT26 colon cancer cells and reduced cardiac toxicity in the Balb/c mice model.

Synthesis and biological evaluation of quercetin and resveratrol peptidyl derivatives as potential anticancer and antioxidant agents

Quercetin and resveratrol are polyphenolic compounds, members of the flavonoid and the stilbene family, respectively, both medicinally important as dietary anticancer and antioxidant agents. They are present in a variety of foods-including fruits, vegetables, tea, wine, as well as other dietary supplements-and are responsible for various health benefits. Different quercetin and resveratrol esters of Leu/Met-enkephalin and tetrapeptide Leu-Ser-Lys-Leu (LSKL) were synthesized as model systems for monitoring the influence of the peptides on biological activity of resveratrol and quercetin. General formula of the main peptidyl-quercetin derivatives is 2-[3-(aa)_n-4-hydroxyphenyl]-3,5,7-tri-hydroxy-4H-1-benzopyran-4-on, and the general formula of the main peptidyl-resveratrol derivatives is (E)-5-[4-(aa)_n)styryl]benzene-1,3-diol. The antioxidant and anticancer activities of prepared compounds were investigated. Significant anticancer activity was obtained for the LSKL-based both quercetin and resveratrol derivatives. All prepared compounds exhibit antioxidant activity, in particular quercetin derivative containing Met-enkephalin.

Probing the interaction of a quercetin bioconjugate with Bcl-2 in living human cancer cells with in-cell NMR spectroscopy

In-cell NMR spectroscopy has emerged as a powerful technique for monitoring biomolecular interactions at an atomic level inside intact cells. However, current methodologies are inadequate at charting intracellular interactions of nonlabeled proteins and require their prior isotopic labeling. Herein, we describe for the first time the monitoring of the quercetin-alanine bioconjugate interaction with the nonlabeled antiapoptotic protein Bcl-2 inside living human cancer cells. STD and Tr-NOESY in-cell NMR methodologies were successfully applied in the investigation of the binding, which was further validated in vitro. In-cell NMR proved a very promising strategy for the real-time probing of the interaction profile of potential drugs with their therapeutic targets in native cellular environments and could, thus, open a new avenue in drug discovery.

Cardioprotective Effects of Nanoemulsions Loaded with Anti-Inflammatory Nutraceuticals against Doxorubicin-Induced Cardiotoxicity

Doxorubicin is a highly active antineoplastic agent, but its clinical use is limited because of its cardiotoxicity. Although nutraceuticals endowed with anti-inflammatory properties exert cardioprotective activity, their bioavailability and stability are inconsistent. In an attempt to address this issue, we evaluated whether bioavailable nanoemulsions loaded with nutraceuticals (curcumin and fresh and dry tomato extracts rich in lycopene) protect cardiomyoblasts (H9C2 cells) from doxorubicin-induced toxicity. Nanoemulsions were produced with a high-pressure homogenizer. H9C2 cells were incubated with nanoemulsions loaded with different nutraceuticals alone or in combination with doxorubicin. Cell viability was evaluated with a modified MTT method. The levels of the lipid peroxidation products malondialdehyde (MDA) and 4-hydroxy-2-butanone (4-HNA), and of the cardiotoxic-related interleukins IL-6, IL-8, IL-1β and IL-10, tumor necrosis factor-alpha (TNF-α), and nitric oxide were analyzed in cardiomyoblasts. The hydrodynamic size of nanoemulsions was around 100 nm. Cell viability enhancement was 35–40% higher in cardiomyoblasts treated with nanoemulsion + doxorubicin than in cardiomyoblasts treated with doxorubicin alone. Nanoemulsions also protected against oxidative stress as witnessed by a reduction of MDA and 4-HNA. Notably, nanoemulsions inhibited the release of IL-6, IL-8, IL-1β, TNF-α and nitric oxide by around 35–40% and increased IL-10 production by 25–27% versus cells not treated with emulsions. Of the nutraceuticals evaluated, lycopene-rich nanoemulsions had the best cardioprotective profile. In conclusion, nanoemulsions loaded with the nutraceuticals described herein protect against cardiotoxicity, by reducing inflammation and lipid oxidative stress. These results set the stage for studies in preclinical models.

Preparation, Characterization, and In Vivo Evaluation of an Oral Multiple Nanoemulsive System for Co-Delivery of Pemetrexed and Quercetin

Co-administration of conventional and natural chemotherapeutics offers synergistic anticancer efficacy while minimizing adverse effects. In this study, an oral co-delivery system for pemetrexed (PMX) and quercetin (QCN) was designed based on water-in-oil-in-water nanoemulsion (NE), which is highly absorbable because it enhances the intestinal membrane permeability of PMX and aqueous solubility of QCN. To create this system, an ion-pairing complex of PMX with N^α-deoxycholyl-l-lysyl-methylester (DCK) was formed and further incorporated with QCN into the NE, yielding PMX/DCK-QCN-NE. The results revealed synergistic inhibitory effects on human lung carcinoma (A549) cell proliferation and migration after combined treatment with PMX/DCK and QCN. The intestinal membrane permeability and cellular uptake of PMX/DCK and QCN from the NE were significantly improved via facilitated transport of PMX by the interaction of DCK with bile acid transporters, as well as NE formulation-mediated alterations in the membrane structure and fluidity, which resulted in 4.51- and 23.9-fold greater oral bioavailability of PMX and QCN, respectively, than each free drug. Tumor growth in A549 cell-bearing mice was also maximally suppressed by 62.7% after daily oral administration of PMX/DCK-QCN-NE compared with controls. Thus, PMX/DCK-QCN-NE is a promising oral nanocarrier of PMX and QCN for synergistic anticancer efficacy and long-term chemotherapy.

Optimization of Quercetin loaded Palm Oil Ester Based Nanoemulsion Formulation for Pulmonary Delivery

In this research, the palm oil ester (POE)- based nanoemulsion formulation containing quercetin for pulmonary delivery was developed. The nanoemulsion formulation was prepared by high energy emulsification method and then further optimized using D-optimal mixture design. The concentration effects of the mixture of POE:ricinoleic acid (RC), ratio 1:1 (1.50-4.50 wt.%), lecithin (1.50-2.50 wt.%), Tween 80 (0.50-1.00 wt.%), glycerol (1.50-3.00 wt.%), and water (88.0-94.9 wt.%) towards the droplet size were investigated. The results showed that the optimum formulation with 1.50 wt.% POE:RC, 1.50 wt.% lecithin, 1.50 wt.% Tween 80, 1.50 wt.% glycerol and 93.90 % water was obtained. The droplet size, polydispersity index (PDI) and zeta potential of the optimized formulation were 110.3 nm, 0.290 and －37.7 mV, respectively. The formulation also exhibited good stability against storage at 4℃ for 90 days. In vitro aerosols delivery evaluation showed that the aerosols output, aerosols rate and median mass aerodynamic diameter of the optimized nanoemulsion were 99.31%, 0.19 g/min and 4.25 µm, respectively. The characterization of physical properties and efficiency for aerosols delivery results suggest that POE- based nanoemulsion containing quercetin has the potential to be used for pulmonary delivery specifically for lung cancer treatment.

Delivering natural products and biotherapeutics to improve drug efficacy

Due to the increasing problem of drug resistance, new and improved medicines are required. Natural products and biotherapeutics offer a vast resource for new drugs; however, challenges, including the cost and time taken for traditional drug discovery processes and the subsequent lack of investment from the pharmaceutical industry, are associated with these areas. New techniques are producing compounds with appropriate activity at a faster rate. While the formulation of these combined with drug-delivery systems offers a promising approach for expanding the drug developments available to modern medicine. Here, various classes of drug-delivery systems are described and the advantages they bring to small molecule and biotherapeutic targeting are highlighted. This is an attractive approach to the pharmaceutical industry and the rising trend in research in this area is examined in brief. [Formula: see text].

Novel nanohydrogel of hyaluronic acid loaded with quercetin alone and in combination with temozolomide as new therapeutic tool, CD44 targeted based, of glioblastoma multiforme

Glioblastoma multiforme is the most common and aggressive primary brain cancer with only ∼3% of patients surviving more than 3 years from diagnosis. Several mechanisms are involved in drug and radiation resistance to anticancer treatments and among them one of the most important factors is the tumor microenvironment status, characterized by cancer cell hypersecretion of interleukins and cytokines. The aim of our research was the synthesis of a nanocarrier of quercetin combined with temozolomide, to enhance the specificity and efficacy of this anticancer drug commonly used in glioblastoma treatment. The nanohydrogel increased the internalization and cytotoxicity of quercetin in human glioblastoma cells and, when co-delivered with temozolomide, contribute to an improved anticancer effect. The nanohydrogel loaded with quercetin had the ability to recognize CD44 receptor, a brain cancer cell marker, through an energy and caveolae dependent mechanism of internalization. Moreover, nanohydrogel of quercetin was able to reduce significantly IL-8, IL-6, and VEGF production in pro-inflammatory conditions with interesting implications on the mechanism of glioblastoma cells drug resistance. In summary, novel CD44 targeted polymeric based nanocarriers appear to be proficient in mediating site-specific delivery of quercetin via CD44 receptor in glioblastoma cells. This targeted therapy lead to an improved therapeutic efficacy of temozolomide by modulating the brain tumor microenvironment.

Vasorelaxant effect of quercetin on cerebral basilar artery in vitro and the underlying mechanisms study

The aim of this study is to investigate the vasorelaxant effect of quercetin on cerebral basilar artery in vitro and provide a preliminary discussion concerning the underlying mechanisms. Using a DMT-isolated micro vessel system, quercetin was found to exhibit a vasodilatory effect on basilar arteries contracted by potassium chloride (KCl), endothelin-1 (ET-1), and 5-hydroxytryptamine (5-HT). The vasorelaxant effect of quercetin was partially attenuated when endothelium cells were removed. L-NAME, indomethacin, and ODQ treatment also decreased the potency of quercetin. In endothelium-denuded rings, the vasorelaxant effect of quercetin was not influenced by K⁺ channel inhibitors. However, quercetin inhibited KCl induced extracellular calcium influx and ET-1 induced transient intracellular calcium release in a Ca²⁺-free solution. In conclusion, quercetin induced relaxation of the basilar artery in vitro is partially dependent on endothelium, which is mainly related to NO and COX pathways. It also induces relaxation through blockage of calcium channels.

CK2 and PI3K are direct molecular targets of quercetin in chronic lymphocytic leukaemia

Despite the encouraging results of the innovative therapeutic treatments, complete remission is uncommon in patients affected by chronic lymphocytic leukaemia, which remains an essentially incurable disease. Recently, clinical trials based on BH3-mimetic drugs showed positive outcomes in subjects with poor prognostic features. However, resistance to treatments occurs in a significant number of patients. We previously reported that the multi-kinase inhibitor quercetin, a natural flavonol, restores sensitivity to ABT-737, a BH3-mimetic compound, in both leukemic cell lines and B-cells isolated from patients. To identify the molecular target of quercetin, we employed a new cell line, HG3, obtained by immortalization of B-cells from a chronic lymphocytic leukaemia patient at the later stage of disease. We confirmed that quercetin in association with ABT-737 synergistically enhances apoptosis in HG3 (combination index < 1 for all fractions affected). We also reported that the cellular uptake of quercetin is extremely rapid, with an intracellular concentration of about 38.5 ng/10⁶ cells, after treatment with 25 μM for 5 min. We demonstrated that the activity of protein kinase CK2, which positively triggers PI₃K/Akt pathway by inactivating PTEN phosphatase, is inhibited by quercetin immediately after its addition to HG3 cells (0–2 min). PI₃K activity was also inhibited by quercetin within 60 min from the treatment. The combined inhibition of CK2 and PI₃K kinase activities by quercetin restored ABT-737 sensitivity and increased lethality in human leukemia cells.

Quercetin attenuates AZT-induced neuroinflammation in the CNS

Highly active anti-retroviral therapy (HAART) is very effective in suppressing HIV-1 replication in patients. However, continuous HAART is required to prevent viral rebound, which may have detrimental effects in various tissues, including persistent neuroinflammation in the central nervous system (CNS). Here, we show that quercetin (3,5,7,3’,4’-pentahydroxy flavones), a natural antioxidant used in Chinese traditional medicines, suppresses the neuroinflammation that is induced by chronic exposure to Zidovudine (azidothymidine, AZT), a nucleoside reverse transcriptase inhibitor (NRTI) that is commonly part of HAART regimens. We found that the up-regulation of pro-inflammatory cytokines and microglial and astrocytic markers induced by AZT (100 mg/kg/day; 8 days) was significantly inhibited by co-administration of quercetin (50 mg/kg/day) in the mouse cortex, hippocampus and spinal cord. We further showed that quercetin attenuated AZT-induced up-regulation of Wnt5a, a key regulator of neuroinflammation. These results suggest that quercetin has an inhibitory effect on AZT-induced neuroinflammation in the CNS, and Wnt5a signaling may play an important role in this process. Our results may further our understanding of the mechanisms of HAART-related neurotoxicity and help in the development of effective adjuvant therapy.

Synthesis of chitin-glucan-aldehyde-quercetin conjugate and evaluation of anticancer and antioxidant activities

In the present study, we have synthesized chitin-glucan-aldehyde-quercetin (chi-glu-ald-que) conjugate via condensation reaction. Synthesis of chitin-glucan-aldehyde (chi-glu-ald) complex was facilitated by the oxidation of chitin-glucan (chi-glu) complex. Formation of conjugate was confirmed by Proton nuclear magnetic resonance spectroscopy (¹H NMR) and Fourier-transform infrared spectroscopy (FT-IR). Morphological studies showed that after grafting of quercetin, several changes on surface were depicted and a more crystalline nature was observed. The chi-glu-ald-que conjugate displayed strong antioxidant activity. It showed 69% of 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical, DPPH* scavenging activity at 1 mg/mL and 72% of 2, 2-azinobis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical cation, ABTS*⁺ scavenging activity at 1 mg/mL concentration, which are much higher than that of chi-glu complex. The anticancer activity of chi-glu-ald-que conjugate was performed in Macrophage cancer cell lines (J774) and biocompatibility was performed in Peripheral blood mononuclear cells (PBMCs). The chi-glu-ald-que conjugate showed excellent cytotoxicity against J774 cell lines but no cytotoxicity towards PBMCs.

Fanconi anaemia and cancer: an intricate relationship

Fanconi anaemia (FA) is a genetic disorder that is characterized by bone marrow failure (BMF), developmental abnormalities and predisposition to cancer. Together with other proteins involved in DNA repair processes and cell division, the FA proteins maintain genome homeostasis, and germline mutation of any one of the genes that encode FA proteins causes FA. Monoallelic inactivation of some FA genes, such as FA complementation group D1 (FANCD1; also known as the breast and ovarian cancer susceptibility gene BRCA2), leads to adult-onset cancer predisposition but does not cause FA, and somatic mutations in FA genes occur in cancers in the general population. Carcinogenesis resulting from a dysregulated FA pathway is multifaceted, as FA proteins monitor multiple complementary genome-surveillance checkpoints throughout interphase, where monoubiquitylation of the FANCD2-FANCI heterodimer by the FA core complex promotes recruitment of DNA repair effectors to chromatin lesions to resolve DNA damage and mitosis. In this Review, we discuss how the FA pathway safeguards genome integrity throughout the cell cycle and show how studies of FA have revealed opportunities to develop rational therapeutics for this genetic disease and for malignancies that acquire somatic mutations within the FA pathway.

Therapeutic charm of quercetin and its derivatives: a review of research and patents

Bioactive polyphenolic compounds derived from plants are being utilized for prevention of various chronic diseases including cancer and cardiovascular disorders. Quercetin, a potential poly-phenolic flavonol, found in onions, apples and berries, has been implicated against cancer proliferation, chronic inflammation and various other oxidative manifestations. Evidences suggested that quercetin negatively regulates the numerous crucial signaling pathways associated with life-threatening diseases. Major signaling pathways including NF-κB, MAPK, PI3K-AKT and mTOR are found to be regulated by quercetin. In addition, several patents have reported recently on quercetin derivatives describing wide therapeutic applications such as anticancer/antiproliferatory, antioxidative/antiaging, antiviral, anti-inflammatory, cardioprotective. Present review emphasizes the chemistry and sources of quercetin followed by description of its broad-spectrum therapeutic potential along with proposed mechanisms of action. Furthermore, this review also highlights the important modifications in the basic chemical structure of quercetin in terms of published patents. Insolubility of the bioactive compounds restricts their medicinal importance which could be overcome by modifications in the chemical structure of so-called derivatives. Most of the patents deal with the modifications in chemical structure of quercetin mainly at hydroxyl groups and C-6 and C-7 positions.

Nanotechnology in oral cancer: A comprehensive review

Oral health could be maintained by application of this technology in prevention, diagnosis and treatment. Oral cancer is a debilitating disease, and numerous research activities are being pursued worldwide to combat this deleterious process. Nanotechnology is very diverse field that has revolutionized the industry and is setting new trends in the management of oral cancer. Hence, we performed a PubMed search on nanotechnology in oral cancer and found 211 articles related to this search. We have reviewed the reported literature to the best of our abilities and summarized the various aspects of nanotechnology, its role in diagnosis - nanodiagnostics and treatment of oral cancer - nanotherapeutics in this article.