The effects of the bioflavonoid quercetin on squamous cell carcinoma of head and neck origin

Australian native fruits and vegetables: Chemical composition, nutritional profile, bioactivity and potential valorization by industries

Australian native plants have adapted themselves to harsh climatic conditions enabling them to produce unique and high levels of secondary metabolites. Native fruits and vegetables have been an integral part of the Indigenous Australian diet and Bush medicine for centuries. They have recently gained popularity owing to their rich dietary fiber, minerals, polyphenolic and antioxidant contents. This review presents a comprehensive summary and critical assessment of the studies performed in the last few decades to understand the phytochemical and nutritional profiles and therapeutic properties of Australian native fruits and vegetables. Furthermore, the potential of these fruits and vegetables as functional food ingredients and in the prevention and treatment of different diseases is discussed. Research on the nutritional and phytochemical profiles and therapeutic activity of Australian vegetables is limited with most studies focused on native fruits. These fruits have demonstrated promising antioxidant, anticancer, anti-inflammatory and antimicrobial activities mostly in in vitro models. More research to a) identify novel bioactive compounds, b) define optimal post-harvest and extraction methods, and c) understand molecular mechanisms of pharmacological activity through preclinical and clinical studies is prudent for the prospective and wider use of Australian native fruits and vegetables by the food, pharmaceutical, and nutraceutical industries.

Development of mushroom polysaccharide and probiotics based solid self-nanoemulsifying drug delivery system loaded with curcumin and quercetin to improve their dissolution rate and permeability: State of the art

The role of mushroom polysaccharides and probiotics as pharmaceutical excipients for development of nanocarriers has never been explored. In the present study an attempt has been made to explore Ganoderma lucidum extract powder (GLEP) containing polysaccharides and probiotics to convert liquid self nanoemulsifying drug delivery system (SNEDDS) into solid free flowing powder. Two lipophilic drugs, curcumin and quercetin were used in this study due to their dissolution rate limited oral bioavailability and poor permeability. These were loaded into liquid SNEDDS by dissolving them into isotropic mixture of Labrafill M1944CS, Capmul MCM, Tween-80 and Transcutol P. The liquid SNEDDS were solidified using probiotics and mushroom polysaccharides as carriers and Aerosil-200 as coating agent. The solidification was carried out using spray drying process. The process and formulation variables for spray drying process of liquid SNEDDS were optimized using Box Behnken Design to attain required powder properties. The release of both drugs from the optimized spray dried (SD) formulation was found to be more than 90%, whereas, it was less than 20% for unprocessed drugs. The results of DSC, PXRD and SEM, showed that the developed L-SNEDDS preconcentrate was successfully loaded onto the porous surface of probiotics, mushroom polysaccharides and Aerosil-200.

The effects of kiwifruit dressing on hypertrophic scars in a rabbit ear model

AIMS

Hypertrophic scars show abnormal responses during healing. These scars, associated with dysregulated growth and excessive collagen formation, can have both functional and cosmetic consequences for patients. The present study evaluated the effects of kiwifruit on hypertrophic scars in a rabbit ear model.

METHODS

This study included 13 New Zealand albino rabbits with full thickness wounds down to the cartilage (four wounds per ear; total: 104 scars). Sixteen days after initial wound formation, one ear of each rabbit was treated with daily kiwifruit dressing, while the other ear (control group) was dressed after normal saline irrigation for 10 days. Harvested skin samples were examined for histopathological, morphometric and immunohistochemical results.

RESULTS

In comparison with the control group, early kiwifruit dressing significantly reduced the scar elevation index, fibroblast count and dermal collagen organisation. The ratio of collagen type III to total collagen immunoreactivity, inflammation and dermal capillary count increased significantly in the treated group, compared to the untreated controls.

CONCLUSION

Based on the findings, early kiwifruit dressing improved the histological features of cutaneous wounds in rabbits. Therefore, this approach may be effective in clinical practice.

An Up-to-Date Review on Citrus Flavonoids: Chemistry and Benefits in Health and Diseases

Flavonoids, the main class of polyphenols, are characterized by the presence of 2-phenyl-benzo-pyrane nucleus. They are found in rich quantities in citrus fruits. Citrus flavonoids are classified into flavanones, flavones, flavonols, polymethoxyflavones and anthocyanins (found only in blood oranges). Flavanones are the most abundant flavonoids in citrus fruits. In many situations, there are structure-function relationships. Due to their especial structures and presence of many hydroxyls, polymethoxies and glycoside moiety, the flavonoids have an array of multiple biological and pharmacological activities. This article provides an updated overview of the differences in chemical structures of the classes and members of citrus flavonoids and their benefits in health and diseases. The review article also sheds light on the mechanisms of actions of citrus flavonoids in the treatment of different diseases, including arthritis, diabetes mellitus, cancer and neurodegenerative disorders as well as liver, kidney and heart diseases. The accumulated and updated knowledge in this review may provide useful information and ideas in the discovery of new strategies for the use of citrus flavonoids in the protection, prevention and therapy of diseases.

Potential Therapeutic Targets of Quercetin, a Plant Flavonol, and Its Role in the Therapy of Various Types of Cancer through the Modulation of Various Cell Signaling Pathways

Polyphenolic flavonoids are considered natural, non-toxic chemopreventers, which are most commonly derived from plants, fruits, and vegetables. Most of these polyphenolics exhibit remarkable antioxidant, anti-inflammatory, and anticancer properties. Quercetin (Qu) is a chief representative of these polyphenolic compounds, which exhibits excellent antioxidant and anticancer potential, and has attracted the attention of researchers working in the area of cancer biology. Qu can regulate numerous tumor-related activities, such as oxidative stress, angiogenesis, cell cycle, tumor necrosis factor, proliferation, apoptosis, and metastasis. The anticancer properties of Qu mainly occur through the modulation of vascular endothelial growth factor (VEGF), apoptosis, phosphatidyl inositol-3-kinase (P13K)/Akt (proteinase-kinase B)/mTOR (mammalian target of rapamycin), MAPK (mitogen activated protein kinase)/ERK1/2 (extracellular signal-regulated kinase 1/2), and Wnt/β-catenin signaling pathways. The anticancer potential of Qu is documented in numerous in vivo and in vitro studies, involving several animal models and cell lines. Remarkably, this phytochemical possesses toxic activities against cancerous cells only, with limited toxic effects on normal cells. In this review, we present extensive research investigations aimed to discuss the therapeutic potential of Qu in the management of different types of cancers. The anticancer potential of Qu is specifically discussed by focusing its ability to target specific molecular signaling, such as p53, epidermal growth factor receptor (EGFR), VEGF, signal transducer and activator of transcription (STAT), PI3K/Akt, and nuclear factor kappa B (NF-κB) pathways. The anticancer potential of Qu has gained remarkable interest, but the exact mechanism of its action remains unclear. However, this natural compound has great pharmacological potential; it is now believed to be a complementary—or alternative—medicine for the prevention and treatment of different cancers.

Pharmacological Properties of Allium cepa, Preclinical and Clinical Evidences; A Review

Onion or Allium cepa (A. cepa) is one of the most important condiment plants grown and consumed all over the world. This plant has various therapeutic effects attributed to its constituents, such as quercetin, thiosulphinates and phenolic acids. In the present article, various pharmacological and therapeutic effects of A. cepa were reviewed. Different online databases using keywords such as onion, A. cepa, therapeutic effects, and pharmacological effects until the end of December 2019 were searched for this purpose. Onion has been suggested to be effective in treating a broad range of disorders, including asthma, inflammatory disorders, dysentery, wounds, scars, keloids and pain. In addition, different studies have demonstrated that onion possesses numerous pharmacological properties, including anti-cancer, anti-diabetic and anti-platelet properties as well as the effect on bone, cardiovascular, gastrointestinal, nervous, respiratory, and urogenital systems effects such as anti-osteoporosis, anti-hypertensive, antispasmodic, anti-diarrheal, neuro-protective, anti-asthmatic and diuretic effects. The present review provides detailed the various pharmacological properties of onion and its constituents and possible underlying mechanisms. The results of multiple studies suggested the therapeutic effect of onion on a wide range of disorders.

The upshot of Polyphenolic compounds on immunity amid COVID-19 pandemic and other emerging communicable diseases: An appraisal

Polyphenols are a large family of more than 10,000 naturally occurring compounds, which exert countless pharmacological, biological and physiological benefits for human health including several chronic diseases such as cancer, diabetes, cardiovascular, and neurological diseases. Their role in traditional medicine, such as the use of a wide range of remedial herbs (thyme, oregano, rosemary, sage, mint, basil), has been well and long known for treating common respiratory problems and cold infections. This review reports on the most highlighted polyphenolic compounds present in up to date literature and their specific antiviral perceptive properties that might enhance the body immunity facing COVID-19, and other viral infectious diseases. In fact, several studies and clinical trials increasingly proved the role of polyphenols in controlling numerous human pathogens including SARS and MERS, which are quite similar to COVID-19 through the enhancement of host immune response against viral infections by different biological mechanisms. Thus, polyphenols ought to be considered as a potential and valuable source for designing new drugs that could be used effectively in the combat against COVID-19 and other rigorous diseases.

Citrus Peel Flavonoids as Potential Cancer Prevention Agents

Citrus fruit and in particular flavonoid compounds from citrus peel have been identified as agents with utility in the treatment of cancer. This review provides a background and overview regarding the compounds found within citrus peel with putative anticancer potential as well as the associated in vitro and in vivo studies. Historical studies have identified a number of cellular processes that can be modulated by citrus peel flavonoids including cell proliferation, cell cycle regulation, apoptosis, metastasis, and angiogenesis. More recently, molecular studies have started to elucidate the underlying cell signaling pathways that are responsible for the flavonoids' mechanism of action. These growing data support further research into the chemopreventative potential of citrus peel extracts, and purified flavonoids in particular. This critical review highlights new research in the field and synthesizes the pathways modulated by flavonoids and other polyphenolic compounds into a generalized schema.

Review: Health Effects of Cocoa Flavonoids

Flavonoids are phenolic substances widely found in fruits and vegetables. Many epidemiological studies associate the ingestion of flavonoids with a reduced risk of cardiovascular disease and certain types of cancer. These effects are due to the physiological activity of flavonoids in the reduction of oxidative stress, inhibiting low-density lipoproteins (LDL) oxidation and platelet aggregation, acting as vasodilators in blood vessels, inhibiting the adherence of monocytes to the vascular endothelium, promoting fibrinolysis, acting as immunomodulators and anti-inflammatory agents and as inhibitors in the different phases of tumour process. Cocoa is an important source of polyphenols, which comprise 12-18% of its total weight on dry basis; the major phenolic compounds are epicatechin, proanthocyanidins and cate-chin. The levels of flavonoids contained are higher than the ones founds in apples, onions or wine, foods known for their high amount of phenolic compounds. Cocoa and cocoa products are important sources of flavonoids in our diet. In the Dutch population chocolate contributes up to 20% of the total flavonoid intake in adults, and in children the percentage is even higher. The bioavailability of these compounds depends on other food constituents, and their interaction with the food matrix. This article reviews current evidence on the health effects of cocoa flavonoids in our diet. The compiled data supports the premise that the consumption of cocoa flavonoids is beneficial to human health.

Biocompatible and biodegradable nanoparticles for enhancement of anti-cancer activities of phytochemicals

Many phytochemicals show promise in cancer prevention and treatment, but their low aqueous solubility, poor stability, unfavorable bioavailability, and low target specificity make administering them at therapeutic doses unrealistic. This is particularly true for (-)-epigallocatechin gallate, curcumin, quercetin, resveratrol, and genistein. There is an increasing interest in developing novel delivery strategies for these natural products. Liposomes, micelles, nanoemulsions, solid lipid nanoparticles, nanostructured lipid carriers and poly (lactide-co-glycolide) nanoparticles are biocompatible and biodegradable nanoparticles. Those nanoparticles can increase the stability and solubility of phytochemicals, exhibit a sustained release property, enhance their absorption and bioavailability, protect them from premature enzymatic degradation or metabolism, prolong their circulation time, improve their target specificity to cancer cells or tumors via passive or targeted delivery, lower toxicity or side-effects to normal cells or tissues through preventing them from prematurely interacting with the biological environment, and enhance anti-cancer activities. Nanotechnology opens a door for developing phytochemical-loaded nanoparticles for prevention and treatment of cancer.

Natural phenolic metabolites with anti-angiogenic properties - a review from the chemical point of view

Considering the many secondary natural metabolites available from plants, phenolic compounds play a particularly important role in human health as they occur in significant amounts in many fruits, vegetables and medicinal plants. In this review natural phenolic compounds of plant origin with significant anti-angiogenic properties are discussed. Thirteen representatives from eight different natural or natural-like phenolic subclasses are presented with an emphasis on their synthesis and methods to modify the parent compounds. When available, the consequence of structural variation on the pharmacological activity of the molecules is described.

Iminoflavones combat 1,2-dimethyl hydrazine-induced aberrant crypt foci development in colon cancer

The aim of the present study was to evaluate the antitumor potential of iminoflavones in in vitro and in vivo anticancer models. Preliminary screening in various cancer cell lines revealed four potential iminoflavones out of which IMF-8 was taken based on its activity against colon cancer cells. This was further confirmed by observing the nuclear changes in the cells by AO/EB and Hoechst 33342 staining studies. In vivo activity was assessed by dimethyl hydrazine-(DMH-) induced colon cancer model in rats. Animals were administered DMH (20 mg/kg, b.w. for 10 weeks and 30 mg/kg b.w., i.p. for 10 weeks) and were supplemented with (IMF-8) iminoflavone-8 (200 mg/kg, p.o. for 14 days). Results showed that DMH induced 100% aberrant crypt foci (ACF) and polyps which were significantly reduced in the IMF-8 treated group. IMF-8 significantly increased the catalase and GSH levels whereas it reduced the TNF-α and IL-6 levels markedly which suggests the antioxidative and anti-inflammatory actions of flavonoids present in IMF-8. The histopathological images of the IMF-8 treated colon showed no signs of mucosal crypt abscess. These findings suggest that the semi-synthetic iminoflavones, IMF-8, effectively inhibit DMH-induced ACFs and colonic crypts by alleviating the oxidative stress and suppressing the inflammation.

Site-specific anticancer effects of dietary flavonoid quercetin

Food-derived flavonoid quercetin, widely distributed in onions, apples, and tea, is able to inhibit growth of various cancer cells indicating that this compound can be considered as a good candidate for anticancer therapy. Although the exact mechanism of this action is not thoroughly understood, behaving as antioxidant and/or prooxidant as well as modulating different intracellular signalling cascades may all play a certain role. Such inhibitory activity of quercetin has been shown to depend first of all on cell lines and cancer types; however, no comprehensive site-specific analysis of this effect has been published. In this review article, cytotoxicity constants of quercetin measured in various human malignant cell lines of different origin were compiled from literature and a clear cancer selective action was demonstrated. The most sensitive malignant sites for quercetin revealed to be cancers of blood, brain, lung, uterine, and salivary gland as well as melanoma whereas cytotoxic activity was higher in more aggressive cells compared to the slowly growing cells showing that the most harmful cells for the organism are probably targeted. More research is needed to overcome the issues of poor water solubility and relatively low bioavailability of quercetin as the major obstacles limiting its clinical use.

Effects of a single application of extractum cepae on the peritendinous adhesion: an experimental study in rabbits

Peritendinous adhesion is an important cause of poor functional outcome after flexor tendon repair. The objective of this study was to investigate the effect of a single intraoperative application of extractum cepae, an extract of dietary onion, on the peritendinous adhesion, using a rabbit model of flexor tendon injury. The first, second, and third digits of the right hind paw of 18 rabbits were used for tendon operations. A standard partial division of the synovial sheath and flexor tendon was done at zone II to stimulate the adhesion formation. In the treatment group (n = 9 rabbits, 27 tendons), the flexor tendon sheath was treated with 50 mg/mL of extractum cepae which was applied locally and allowed to infiltrate for 5 minutes, the skin was sutured without suturing the sheath and the tendons. The same operation was done for the control group (n = 9 rabbits, 27 tendons) and 1 mL of normal saline solution was applied locally. Biomechanical and histologic evaluations of the specimens were done after 3 weeks. Tendons from the first toes were used for biomechanical studies. The second and third toe tendons were used for histopathologic evaluation. We have compared the peritendinous adhesions and the ultimate forces in the control and treated tendons. There were no statistically significant differences between the 2 groups with respect to the ultimate loads. Adhesion formation was absent in 1 tendon (5.5%), slight in 8 (44.4%), moderate in 6 (33.3), and severe in 3 tendons (16.7%) in the extractum cepae treated group (n = 18); while in the control group (n = 18), it was absent in 1 tendon (5.5%), slight in 1 tendon (5.5%), moderate in 3 (16.6%), and severe in 13 (72.4%) tendons. There was a significant reduction (P = 0.01) in the peritendinous adhesion in the treated group comparing to the control group. The problem of adhesion formation may be minimized using a single intraoperative application of extractum cepae.

The dietary bioflavonoid, quercetin, selectively induces apoptosis of prostate cancer cells by down-regulating the expression of heat shock protein 90

BACKGROUND

Human and animal studies have suggested that diet-derived flavonoids, in particular quercetin may play a beneficial role by preventing or inhibiting oncogenesis, but the underlying mechanism remains unclear. The aim of this study is to evaluate the effect(s) of quercetin on normal and malignant prostate cells and to identify the target(s) of quercetin's action.

METHODOLOGY

We addressed this question using cells in culture and investigated whether quercetin affects key biological processes responsible for tumor cell properties such as cell proliferation and apoptosis and also studied the effect of quercetin on the proteome of prostate cancer cells using difference gel electrophoresis (DIGE) to assess changes in the expression of relevant proteins.

RESULTS

Our findings demonstrate that quercetin treatment of prostate cancer cells results in decreased cell proliferation and viability. Furthermore, we demonstrate that quercetin promotes cancer cell apoptosis by down-regulating the levels of heat shock protein (Hsp) 90. Depletion of Hsp90 by quercetin results in decreased cell viability, levels of surrogate markers of Hsp90 inhibition (intracellular and secreted), induced apoptosis and activation of caspases in cancer cells but not in normal prostate epithelial cells. Knockdown of Hsp90 by short interfering RNA also resulted in induction apoptosis similar to quercetin in cancer cells as indicated by annexin V staining.

CONCLUSION

Our results demonstrate that quercetin down-regulates the expression of Hsp90 which, in turn, induces inhibition of growth and cell death in prostate cancer cells while exerting no quantifiable effect on normal prostate epithelial cells.

Quercetin inhibits choroidal and retinal angiogenesis in vitro

BACKGROUND

Quercetin is a natural substance found abundantly in grapes, red wine and other food products. In this study, we examined the effect of quercetin on choroidal and retinal angiogenesis in vitro using rhesus choroids-retina endothelial cell line (RF/6A).

METHODS

RF/6A cells were cultured in Dulbecco's Modified Eagle's Medium (DMEM) containing 10% fetal bovine serum. Then cells were treated with different concentrations (from 0 to 100 microM) of quercetin. The cell proliferation was assessed using choromogenic methylthiazol tetrazolium bromide (MTT) dye after 24, 48 and 72 hours. Cell migration after 24-hour incubation with quercetin was investigated by wound assay. Following exposure to the various concentrations of quercetin for 24 hours, tube formation on matrigel by endothelial cells was also analyzed. Apoptosis was measured by flow cytometry using annexin V-FITC and propidium iodide staining.

RESULTS

Quercetin inhibits endothelial cell proliferation in a dose-dependent fashion; 10.1%, 42.6% and 65.2% inhibition on treating with 10, 50 and 100 microM Quercetin respectively. The migration and tube formation of RA/6A cells were also significantly inhibited by quercetin in a dose-dependent manner. Flow cytometric analysis showed that the percentages of apoptotic cells were slightly increased only in 100 microM quercetin-treated cells.

CONCLUSIONS

Our results show that quercetin inhibits choroidal and retinal angiogenesis in vitro. Further studies are ongoing to evaluate this drug as a potential candidate for the treatment of choroidal or retinal neovascularization.

Suppression of tumor growth and invasion in 9,10 dimethyl benz(a) anthracene induced mammary carcinoma by the plant bioflavonoid quercetin

Administration of quercetin, a common polyphenolic component of many vascular and edible plants including vegetables, fruits and tea significantly reduced the tumor volume in rats induced for mammary carcinoma using dimethyl benz (a) anthracene (DMBA). Dose response was assessed, by treating the animals with different doses (15-45 mg/kgbw) of quercetin and 25 mg/kgbw was taken as effective dose. Quercetin was administered as an intra tumoral injection once a week for 4 weeks. Serum levels of carcino embryonic antigen (CEA), a potent marker for tumor growth and invasion was significantly decreased on quercetin treatment. Quercetin caused a significant decrease in the activities of acid phosphatase and Cathepsin D in serum of experimental animals. Activities of lysosomal enzymes- (beta-D galactosidase, beta-D glucuronidase, beta-D glucosidase and sialidase), in serum and tissue were significantly altered in DMBA animals compared to control animals. However, quercetin treatment caused no significant change in lysosomal enzyme activities in tissues, whereas the activities were significantly lowered in serum. Partial purification of tissue type plasminogen activator (t-PA) from the tumor and kidney showed increased activity in the DMBA induced animals. Serum urokinase, -like plasminogen activator (u-PA) was also increased in animals with tumor, indicating tumor invasion. Administration of quercetin caused a significant decrease of both t-PA and u-PA. In conclusion, the present study suggests the possible role of quercetin in primary and invasive mammary tumor treatment. The above observations in vivo warrant further studies, due to the easy availability, common occurrence and low toxicity of this dietary bioflavonoid.

Liposomal Quercetin Efficiently Suppresses Growth of Solid Tumors in Murine Models

PURPOSE

Quercetin is a potent chemotherapeutic drug. Clinical trials exploring different schedules of administration of quercetin have been hampered by its extreme water insolubility. To overcome this limitation, this study is aimed to develop liposomal quercetin and investigate its distribution in vivo and antitumor efficacy in vivo and in vitro.

EXPERIMENTAL DESIGN

Quercetin was encapsulated in polyethylene glycol 4000 liposomes. Biodistribution of liposomal quercetin i.v. at 50 mg/kg in tumor-bearing mice was detected by high-performance liquid chromatography. Induction of apoptosis by liposomal quercetin in vitro was tested. The antitumor activity of liposomal quercetin was evaluated in the immunocompetent C57BL/6N mice bearing LL/2 Lewis lung cancer and in BALB/c mice bearing CT26 colon adenocarcinoma and H22 hepatoma. Tumor volume and survival time were observed. The mechanisms underlying the antitumor effect of quercetin in vivo was investigated by detecting the microvessel density, apoptosis, and heat shock protein 70 expression in tumor tissues.

RESULTS

Liposomal quercetin could be dissolved in i.v. injection and effectively accumulate in tumor tissues. The half-time of liposomal quercetin was 2 hours in plasma. The liposomal quercetin induced apoptosis in vitro and significantly inhibited tumor growth in vivo in a dose-dependent manner. The optimal dose of liposomal quercetin resulted in a 40-day survival rate of 40%. Quantitative real-time PCR showed that liposomal quercetin down-regulated the expression of heat shock protein 70 in tumor tissues. Immunohistochemistry analysis showed that liposomal quercetin inhibited tumor angiogenesis as assessed by CD31 and induced tumor cell apoptosis.

CONCLUSIONS

Our data indicated that pegylated liposomal quercetin can significantly improve the solubility and bioavailability of quercetin and can be a potential application in the treatment of tumor.

Nutritional and botanical modulation of the inflammatory cascade--eicosanoids, cyclooxygenases, and lipoxygenases--as an adjunct in cancer therapy

Emerging on the horizon in cancer therapy is an expansion of the scope of treatment beyond cytotoxic approaches to include molecular management of cancer physiopathology. The goal in these integrative approaches, which extends beyond eradicating the affected cells, is to control the cancer phenotype. One key new approach appears to be modulation of the inflammatory cascade, as research is expanding that links cancer initiation, promotion, progression, angiogenesis, and metastasis to inflammatory events. This article presents a literature review of the emerging relationship between neoplasia and inflammatory eicosanoids (PGE2 and related prostaglandins), with a focus on how inhibition of their synthesizing oxidases, particularly cyclooxygenase (COX), offers anticancer actions in vitro and in vivo. Although a majority of this research emphasizes the pharmaceutical applications of nonsteroidal anti-inflammatory drugs and selective COX-2 inhibitors, these agents fail to address alternate pathways available for the synthesis of proinflammatory eicosanoids. Evidence is presented that suggests the inhibition of lipoxygenase and its by-products-LTB4, 5-HETE, and 12-HETE-represents an overlooked but crucial component in complementary cancer therapies. Based on the hypothesis that natural agents capable of modulating both lipoxygenase and COX may advance the efficacy of cancer therapy, an overview and discussion is presented of dietary modifications and selected nutritional and botanical agents (notably, omega-3 fatty acids, antioxidants, boswellia, bromelain, curcumin, and quercetin) that favorably influence eicosanoid production.

Pharmacognosy: phytomedicines and their mechanisms

The more a critical look at the medicinal properties of plants is undertaken, the more it will be realized that nature does not make it easy to find all there is to know about them and the complexities of their interactions. An illustration of this can be found in one of the earlier scientific studies on phytomedicines, the Nobel laureate Albert Szent-Györgyi and his colleagues [170] found that flavanone extracts from the Capsicum spp contain an ascorbate-protective factor. It has now been repeatedly shown that the electron-donating properties of the phytochemical flavonoids, providing both nutritive and chemotherapeutic benefits, are the basis of their antioxidant action [171-175]. Studies by zoologists have demonstrated that animals, by selectively choosing specific plants, soils, and clays, maintain their health and treat themselves in times of ill health. The term zoopharmacognosy, now well researched, has been coined to describe the study of this recognized phenomenon. Long ago, Isaac Newton stated that for every action, there is an equal and opposite reaction. The same may be seen in plants and plant material. The same may be said of life in general. At the most basic concept, we are talking of electrons and their activities.

Quercetin, a dietary-derived flavonoid, possesses antiangiogenic potential

Quercetin, a dietary-derived flavonoid, suppresses tumor growth in vitro and in vivo, and inhibits the activity of tyrosine kinase. The effects of quercetin on the angiogenic process were examined in this study. Quercetin was found to inhibit several important steps of angiogenesis including proliferation, migration, and tube formation of human microvascular dermal endothelial cells in a dose-dependent manner. Additionally, the effect of quercetin on endothelial cell proliferation was confirmed using human umbilical vein endothelial cells. The activity of quercetin on the proliferation of endothelial cells was stronger than that on A549, BEL-7402, MKN-45 tumor cells and NIH-3T3 fibroblast cells. The chicken chorioallantoic membrane assay revealed that addition of quercetin displayed an antiangiogenic effect in vivo. After exposure to quercetin, a decrease in the expression and activity of matrix metalloproteinase-2, which is involved in the angiogenic process of migration, invasion, and tube formation, was observed by reverse transcription-polymerase chain reaction (RT-PCR) and gelatin zymography. These findings suggest that quercetin has antiangiogenic potential and that this effect may be related to an influence on the expression and activity of matrix metalloproteinase-2.

Study on the inhibitory effects of Korean medicinal plants and their main compounds on the 1,1-diphenyl-2-picrylhydrazyl radical

A 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-generating system was used to evaluate the antioxidant properties of Korean medicinal plants that have been used widely as folk medicines for several disorders, as well as compounds isolated from them. Among the Rosaceae, Rosa rugosa and Rosa davurica showed strong DPPH radical-scavenging activity. The most effective medicinal plant from families other than Rosaceae was Cedrela sinensis, followed in order by Nelumbo nucifera, Eucommia ulmoides, Zanthoxylum piperitum, Cudrania tricuspidata and Houttuynia cordata. These results serve as a good index of the free radical-scavenging activities of Korean medicinal plants. Furthermore, the polyphenols isolated from these plants, procyanidin B-3, (+)-catechin, gallic acid, methyl gallate, quercetin, quercetin-3-O-beta-D-glucoside, quercetin-3-O-beta-galactoside, quercetin-3-O-rutinose and kaempferol, exerted strong DPPH radical-scavenging activity. These results suggest that the Korean medicinal plants and the polyphenols isolated from them that exhibited effective radical-scavenging activity may be promising agents for scavenging free radicals and treating diseases associated with excess free radicals.

Effect of Mederma on hypertrophic scarring in the rabbit ear model

Currently accepted conservative treatments of hypertrophic scars are limited to steroid injections, radiation therapy, and silicone occlusive therapy. However, the use of Mederma for these problematic lesions has become quite prevalent in the clinical setting. Little scientific evidence exists to support the efficacy of this product in reducing hypertrophic scars. The aim of this study was to study the effects of Mederma on hypertrophic scars in the rabbit hypertrophic scar model, allowing the histologic quantification of scar elevation, dermal collagen organization, vascularity, and inflammation and the gross examination of scar erythema. Full-thickness wounds down to cartilage, four per ear, were created in four New Zealand White rabbits, for a total of 32 scars. Twenty-eight days after the initial wounding, the hypertrophic scars were photographed, and treatment of half of the scars on each ear was begun with Mederma three times per day for a total of 4 weeks. The untreated scars served as control scars and were left exposed to air. After 4 weeks of treatment, the scars were once again photographed. The rabbits were then killed, and the scars were analyzed histologically. The pretreatment and posttreatment photographs were compared by using computer quantification of magenta, yellow, and cyan expression within the scars. Histologic analysis demonstrated no significant reduction in scar hypertrophy or scar elevation index. However, a significant improvement in dermal collagen organization was noted on comparing Mederma-treated scars with untreated control scars (p < 0.05). No significant difference in dermal vascularity or inflammation was noted. Computer analysis of the scar photographs demonstrated no significant reduction in scar erythema with Mederma treatment. The active product in Mederma, allium cepa, has as its derivative quercetin, a bioflavonoid noted for its antiproliferative effects on both normal and malignant cells, and its antihistamine release effects. These properties could theoretically prove beneficial in reversing the inflammatory and proliferative responses noted in hypertrophic scars. Despite the authors' inability to demonstrate a reduction in scar hypertrophy, the improvement in collagen organization noted in the Mederma-treated scars suggests it may have an effect on the pathophysiology of hypertrophic scar formation.

Induction of rat liver cytochrome P450 isoenzymes CYP 1A and CYP 2B by different fungicides, nitrofurans, and quercetin

The genotoxic activity of environmental xenobiotics is manifested either in their direct interaction with cellular genetic material or in provoking secondary events, among which reactive oxygen species (ROS) production is a common phenomenon. Both pathways can be mediated by the activity of the cytochrome P450 monooxygenase system. We studied induction of the CYP 1A or CYP 2B monooxygenases in rat liver by the fungicides: thiram, captan, captafol, dodine and the drugs: nitrofurazone, furazolidone and the plant flavonoid: quercetin. A cytochrome P450 induction assay (CYPIA test) was used. S9 prepared from livers of rats treated with the test compounds were used to activate ethidium bromide (EtBr) (CYP 1A isoenzyme) or cyclophosphamide (CPA) (CYP 2B isoenzyme) in the Ames test. It was found that among the tested compounds, the most potent inducer of CYP 1A was furazolidone (3 x 80 mg/kg). Less potent was thiram (1 x 100mg/kg), as well as quercetin (3 x 80 mg/kg), and captafol (1 x 30 mg/kg). On the other hand, thiram (1 x 100 mg/kg), captafol (1 x 30 mg/kg), and quercetin (3 x 80 mg/kg) were most potent in the CYP 2B isoenzyme induction, while furazolidone (3 x 80 mg/kg), and nitrofurazone (3 x 80 mg/kg) appeared to be less potent in this respect. Captan and dodine (3 x 80 mg/kg) did not affect the activity of any of the cytochrome P450 isoenzymes.

Effects of flavonols on the generation of superoxide anion radicals by xanthine oxidase and stimulated neutrophils

The effects of three aglycon flavonols (myricetin, quercetin, and kaempferol) and the natural glycoside rutin on superoxide anion radical generating systems were investigated. Quercetin, myricetin, and kaempferol inhibited the formation of uric acid from xanthine by xanthine oxidase, while rutin was ineffective. The generation of superoxide anion radicals by this system was determined by either reduction of cytochrome c or Pholasin luminescence. A scavenging of superoxide was only observed for myricetin and to a small extent for rutin. All flavonols tested inhibited the Pholasin luminescence of fMet-Leu-Phe-stimulated neutrophils. Rutin influenced the oxidative burst of neutrophils in the same way as wortmannin and LY294002, two inhibitors of the phosphoinositide 3-kinase gamma. Indeed, rutin inhibited the activity of this enzyme, whereas the three other flavonols showed no effect. Thus, an inhibition of enzymes involved in signaling rather than a scavenging of superoxide anion radicals dominates in fMet-Leu-Phe-stimulated neutrophils exposed to flavonols.

Food sources of phytoestrogens and breast cancer risk in Mexican women

We analyzed the intake of selected foods that contain phytoestrogens in relation to breast cancer (BC) risk using data from a hospital-based case-control study performed in Mexico City from 1994 to 1995. A total of 198 women with BC, aged 21-79 years, were individually age matched to an identical number of women with no breast disease. By a direct interview, information on socioeconomic characteristics and diet was obtained. A semiquantitative questionnaire was used to estimate the frequency of consumption of 95 foods. The effect of selected foods that contain phytoestrogens on BC risk was estimated using logistic regression models. The adjusted odds ratio for the consumption of more than one slice of onion per day and BC was 0.27 (95% confidence interval = 0.16-0.47), with a statistically significant trend (p < 0.001). This protective effect remained after adjustment for known risk factors of BC. Among premenopausal women, there was also a protective and significant effect due to the intake of lettuce and spinach and nonsignificant protective effects for the consumption of apples and herbal tea. Additional studies aimed at evaluating the potential protective effect of particular phytoestrogens on BC risk are needed.

Resveratrol and quercetin inhibit angiogenesis in vitro

Resveratrol and quercetin are polyphenolic compounds found in grapes, red wine and other food products. In this study, we examined the effect of resveratrol and quercetin on the inhibition of angiogenesis in vitro. Resveratrol and quercetin inhibited the growth of bovine aorta endothelial (BAE) cells in a concentration-dependent manner (6-100 microM).The migration of BAE was obviously inhibited by resveratrol and weakly inhibited by quercetin. When the lengths of all tubes constructed in the 3-D culture system with or without resveratrol or quercetin were measured, resveratrol was found to inhibit the tube formation of BAE cells in a concentration-dependent manner (6-100 microM). On the other hand, quercetin at concentrations above 100 microM significantly inhibited the tube formation of vascular endothelial cells. From these results, we suggest that resveratrol and quercetin may prove useful in the development of useful therapeutic agents or preventive food factors for tumor angiogenesis.

Dietary antioxidants during cancer chemotherapy: impact on chemotherapeutic effectiveness and development of side effects

Several studies suggest that dietary supplementation with antioxidants can influence the response to chemotherapy as well as the development of adverse side effects that results from treatment with antineoplastic agents. Administration of antineoplastic agents results in oxidative stress, i.e., the production of free radicals and other reactive oxygen species (ROS). Oxidative stress reduces the rate of cell proliferation, and that occurring during chemotherapy may interfere with the cytotoxic effects of antineoplastic drugs, which depend on rapid proliferation of cancer cells for optimal activity. Antioxidants detoxify ROS and may enhance the anticancer effects of chemotherapy. For some supplements, activities beyond their antioxidant properties, such as inhibition of topoisomerase II or protein tyrosine kinases, may also contribute. ROS cause or contribute to certain side effects that are common to many anticancer drugs, such as gastrointestinal toxicity and mutagenesis. ROS also contribute to side effects that occur only with individual agents, such as doxorubicin-induced cardiotoxicity, cisplatin-induced nephrotoxicity, and bleomycin-induced pulmonary fibrosis. Antioxidants can reduce or prevent many of these side effects, and for some supplements the protective effect results from activities other than their antioxidant properties. Certain side effects, however, such as alopecia and myelosuppression, are not prevented by antioxidants, and agents that interfere with these side effects may also interfere with the anticancer effects of chemotherapy.

Anti-genotoxicity of galangin as a cancer chemopreventive agent candidate

Flavonoids are polyphenolic compounds that are present in plants. They have been shown to possess a variety of biological activities at non-toxic concentrations in organisms. Galangin, a member of the flavonol class of flavonoid, is present in high concentrations in medicinal plants (e.g. Alpinia officinarum) and propolis, a natural beehive product. Results from in vitro and in vivo studies indicate that galangin with anti-oxidative and free radical scavenging activities is capable of modulating enzyme activities and suppressing the genotoxicity of chemicals. These activities will be discussed in this review. Based on our review, galangin may be a promising candidate for cancer chemoprevention.

Chemoprevention studies of the flavonoids quercetin and rutin in normal and azoxymethane-treated mouse colon

In this study we investigated the chemopreventive effects of quercetin and rutin when added to standard AIN-76A diet and fed to normal and azoxymethane (AOM)-treated mice. Early changes in colonic mucosa were analyzed, including colonic cell proliferation, apoptotic cell death, cyclin D(1) expression and focal areas of dysplasia (FAD). The findings show that the number of colonic epithelial cells per crypt column increased (P: < 0.01) in each normal mouse group fed the flavonoids; AOM administration increased colonic crypt cell proliferation and resulted in a marked rise of bromodeoxyuridine-labeled cells in the lower proliferative zone of the crypt. Both supplementary dietary quercetin and rutin increased the apoptotic index and caused a redistribution of apoptotic cells along the crypt axis in normal mice fed a standard AIN-76A diet. The number of apoptotic cells/column and apoptotic indices markedly increased (P: < 0.01) in the AOM-treated group compared with untreated animals; apoptotic cells expanded throughout the colonic crypts after flavonoid supplementation and AOM administration. Positive cyclin D(1) expression was detected in mice on diets supplemented either with quercetin (P: < 0.01) or rutin (P: < 0.05). AOM administration resulted in the formation of FAD. Both the number of mice exhibiting FAD and the total numer of FAD observed were significantly reduced (P: < 0.01) in AOM-treated animals fed flavonoids compared with mice maintained on the standard AIN-76A diet. Surprisingly, however, quercetin alone was able to induce FAD in 22% of normal mice fed the standard AIN-76A diet.

Signal transduction events elicited by natural products: role of MAPK and caspase pathways in homeostatic response and induction of apoptosis

Many natural products elicit diverse pharmacological effects. Using two classes of potential chemopreventive compounds, the phenolic compounds and the isothiocyanates, we review the potential utility of two signaling events, the mitogen-activated protein kinases (MAPKs) and the ICE/Ced-3 proteases (caspases) stimulated by these agents in mammalian cell lines. Studies with phenolic antioxidants (BHA, tBHQ), and natural products (flavonoids; EGCG, ECG, and isothiocyanates; PEITC, sulforaphane), provided important insights into the signaling pathways induced by these compounds. At low concentrations, these chemicals may activate the MAPK (ERK2, JNK1, p38) leading to gene expression of survival genes (c-Fos, c-Jun) and defensive genes (Phase II detoxifying enzymes; GST, QR) resulting in survival and protective mechanisms (homeostasis response). Increasing the concentrations of these compounds will additionally activate the caspase pathway, leading to apoptosis (potential cytotoxicity). Further increment to suprapharmacological concentrations will lead to nonspecific necrotic cell death. The wider and narrow concentration ranges between the activation of MAPK/gene induction and caspases/cell death exhibited by phenolic compounds and isothiocyanates, respectively, in mammalian cells, may reflect their respective therapeutic windows in vivo. Consequently, the studies of signaling pathways elicited by natural products will advance our understanding of their efficacy and safety, of which many may become important therapeutic drugs of the future.

Effect of antiproliferative flavonoids on ascorbic acid accumulation in human colon adenocarcinoma cells

Dietary flavonoids were found to be antiproliferative for human colon cancer cells, Caco-2 and HT-29, and rat nontransformed intestinal crypt cells, IEC-6. The antiproliferative potency was found to be structure-dependent. We report here a correlation between the antiproliferative potency of these flavonoids and their ability to inhibit cellular accumulation of ascorbic acid (vitamin C). Caco-2, HT-29 and IEC-6 cells were found to accumulate ascorbic acid in a sodium-dependent fashion although some ascorbic acid may also enter the cells through sodium-independent mechanisms. Flavonoids that have been found to be antiproliferative, quercetin and genistein, inhibited the accumulation of ascorbic acid. The inhibition was dose-dependent and could be observed after as short as 10-min of incubation. The degree of inhibition of accumulation was more during rapid cell division as compared to post-confluency Caco-2 cells. Flavonoids that were found to show little antiproliferative effect, naringenin and catechin, also had little effect on ascorbic acid accumulation. The antiproliferative property of flavonoids could be linked to their ascorbic acid deprivation property.

Antiproliferative potency of structurally distinct dietary flavonoids on human colon cancer cells

Dietary flavonoids are known to be antiproliferative and may play an important role in cancer chemoprevention, especially cancers of the gastrointestinal tract, because of a direct contact with food. This study was designed to compare the antiproliferative potency of several structurally distinct dietary flavonoids in colon cancer cells, Caco-2 and HT-29, and in rat non-transformed intestinal crypt cells, IEC-6. Flavonoids varied significantly in their antiproliferative potency depending on the structural features but the observations were consistent among the three cell lines studied. Of the two most potent flavonoids, quercetin and genistein, the effect was found to be dose-dependent and chromatin condensation, an indication of apoptosis, was noticed. Quercetin was found to distribute throughout the cell with higher amounts in the perinuclear and nucleoli areas. The lack of specific cell membrane enrichment by quercetin was consistent with its lack of effect on the transepithelial resistance. While several flavonoids including quercetin were found to be unstable, the chemical instability did not correlate with the antiproliferative potency, although it may contribute to the antiproliferative effect.

Modulation of toxicity by dietary and environmental factors

Both epidemiological and experimental evidence indicate that environmental factors may modulate chemical toxicity. Of these, dietary factors have been most thoroughly studied and shown to modulate a number of toxic processes including carcinogenesis. Total energy intake and specific nutrients (protein and specific amino acids, vitamins, and minerals) have been shown to be active in this regard as have a number of non-nutritive dietary factors, most notably phenolic and sulphur-containing compounds, and indoles. The mechanisms by which dietary factors might influence toxicity include effects on bioavailability, phase I or phase II metabolism, scavenging of reactive metabolites, induction of DNA repair processes, inhibition of cell proliferation, induction of differentiation or apoptosis and effects on the immune system. These factors are discussed with emphasis on dietary exposure to modulating factors.

Selected novel flavones inhibit the DNA binding or the DNA religation step of eukaryotic topoisomerase I

Topoisomerases are involved in many aspects of DNA metabolism such as replication and transcription reactions. Camptothecins, which stabilize the covalent intermediate of topoisomerase I and DNA are effective, though toxic, drugs for cancer therapy. In this study, a new class of topoisomerase I inhibitors was identified, and their mode of action was characterized using recombinant human topoisomerase I preparations and human HL-60 leukemic cells. Quercetin and the related natural flavones, acacetin, apigenin, kaempferol, and morin, inhibit topoisomerase I-catalyzed DNA religation. In contrast to camptothecin, these compounds do not act directly on the catalytic intermediate and also do not interfere with DNA cleavage. However, formation of a ternary complex with topoisomerase I and DNA during the cleavage reaction inhibits the following DNA religation step. 3,3',4',7-Tetrahydroxy-substituted flavones stabilize the covalent topoisomerase I-DNA intermediate most efficiently. Enhanced formation of covalent topoisomerase I-DNA complexes was also demonstrated in human HL-60 cells. In contrast, synthetic 3,5'-dibromo- 4'-hydroxy-3-methylflavones bind selectively to topoisomerase I in its non-DNA-bound form and block the following DNA binding step. As a consequence, these synthetic flavonoids are capable of counteracting topoisomerase I-directed effects of camptothecin. Inhibition of DNA binding is obtained by voluminous hydrophobic substituents in 6-position of the flavone structure. Our data show that selective inhibitors of both half-reactions of topoisomerase I can be derived from the flavone structure.

Inhibition of human breast cancer cell proliferation and delay of mammary tumorigenesis by flavonoids and citrus juices

Two citrus flavonoids, hesperetin and naringenin, found in oranges and grapefruit, respectively, and four noncitrus flavonoids, baicalein, galangin, genistein, and quercetin, were tested singly and in one-to-one combinations for their effects on proliferation and growth of a human breast carcinoma cell line, MDA-MB-435. The concentration at which cell proliferation was inhibited by 50% (IC50), based on incorporation of [3H]thymidine, varied from 5.9 to 140 micrograms/ml for the single flavonoids, with the most potent being baicalein. IC50 values for the one-to-one combinations ranged from 4.7 micrograms/ml (quercetin + hesperetin, quercetin + naringenin) to 22.5 micrograms/ml (naringenin + hesperetin). All the flavonoids showed low cytotoxicity (> 500 micrograms/ml for 50% cell death). Naringenin is present in grapefruit mainly as its glycosylated form, naringin. These compounds, as well as grapefruit and orange juice concentrates, were tested for their ability to inhibit development of mammary tumors induced by 7,12-dimethylbenz[a]anthracene (DMBA) in female Sprague-Dawley rats. Two experiments were conducted in which groups of 21 rats were fed a semipurified diet containing 5% corn oil and were given a 5-mg dose of DMBA intragastrically at approximately 50 days of age while in diestrus. One week later, individual groups were given double-strength grapefruit juice or orange juice or fed naringin or naringenin at levels comparable to that provided by the grapefruit juice; in the second experiment, the rats were fed a semipurified diet containing 20% corn oil at that time. As expected, rats fed the high-fat diet developed more tumors than rats fed the low-fat diet, but in both experiments tumor development was delayed in the groups given orange juice or fed the naringin-supplemented diet compared with the other three groups. Although tumor incidence and tumor burden (grams of tumor/rat) were somewhat variable in the different groups, rats given orange juice had a smaller tumor burden than controls, although they grew better than any of the other groups. These experiments provide evidence of anticancer properties of orange juice and indicate that citrus flavonoids are effective inhibitors of human breast cancer cell proliferation in vitro, especially when paired with quercetin, which is widely distributed in other foods.

The dietary anticancer agent ellagic acid is a potent inhibitor of DNA topoisomerases in vitro

Ellagic acid and 12 related agents have been tested for their ability to inhibit the activities of human DNA topoisomerase (topo) I and II. Using specific in vitro assays, we found ellagic acid and flavellagic acid to be potent inhibitors of the catalytic activities of the two topoisomerases. The minimum concentration required to inhibit > or = 50% of catalytic activity (IC50) of ellagic acid was determined at 0.6 and 0.7 micrograms/ml for topo I and topo II, respectively. Flavellagic acid's IC50 was determined at 3.0 and 3.6 micrograms/ml for topo I and topo II, respectively. Unlike topoisomerase poisons, these two plant phenols did not trap the enzyme-DNA reaction intermediate, known as the cleavable complex. In contrast, ellagic acid prevented other topo I and topo II poisons from stabilizing the cleavable complex, suggesting that the mode of its action is that of an antagonist. Structure-activity studies identified the 3,3'-hydroxyl groups and the lactone groups as the most essential elements for the topoisomerase inhibitory actions of plant phenols. On the basis of these findings and other properties of ellagic acid, a mechanistic model for the documented anticarcinogenic effects of the agent is proposed.