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Being secondary plant metabolites, polyphenols represent a large and diverse group of substances abundantly present in a majority of fruits, herbs and vegetables. The current contribution is focused on their bioavailability, antioxidative and anticarcinogenic properties. An overview of extraction methods is also given, with supercritical fluid extraction highlighted as a promising eco-friendly alternative providing exceptional separation and protection from degradation of unstable polyphenols. The protective role of polyphenols against reactive oxygen and nitrogen species, UV light, plant pathogens, parasites and predators results in several beneficial biological activities giving rise to prophylaxis or possibly even to a cure for several prevailing human diseases, especially various cancer types. Omnipresence, specificity of the response and the absence of or low toxicity are crucial advantages of polyphenols as anticancer agents. The main problem represents their low bioavailability and rapid metabolism. One of the promising solutions lies in nanoformulation of polyphenols that prevents their degradation and thus enables significantly higher concentrations to reach the target cells. Another, more practiced, solution is the use of mixtures of various polyphenols that bring synergistic effects, resulting in lowering of the required therapeutic dose and in multitargeted action. The combination of polyphenols with existing drugs and therapies also shows promising results and significantly reduces their toxicity.

Flavonoids are phytochemical compounds present in many plants, fruits, vegetables, and leaves, with potential applications in medicinal chemistry. Flavonoids possess a number of medicinal benefits, including anticancer, antioxidant, anti-inflammatory, and antiviral properties. They also have neuroprotective and cardio-protective effects. These biological activities depend upon the type of flavonoid, its (possible) mode of action, and its bioavailability. These cost-effective medicinal components have significant biological activities, and their effectiveness has been proved for a variety of diseases. The most recent work is focused on their isolation, synthesis of their analogs, and their effects on human health using a variety of techniques and animal models. Thousands of flavonoids have been successfully isolated, and this number increases steadily. We have therefore made an effort to summarize the isolated flavonoids with useful activities in order to gain a better understanding of their effects on human health.

Purpose We tested the hypothesis that polyphenol-rich extracts can reduce endoplasmic reticulum (ER) stress induced by a high-fat diet (HFD) in skeletal muscle of mice. Methods Mice were randomly assigned to four groups receiving during 20 weeks either a standard chow control (CTRL), or a HFD supplemented, or not, with pomegranate (HFD + P) or green tea (HFD + GT) extracts. After the nutritional intervention, mice were killed and gastrocnemius muscles were taken. Proteins and mRNA were measured by Western blot and RT-qPCR, respectively. Results Body weight gain and visceral fat were higher in HFD, HFD + P and HFD + GT than in CTRL. The markers of the unfolded protein response BiP, XBP1u, XBP1s and ATF4 were higher only in HFD. In HFD + P and HFD + GT, this increase was not observed except for CHOP, which was elevated in all HFD groups. HFD increased also markers of ubiquitin–proteasome pathway, autophagy and oxidative stress, which were kept low in HFD + P and HFD + GT groups. Conclusion Our data provide evidence for a protective effect of pomegranate and green tea extracts against ER stress, oxidative stress and protein degradation induced by HFD in skeletal muscle. They give arguments for a usefulness of these natural nutritional compounds to fight against cellular dysfunctions related to fat excess.

Natural antioxidants are widely distributed in food and medicinal plants. These natural antioxidants, especially polyphenols and carotenoids, exhibit a wide range of biological effects, including anti-inflammatory, anti-aging, anti-atherosclerosis and anticancer. The effective extraction and proper assessment of antioxidants from food and medicinal plants are crucial to explore the potential antioxidant sources and promote the application in functional foods, pharmaceuticals and food additives. The present paper provides comprehensive information on the green extraction technologies of natural antioxidants, assessment of antioxidant activity at chemical and cellular based levels and their main resources from food and medicinal plants.

Tea is widely consumed all over the world. Generally, tea is divided into six categories: White, green, yellow, oolong, black, and dark teas, based on the fermentation degree. Tea contains abundant phytochemicals, such as polyphenols, pigments, polysaccharides, alkaloids, free amino acids, and saponins. However, the bioavailability of tea phytochemicals is relatively low. Thus, some novel technologies like nanotechnology have been developed to improve the bioavailability of tea bioactive components and consequently enhance the bioactivity. So far, many studies have demonstrated that tea shows various health functions, such as antioxidant, anti-inflammatory, immuno-regulatory, anticancer, cardiovascular-protective, anti-diabetic, anti-obesity, and hepato-protective effects. Moreover, it is also considered that drinking tea is safe to humans, since reports about the severe adverse effects of tea consumption are rare. In order to provide a better understanding of tea and its health potential, this review summarizes and discusses recent literature on the bioactive components, bioavailability, health functions, and safety issues of tea, with special attention paid to the related molecular mechanisms of tea health functions.

This review offers a systematic understanding about how polyphenols target multiple inflammatory components and lead to anti-inflammatory mechanisms. It provides a clear understanding of the molecular mechanisms of action of phenolic compounds. Polyphenols regulate immunity by interfering with immune cell regulation, proinflammatory cytokines' synthesis, and gene expression. They inactivate NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) and modulate mitogen-activated protein Kinase (MAPk) and arachidonic acids pathways. Polyphenolic compounds inhibit phosphatidylinositide 3-kinases/protein kinase B (PI3K/AkT), inhibitor of kappa kinase/c-Jun amino-terminal kinases (IKK/JNK), mammalian target of rapamycin complex 1 (mTORC1) which is a protein complex that controls protein synthesis, and JAK/STAT. They can suppress toll-like receptor (TLR) and pro-inflammatory genes' expression. Their antioxidant activity and ability to inhibit enzymes involved in the production of eicosanoids contribute as well to their anti-inflammation properties. They inhibit certain enzymes involved in reactive oxygen species ROS production like xanthine oxidase and NADPH oxidase (NOX) while they upregulate other endogenous antioxidant enzymes like superoxide dismutase (SOD), catalase, and glutathione (GSH) peroxidase (Px). Furthermore, they inhibit phospholipase A2 (PLA2), cyclooxygenase (COX) and lipoxygenase (LOX) leading to a reduction in the production of prostaglandins (PGs) and leukotrienes (LTs) and inflammation antagonism. The effects of these biologically active compounds on the immune system are associated with extended health benefits for different chronic inflammatory diseases. Studies of plant extracts and compounds show that polyphenols can play a beneficial role in the prevention and the progress of chronic diseases related to inflammation such as diabetes, obesity, neurodegeneration, cancers, and cardiovascular diseases, among other conditions.

Polyphenols, found abundantly in plants, display many anticarcinogenic properties including their inhibitory effects on cancer cell proliferation, tumor growth, angiogenesis, metastasis, and inflammation as well as inducing apoptosis. In addition, they can modulate immune system response and protect normal cells against free radicals damage. Most investigations on anticancer mechanisms of polyphenols were conducted with individual compounds. However, several studies, including ours, have indicated that anti-cancer efficacy and scope of action can be further enhanced by combining them synergistically with chemically similar or different compounds. While most studies investigated the anti-cancer effects of combinations of two or three compounds, we used more comprehensive mixtures of specific polyphenols and mixtures of polyphenols with vitamins, amino acids and other micronutrients. The mixture containing quercetin, curcumin, green tea, cruciferex, and resveratrol (PB) demonstrated significant inhibition of the growth of Fanconi anemia head and neck squamous cell carcinoma and dose-dependent inhibition of cell proliferation, matrix metalloproteinase (MMP)-2 and -9 secretion, cell migration and invasion through Matrigel. PB was found effective in inhibition of fibrosarcoma HT-1080 and melanoma A2058 cell proliferation, MMP-2 and -9 expression, invasion through Matrigel and inducing apoptosis, important parameters for cancer prevention. A combination of polyphenols (quercetin and green tea extract) with vitamin C, amino acids and other micronutrients (EPQ) demonstrated significant suppression of ovarian cancer ES-2 xenograft tumor growth and suppression of ovarian tumor growth and lung metastasis from IP injection of ovarian cancer A-2780 cells. The EPQ mixture without quercetin (NM) also has shown potent anticancer activity in vivo and in vitro in a few dozen cancer cell lines by inhibiting tumor growth and metastasis, MMP-2 and -9 secretion, invasion, angiogenesis, and cell growth as well as induction of apoptosis. The presence of vitamin C, amino acids and other micronutrients could enhance inhibitory effect of epigallocatechin gallate (EGCG) on secretion of MMPs. In addition, enrichment of NM with quercetin (EPQ mix) enhanced anticancer activity of NM in vivo. In conclusion, polyphenols, especially in combination with other polyphenols or micronutrients, have been shown to be effective against multiple targets in cancer development and progression, and should be considered as safe and effective approaches in cancer prevention and therapy.

Polyphenols are potent micronutrients that can be found in large quantities in various food sources and spices. These compounds, also known as phenolics due to their phenolic structure, play a vital nutrient-based role in the prevention of various diseases such as diabetes, cardiovascular diseases, neurodegenerative diseases, liver disease, and cancers. However, the function of polyphenols in disease prevention and therapy depends on their dietary consumption and biological properties. According to American Cancer Society statistics, there will be an expected rise of 23.6 million new cancer cases by 2030. Due to the severity of the increased risk, it is important to evaluate various preventive measures associated with cancer. Relatively recently, numerous studies have indicated that various dietary polyphenols and phytochemicals possess properties of modifying epigenetic mechanisms that modulate gene expression resulting in regulation of cancer. These polyphenols and phytochemicals, when administrated in a dose-dependent and combinatorial-based manner, can have an enhanced effect on epigenetic changes, which play a crucial role in cancer prevention and therapy. Hence, this review will focus on the mechanisms of combined polyphenols and phytochemicals that can impact various epigenetic modifications such as DNA methylation and histone modifications as well as regulation of non-coding miRNAs expression for treatment and prevention of various types of cancer.

Cancer is defined as the abnormal cell growth that can cause life-threatening malignancies with high financial costs for patients as well as the health care system. Natural polyphenols have long been used for the prevention and treatment of several disorders due to their antioxidant, anti-inflammatory, cytotoxic, antineoplastic, and immunomodulatory effects discussed in the literature; thus, these phytochemicals are potentially able to act as chemopreventive and chemotherapeutic agents in different types of cancer. One of the problems regarding the use of polyphenolic compounds is their low bioavailability. Different types of formulations have been designed for the improvement of bioavailability of these compounds, nanonization being one of the most notable approaches among them. This study aimed to review current data on the nanoformulations of natural polyphenols as chemopreventive and chemotherapeutic agents and to discuss their molecular anticancer mechanisms of action. Nanoformulations of natural polyphenols as bioactive agents, including resveratrol, curcumin, quercetin, epigallocatechin-3-gallate, chrysin, baicalein, luteolin, honokiol, silibinin, and coumarin derivatives, in a dose-dependent manner, result in better efficacy for the prevention and treatment of cancer. The impact of nanoformulation methods for these natural agents on tumor cells has gained wider attention due to improvement in targeted therapy and bioavailability, as well as enhancement of stability. Today, several nanoformulations are designed for delivery of polyphenolic compounds, including nanosuspensions, solid lipid nanoparticles, liposomes, gold nanoparticles, and polymeric nanoparticles, which have resulted in better antineoplastic activity, higher intracellular concentration of polyphenols, slow and sustained release of the drugs, and improvement of proapoptotic activity against tumor cells. To conclude, natural polyphenols demonstrate remarkable anticancer potential in pharmacotherapy; however, the obstacles in terms of their bioavailability in and toxicity to normal cells, as well as targeted drug delivery to malignant cells, can be overcome using nanoformulation-based technologies, which optimize the bioefficacy of these natural drugs.

The prevalence of obesity has steadily increased worldwide over the past three decades. The conventional approaches to prevent or treat this syndrome and its associated complications include a balanced diet, an increase energy expenditure, and lifestyle modification. Multiple pharmacological and non-pharmacological interventions have been developed with the aim of improving obesity complications. Recently, the use of functional foods and their bioactive components is considered a new approach in the prevention and management of this disease. Due to their biological properties, polyphenols may be considered as nutraceuticals and food supplement recommended for different syndromes. Polyphenols are a class of naturally-occurring phytochemicals, some of which have been shown to modulate physiological and molecular pathways involved in energy metabolism. Polyphenols could act in the stimulation of β-oxidation, adipocyte differentiation inhibition, counteract oxidative stress, etc. In this narrative review, we considered the association between polyphenols (resveratrol, quercetin, curcumin, and some polyphenolic extracts) and obesity, focusing on human trials. The health effects of polyphenols depend on the amount consumed and their bioavailability. Some results are contrasting, probably due to the various study designs and lengths, variation among subjects (age, gender, ethnicity), and chemical forms of the dietary polyphenols used. But, in conclusion, the data so far obtained encourage the setting of new trials, necessary to validate benefic role of polyphenols in obese individuals.