Bioavailability and Antioxidant Activity of Black Chokeberry (Aronia melanocarpa) Polyphenols: in vitro and in vivo Evidences and Possible Mechanisms of Action: A Review

Abstract: Black chokeberry (Aronia melanocarpa) is a distinctive berry with a high content of polyphenol compounds and possesses one of the highest in vitro antioxidant activities among fruits. The bioavailability of aronia polyphenols seems to be low, but there is ample evidence for chokeberry health benefits including antidiabetic, cardioprotective, hepatoprotective, antimutagenic, and anticarcinogenic effects. This review presents the available information for the bioavailability and antioxidant activity of chokeberry polyphenols and explains the possible mechanisms of action in vivo in the prevention and treatment of oxidative stress‐related diseases. The review shows the available data for chokeberry antioxidant activity in vitro, in isolated cells and cell lines, and in vivo, in both human subjects and animals. It is evident that in vivo antioxidant action of chokeberry extends far beyond radical scavenging and includes suppression of reactive oxygen and nitrogen species formation, inhibition of prooxidant enzymes, restoration of antioxidant enzymes, and probably cellular signaling to regulate the level of antioxidant compounds and enzymes. The original contribution of this work is that it compiles the available information up to date and outlines the gaps and future directions in the assessment of chokeberry antioxidant action in vivo.     

Absorption,metabolism, anti-cancer effect and molecular targets of epigallocatechin gallate (EGCG): An updated review

Green tea is one of the most popular beverages in the world, especially in Asian countries. Consumption of green tea has been demonstrated to possess many health benefits, which mainly attributed to the main bioactive compound epigallocatechin gallate (EGCG), a flavone-3-ol polyphenol, in green tea. EGCG is mainly absorbed in the intestine, and gut microbiota play a critical role in its metabolism prior to absorption. EGCG exhibits versatile bioactivities, with its anti-cancer effect most attracting due to the cancer preventive effect of green tea consumption, and a great number of studies intensively investigated its anti-cancer effect. In this review, we therefore, first stated the absorption and metabolism process of EGCG, and then summarized its anti-cancer effect in vitro and in vivo, including its manifold anti-cancer actions and mechanisms, especially its anti-cancer stem cell effect, and next highlighted its various molecular targets involved in cancer inhibition. Finally, the anti-cancer effect of EGCG analogs and nanoparticles, as well as the potential cancer promoting effect of EGCG were also discussed. Understanding of the absorption, metabolism, anti-cancer effect and molecular targets of EGCG can be of importance to better utilize it as a chemopreventive and chemotherapeutic agent.     

Chemistry and Biological Activities of Processed Camellia sinensis Teas: A Comprehensive Review

Tea is a typical processed beverage from the fresh leaves of Camellia sinensis [Camellia sinensis (L.) O. Kuntze] or Camellia assamica [Camellia sinensis var. assamica (Mast.) Kitamura] through different manufacturing techniques. The secondary metabolites of fresh tea leaves are mainly flavan‐3‐ols, phenolic acids, purine alkaloids, condensed tannins, hydrolysable tannins, saponins, flavonols, and their glycoside forms. During the processing, tea leaves go through several steps, such as withering, rolling, fermentation, postfermentation, and roasting (drying) to produce different types of tea. After processing, theaflavins, thearubigins, and flavan‐3‐ols derivatives emerge as the newly formed compounds with a corresponding decrease in concentrations of catechins. Each type of tea has its own critical process and presents unique chemical composition and flavor. The components among different teas also cause significant changes in their biological activities both in vitro and in vivo. In the present review, the progress of tea chemistry and the effects of individual unit operation on components were comprehensively described. The health benefits of tea were also reviewed based on the human epidemiological and clinical studies. Although there have been multiple studies about the tea chemistry and biological activities, most of existing results are related to tea polyphenols, especially (‐)‐epigallocatechin gallate. Other compounds, including the novel compounds, as well as isomers of amino acids and catechins, have not been explored in depth.     

Polyphenols Extracted from Black Tea (Camellia sinensis) Residue by Hot‐Compressed Water and Their Inhibitory Effect on Pancreatic Lipase in vitro

Abstract: Polyphenols, retained in black tea wastes following the commercial production of tea beverages, represent an underutilized resource. The purpose of this study was to investigate the potential use of hot‐compressed water (HCW) for the extraction of pancreatic lipase‐inhibiting polyphenols from black tea residues. Black tea residues were treated with HCW at 10 °C intervals, from 100 to 200 °C. The resulting extracts were analyzed using high‐performance liquid chromatography‐mass spectrometry and assayed to determine their inhibitory effect on pancreatic lipase activity in vitro. Four theaflavins (TF), 5 catechins, 2 quercetin glycosides, quinic acid, gallic acid, and caffeine were identified. The total polyphenol content of extracts increased with increasing temperature but lipase inhibitors (TF, theaflavin 3‐O‐gallate, theaflavin 3′‐O‐gallate, theaflavin 3,3′‐O‐gallate, epigallocatechin gallate, and epicatechin gallate) decreased over 150 °C. All extracts inhibited pancreatic lipase but extracts obtained at 100 to 140 °C showed the greatest lipase inhibition (IC₅₀s of 0.9 to 1.3 μg/mL), consistent with the optimal extraction of TFs and catechins except catechin by HCW between 130 and 150 °C. HCW can be used to extract pancreatic lipase‐inhibiting polyphenols from black tea waste. These extracts have potential uses, as dietary supplements and medications, for the prevention and treatment of obesity. Practical Application: Active forms of lipase inhibitors can be recovered from black tea residues. They could be used as dietary supplements or medications.     

Salvianolic acid B inhibits low‐density lipoprotein oxidation and neointimal hyperplasia in endothelium‐denuded hypercholesterolaemic rabbits

BACKGROUND: Atherosclerosis and restenosis are inflammatory responses involving free radicals and lipid peroxidation and may be prevented/cured by antioxidant‐mediated lipid peroxidation inhibition. Salvianolic acid (Sal B), a water‐soluble antioxidant obtained from a Chinese medicinal herb, is believed to have multiple preventive and therapeutic effects against human vascular diseases. In this study the in vitro and in vivo inhibitory effects of Sal B on oxidative stress were determined. RESULTS: In human aortic endothelial cells (HAECs), Sal B reduced oxidative stress, inhibited low‐density lipoprotein (LDL) oxidation and reduced oxidised LDL‐induced cytotoxicity. Sal B inhibited Cu²⁺‐induced LDL oxidation in vitro (with a potency 16.3 times that of probucol) and attenuated HAEC‐mediated LDL oxidation as well as reactive oxygen species (ROS) production. In cholesterol‐fed New Zealand White rabbits (with probucol as positive control), Sal B intake reduced Cu²⁺‐induced LDL oxidation, lipid deposition in the thoracic aorta, intimal thickness of the aortic arch and thoracic aorta and neointimal formation in the abdominal aorta. CONCLUSION: The data obtained in this study suggest that Sal B protects HAECs from oxidative injury‐mediated cell death via inhibition of ROS production. The antioxidant activity of Sal B may help explain its efficacy in the treatment of vascular diseases. Copyright © 2010 Society of Chemical Industry     

Kaempferol induced apoptosis via endoplasmic reticulum stress and mitochondria‐dependent pathway in human osteosarcoma U‐2 OS cells

Kaempferol is a natural flavonoid. Previous studies have reported that kaempferol has anti‐proliferation activities and induces apoptosis in many cancer cell lines. However, there are no reports on human osteosarcoma. In this study, we investigate the anti‐cancer effects and molecular mechanisms of kaempferol in human osteosarcoma cells. Our results demonstrate that kaempferol significantly reduces cell viabilities of U‐2 OS, HOB and 143B cells, especially U‐2 OS cells in a dose‐dependent manner, but exerts low cytotoxicity on human fetal osteoblast progenitor hFOB cells. Comet assay, DAPI staining and DNA gel electrophoresis confirm the effects of DNA damage and apoptosis in U‐2 OS cells. Flow cytometry detects the increase of cytoplasmic Ca²⁺ levels and the decrease of mitochondria membrane potential. Western blotting and fluorogenic enzymatic assay show that kaempferol treatment influences the time‐dependent expression of proteins involved in the endoplasmic reticulum stress pathway and mitochondrial signaling pathway. In addition, pretreating cells with caspase inhibitors, BAPTA or calpeptin before exposure to kaempferol increases cell viabilities. The anti‐cancer effects of kaempferol in vivo are evaluated in BALB/c^nu/nu mice inoculated with U‐2 OS cells, and the results indicate inhibition of tumor growth. In conclusion, kaempferol inhibits human osteosarcoma cells in vivo and in vitro.     

Polyphenols as active ingredients for cosmetic products

Polyphenols are secondary plant metabolites with antioxidant, anti‐inflammatory and anti‐microbial activity. They are ubiquitously distributed in the plant kingdom; high amounts contain, for example, green tea and grape seeds. Polyphenolic extracts are attractive ingredients for cosmetics and pharmacy due to their beneficial biological properties. This review summarizes the effects of polyphenols in the context of anti‐ageing activity. We have explored in vitro studies, which investigate antioxidant activity, inhibition of dermal proteases and photoprotective activity, mostly studied using dermal fibroblasts or epidermal keratinocytes cell lines. Possible negative effects of polyphenols were also discussed. Further, some physicochemical aspects, namely the possible interactions with emulsifiers and the influence of the cosmetic formulation on the skin delivery, were reported. Finally, few clinical studies, which cover the anti‐ageing action of polyphenols on the skin after topical application, were reviewed.     

Effect of irradiation on the antioxidative and antigenotoxic activities of a green tea leaf and stem extract

Green tea (Camellia sinensis) leaf and stem extract, a major byproduct of the green tea industry, was investigated for its antioxidative and antigenotoxic activities after 20 kGy of irradiation. In vitro antioxidative activities, including 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical scavenging, hydrogen peroxide inhibition, tyrosinase inhibition activities, and the reducing power were tested. Green tea leaf extract (GTLE) had higher antioxidative activities than the green tea stem extract (GTSE). Irradiation of 20 kGy to GTLE showed a decreasing tendency in DPPH radical, hydrogen peroxide‐scavenging activities, and reducing power, while that to GTSE showed an increasing tendency of the antioxidative activities. Tyrosinase inhibition activity showed no difference on irradiation, in GTLE and GTSE. Overall, irradiation had positive influences on the antioxidative activity in the GTSE more than in the GTLE. Antigenotoxic effect of the green tea extracts on an oxidative DNA damage in human leucocytes by a DNA comet assay also indicated a protective effect of GTLE. The irradiated GTLE began to decrease the DNA damage significantly at 10 μg mL^?1, which showed a higher inhibition activity than the non‐irradiated GTLE. The non‐irradiated and irradiated GTSE showed similar inhibition trends and they were comparable with that of the GTLE. Results suggest that the extract of GTSE, a major byproduct of the green tea industry, can be considered as a cost‐effective functional ingredient for industrial applications. Furthermore, irradiation of the GTSE may have beneficial effects on its functional activity.     

Effect of addition of Agaricus blazei mushroom residue to milk enriched with Omega‐3 on the prevention of lipid oxidation and bioavailability of bioactive compounds after in vitro gastrointestinal digestion

The residue from a hydroalcoholic extract of the mushroom Agaricus blazei (MAR) was evaluated for phenolic compounds, flavonoids and antioxidant activity. The ability of MAR to slow the oxidation of Omega‐3 resulting from light exposure in milk matrix, and its bioavailability after in vitro digestion was investigated. MAR presented phenolic compounds and flavonoids and showed antioxidant activity. At each concentration, addition of MAR to Omega‐3‐supplemented milk inhibited the production of conjugated dienes and malonaldehyde compared with samples without MAR. The bioavailability assay showed that polyphenols were still present after in vitro digestion and had antioxidant activity.     

Bilberry and its main constituents have neuroprotective effects against retinal neuronal damage in vitro and in vivo

Our aim was to determine whether a Vaccinium myrtillus (bilberry) anthocyanoside (VMA) and/or its main anthocyanidin constituents (cyanidin, delphinidin, and malvidin) can protect retinal ganglion cells (RGCs) against retinal damage in vitro and in vivo. In RGC cultures (RGC‐5, a rat ganglion cell‐line transformed using E1A virus) in vitro, cell damage and radical activation were induced by 3‐(4‐morpholinyl) sydnonimine hydrochloride (SIN‐1, a peroxynitrite donor). Cell viability was measured using a water‐soluble tetrazolium salt assay. Intracellular radical activation within RGC‐5 cells was evaluated using 5‐(and‐6)‐chloromethyl‐2,7‐dichlorodihydrofluorescein diacetate acetyl ester (CM‐H₂DCFDA). Lipid peroxidation was assessed using the supernatant fraction of mouse forebrain homogenates. In mice in vivo, we evaluated the effects of VMA on N‐methyl‐D ‐aspartic acid (NMDA)‐induced retinal damage using hematoxylin‐eosin and terminal deoxynucleotidyl transferase‐mediated dUTP nick‐end labeling (TUNEL) stainings. VMA and all three anthocyanidins (i) significantly inhibited SIN‐1‐induced neurotoxicity and radical activation in RGC‐5, (ii) concentration‐dependently inhibited lipid peroxidation in mouse forebrain homogenates. Intravitreously injected VMA significantly inhibited the NMDA‐induced morphological retinal damage and increase in TUNEL‐positive cells in the ganglion cell layer. Thus, VMA and its anthocyanidins have neuroprotective effects (exerted at least in part via an anti‐oxidation mechanism) in these in vitro and in vivo models of retinal diseases.     

Vinegar Functions on Health: Constituents,Sources, and Formation Mechanisms

Vinegars are one of only a few acidic condiments throughout the world. Vinegars can mainly be considered grain vinegars and fruit vinegars, according to the raw materials used. Both grain vinegars and fruit vinegars, which are fermented by traditional methods, possess a variety of physiological functions, such as antibacteria, anti‐infection, antioxidation, blood glucose control, lipid metabolism regulation, weight loss, and anticancer activities. The antibacteria and anti‐infection abilities of vinegars are mainly due to the presence of organic acids, polyphenols, and melanoidins. The polyphenols and melanoidins also provide the antioxidant abilities of vinegars, which are produced from the raw materials and fermentation processes, respectively. The blood glucose control, lipid metabolism regulation, and weight loss capabilities from vinegars are mainly due to acetic acid. Besides caffeoylsophorose (inhibits disaccharidase) and ligustrazine (improves blood circulation), other functional ingredients present in vinegars provide certain health benefits as well. Regarding anticancer activities, several grain vinegars strongly inhibit the growth of some cancer cells in vivo or in vitro, but related functional ingredients remain largely unknown, except tryptophol in Japanese black soybean vinegar. Considering the discovering of various functional ingredients and clarifying their mechanisms, some vinegars could be functional foods or even medicines, depending on a number of proofs that demonstrate these constituents can cure chronic diseases such as diabetes or cardiovascular problems.     

Pomegranate and its Many Functional Components as Related to Human Health: A Review

Abstract: Pomegranate (Punica granatum L.) is an ancient fruit that is widely consumed as fresh fruit and juice. The use of pomegranate fruit dates from ancient times and reports of its therapeutic qualities have echoed throughout the ages. Both in vitro and in vivo studies have demonstrated how this fruit acts as antioxidant, antidiabetic, and hypolipidemic and shows antibacterial, antiinflammatory, antiviral, and anticarcinogenic activities. The fruit also improves cardiovascular and oral health. These beneficial physiological effects may also have preventive applications in a variety of pathologies. The health benefits of pomegranate have been attributed to its wide range of phytochemicals, which are predominantly polyphenols, including primarily hydrolyzable ellagitannins, anthocyanins, and other polyphenols. The aim of this review was to present an overview of the functional, medical, and physiological properties of this fruit.     

Rethinking the Mechanism of the Health Benefits of Proanthocyanidins: Absorption,Metabolism, and Interaction with Gut Microbiota

Proanthocyanidins, as the oligomers or polymers of flavan‐3‐ol, are widely discovered in plants such as fruits, vegetables, cereals, nuts, and leaves, presenting a major part of dietary polyphenols. Although proanthocyanidins exert several types of bioactivities, such as antioxidant, antimicrobial, cardioprotective, and neuroprotective activity, their exact mechanisms remain unclear. Due to the complexity of the structure of proanthocyanidins, such as their various monomers, different linkages and isomers, investigation of their bioavailability and metabolism is limited, which further hinders the explanation of their bioactivities. Since the large molecular weight and degree of polymerization limit the bioavailability of proanthocyanidins, the major effective site of proanthocyanidins is proposed to be in the gut. Many studies have revealed the effects of proanthocyanidins from different sources on changing the composition of gut microbiota based on in vitro and in vivo models and the bioactivities of their metabolites. However, the metabolic routes of proanthocyanidins by gut microbiota and their mutual interactions are still sparse. Thus, this review summarizes the chemistry, absorption, and metabolic pathways of proanthocyanidins ranging from monomers to polymers, as well as the mutual interactions between proanthocyanidins and gut microbiota, in order to better understand how proanthocyanidins exert their health‐promoting functions.     

Estimation of the Bioavailability of Iron and Phosphorus in Cereals using a Dynamic In Vitro Gastrointestinal Model

A recently developed in vitro gastrointestinal model was evaluated for the estimation of the bioavailability of Fe and phosphorus and its correlation with biovailability in vivo. In vitro experiments were carried out without and with phytase supplementation (750 FTU kg^-1 feed) using rapeseed, sunflowerseed, wholewheat and white wheat flour. Phytase addition during in vitro digestion of rapeseed and sunflowerseed resulted in markedly increased dialysability of iron (67% and 20%) and phosphorus (31% and 66%). The release of free phosphorus during digestion of wholewheat and white wheat flour in the in vitro gastrointestinal model was observed to be correlated with the endogenous phytase activity in wheat. Comparison with different in vivo studies revealed that the in vitro gastrointestinal model could be used for a relative estimation of the bioavailability of Fe and phosphorus. © 1997 SCI.     

No Influence of Exogenous Hyaluronan on the Behavior of Human Cancer Cells or Endothelial Cell Capillary Formation

Hyaluronan (HA), a type of glycosaminoglycan used to construct the extracellular matrix, is involved in the proliferation and motility of cells, including cancer cells. The aim of this study was to determine whether exogenous HA has an influence on cancer in vitro and in vivo. High‐molecular‐weight HA (900 kDa) and low‐molecular‐weight HA (10 kDa) were added to several types of cancer cell lines in vitro, and proliferation and invasion were assessed. The effect of HA on capillary formation by human umbilical vein endothelial cells was also analyzed. The results showed that both types of HA had no apparent effect on cellular proliferation, invasion, or capillary formation. In an animal study, the 2 types of HA were orally administered to tumor‐bearing mice at a dosage of 200 mg/kg/d for 4 wk. Analysis using an in vivo imaging system revealed that tumor proliferation and metastasis were not greatly altered by HA administration. Furthermore, CD31 immunohistochemical staining revealed no obvious change in tumor microvessels. Taken together, these results demonstrate that exogenously administered HA has little effect on cancer. This study may support the safety of various forms of HA administration, including oral intake.     

Influence of in vitro gastrointestinal digestion on the bioavailability and antioxidant activity of polyphenols from Ipomoea batatas leaves

Sweet potato leaves (SPL) are natural by‐products rich in bioactive compounds, particularly polyphenols, and can be consumed as a vegetable. This work aims to investigate the influence of in vitro gastrointestinal digestion on the bioavailability and antioxidant activities of polyphenols from SPL. The phenolic compounds of sweet potato leaf extracts (SPLE) were quite stable in gastric phase. However, the amount of phenolic compounds decreased during transition from the acidic gastric environment to the alkaline intestinal environment. The bioavailability of phenolic compounds of SPLE was 13.36%. The ABTS^·+ scavenging capabilities and reducing power of SPLE were not affected during gastric digestion. Antioxidant activity increased after intestinal digestion. This research suggested that phenolic compounds of SPLE were sufficiently available for absorption. This study also provides useful information on the potential commercial value of SPL.     

The mechanism of interactions between tea polyphenols and porcine pancreatic alpha‐amylase: Analysis by inhibition kinetics,fluorescence quenching,differential scanning calorimetry and isothermal titration calorimetry

1 Scope

This study aims to use a combination of biochemical and biophysical methods to derive greater mechanistic understanding of the interactions between tea polyphenols and porcine pancreatic α‐amylase (PPA).

2 Methods and results

The interaction mechanism was studied through fluorescence quenching (FQ), differential scanning calorimetry (DSC) and isothermal titration calorimetry (ITC) and compared with inhibition kinetics. The results showed that a higher quenching effect of polyphenols corresponded to a stronger inhibitory activity against PPA. The red‐shift of maximum emission wavelength of PPA bound with some polyphenols indicated a potential structural unfolding of PPA. This was also suggested by the decreased thermostability of PPA with these polyphenols in DSC thermograms. Through thermodynamic binding analysis of ITC and inhibition kinetics, the equilibrium of competitive inhibition was shown to result from the binding of particularly galloylated polyphenols with specific sites on PPA. There were positive linear correlations between the reciprocal of competitive inhibition constant (1/K_ic), quenching constant (K_FQ) and binding constant (K_itc).

3 Conclusion

The combination of inhibition kinetics, FQ, DSC and ITC can reasonably characterize the interactions between tea polyphenols and PPA. The galloyl moiety is an important group in catechins and theaflavins in terms of binding with and inhibiting the activity of PPA.     

Interactions of tea polyphenols with intestinal microbiota and their implication for anti-obesity

Tea polyphenols (TP) are the main components in tea. Studies in vitro have shown they have significant biological activity; however, the results are inconsistent with experiments in vivo. For the low bioavailability, most TP are thought to remain in the gut and metabolized by intestinal bacteria. In the gut, the unabsorbed TP are metabolized to a variety of derivative products by intestinal flora, which may accumulate to exert beneficial effects. Numerous studies have shown that TP can inhibit obesity and its related metabolism disorders effectively. Meanwhile, it has demonstrated that TP and their derivatives may modulate intestinal micro-ecology. The understanding of the interaction between TP and intestinal microbiota will allow us to better evaluate the contribution of microbial metabolites of TP to anti-obesity activity. This review showed implications for the use of TP as functional food with potential therapeutic utility against obesity by modulating intestinal microbiota, contributing to the improvement of human health. © 2019 Society of Chemical Industry     

Esterification of Quercetin Increases Its Transport Across Human Caco‐2 Cells

Plant polyphenols showed useful biochemical characteristics in vitro; however, the assessments of their clinical applications in vivo are restricted by their limited bioavailability due to their strong resistance to 1st‐pass effects during absorption. In order to improve the bioavailability of quercetin (QU), the ester derivative of QU (3,3′,4′,5,7‐pentahydroxy flavones, TAQU) was synthesized, followed by examining the oil–water partition coefficient as well as the transport mechanisms of QU and its ester derivative (TAQU) using human Caco‐2 cells. The transport characteristics of QU and TAQU transport under different conditions (different concentrations, time, pH, temperature, tight junctions, and potential transporters) were systematically investigated. Results showed that QU had a lower permeability coefficient (2.82 × 10^?6 cm/s) for apical‐to‐basolateral (AP‐BL) transport over 5 to 50 μM, whereas the transport rate for AP to BL flux of TAQU (5.23 × 10^?6 cm/s) was significantly greater than that of QU. Paracellular pathways were not involved during the transport of both QU and TAQU. QU was poorly absorbed by active transport, whereas TAQU was mostly absorbed by passive diffusion. Efflux transporters, P‐glycoproteins, multidrug resistance proteins were proven to participate in the transport process of QU, but not in that of TAQU. These results suggested that improving the lipophicity of QU by esterification could increase the transport of QU across Caco‐2 cells.