Nanoemulsion delivery system of tea polyphenols enhanced the bioavailability of catechins in rats

Opportunities and challenges for the nanodelivery of green tea catechins in functional foods

Green tea, the least processed tea product, is scientifically known for its rich antioxidant content originating from polyphenols, especially catechins. The most potent green tea catechin is epigallocatechin-3-gallate (EGCG), which is responsible for a wide range of health benefits including anticancer, antidiabetics, and anti-inflammatory properties. However, green tea catechins (GTCs) are very labile under both environmental and gastrointestinal conditions; their chemical stability and bioavailability primarily depend on the processing and formulation conditions. Nanocarriers can protect GTCs against such conditions, and consequently, can be applicable for designing nanodelivery systems suitable for GTCs. In this review, the latest findings about both opportunities and limitations for the nanodelivery of GTCs and their incorporation into various functional food products are discussed. The scientific findings so far confirm that nanodelivery of GTCs can be an efficient approach towards the enhancement of their health-promoting effects with a minimal dose, controlled and targeted release, lessening the dose-related toxicity, and the efficient incorporation into functional foods. However, further investigation is yet needed to fully explain the cellular mechanisms of action of GTCs on human health and to elucidate the effect of encapsulation on their bioefficacy using well-designed, systematic, long-term, and large-scale clinical interventions. There also exists a substantial concern regarding the safety of the manufactured nanoparticles, their absorption, and the associated release mechanisms.

Potential Role of Natural Polyphenols against Protein Aggregation Toxicity: In Vitro, In Vivo, and Clinical Studies

One of the main features of neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease is the amyloidogenic behavior of disease-specific proteins including amyloid β, tau, α-synuclein, and mutant Huntingtin which participate in the formation, accumulation, and deposition of toxic misfolded aggregates. Consequently, these proteins not only associated with the progress of their respective neurodegenerative pathologies but also qualify as disease-specific biomarkers. The aim of using natural polyphenols is to target amyloid-dependent proteopathies by decreasing free radical damage and inhibiting and dissolving amyloid fibrils. We explore the effectiveness of the polyphenols epigallocatechin-3-gallate, oleuropein aglycone, and quercetin on their ability to inhibit aggregation of amyloid β, tau, and α-synuclein and mitigate other pathological features for Alzheimer's disease and Parkinson's disease. The analysis was carried from in vitro and cell line studies to animal models and clinical trials. This Review describes the use of phytochemical compounds as prophylactic agents for Alzheimer's disease, Parkinson's disease, and other proteopathies.

Role of the Encapsulation in Bioavailability of Phenolic Compounds

Plant-derived phenolic compounds have multiple positive health effects for humans attributed to their antioxidative, anti-inflammatory, and antitumor properties, etc. These effects strongly depend on their bioavailability in the organism. Bioaccessibility, and consequently bioavailability of phenolic compounds significantly depend on the structure and form in which they are introduced into the organism, e.g., through a complex food matrix or as purified isolates. Furthermore, phenolic compounds interact with other macromolecules (proteins, lipids, dietary fibers, polysaccharides) in food or during digestion, which significantly influences their bioaccessibility in the organism, but due to the complexity of the mechanisms through which phenolic compounds act in the organism this area has still not been examined sufficiently. Simulated gastrointestinal digestion is one of the commonly used in vitro test for the assessment of phenolic compounds bioaccessibility. Encapsulation is a method that can positively affect bioaccessibility and bioavailability as it ensures the coating of the active component and its targeted delivery to a specific part of the digestive tract and controlled release. This comprehensive review aims to present the role of encapsulation in bioavailability of phenolic compounds as well as recent advances in coating materials used in encapsulation processes. The review is based on 258 recent literature references.

Genome-wide analysis and metabolic profiling unveil the role of peroxidase CsGPX3 in theaflavin production in black tea processing

Plucked tea leaves can be processed into black tea (Camellia sinensis), which is rich in health-promoting molecules, including flavonoid antioxidants. During black tea processing, theaflavins (TFs) and thearubigins (TRs) are generated via the successive oxidation of catechins by endogenous polyphenol oxidase (PPO)- or peroxidase (POD)-mediated reactions. This process must be well controlled to achieve the proper TF/TR ratio, which is an important quality parameter of the tea beverage. However, little is known about the POD/PPO catalyzed TF formation process at the molecular genetic level. Here, we identified and characterized the POD genes responsible for TF production in tea. Genome-wide analysis of POD/PPO family genes, metabolite profiling, and expression analysis of PPO/POD genes in tea leaves enabled us to select several PPO/POD genes potentially involved in TF production. Differential gene expression in plant tissues and enzyme activity in several tea varieties traditionally used for processing of various beverage types indicate that black tea processing primarily depends on PPO/POD activity. Among these POD/PPO genes, the POD CsGPX3 is involved in the generation of TFs during black tea processing. The capacity of PPO/POD-catalysed TF production is potentially used for controlling catechin oxidation during black tea processing and could be used to create molecular markers for breeding of tea plant varieties suitable for the production of high-quality black tea beverages.

Comparison of In Vitro and In Vivo Antioxidant Activities of Six Flavonoids with Similar Structures

The in vitro and in vivo antioxidant activities of six flavonoids with similar structures, including epicatechin (EC), epigallocatechin (EGC), procyanidin B2 (P), quercetin (Q), taxifolin (T), and rutin (R) were compared. The structures of the six flavonoids and their scavenging activities for 2,2-diphenyl-1-picrylhydrazyl (DPPH•) and 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS⁺) radicals were closely related. The flavonoids decreased serum contents of malondialdehyde (MDA) and nitric oxide (NO), and increased serum total antioxidative capacity (T-AOC), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) levels to different degrees in d-galactose-treated mice. The changes in mRNA expression of liver GSH-Px1, CAT, SOD1, and SOD2 by d-galactose were dissimilarly restored by the six flavonoids. Moreover, the six flavonoids differentially prevented the inflammatory response caused by oxidative stress by inhibiting interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α levels, and restoring IL-10 levels. These six flavonoids from two subclasses revealed the following antioxidant capability: P > EC, EGC > EC, Q > T, Q > R. Our results indicate that (1) the pyrogallol, dimerization, and C2=C3 double bonds of flavonoids enhanced antioxidant activity and (2) the C3 glycosylation of flavonoids attenuated antioxidant capacity.

Nanotechnology improves delivery efficiency and bioavailability of tea polyphenols

Tea polyphenols (TPP) have shown various biological activities. However, due to their poor stability in the gastrointestinal (GI) tract, TPP exhibit low absorption and bioavailability which limit their applications in food fields. Recently, several studies have focused on the utilization of nanotechnology to solve these problems. In this review, we introduced the embedding materials and methods of TPP-loaded nanoparticles and the potential mechanisms for improving bioavailability, such as to protect TPP from pH stress, enzymes and ions of the GI tract, and increase of the permeability. Furthermore, future challenges and application prospects of nanoparticles as carriers for the delivery of TPP were also discussed. PRACTICAL APPLICATIONS: Nanotechnology is currently an emerging field in food science, which can be employed to increase the systemic delivery and bioavailability of phytochemicals. Due to the improved bioavailability, TPP-loaded nanoparticles can be developed as potential functional food. A better understanding of the nano-embedding technology and the potential mechanisms will allow us to better utilize nanomaterials to increase the bioavailability of TPP and expand their applications.

Potential Therapeutic Targets of Epigallocatechin Gallate (EGCG), the Most Abundant Catechin in Green Tea, and Its Role in the Therapy of Various Types of Cancer

Epigallocatechin-3-gallate (EGCG), an active compound of green tea and its role in diseases cure and prevention has been proven. Its role in diseases management can be attributed to its antioxidant and anti-inflammatory properties. The anti-cancer role of this green tea compound has been confirmed in various types of cancer and is still being under explored. EGCG has been proven to possess a chemopreventive effect through inhibition of carcinogenesis process such as initiation, promotion, and progression. In addition, this catechin has proven its role in cancer management through modulating various cell signaling pathways such as regulating proliferation, apoptosis, angiogenesis and killing of various types of cancer cells. The additive or synergistic effect of epigallocatechin with chemopreventive agents has been verified as it reduces the toxicities and enhances the anti-cancerous effects. Despite its effectiveness and safety, the implications of EGCG in cancer prevention is certainly still discussed due to a poor bioavailability. Several studies have shown the ability to overcome poor bioavailability through nanotechnology-based strategies such as encapsulation, liposome, micelles, nanoparticles and various other formulation. In this review, we encapsulate therapeutic implication of EGCG in cancer management and the mechanisms of action are discussed with an emphasis on human clinical trials.

Tea from the Food Science Perspective: An Overview

Tea (Camelia sinensis L.) is one of the main beverages known and consumed all around the world. Quality of tea is not only linked to the raw material but also to the processing steps that influence on the biochemical and sensory characteristics of each type of tea. This overview is focused on the differences in the production and composition of the main types of teas present in the market, highlighting not only their chemical and sensory characteristics, but also the importance of this plant from the food science viewpoint related to its several applications.

Formulation and Application of Nanoemulsions for Nutraceuticals and Phytochemicals

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Recent trends in research and investigation on nanoemulsion based products is the result of many reasons such as food security as a global concern, increasing demand for highly efficient food and agricultural products and technological need for products with the ability of manipulation and optimization in their properties. Nanoemulsions are defined as emulsions made up of nano sized droplets dispersed in another immiscible liquid which exhibit properties distinguishing them from conventional emulsions and making them suitable for encapsulation, delivery and formulations of bioactive ingredients in different fields including drugs, food and agriculture. The objective of this paper is to present a general overview of nanoemulsions definition, their preparation methods, properties and applications in food and agricultural sectors. Due to physicochemical properties of the nanoemulsion composition, creating nanosized droplets requires high/low energy methods that can be supplied by special devices or techniques. An overview about the mechanisms of these methods is also presented in this paper which are commonly used to prepare nanoemulsions. Finally, some recent works about the application of nanoemulsions in food and agricultural sectors along with challenges and legislations restricting their applications is discussed in the last sections of the current study.

Application of nano/microencapsulated phenolic compounds against cancer

Nowadays, polyphenols as bioactive compounds are being used in producing anti-cancer drugs. Low stability against harsh environmental conditions, untargeted release, low solubility, and low absorption of pure phenolic molecules are significant barriers, which decrease the functions of polyphenols. Recently, the nanoencapsulation processes have been applied to overcome these restrictions, in which the anti-cancer activity of polyphenols has been noticeably increased. This review will focus on the anti-cancer activity of polyphenols, and the effect of loading polyphenolics into various micro/nanoencapsulation systems on their anti-cancer activity. Different encapsulation systems such as lipid and polymer based nanoparticles, and solid form of encapsulated phenolic molecules by nano-spray dryer and electrospinnig have been used for loading of polyphenols. Incorporation of phenolic molecules into various carriers inevitably increases their anti-cancer activity. Because, in this way, encapsulated cargos can provide a targeted release, which will increase the bioavailability of phenolic molecules and their functions such as absorption into cancer cell.

Transcriptome and Metabolic Profiling Unveiled Roles of Peroxidases in Theaflavin Production in Black Tea Processing and Determination of Tea Processing Suitability

Theaflavins (TFs) are generated by endogenous polyphenol oxidase (PPO)- and peroxidase (POD)-catalyzed catechins oxidation during black tea processing, which needs to be well-controlled to obtain a proper TFs/thearubigins (TRs) ratio for better quality. Not all leaves from any tea plant cultivars or varieties are suitable for making high-quality black teas, regardless of the processing techniques. The mechanisms underlying TFs formation and the main factors determining the tea leaf processing suitability are not fully understood. We here integrated transcriptome and metabolite profiling of tea leaves to unveil how enzymes or metabolites in leaves are changed during black tea processing. The information enabled us to identify several PPO and POD genes potentially involved in tea processing for TF production. We characterized a POD gene, whose recombinant enzyme showed TF creation activity. The capacity for POD-catalyzed TF production could be used as a molecular marker for breeding tea plant varieties suitable for high-quality black tea production.

Development of catechin-phospholipid complex to enhance the bioavailability and modulatory potential against cadmium-induced oxidative stress in rats liver

The natural flavonoid (catechin) has been shown to possess a multitude of pharmacological activities. However, oral administrated catechin (CT) failed to fulfil its therapeutic potential due to poor absorption and low bioavailability. Thus, is a pressing need to develop a new approach from to increase its intestinal absorption and improved bioavailability. In this work, we intended the increase the bioavailability of CT by preparing catechin-phospholipid complex (CT-PH) and evaluate the protective effect of CT-PH complex against cadmium caused liver injuries in rats. Oral bioavailability of CT and CT-PH complex was evaluated in rats and the plasma CT was estimated by HPLC analysis. The greater absorption of CT-PH complex rats indicated that improved bioavailability. Liver function markers, lipid peroxidation, protein oxidation, antioxidant status and histopathological changes were determined in normal and treated rats. Moreover, biochemical analysis and histopathological examinations indicated that CT-PH provided better protection to rat liver than free CT.

Health Functions and Related Molecular Mechanisms of Tea Components: An Update Review

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.

Food-Grade Nanoemulsions: Preparation, Stability and Application in Encapsulation of Bioactive Compounds

Nanoemulsions have attracted significant attention in food fields and can increase the functionality of the bioactive compounds contained within them. In this paper, the preparation methods, including low-energy and high-energy methods, were first reviewed. Second, the physical and chemical destabilization mechanisms of nanoemulsions, such as gravitational separation (creaming or sedimentation), flocculation, coalescence, Ostwald ripening, lipid oxidation and so on, were reviewed. Then, the impact of different stabilizers, including emulsifiers, weighting agents, texture modifiers (thickening agents and gelling agents), ripening inhibitors, antioxidants and chelating agents, on the physicochemical stability of nanoemulsions were discussed. Finally, the applications of nanoemulsions for the delivery of functional ingredients, including bioactive lipids, essential oil, flavor compounds, vitamins, phenolic compounds and carotenoids, were summarized. This review can provide some reference for the selection of preparation methods and stabilizers that will improve performance in nanoemulsion-based products and expand their usage.

Enrichment of Eucalyptus oil nanoemulsion by micellar nanotechnology: transdermal analgesic activity using hot plate test in rats' assay

Eucalyptus globulus is an aromatic medicinal plant which known for its 1,8-cineole main pharmacological constituent exhibits as natural analgesic agent. Eucalyptus globulus-loaded micellar nanoparticle was developed via spontaneous emulsification technique and further evaluation for its analgesic efficacy study, in vivo analgesic activity assay in rats. The nanoemulsion system containing Eucalyptus-micelles was optimized at different surfactant types (Tween 40, 60 and 80) and concentrations (3.0, 6.0, 9.0, 12.0, 15.0, and 18.0 wt. %). These formulations were characterized by thermodynamically stability, viscosity, micelles particle size, pH, and morphology structure. The spontaneous emulsification technique offered a greener micelles formation in nanoemulsion system by slowly titrated of organic phase, containing Eucalyptus globulus (active compound), grape seed oil (carrier oil) and hydrophilic surfactant into aqueous phase, and continuously stirred for 30 min to form a homogeneity solution. The characterizations evaluation revealed an optimized formulation with Tween 40 surfactant type at 9.0 wt. % of surfactant concentration promoted the most thermodynamic stability, smaller micelles particle size (d = 17.13 ± 0.035 nm) formed with spherical shape morphological structure, and suitable in viscosity (≈2.3 cP) and pH value (6.57) for transdermal purpose. The in vivo analgesic activity assay of optimized emulsion showed that the transdermal administration of micellar nanoparticle of Eucalyptus globulus on fore and hind limb of rats, possessed the central and peripheral analgesic effects by prolonged the rats pain responses towards the heat stimulus after being put on top of hot plate (55 °C), with longest time responses, 40.75 s at 60 min after treatment administration. Thus, this study demonstrated that micellar nanoparticle of Eucalyptus globulus formed in nanoemulsion system could be promising as an efficient transdermal nanocarrier for the analgesic therapy alternative.

Essential oils and their bioactive compounds as green preservatives against fungal and mycotoxin contamination of food commodities with special reference to their nanoencapsulation

Fungal and mycotoxin contamination of stored food items is of utmost concern throughout the world due to their hazardous effects on mammalian systems. Most of the synthetic chemicals used as preservatives have often been realised to be toxic to humans and also cause adverse environmental effects. In this respect, use of different plant products especially essential oils (EOs) and their bioactive compounds has been recognized as a green strategy and safer alternatives to grey synthetic chemicals in view of their long traditional use. The current nanoencapsulation technology has strengthened the prospective of EOs and their bioactive compounds in food preservation by enhancing their bioactivity and mitigating other problems regarding their large-scale application. Although, the antimicrobial potential of EOs and their bioactive compounds has been reviewed time to time by different food microbiologists, but very less is known about their mode of action. Based on these backgrounds, the present article provides an account on the antifungal and antimycotoxigenic mode of action of EOs as well as their bioactive compounds. In addition, the article also deals with the application of currently used nanoencapsulation approach to improve the stability and efficacy of EOs and their bioactive compounds against mycotoxigenic fungi causing deterioration of stored food items so as to recommend their large-scale application for safe preservation and enhancement of shelf life of food items during storage.

Tomato lectin-modified nanoemulsion-encapsulated MAGE1-HSP70/SEA complex protein vaccine: Targeting intestinal M cells following peroral administration

Vaccines administered orally enable the stimulation of both the mucous membrane and system immune responses. However, tumor vaccines, whose effective elements are antigen protein molecules or gene-encoding antigens, are hardly accustomed to the harsh gastrointestinal environment. Here, we explored an oral nanoecapsulated tumor vaccine complex to evaluate the anti-tumor effect. Tomato lectin (TL) was modified on the surface of a nanoemulsion (NE) composed of MAGE1-HSP70/SEA (MHS). C57BL/6 mice were immunized with NE (-), NE (MHS) and TL-NE (MHS) via po. or sc. administration. Additionally, the cellular immunocompetence was detected by the enzyme-linked immunospot assay and lactate dehydrogenase release assay. Serum antibody titers were analyzed using the enzyme-linked immuno sorbent assay. Next, the therapeutic and tumor challenge assays were performed. The TL-NE (MHS) particles were 20 ± 5 nm in diameter and could resist pepsin and trypsin digestion. The cellular immune responses elicited by TL-NE (MHS) perioral were stronger than those by TL-NE (MHS)-sc. (p < 0.05) when targeted to B16-MAGE1 tumor cells. The levels of MAGE-1 antibody induced by TL-NE (MHS) via the oral route was higher than control group (p < 0.05). The percentage of CD4+ and CD8+ T cells in TL-NE (MHS)-po. group was more than other groups (p < 0.05). Furthermore, oral TL-NE (M)HScould delay tumor growth and defer tumor occurrence and tumor recurrence after resection in mice challenged with B16-MAGE-1 tumor cells. The study suggested that the oral TL-NE (MHS) vaccine delivery system is feasible to improve the vaccine protection effect and may have broad application in cancer therapy.

Nanoemulsions in CNS drug delivery: recent developments, impacts and challenges

Despite enormous efforts, treatment of CNS diseases remains challenging. One of the main issues causing this situation is limited CNS access for the majority of drugs used as part of the therapeutic regimens against life-threatening CNS diseases. Regarding the inarguable position of the nanocarrier systems in neuropharmacokinetic enhancement of the CNS drugs, this review discusses the latest findings on nanoemulsions (NEs) as one of the most promising candidates of this type, to overcome the challenges of CNS drug delivery. Future development of NE-based CNS drug delivery needs to consider so many aspects not only from a physicochemical point of view but also related to the biointerface of these very small droplets before achieving clinical value.

DOX-assisted functionalization of green tea polyphenol nanoparticles for effective chemo-photothermal cancer therapy

Green tea polyphenol nanoparticles with chemotherapeutic and photothermal performance exhibited effective anti-tumor effects in vivo with intravenous injection.

Ultrasonic-Assisted Fabrication of Concentrated Triglyceride Nanoemulsions and Nanogels

In many food products such as gels, pastes, jellies, creams, sausages, and selected dressings or spreads, it is desirable to formulate concentrated triglyceride nanoemulsions so as to deliver lipophilic functional agents. In this study, the ability of ultrasonication to form nanoemulsions and nanogels containing high concentration of sunflower oil was investigated in the presence of sodium dodecyl sulfate (SDS) as a surfactant. The influence of SDS and oil concentration and duration of sonication on the physical stability, mean droplet diameter, and rheological properties of emulsions were determined. Ultrasonication for up to 9 min was highly effective on fabrication of stable nanoemulsions (an average droplet size of 158-171 nm) at low oil/surfactant ratio (10:0.7). The viscosity and storage modulus increased with decreasing the droplet size particularly at higher oil concentrations. The viscous nanoemulsions (containing 60, 50, and 40 wt % oil) transformed into viscoelastic gels when sonicated for 3, 9, and 30 min, respectively. On the basis of the findings of the present study, such textural and rheological modifications, resulted from droplet size decreasing, could be potentially useful in designing reduced fat gel-like products.

Improved absorption of β-carotene by encapsulation in an oil-in-water nanoemulsion containing tea polyphenols in the aqueous phase

β-Carotene (BC) serves as an important source of provitamin A and natural edible pigment, but the application is limited because of its instability and low oral-bioavailability. A tea polyphenols-β-carotene (TP-BC) oil-in-water (O/W) nanoemulsion was prepared with the core oil phase containing BC and the water phase containing TP. During storage at three different temperatures (4, 25 and 35 °C), the TP-BC nanoemulsion had a better stability and higher retention rate of BC than BC nanoemulsion. An in vitro simulated digestion assay indicated that the BC recovery rates of TP-BC nanoemulsion at digestion phases I and II were significantly increased compared to the BC nanoemulsion. An in vivo absorption study showed that TP-BC nanoemulsion had higher conversion efficiency on vitamin A compared to the BC nanoemulsion. These results suggested that tea polyphenols are effective ingredients for improving the oral-bioavailability of BC.

Effect of ultrasound treatment on the properties of nano-emulsion films obtained from hazelnut meal protein and clove essential oil

Hazelnut meal protein (4% (w/v)) and clove essential oil (CEO) (3% (v/v)) were homogenized with ultrasound (US) at different times (2, 4 and 6 min) and amplitudes (50, 75 and 100%) to obtain nano-emulsion films. Film forming nano-emulsions (FFNs) were analyzed for average particle size (D_z) and zeta potential, and edible film characterization were evaluated depending on US treatment, as well as antibacterial and antioxidant activities. D_z values and zeta potential of FFNs decreased with increasing acoustic energy delivered to nano-emulsion system. Thickness and water solubility of films significantly decreased with increasing US treatment. Films became more transparent depending on US treatment probably due to particle size reduction. Tensile strength (TS) of films significantly increased with US treatment, while elongation at break (EAB) slightly increased. Microstructure of films became more homogeneous after US treatment and caused to lower water vapor permeability. Enrichment with CEO has given the films antibacterial activity against L. monocytogenes, B. subtilis, S. aureus, P. aeruginosa and E. coli, and antioxidant activity, and US application has improved these activities. US technology can be used to improve mechanical, barrier and antimicrobial properties of hazelnut meal protein based edible films enriched with CEO.