Techniques for Extraction of Green Tea Polyphenols: A Review

Comprehensive polyphenolic profiling, antioxidant, antimicrobial, and cytotoxicity studies of Rhynchostylis retusa (L.) Blume: a medicinal orchid

Rhynchostylis retusa (L.) Blume, commonly known as the Foxtail orchid, has garnered worldwide attention for its diverse medicinal properties. In this study, root extract and its fractions were evaluated for total polyphenols, flavonoids, targeted polyphenols, and antioxidant potential. The antimicrobial activity was assessed against Gram-positive and Gram-negative bacterial strains while cytotoxicity was assessed using the A549 and HCT-116 cell lines. The investigations showed that chloroform and ethyl acetate are the most effective solvents for fractionation of polyphenols from the parent extract. These fractions also exhibited strong antioxidant and cytotoxic potentials. The chloroform fraction showed maximum cell death of 87.35 and 92.36% in A549 and HCT- 116 cell lines respectively. All samples showed growth inhibition against bacterial strains except the n-hexane fraction, whereas the n-butanol fraction showed comparable antimicrobial activity with the tetracycline standard. The possible health benefits and thereby, application of R. retusa were thus revealed in this investigation.

Dietary Polyphenols: Review on Chemistry/Sources, Bioavailability/Metabolism, Antioxidant Effects, and Their Role in Disease Management

Polyphenols, as secondary metabolites ubiquitous in plant sources, have emerged as pivotal bioactive compounds with far-reaching implications for human health. Plant polyphenols exhibit direct or indirect associations with biomolecules capable of modulating diverse physiological pathways. Due to their inherent abundance and structural diversity, polyphenols have garnered substantial attention from both the scientific and clinical communities. The review begins by providing an in-depth analysis of the chemical intricacies of polyphenols, shedding light on their structural diversity and the implications of such diversity on their biological activities. Subsequently, an exploration of the dietary origins of polyphenols elucidates the natural plant-based sources that contribute to their global availability. The discussion extends to the bioavailability and metabolism of polyphenols within the human body, unraveling the complex journey from ingestion to systemic effects. A central focus of the review is dedicated to unravelling the antioxidant effects of polyphenols, highlighting their role in combating oxidative stress and associated health conditions. The comprehensive analysis encompasses their impact on diverse health concerns such as hypertension, allergies, aging, and chronic diseases like heart stroke and diabetes. Insights into the global beneficial effects of polyphenols further underscore their potential as preventive and therapeutic agents. This review article critically examines the multifaceted aspects of dietary polyphenols, encompassing their chemistry, dietary origins, bioavailability/metabolism dynamics, and profound antioxidant effects. The synthesis of information presented herein aims to provide a valuable resource for researchers, clinicians, and health enthusiasts, fostering a deeper understanding of the intricate relationship between polyphenols and human health.

Exploring the potential of biologically active phenolic acids from marine natural products as anticancer agents targeting the epidermal growth factor receptor

The epidermal growth factor receptor (EGFR) dimerizes upon ligand bindings to the extracellular domain that initiates the downstream signaling cascades and activates intracellular kinase domain. Thus, activation of autophosphorylation through kinase domain results in metastasis, cell proliferation, and angiogenesis. The main objective of this research is to discover more promising anti-cancer lead compound against EGRF from the phenolic acids of marine natural products using in-silico approaches. Phenolic compounds reported from marine sources are reviewed from previous literatures. Furthermore, molecular docking was carried out using the online tool CB-Dock. The molecules with good docking and binding energies scores were subjected to ADME, toxicity and drug-likeness analysis. Subsequently, molecules from the docking experiments were also evaluated using the acute toxicity and MD simulation studies. Fourteen phenolic compounds from the reported literatures were reviewed based on the findings, isolation, characterized and applications. Molecular docking studies proved that the phenolic acids have good binding fitting by forming hydrogen bonds with amino acid residues at the binding site of EGFR. Chlorogenic acid, Chicoric acid and Rosmarinic acid showed the best binding energies score and forming hydrogen bonds with amino acid residues compare to the reference drug Erlotinib. Among these compounds, Rosmarinic acid showed the good pharmacokinetics profiles as well as acute toxicity profile. The MD simulation study further revealed that the lead complex is stable and could be future drug to treat the cancer disease. Furthermore, in a wet lab environment, both in-vitro and in-vivo testing will be employed to validate the existing computational results.Communicated by Ramaswamy H. Sarma.

Dissecting the role of microorganisms in tea production of different fermentation levels: a multifaceted review of their action mechanisms, quality attributes and future perspectives

Tea is one of the most popular beverages worldwide, with several health benefits attributed for its rich chemical composition and further associated with fermentation process to improve its quality attributes. Most tea types originate from the leaves of Camellia sinensis with differences in fermentation levels yielding black tea, green tea, pouchong tea, oolong tea. Teas like pu-erh or kombucha to encompass both green and red types are further post-fermented. Tea fermentation is a traditional process involving physical, biochemical, and microbial changes which are associated with improved organoleptic characters, nutritive value, and health outcomes. The production of fermented tea relies on naturally occurring enzymes and microbial metabolic activities. This review focuses on presenting a holistic overview on the effect of different microorganisms including bacteria, yeast, and fungi on the biochemical changes and sensory attributes of fermented tea products reported in research articles along the last 15 years. Moreover, production conditions and major biochemical changes are dissected to present the best factors influencing fermented tea quality. This review presents an evidence-based reference for specialists in tea industry to optimize tea fermentation process for targeted attributes.

Antibacterial Activity of the Green Synthesized Plasmonic Silver Nanoparticles with Crystalline Structure against Gram-Positive and Gram-Negative Bacteria

Nanoparticles (NPs) have attracted considerable interest in numerous fields, including agriculture, medicine, the environment, and engineering. The use of green synthesis techniques that employ natural reducing agents to reduce metal ions and form NPs is of particular interest. This study investigates the use of green tea (GT) extract as a reducing agent for the synthesis of silver NPs (Ag NPs) with crystalline structure. Several analytical techniques, including UV-visible spectrophotometry, Fourier transform infrared (FTIR) spectroscopy, high-resolution transmission electron microscopy (HR-TEM), and X-ray diffraction (XRD), were used to characterize the synthesized Ag NPs. The results of UV-vis revealed that the biosynthesized Ag NPs exhibited an absorbance plasmonic resonance peak at 470 nm. According to FTIR analyses, the attachment of Ag NPs to polyphenolic compounds resulted in a decrease in intensity and band shifting. In addition, the XRD analysis confirmed the presence of sharp crystalline peaks associated with face-centered cubic Ag NPs. Moreover, HR-TEM revealed that the synthesized particles were spherical and 50 nm in size on average. The Ag NPs demonstrated promising antimicrobial activity against Gram-positive (GP) bacteria, Brevibacterium luteolum and Staphylococcus aureus, and Gram-negative (GN) bacteria, Pseudomonas aeruginosa and Escherichia coli, with a minimal inhibitory concentration (MIC) of 6.4 mg/mL for GN and 12.8 mg/mL for GP. Overall, these findings suggest that Ag NPs can be utilized as effective antimicrobial agents.

Ultrasonic-assisted enzymatic improvement of polyphenol content, antioxidant potential, and in vitro inhibitory effect on digestive enzymes of Miang extracts

The aims of this research were to optimize the ultrasonic-assisted enzymatic extraction of polyphenols under Miang and tannase treatment conditions for the improvement of antioxidant activity of Miang extracts via response surface methodology. Miang extracts treated with and without tannase were investigated for their inhibitory effects on digestive enzymes. The optimal conditions for ultrasonic-assisted enzymatic extraction of the highest total polyphenol (TP) (136.91 mg GAE/g dw) and total flavonoid (TF) (5.38 mg QE/g dw) contents were as follows: 1 U/g cellulase, 1 U/g xylanase, 1 U/g pectinase, temperature (74 °C), and time (45 min). The antioxidant activity of this extract was enhanced by the addition of tannase obtained from Sporidiobolus ruineniae A45.2 undergoing ultrasonic treatment and under optimal conditions (360 mU/g dw, 51 °C for 25 min). The ultrasonic-assisted enzymatic extraction selectively promoted the extraction of gallated catechins from Miang. Tannase treatment improved the ABTS and DPPH radical scavenging activities of untreated Miang extracts by 1.3 times. The treated Miang extracts possessed higher IC₅₀ values for porcine pancreatic α-amylase inhibitory activity than those that were untreated. However, it expressed approximately 3 times lower IC₅₀ values for porcine pancreatic lipase (PPL) inhibitory activity indicating a marked improvement in inhibitory activity. The molecular docking results support the contention that epigallocatechin, epicatechin, and catechin obtained via the biotransformation of the Miang extracts played a crucial role in the inhibitory activity of PPL. Overall, the tannase treated Miang extract could serve as a functional food and beneficial ingredient in medicinal products developed for obesity prevention.

Bidirectional Effects of Mao Jian Green Tea and Its Flavonoid Glycosides on Gastrointestinal Motility

Mao Jian Tea (MJT) has been generally consumed as a digestive aid for more than a hundred years in the Shanxi province of China. However, determination of its efficacy still remains elusive. This study investigated the effect of Mao Jian Green Tea (MJGT) on gastrointestinal motility. The biphasic effects of the hydro extracts of MJGT on gastric emptying and small intestinal propulsion of rats were identified in vivo; namely, the low (MJGT_L) and medium (MJGT_M) concentrations promoted gastrointestinal motility (p < 0.05), whereas the high concentration (MJGT_H) showed the opposite effect (p < 0.01). The expression levels of the gastric hormones, GAS, MTL and VIP (p < 0.05) were consistent with the gastrointestinal motility variation, with the exception of MTL in MJGT_H group (p > 0.01). Two flavonoids, eriodictyol (0.152 mg/mL) and luteolin (0.034 mg/mL), and the corresponding glycosides eriodictyol-7-O-glucoside (0.637 mg/mL) and luteolin-7-O-glucoside (0.216 mg/mL), dominated the hydro extracts identified by HPLC and UPLC-ESI-MS. These compounds can regulate the muscle strip contractions isolated from the gastrointestinal tissues. Additionally, the different concentrations also influenced the gut microbiota accordingly characterized by 16S rDNA gene sequencing. The MJGT_L boosted several probiotic bacteria, such as Muribaculaceae (1.77-fold), Prevotellaceae (1.85-fold) and Lactobacillaceae (2.47-fold), and suppressed the pathogenic species such as Staphylococcaceae (0.03-fold) that, conversely, was enriched in the MJGT_H group (1.92-fold). Therefore, the biphasic effect indicated that the dosage of the herbal tea should not be overlooked.

Variation in the Optical Properties of PEO-Based Composites via a Green Metal Complex: Macroscopic Measurements to Explain Microscopic Quantum Transport from the Valence Band to the Conduction Band

In this study, a green chemistry method was used to synthesize polymer composites based on polyethylene oxide (PEO). The method of the remediation of metal complexes used in this study is an environmentally friendly procedure with a low cost. Zinc metal ion (Zn²⁺)-polyphenol (PPHNL) complexes were synthesized for two minutes via the combination of a black tea leaf (BTL) extract solution with dissolved Zn-acetate. Then, UV-Vis and FTIR were carried out for the Zn-PPHNL complexes in a liquid and solid. The FTIR spectra show that BTLs contain sufficient functional groups (O-H, C-H, C=O, C=C, C-O, C-N, and N-H), PPHNL, and conjugated double bonds to produce metal complexes by capturing the cations of Zn-acetate salt. Moreover, FTIR of the BTL and Zn-PPHNL complexes approves the formation of the Zn-PPHNL complex over the wide variation in the intensity of bands. The UV absorption spectra of BTL and Zn-PPHNL indicate complex formation among tea PPHNL and Zn cations, which enhances the absorption spectra of the Zn-PPHNL to 0.1 compared to the figure of 0.01 associated with the extracted tea solution. According to an XRD analysis, an amorphous Zn-PPHNL complex was created when Zn²⁺ ions and PPHNL interacted. Additionally, XRD shows that the structure of the PEO composite becomes a more amorphous structure as the concentration of Zn-PPHNL increases. Furthermore, morphological study via an optical microscope (OM) shows that by increasing the concentration of Zn-PPHNL in a PEO polymer composite the size of the spherulites ascribed to the crystalline phase dramatically decreases. The optical properties of PEO: Zn-PPHNL films, via UV-Vis spectroscopy, were rigorously studied. The E_g is calculated by examining the dielectric loss, which is reduced from 5.5 eV to 0.6 eV by increasing the concentration of Zn-PPHNL in the PEO samples. In addition, Tauc's form was used to specify the category of electronic transitions in the PEO: Zn-PPHNL films. The impact of crystalline structure and morphology on electronic transition types was discussed. Macroscopic measurable parameters, such as the refractive index and extinction coefficient, were used to determine optical dielectric loss. Fundamental optical dielectric functions were used to determine some key parameters. From the viewpoint of quantum transport, electron transitions were discussed. The merit of this work is that microscopic processes related to electron transition from the VB to the CB can be interpreted interms of measurable macroscopic quantities.

Extraction techniques in food industry: Insights into process parameters and their optimization

This review presents critical evaluation of the key parameters that affect the extraction of targeted components, giving due consideration to safety and environmental aspects. The crucial aspects of the extraction technologies along with protocols and process parameters for designing unit operations have been emphasized. The parameters like solvent usage, substrate type, concentration, particle size, temperature, quality and storage of extract as well as stability of extraction have been elaborately discussed. The process optimization using mathematical and computational modeling highlighting information and communication technologies have been given importance aiming for a green and sustainable industry level scaleup. The findings indicate that the extraction processes vary significantly depending on the category of food and its structure. There is no single extraction method or universal set of process conditions identified for extracting all value-added products from respective sources. A comprehensive understanding of process parameters and their optimization as well as synergistic combination of multiple extraction processes can aid in enhancement of the overall extraction efficiency. Future efforts must be directed toward the design of integrated unit operations that cause minimal harm to the environment along with investigations on economic feasibility to ensure sustainable extraction systems.

Chemico-biological aspects of (-)-epigallocatechin-3-gallate (EGCG) to improve its stability, bioavailability and membrane permeability: Current status and future prospects

Natural products have been a bedrock for drug discovery for decades. (-)-Epigallocatechin-3-gallate (EGCG) is one of the widely studied natural polyphenolic compounds derived from green tea. It is the key component believed to be responsible for the medicinal value of green tea. Significant studies implemented in in vitro, in cellulo, and in vivo models have suggested its anti-oxidant, anti-cancer, anti-diabetic, anti-inflammatory, anti-microbial, neuroprotective activities etc. Despite having such a wide array of therapeutic potential and promising results in preclinical studies, its applicability to humans has encountered with rather limited success largely due to the poor bioavailability, poor membrane permeability, rapid metabolic clearance and lack of stability of EGCG. Therefore, novel techniques are warranted to address those limitations so that EGCG or its modified analogs can be used in the clinical setup. This review comprehensively covers different strategies such as structural modifications, nano-carriers as efficient drug delivery systems, synergistic studies with other bioactivities to improve the chemico-biological aspects (e.g., stability, bioavailability, permeability, etc.) of EGCG for its enhanced pharmacokinetics and pharmacological properties, eventually enhancing its therapeutic potentials. We think this review article will serve as a strong platform with comprehensive literature on the development of novel techniques to improve the bioavailability of EGCG so that it can be translated to the clinical applications.

Dietary Polyphenols: Extraction, Identification, Bioavailability, and Role for Prevention and Treatment of Colorectal and Prostate Cancers

Fruits, vegetables, and other edible plants in our diet have numerous health benefits, due to the bioactive compounds in these food items, including polyphenols. These plants are a rich and promising source of natural products and phytochemicals that can be used to treat and prevent numerous diseases and prevent the progression of cancer. Dietary polyphenols exhibit chemo-preventive and therapeutic effects against various ailments, including several types of cancer. The current study focuses on polyphenol’s traditional and advanced extraction methods, with supercritical extraction as a novel approach. It also deals with their identification, bioavailability, and role in preventing and treating colorectal and prostate cancers. Additionally, the article covers the literature that deals with the anticancer activities of polyphenols, as well as their potential use as anticancer agents.

Effect of Catechins on Upper Respiratory Tract Infections in Winter: A Randomized, Placebo-Controlled, Double-Blinded Trial

Tea catechins are plant-derived compounds that improve immune functions. Previous randomized control trials have demonstrated the efficacy of primarily epi-type catechins against upper respiratory tract infections (URTIs). Green tea can be consumed in several ways, including popular bottled beverages. These beverages, however, require sterilization during manufacturing, which results in catechin isomerization. We conducted a randomized, double-blinded, placebo-controlled trial involving healthy Japanese participants to evaluate whether catechin consumption via bottled beverages has an alleviating effect on the duration and severity of URTIs in winter. The catechin group (490 mg catechin, 0.14%, containing 59% epi-type catechin, n = 55) showed reduced durations of running nose, nasal congestion, and headache, compared with the placebo group (0 mg catechin, n = 54; p = 0.013, 0.018, and <0.001, respectively). Furthermore, when considering physical symptoms, the duration of nasopharyngeal symptoms improved significantly in the catechin group (p < 0.001) compared with that in the control group. The daily consumption of catechin thus reduced the duration and severity of URTIs in healthy men and women. Humans are regularly exposed to several potential infectious threats, and the oral administration of heat-epimerized tea catechins might help prevent and reduce the severity of URTIs.

Omics Analyses of Intestinal Microbiota and Hypothalamus Clock Genes in Circadian Disturbance Model Mice Fed with Green Tea Polyphenols

Green tea polyphenols (GTP) have similar activities as prebiotics, which effectively regulate the structure of intestinal flora and affect their metabolic pathways. The intestinal flora is closely related to the host's circadian rhythm, and the supplementation with GTP may be an effective way to improve circadian rhythm disorders. In this study, we established a mouse model of circadian rhythm disturbance of anthropogenic flora to investigate the regulation mechanism of GTP on the host circadian rhythms. After 4 weeks of GTP administration, the results showed that GTP significantly alleviated the structural disorder of intestinal microbiota, thus effectively regulating related metabolites associated with brain nerves and circadian rhythms. Moreover, single-cell transcription of the mouse hypothalamus suggested that GTP up-regulated the number of astrocytes and oligodendrocytes and adjusted the expression of core clock genes Csnk1d, Clock, Per3, Cry2, and BhIhe41 caused by circadian disruption. Therefore, this study provided evidence that GTP can improve the physiological health of hosts with the circadian disorder by positively affecting intestinal flora and related metabolites and regulating circadian gene expression.

Influence of the extraction method on the recovery of bioactive phenolic compounds from food industry by-products

Agro-foodindustries generate colossal amounts of non-edible waste and by-products, easily accessible as raw materials for up-cycling active phytochemicals. Phenolic compounds are particularly relevant in this field given their abundance in plant residues and the market interest of their functionalities (e.g. natural antioxidant activity) as part of nutraceutical, cosmetological and biomedical formulations. In "bench-to-bedside" achievements, sample extraction is essential because valorization benefits from matrix desorption and solubilization of targeted phytocompounds. Specifically, the composition and polarity of the extractant, the optimal sample particle size and sample:solvent ratio, as well as pH, pressure and temperature are strategic for the release and stability of mobilized species. On the other hand, current green chemistry environmental rules require extraction approaches that eliminate polluting consumables and reduce energy needs. Thus, the following pages provide an update on advanced technologies for the sustainable and efficient recovery of phenolics from plant matrices.

Development and Validation of Near-Infrared Methods for the Quantitation of Caffeine, Epigallocatechin-3-gallate, and Moisture in Green Tea Production

The quality of tea leaves (e.g., their color, appearance, and taste) can be directly influenced by the tea production process, which is closely connected with the content of a number of chemical components formed during the production of the tea leaves. However, the production process is now controlled by people's experience, making its quality significantly different. NIRS is a time-saving, cost-saving, and nondestructive method. Therefore, it is necessary to introduce NIRS technology into the quality control of the tea production process. In this study, a quantitative analysis model of caffeine, epigallocatechin-3-gallate (EGCG), and moisture content was established by near-infrared spectroscopy (NIRS) which was united simultaneously with partial least squares (PLSR) for online process monitoring of tea production. The model parameters show that the established model has fine robustness and outstanding measuring accuracy. Then, the feasibility of the established method is verified by the traditional method. Through the verification of the precision of the instrument and the stability of the sample, it is clarified that the model can be further utilized to monitor tea product quality online in a productive process.

Kombucha Tea-A Double Power of Bioactive Compounds from Tea and Symbiotic Culture of Bacteria and Yeasts (SCOBY)

Kombucha is a low alcoholic beverage with high content of bioactive compounds derived from plant material (tea, juices, herb extracts) and metabolic activity of microorganisms (acetic acid bacteria, lactic acid bacteria and yeasts). Currently, it attracts an increasing number of consumers due to its health-promoting properties. This review focuses on aspects significantly affecting the bioactive compound content and biological activities of Kombucha tea. The literature review shows that the drink is characterized by a high content of bioactive compounds, strong antioxidant, and antimicrobial properties. Factors that substantially affect these activities are the tea type and its brewing parameters, the composition of the SCOBY, as well as the fermentation parameters. On the other hand, Kombucha fermentation is characterized by many unknowns, which result, inter alia, from different methods of tea extraction, diverse, often undefined compositions of microorganisms used in the fermentation, as well as the lack of clearly defined effects of microorganisms on bioactive compounds contained in tea, and therefore the health-promoting properties of the final product. The article indicates the shortcomings in the current research in the field of Kombucha, as well as future perspectives on improving the health-promoting activities of this fermented drink.

Green Strategy–Based Synthesis of Silver Nanoparticles for Antibacterial Applications

Antibiotics have been the nucleus of chemotherapy since their discovery and introduction into the healthcare system in the 1940s. They are routinely used to treat bacterial infections and to prevent infections in patients with compromised immune systems and enhancing growth in livestock. However, resistance to last-resort antibiotics used in the treatment of multidrug-resistant infections has been reported worldwide. Therefore, this study aimed to evaluate green synthesized nanomaterials such as silver nanoparticles (AgNPs) as alternatives to antibiotics. UV-vis spectroscopy surface plasmon resonance peaks for AgNPs were obtained between 417 and 475 nm. An X-ray diffraction analysis generated four peaks for both Prunus africana extract (PAE) and Camellia sinensis extract (CSE) biosynthesized AgNPs positioned at 2θ angles of 38.2°, 44.4°, 64.5°, and 77.4° corresponding to crystal planes (111), (200), (220), and (311), respectively. A dynamic light-scattering analysis registered the mean zeta potential of +6.3 mV and +0.9 mV for PAE and CSE biosynthesized nanoparticles, respectively. Fourier transform infrared spectroscopy spectra exhibited bands corresponding to different organic functional groups confirming the capping of AgNPs by PAE and CSE phytochemicals. Field emission scanning electron microscopy imaging showed that AgNPs were spherical with average size distribution ranging from 10 to 19 nm. Biosynthesized AgNPs exhibited maximum growth inhibitory zones of 21 mm with minimum inhibitory concentration and minimum bactericidal concentration of 125 and 250 μg/ml, respectively, against carbapenem-resistant bacteria.

Recent advances in extraction technologies for recovery of bioactive compounds derived from fruit and vegetable waste peels: A review

Fruits and vegetables are the most important commodities of trade value among horticultural produce. They are utilized as raw or processed, owing to the presence of health-promoting components. Significant quantities of waste are produced during fruits and vegetables processing that are majorly accounted by waste peels (∼90-92%). These wastes, however, are usually exceptionally abundant in bioactive molecules. Retrieving these valuable compounds is a core objective for the valorization of waste peel, besides making them a prevailing source of beneficial additives in food and pharmaceutical industry. The current review is focused on extraction of bioactive compounds derived from fruit and vegetable waste peels and highlights the supreme attractive conventional and non-conventional extraction techniques, such as microwave-assisted, ultrasound assisted, pulsed electric fields, pulsed ohmic heating, pressurized liquid extraction, supercritical fluid extraction, pressurized hot water, high hydrostatic pressure, dielectric barrier discharge plasma extraction, enzyme-assisted extraction and the application of "green" solvents say as well as their synergistic effects that have been applied to recover bioactive from waste peels. Superior yields achieved with non-conventional technologies were identified to be of chief interest, considering direct positive economic consequences. This review also emphasizes leveraging efficient, modern extraction technologies for valorizing abundantly available low-cost waste peel, to achieve economical substitutes, whilst safeguarding the environment and building a circular economy. It is supposed that the findings discussed though this review might be a valuable tool for fruit and vegetable processing industry to imply an economical and effectual sustainable extraction methods, converting waste peel by-product to a high added value functional product.

Fruit by-products: the potential natural sources of antioxidants and α-glucosidase inhibitors

The present effort was to obtain extracts from various fruit by-products using three extraction systems and to evaluate their polyphenolic content, antioxidant, and α-glucosidase inhibition activity. The fruit by-products were pre-processed by washing, drying, and milling methods to produce the powder. The powder samples were used to obtain extracts using pressurized hot-water (PHWE), enzyme-assisted (EnE) and organic solvent extraction (OSE) systems. The total phenolic content (TPC), total flavonoid content (TFC), antioxidant and α-glucosidase inhibition activity in all samples were assessed by Folin-Ciocalteu, AlCl₃ colorimetric, DPPH^· & ABST^·+ and α-glucosidase inhibitory methods. The results showed that the extracts of peel, seed and other by-products exhibited outstanding TPC, TFC, and strongest antioxidant and α-glucosidase inhibition activity, eventually higher than edible parts of the fruits. For instance, the highest TPC among the peels of various fruits were in mango peel (in all cultivar) followed by litchi peel, banana peel cv. sagor, jackfruit peel, pineapple peel, papaya peel, banana peel cv. malbhog and desi on average in all tested extraction systems. PHWE system yielded significantly (p < 0.05) higher TPC and TFC than other extraction systems. In case of misribhog mango variety, the TPC (mg GAE/g DM) in peels were 180.12 ± 7.33, 73.52 ± 2.91 and 36.10 ± 3.48, and in seeds were 222.62 ± 12.11, 76.18 ± 2.63 and 42.83 ± 12.52 for PHWE, EnE and OSE respectively. This work reported the promising potential of underutilized fruit by-products as new sources to manufacture ingredients and nutraceuticals for foods and pharmaceutical products.

Castanea sativa shells: A review on phytochemical composition, bioactivity and waste management approaches for industrial valorization

Castanea sativa is an outstanding species that represents a valuable natural resource for rural populations. C. sativa shells (CSS), an abundant agro-industrial by-product generated during chestnut peeling process, is commonly discarded or used as fuel. Nevertheless, CSS produced are not depleted by this application and huge amounts are still available, being particularly rich in bioactive compounds (polyphenols, vitamin E, lignin and oligosaccharides) with health benefits. Phytochemical studies reported not only antioxidant and antimicrobial activities, but also anti-inflammatory, anticancer, hypolipidemic, hypoglycemic and neuroprotective activities. The application of a suitable extraction technique is required for the isolation of bioactive compounds, being green extraction technologies outstanding for the industrial recovery of chestnut shells' bioactive compounds. CSS were highlighted as remarkable sources of functional ingredients with promising applications in food and nutraceutical fields, mainly as natural antioxidants and effective prebiotics. This review aims to summarize the phytochemical composition and pro-healthy properties of CSS, emphasizing the sustainable extraction techniques employed in the recovery of bioactive compounds and their potential applications in food and nutraceutical industries.

Techniques and modeling of polyphenol extraction from food: a review

There is a growing demand for vegetal food having health benefits such as improving the immune system. This is due in particular to the presence of polyphenols present in small amounts in many fruits, vegetables and functional foods. Extracting polyphenols is challenging because extraction techniques should not alter food quality. Here, we review technologies for extracting polyphenolic compounds from foods. Conventional techniques include percolation, decoction, heat reflux extraction, Soxhlet extraction and maceration, whereas advanced techniques are ultrasound-assisted extraction, microwave-assisted extraction, supercritical fluid extraction, high-voltage electric discharge, pulse electric field extraction and enzyme-assisted extraction. Advanced techniques are 32-36% more efficient with approximately 15 times less energy consumption and producing higher-quality extracts. Membrane separation and encapsulation appear promising to improve the sustainability of separating polyphenolic compounds. We present kinetic models and their influence on process parameters such as solvent type, solid and solvent ratio, temperature and particle size.

Tea eggs-inspired high-strength natural polymer hydrogels

Natural polymer (NP) hydrogels are an irreplaceable class of biomaterials owing to their identified biosafety; however, the intrinsic poor mechanical strengths severely limit their applications as structural tissue engineering scaffolds. Inspired by the stiffening albumen gel of tea eggs, a traditional Chinese snack, high-strength NP hydrogels are constructed by simply soaking in aqueous solution of tea polyphenols (TP), an active ingredient extracted from tea. The TP-treated representative NP hydrogels exhibit considerably enhanced multifaceted mechanical properties with maximum 19-/30-, 8.4-, 6.1-, 72-fold increases in tensile/compressive strengths, Young's modulus, elongation at break and facture toughness, respectively, compared with pristine hydrogels, primarily due to the hydrogen bonding interactions between TP and NP chains. The TP-treated NP hydrogels can resist different large deformations, which cannot be achieved by their original species at all. In aqueous solution, the TP-treated NP hydrogels can still maintain robust mechanical performances, in spite of somewhat decline in strengths with release of TP, which just favorably affords increased water contents, antibacterial and antioxidant activities. GelMA-TP hydrogel is shown to facilitate wound healing in a full-thickness skin defect model. Importantly, the weak 3D printed GelMA scaffolds are significantly strengthened by TP treatment, broadening the possibility for customizing individualized bioscaffolds.

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Tea eggs-inspired high-strength natural polymer (NP) hydrogels are prepared.

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Tea polyphenols strengthen considerably 3D-printed NP hydrogel scaffolds.

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The NP-TP hydrogels exhibit antibacterial and antioxidant activities.

Salivary pellicle modification with polyphenol-rich teas and natural extracts to improve protection against dental erosion

OBJECTIVE

To investigate the modification of the salivary pellicle with different polyphenol-rich teas and natural extracts for the protection against dental erosion.

METHODS

We performed two experiments: one with teas (Green tea, Black tea, Peppermint tea, Rosehip tea, negative control [NC]) and other with natural extracts (Grape seed, Grapefruit seed, Cranberry, Propolis, NC), where NC was deionized water. A total of 150 enamel specimens were used (n = 15/group). Both experiments followed the same design, consisting of 5 cycles of: salivary pellicle formation (30 min, 37 °C), modification with the solutions (30 min, 25 °C), further salivary pellicle formation (60 min, 37 °C) and erosive challenge (1 min, 1% citric acid, pH 3.6). Relative surface microhardness (rSMH), relative surface reflection intensity (rSRI) and amount of calcium release (CaR) were evaluated. Data were analysed with Kruskal-Wallis and Wilcoxon rank sum tests with Bonferroni correction (α = 0.05).

RESULTS

Regarding teas, Black and Green teas showed the best protection against dental erosion, presenting higher rSMH and lower CaR than NC. Peppermint tea was not different to NC and Rosehip tea caused erosion, showing the highest CaR and greatest loss of SMH and SRI. Regarding natural extracts, Grape seed and Grapefruit seed extracts presented the best protective effect, with significantly higher rSMH and lower CaR. Cranberry caused significantly more demineralization; and Propolis did not differ from NC.

CONCLUSION

Green tea, Black tea, Grape seed extract and Grapefruit seed extract were able to modify the salivary pellicle and improve its protective effect against enamel erosion, but Rosehip tea and Cranberry extract caused erosion.

CLINICAL RELEVANCE

Some some bio-products, such as teas and natural extracts, improve the protective effect of the salivary pellicle against enamel erosion. More studies should be performed in order to test the viability of their use as active ingredients for oral care products.

Ionic liquid@β-cyclodextrin-gelatin composite membrane for effective separation of tea polyphenols from green tea

A new kind of multi-component membrane was prepared by combining gelatin solution, porogen and an inclusion complex of ionic liquid (IL) and beta-cyclodextrin (β-CD) in a simple physical manner for selective separation of tea polyphenols (TPs) from green tea crude extracts. After screening, it was found that the resulting membrane containing the IL of dicationic N-vinylimidazole proline salt ([VIm]₂C₃[l-pro]₂) had the excellent performance for the enrichment of the target molecules. Then the newly-developed film was comprehensively characterized by scanning electron microscopy, conductivity, thermogravimetry and spectral analysis. Under pressure driving, the adsorption from an aqueous solution of a mixture of TPs and theophylline on IL@β-CD-Gel membrane showed that the adsorption capacity for TPs was 303.45 mg/g with removal percentages of 94.38%. The experimental data fit well with pseudo-second-order model and Freundlich model. By using this composite material, a new technology of membrane separation for selective adsorption of TPs was finally established.

Rapid Screening α-Glucosidase Inhibitors from Natural Products by At-Line Nanofractionation with Parallel Mass Spectrometry and Bioactivity Assessment

In this study, a novel at-line nanofractionation screening platform was successfully developed for the rapid screening and identification of α-glucosidase inhibitors from natural products. A time-course bioassay based on high density well-plates was performed in parallel with high resolution mass spectrometry (MS), providing a straightforward and rapid procedure to simultaneously obtain chemical and biological information of active compounds. Through multiple nanofractionations into the same well-plate and comparisons of the orthogonal separation results of hydrophilic interaction liquid chromatography (HILIC) and reversed-phase liquid chromatography (RPLC), the α-glucosidase inhibitors can be accurately identified from co-eluates. The screening platform was comprehensively evaluated and validated, and was applied to the screenings of green tea polyphenols and Ginkgo folium flavonoids. After accurate peak shape and retention time matching between the bioactivity chromatograms and MS chromatograms, ten α-glucosidase inhibitors were successfully screened out and identified. The proposed screening method is rapid, effective and can avoid ignoring low abundant/active inhibitors.

Extraction of Flavonoids From Natural Sources Using Modern Techniques

Flavonoids are one of the main groups of polyphenols found in natural products. Traditional flavonoid extraction techniques are being replaced by advanced techniques to reduce energy and solvent consumption, increase efficiency and selectivity, to meet increased market demand and environmental regulations. Advanced technologies, such as microwaves, ultrasound, pressurized liquids, supercritical fluids, and electric fields, are alternatives currently being used. These modern techniques are generally faster, more environmentally friendly, and with higher automation levels compared to conventional extraction techniques. This review will discuss the different methods available for flavonoid extraction from natural sources and the main parameters involved (temperature, solvent, sample quantity, extraction time, among others). Recent trends and their industrial importance are also discussed in detail, providing insight into their potential. Thus, this paper seeks to review the innovations of compound extraction techniques, presenting in each of them their advantages and disadvantages, trying to offer a broader scope in the understanding of flavonoid extraction from different plant matrices.

Controlling the Antioxidant Activity of Green Tea Extract through Encapsulation in Chitosan-Citrate Nanogel

Applying bioactive ingredients in the formulation of foods instead of artificial preservatives is problematic because bioactive ingredients are unstable and sensitive to environmental conditions. The present study aimed to control the antioxidant activity of green tea extract (GT) through encapsulating in chitosan nanoparticles (CS-NP). The synthesized nanoparticles were analyzed by using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). The encapsulation efficiency (EE), particle size, zeta potential, and polydispersity index (PDI) of GT-loaded CS-nanoparticles (CS-NP-GT) were assessed. Based on the results, the particle size and zeta potential related to the ratio of CS to GT of 1 : 0.5 were obtained as 135.43 ± 2.52 nm and 40.40 ± 0.2 mV, respectively. Furthermore, the results of FT-IR and XRD confirmed the validity of encapsulating GT in CS-NP. In addition, the antioxidant activity of GT increased after nanoencapsulation since the IC50 value of CS-NP-GT decreased to 6.13 ± 0.12 μg/ml. Finally, applying these particles for delivering GT polyphenols in foods is regarded as promising.

Green-Sustainable Recovery of Phenolic and Antioxidant Compounds from Industrial Chestnut Shells Using Ultrasound-Assisted Extraction: Optimization and Evaluation of Biological Activities In Vitro

Chestnut processing industry generates large amounts of by-products, including leaves, burs and shells that are a source of bioactive compounds. The purpose of this study was to establish an ultrasound-assisted extraction (UAE) of phenolic and antioxidant compounds from industrial chestnut shells. A central composite design (CCD) was conducted to analyze the effects of time (4–46 min) and temperature (34–76 °C) in the antioxidant activity (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and ferric reducing antioxidant power (FRAP)) and total phenolic compounds (TPC) of chestnut shells extracts. The optimal extraction conditions were obtained at 70 °C for 40 min. The optimal extract was characterized regarding phenolic profile, radical scavenging capacity, and effects on intestinal and dermal cell lines. The optimal extract revealed high amounts of ellagic acid (40.4 µg/mg dw), followed by caffeic acid derivative (15.4 µg/mg dw) and epigallocatechin (15.3 µg/mg dw). Indeed, the extract exhibited the highest scavenging efficiencies against NO● (IC₅₀ = 0.1 µg/mL) and HOCl (IC₅₀ = 0.7 µg/mL) and did not conducted to a decrease on HaCaT and HFF-1 viability up to 100 μg/mL. Oppositely, a decrease on Caco-2 and HT29-MTX viability was observed. This study suggests that UAE could be a sustainable option to valorize chestnut shells as raw material for different industries.

Polyphenols from Stevia rebaudiana (Bertoni) leaves and their functional properties

The major polyphenol components from Stevia rebaudiana (Bertoni) leaves (PPS) are chlorogenic acids, a polyphenol family of esters, including hydroxycinnamic acids with quinic acid, which possesses excellent hydrophilic antioxidant activity and other therapeutic properties. As an abundant byproduct during production of steviol glycosides, the PPS would be a new antioxidantive food resource or additives applied in foods and drugs with antidiabetic function. Extracting PPS from S. rebaudiana (Bertoni) leaves together with steviol glycosides would be an economic process, which will change most operation process in current Stevia factories. The quantification of PPS needs to be unified for regulation. In view of the current regulation status of polyphenols and extracts from Stevia, the PPS would be ready to go to the market with few regulation barriers in the near future. This review will summarize the analysis, extraction, and some functional properties of PPS, such as antioxidant, antidiabetic, antimicrobial, anti-inflammatory, and anticancer.