Ultrasound-assisted Water Research Articles

Thermally-stable, solid-solid phase change materials based on dynamic metal-ligand coordination for efficient thermal energy storage

• A novel SSPCM based on dynamic metal-ligand bonds was successfully prepared. • The devised DS-PCMs can be reprocessed in two simple and convenient ways. • The DS-PCMs have superior energy storage ability and thermoplastic performance. Thermal energy storage offers enormous potential for the development of modern energy technologies. Solid-solid phase-change materials (SSPCMs) have drawn great attention due to their efficient energy utilization and excellent thermal stability. However, it is still a challenge to synthesize SSPCMs capable of the intriguing properties of reprocessability and recyclability. Herein, we reported an effective strategy to construct dynamic cross-linked SSPCMs, namely DS-PCMs, through incorporating reversible metal-ligand coordination. The synthesized DS-PCMs can keep in a solid state during the phase change process with a high latent heat storage capacity of up to 99.3 J/g. Especially, the energy storage capacity, chemical structure and thermal stability of the reprocessed DS-PCMs can be consistent with that of original one after being reprocessed by hot pressing and ultrasound-assisted water solution casting. Additionally, these DS-PCMs have repeatable thermo-plasticity to manipulate permanent various 3D shapes without complex molds. Briefly, these designed DS-PCMs simultaneously have excellent stability, dual reprocessability, and reconfigurable thermoplastic performance. Our works provide a facile design strategy to prepare reprocessable SSPCMs, unlocking opportunities for the sustainable use of phase change materials.

Preparation, characterization, and antibacterial properties of “green” synthesis of Ag nanoparticles and AgNPs/kaolin composite

The present work describes "green" method of silver nanoparticles (AgNPs) synthesis using an aqueous extract of grape pomace (GPE)as a reducing and capping agent and preparation of Ag-NPs/kaolin composite. The grape pomace extract (GPE) was prepared by the ultrasound-assisted water extraction with subsequent oxidation by oxygen purge and characterized by liquid chromatography–mass spectroscopy (LC–MS), total phenolic (TPC) and total flavonoid contents (TFC). AgNPs were characterized by UV–vis spectroscopy, dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX). The prepared GPE– AgNPs/Kaolin composite contained 1.26% of silver nanoparticles as was estimated using SEM and EDX techniques. The GPE– AgNPs/Kaolin composite exhibited an antimicrobial activity on the growth of Escherichia coli and Bacillus subtilis.

Hypoglycemic and antioxidant effects of green tomato ( Physalis ixocarpa Brot.) calyxes’ extracts

The aim of this study was to evaluate the hypoglycemic and antioxidant potential of green tomato (Physalis ixocarpa Brot.) calyxes' extracts. Three methods were used to obtain the extracts: maceration (M), ultrasound-assisted (US), and infusion. Regarding in vitro hypoglycemic evaluation, glucose diffusion assay and enzymatic inhibitory action of α-amylase and α-glucosidase were performed. Whereas, for in vivo assessment an oral starch tolerance test (OSTT) was tested with aqueous extracts [infusion (40mg/kg b. wt.), maceration (M) water (98mg/kg b. wt.), and US water (82.24mg/kg b. wt.)] on male Wistar rats. Additionally, in vitro antioxidant activity of P. ixocarpa calyxes' was evaluated through inhibition of scavenging radical assay and lipid peroxidation. Extracts decreased the glucose diffusion in a range of 18%-56% compared with the negative control. Additionally, extracts inhibited α-amylase (above 80%) and α-glucosidase enzymes (above 90%). All groups treated with P. ixocarpa calyxes' significantly reduced the glucose levels at 120min (infusion=13.3%, M Water=12.7%, and US Water=19.4%) in comparison with the negative control, and similar levels to acarbose at 120min (13.1%). Finally, extracts showed IC50 values in a range of 2.5-6.6µg/µl for radical scavenging, and 118-199µg/µl for lipid oxidation. Our results show that P. ixocarpa calyxes' extracts induce hypoglycemia and antioxidant effects in vitro and in vivo. PRACTICAL APPLICATIONS: The green tomato is usually consumed in Mexico, the United States, and Central America. This fruit grows inside a calyx, which is considered an agro-food waste. However, some regions of Latin America have a traditional medicine purpose for diabetes affections. To the best of our knowledge, there are no published data that supports its hypoglycemic action. The information provided will be useful to nutraceutical applications that allow value-added products and sustainable green tomato production.

The Effects of Washing Techniques on Thermal Combustion Properties of Sewage Sludge Chars

Sewage sludge chars were subjected to washing to produce a clean solid fuel of superior quality. First, sewage sludge was converted into chars at different carbonization temperatures (400–700 °C), and then the produced chars were washed with various washing techniques, i.e., water (W), hydrochloric acid (HCl), ethylenediamine tetraacetic acid (EDTA) and ultrasound-assisted water to further reduce ash and heavy metal contents. The washed chars were systematically characterized and their fuel properties were analyzed. The results indicated that all washing techniques decreased ash content of chars and improved their fuel ratio. The washed chars exhibited higher heating values, lower slagging and ash fouling indexes and higher combustion reactivity, indicating the better quality of the derived fuels. Among the washing techniques, HCl washing was the most efficient process as carbon content increased by 20%, while ash content decreased by 50%. The fuel ratio as well as slagging and ash fouling indexes were significantly improved. Furthermore, the combustion reactivity showed similar pattern to coal with high conversion rate suggesting the enhanced thermal stability of the fuel. In conclusion, pyrolysis as a single process seems inefficient to produce high quality chars; however, coupling pyrolysis with washing can yield chars with satisfactory fuel properties.

Construction of a novel supramolecular self‐assembly photocatalyst for full visible light spectrum photooxidation of phenol

AbstractThe sluggish full visible light response of organic supramolecular catalysts is a challenge that greatly restricts their development in the photocatalytic field. Herein, we successfully fabricated a K, Cl‐codoped Bi2WO6/perylene‐diimide(PDI) catalyst with a novel, general, and facile ultrasound assisted water bath heating method. The UV adsorption onset of K, Cl‐codoped Bi2WO6/PDI is redshifted from 750 to 760 nm compared with that of the heterojunction of Bi2WO6/PDI. Under visible light, the phenol is thoroughly mineralized into CO2 and H2O, and the phenol degradation rate was three times higher than that of pure Bi2WO6/PDI. The electrons transfer from PDI to K‐ and Cl‐codoped Bi2WO6/PDI according to the charge density difference calculation. The built‐in potential of K‐ and Cl‐codoped Bi2WO6/PDI could increase from 2.09 to 5.54 eV. The excellent full visible light spectrum photooxidation of phenol is attributed to the suitably strong built‐in potential at the heterojunction between PDI and K, Cl‐codoped Bi2WO6.

Integrated biorefinery of aquatic fern Azolla filiculoides for enhanced extraction of phenolics, protein, and lipid and methane production from the residues

Azolla filiculoides is an aquatic fern native to tropical regions, and because of its unique composition, it was subjected to integrated biorefineries for biochemicals and bioenergy production. The compositional analysis showed that its raw biomass contained 41.4% carbohydrates, comprising galactan, glucan, and arabinan, 12% lignin, and 10.3% inorganic matter. Lipids, proteins, and phenolic compounds were extracted from the biomass and analyzed by different methods to enhance extraction yield and estimate their nutritional values. The residues remained after the (sequential) extraction of the major biochemicals was subjected to biogas production. A maximum lipid yield of 18.1% was obtained from the biomass, which was rich in palmitic acid and eicosapentaenoic acid (EPA). EPA, an omega-3 fatty acid with wide applications as a food supplement, accounted for 39.8% of total fatty acids, corresponding to 72 mg/g biomass. Two protein extraction methods, i.e., ultrasound-assisted water followed by sodium hydroxide extraction and sequential extraction by hot trichloroacetic acid, were applied. Using the first method at the optimum conditions, up to 24.4% protein was obtained, while a maximum 11.9% water-soluble protein was isolated by applying ultrasound-assisted extraction. In the amino acid profile of the fern protein, glutamic acid was the most abundant component with 20.5%, followed by threonine. Up to 37.9% of total amino acids were composed of essential amino acids that showed a high nutritional value of the fern protein. The total phenolic content of 27.2 mg gallic acid equivalent per 100 g of biomass was obtained. In the HPLC analysis, chlorogenic acid, luteolin, caffeic acid, and tannic acid were detected in which caffeic acid had the highest concentration of 18.5 mg/100 g raw material. Tannic acid removal was the most effective pretreatment for enhanced biomethane production. A maximum cumulative methane yield of 250.1 mL/g-VS was obtained from tannic acid-free biomass, which was 12% higher than that of the raw biomass.

Effect of Pterocladia capillacea Seaweed Extracts on Growth Parameters and Biochemical Constituents of Jew’s Mallow

We performed field experiments to evaluate the influence of two extraction treatments, seaweed (Pterocladia capillacea S.G. Gmelin) water extraction (WE) and ultrasound-assisted water extraction (USWE) at three concentrations (5%, 10%, and 15%), as well as control NPK traditional mineral fertilizer on the growth, yield, minerals, and antioxidants of Jew’s Mallow (Corchorus olitorius L.) during the two seasons of 2016 and 2017 in Egypt. Plant height, number of leaves, and fresh weight of WE10 treatment were the highest (p < 0.05) as 59.67 cm, 10.67 and 2.41 kg m−2 in 2016, respectively, and 57.33 cm, 11.00 and 2.32 kg m−2 in 2017, respectively. WE10 and USWE5 treatments produced the highest dry matter (17.07%) in 2016 and (16.97%) in 2017, respectively. WE10 plants had an increased water productivity of 41.2% relative to control plants in both seasons. The highest chlorophyll ‘a’ was recorded after the WE10 treatment in 2016 and 2017 (17.79 μg g−1 and 17.84 μg g−1, respectively). The highest levels of total antioxidant capacity, total phenolics, and total flavonoids were also recorded after the WE10 treatment. Application of WE10 boosted growth, yield, minerals, and antioxidants of Jew’s Mallow. The CROPWAT model was used to estimate the evapotranspiration, irrigation water requirements, and yield response to irrigation scheduling. Our data showed a yield reduction in the initial growth stage if a limited amount of water was provided. Therefore, irrigation water should be provided during the most important stages of crop development with the choice of effective irrigation practices to avoid water losses, as this helps to maximize yield.

Effect of ultrasound assisted heating on structure and antioxidant activity of whey protein peptide grafted with galactose

This work investigated the structure and antioxidant activity of Maillard reaction products of whey protein peptides grafted with galactose through ultrasound assisted water bath heating. The Maillard reaction time was 180 min including 0, 15, 30, 45, and 60 min ultrasound assisted water-bath heating performed at the beginning of the reaction. The results revealed that the intermolecular motion of the amino group and the carboxyl group of each amino acid was accelerated, and the secondary structures of whey protein peptides were changed by grafted galactose through ultrasound assisted heating. When subjected to the ultrasound treatment for 60 min, the reducing power of whey protein isolate (WPI) and conjugated whey protein peptides (WPP) reached 0.481 and 0.686, respectively. Additionally, the ABTS+ radical-scavenging activity of WPI and WPP reached 42.19% and 49.05%, respectively. These results were significantly higher (P < 0.05) than those obtained using the water bath alone. The maximum of DPPH radical scavenging activity of WPI and WPP conjugates was 54.89% and 81.50%, respectively, with an ultrasound treatment of 30 min, which was also higher than that of the water bath alone (P < 0.05). WPPGa showed significant structural, differences and higher antioxidant activity than WPIGa (P < 0.05).

Optimization of Ultrasound-Assisted Extraction of Anthocyanins and Phenolic Compounds from Black Soybeans (Glycine max L.)

Black soybeans have been reported to contain high antioxidant content, including anthocyanins. Ultrasound-assisted water extraction of antioxidants from Korean black soybeans (Glycine max [L.] Merr. Cheongja4ho) was investigated for the first time. A three-level, three-factor Box-Behnken design using a response surface methodology (RSM) was employed to optimize the conditions for the maximum yields of three dependent variables, including total anthocyanin content, total phenol content, and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activity, based on 17 different experiments. The solid-liquid ratio (X1, 1/30–1/50 g mL−1), extraction time (X2, 1–9 min), and amplitude (X3, 20–100%) significantly affected three dependent variables. The optimized conditions were solid-liquid ratio of 49.1 g mL−1, extraction time of 8.59 min, and amplitude of 81.4%. At the optimum point, the total anthocyanin content, total phenol content, and ABTS•+ scavenging activity were 66.44, 940.96, and 242.45 mg 100 g−1. The difference (%) between the predicted and experimental values was less than 6.40%, indicating that the model fits well. The conditions optimized for ultrasound-assisted water extraction of antioxidants from black soybeans can be applied as an efficient technique for extracting anthocyanins in plants on a larger scale.

Optimization of ultrasound-assisted water extraction of flavonoids from Psidium guajava leaves by response surface analysis

Psidium guajava leaves are rich in health-promoting flavonoids compounds. For better utilization of the resource, the ultrasound-assisted aqueous extraction was investigated using Box-Behnken design under response surface methodology. A high coefficient of determination (R2 = 97.8%) indicated good agreement between the experimental and predicted values of flavonoids yield. The optimal extraction parameters to obtain the highest total flavonoids yield were ultrasonic power of 407.41 W, extraction time of 35.15 min, and extraction temperature of 72.69 °C. The average extraction rate of flavonoids could reach 5.12% under the optimum conditions. Besides, HPLC analysis and field emission scanning electron microscopy indicated that the ultrasonic treatment did not change the main component of flavonoids during extraction process and the higher flavonoids content was attributed by the disruption of the cell walls of guava particles. Thus, the extraction method could be applied successfully for large-scale extraction of total flavonoids from guava leaves.

Structure and radio‐protective effects of sulfated Auricularia auricula polysaccharides

Radiation-protective effects of sulfated polysaccharides (SNAAP80) from Auricularia auricular were studied. Crude polysaccharides were extracted using ultrasound-assisted water extraction. Bioactive polysaccharide fragments were screened using ethanol precipitation with an in vitro antioxidant activity test. The chlorosulfonic acid-dimethylformamide method was used to obtain the sulfated polysaccharide. Monosaccharide composition and molecular weight were determined using GC-MS and HPLC-GPC, respectively. IR, UV, and SEM were used for structural characterization. The antiradiation effect of SNAAP80 was studied using a 60Co-γ radiation model in mice. The results showed that the SNAAP80, with a degree of substitution of 0.514, was composed of glucose and mannose. A bioactivity analysis showed that the SNAAP80 increased the organ indexes, phagocytosis index, stimulation index, and the superoxide dismutase, glutathione peroxidase, catalase, and lactate dehydrogenase activity. The SNAAP80 decreased TBARS, IL-2, IL-12, INF-γ, protein carbonyls, creatinine, and blood urea nitrogen. The results suggested that SNAAP80 had an effective radiation-protective effect. Practical applications Auricularia auricula is a commonly cultivated commercial mushroom in East Asia; it is also called “wood ear” in China and “black fungus” in Russia. Many published studies regarding polysaccharides from A. auricula have shown their beneficial health effects for both humans and animals. A. auricula is acknowledged for its pharmaceutical effects such as inhibiting lipid peroxidation, decreasing liver damage, hypolipidemic properties and so on. Functional activity of polysaccharides is related to their solubility. The activities of polysaccharide NAAP80 from A. auricular were restricted because of its poor solubility. Therefore, it was modified by chlorosulphonic acid-N,N dimethylformamide to obtain SNAAP80 which has a significantly higher solubility. Antiradiation effect of SNAAP80 has been studied in this paper, and its potential application in antiradiation may be relevant to space exploration, the military, daily health care, and therapeutic medications.

Static, Kinetic, and Isotherm Adsorption Performances of Macroporous Adsorbent Resins for Recovery and Enrichment of Bioactive Procyanidins from Cranberry Pomace.

This study examined the ability of five Amberlite resins coupled with ultrasound-assisted water extraction for the recovery and enrichment of bioactive procyanidins and total phenolics from cranberry pomace. Static adsorption showed that XAD-7HP had the highest adsorption capacity for procyanidins (52.2mg/g resin) and total phenolics (99.1mg/g resin) whereas XAD-761 had the lowest. Adsorption of procyanidins fitted better to pseudo-second-order kinetics than pseudo-first-order kinetics. Isotherm adsorption on XAD-7HP suggested that Langmuir isotherm was a better model to describe the adsorption of procyanidins while Kemkin-Pyzhev equation was better for total phenolics based on higher coefficient of determinations (R2 ). Dynamic tests on XAD-7HP suggested that the flow rate of 7 and 8 mL/min were the optimum conditions for adsorption and desorption of procyanidins, respectively. Measurements using HPLC revealed that adsorption increased the contents of procyanidins and total phenolics by 4.57- and 4.73-folds, respectively, compared to the initial extracts. This research showed that Amberlite XAD-7HP resin adsorption coupled with ultrasound-assisted water extraction is an efficient method to separate and concentrate procyanidins from cranberry pomace.

Comparative study of ultrasound assisted water and surfactant flooding

Ultrasound technique is an economic advantageous and environmental friendly unconventional enhanced oil recovery (EOR) method that has been of great interest to researchers and reservoir engineers. The integration of ultrasound with water flooding and ultrasound with surfactant has been proven to be effective in increasing oil recovery by decreasing surfactant adsorption. Previous studies focused on the phase behaviour of surfactant-brine-oil to determine if ultrasonic with surfactant can actually decrease the rate of surfactant consumption. However, phase behaviour alone cannot answer this question. In this study therefore, the role of critical micelle concentration (CMC) in ultrasound assisted surfactant flooding, and the effect of surfactant concentration on oil recovery during ultrasound at different intensities were investigated. An unconsolidated sand-pack model placed inside an ultrasonic bath and ultrasonic radiation was used for this purpose. Ultrasound assisted water and surfactant flooding improve recovery up to 11% and 12% respectively. The formation of micro-emulsion (micelles) during surfactant flooding in the presence of ultrasonic wave was the most significant mechanism responsible for the increased recovery. Ultrasound vibration is more efficient at higher concentration of surfactant, preferably above CMC and at higher intensity of ultrasound.

Detection of over 100 selenium metabolites in selenized yeast by liquid chromatography electrospray time-of-flight mass spectrometry.

The characterization of the selenometabolome of Selenized(Se)-yeast, that is the fraction of water soluble low-molecular weight Se-metabolites produced in Se-yeast is of paramount interest to expand the knowledge on the composition of this food supplement. In this work, we have applied liquid chromatography electrospray time-of-flight mass spectrometry (LC-TOFMS) to search for Se-species from the low molecular weight range fraction of the selenized yeast used for food supplements. Prior to LC-TOFMS, sample treatment consisted of ultrasound assisted water extraction followed by size exclusion fractionation assisted with off-line inductively coupled plasma mass spectrometry detection of isotope 82Se. The fraction corresponding to low-molecular weight species was subjected to LC-TOFMS using electrospray ionization in the positive ion mode. The detection of the suspected selenized species has been based on the information obtained from accurate mass measurements of both the protonated molecules and fragments from in-source CID fragmentation; along with the characteristic isotope pattern exhibited by the presence of Se. The approach enables the detection of 103 selenized species, most of them not previously reported, in the range from ca. 300-650Da. Besides the detection of selenium species, related sulphur derivate metabolites were detected based on the accurate mass shift due to the substitution of sulphur and selenium.

Rheological and structural properties of fish scales gelatin: Effects of conventional and ultrasound-assisted extraction

ABSTRACTIn this study, the rheological and structural properties of extracted fish scales gelatin by conventional water bath (CWB) and ultrasound-assisted water bath (UWB) at different temperatures (60°C, 70°C and 80°C) were studied. Rheological behaviours showed that the extracted fish scales gelatin by UWB at 60°C possessed the highest storage modulus (5000 Pa), gelation point (22.94°C), melting point (29.54°C), and apparent viscosity than the others. X-ray showed that high temperature and ultrasound reduced the triple-helix content of fish scales gelatin along with decreasing gelling properties. Atomic force microscopy showed that the largest aggregates could be observed in the surface of UWB60. Therefore, UWB proved to be a promising technology in the extraction of high-quality fish gelatin.

Simultaneous ultrasound-assisted water extraction and β-cyclodextrin encapsulation of polyphenols from Mangifera indica stem bark in counteracting TNFα-induced endothelial dysfunction

This study proposes an alternative technique to prevent heat degradation induced by classic procedures of bioactive compound extraction, comparing classical maceration/decoction in hot water of polyphenols from Mango (Mangifera indica L.) (MI) with ultrasound-assisted extraction (UAE) in a water solution of β-cyclodextrin (β-CD) at room temperature and testing their biological activity on TNFα-induced endothelial dysfunction. Both extracts counteracted TNFα effects on EAhy926 cells, down-modulating interleukin-6, interleukin-8, cyclooxygenase-2 and intracellular adhesion molecule-1, while increasing endothelial nitric oxide synthase levels. β-CD extract showed higher efficacy in improving endothelial function. These effects were abolished after pre-treatment with the oestrogen receptor inhibitor ICI1182,780. Moreover, the β-CD extract induced Akt activation and completely abolished the TNFα-induced p38MAPK phosphorylation. UAE and β-CD encapsulation provide an efficient extraction protocol that increases polyphenol bioavailability. Polyphenols from MI play a protective role on endothelial cells and may be further considered as oestrogen-like molecules with vascular protective properties.

Polyphenol extraction and characterization of Justicia secunda Vahl leaves for traditional medicinal uses

Water extracts of Justicia secunda leaves are used by village communities in southern countries to prepare traditional medicines at home. The beverage is usually obtained by boiling the plant in water. On a pilot plant scale, water extracts were processed using an extraction–concentration procedure achieved in a three-step process, including ultrasound-assisted water extraction followed by cross-flow microfiltration of the crude extract and its concentration by reverse osmosis. As the processing conditions were milder than for homemade preparations, the extract obtained was enriched in natural leaf flavonoids. At each step of the pilot plant process, the co-products obtained were analyzed for total polyphenol and total flavonoid contents by the UV–vis spectrophotometric method. The process allowed a better leaf water-extraction of polyphenol compounds than the homemade extraction. The crude extract was concentrated 28 times (v/v) at room temperature by membrane volume reduction, and the total content of polyphenol compounds of the concentrated extract was 17 times higher than those of the crude extract. Individual polyphenol compounds were characterized by HPLC-DAD analysis at λmax=325nm. Additional structure characterization was carried out for the two major flavonoid compounds found (65% of total HPLC-DAD peak area of the flavones-type compounds) in the water extracts by tandem mass spectrometry (LC–ESI-MS2) and by nuclear magnetic resonance (1H NMR, 13C NMR). They were identified as luteolin 7-O-[β-glucopyranosyl-(1→2)-β-rhamnosyl-(1→6)] β-glucopyranoside and luteolin 7-O-[β-apiofuranosyl-(1→2)]-β-xylopyranoside.

Lab and pilot-scale ultrasound-assisted water extraction of polyphenols from apple pomace

Apple pomace, a residue from juice or cider production, shows high content of exploitable polyphenols. In this work, apple pomace was submitted to an Ultrasound-Assisted Extraction (UAE) in order to produce extracts rich in antioxidants. After a preliminary study, a solid/liquid ratio of 150mg of dry material per mL was used, and optimized conditions obtained by response surface methodology for polyphenols water-extraction were 40°C, 40min and 0.764W/cm2. A comparison showed Total Phenolics Content (TPC) obtained by UAE was 30% higher than the content obtained by Conventional Extraction (CE)(555 and 420mg of catechin equivalent per 100g of dry weight, respectively) and both methods presented the same extraction kinetics. Furthermore, extracts obtained by ultrasound showed higher antioxidant activity, which was confirmed by HPLC analysis, that revealed main polyphenols were not degraded under the applied conditions. The large scale experiments of this ultrasound procedure showed a potential industrial application.

Optimization of anthocyanin, flavonol and phenolic acid extractions from Delonix regia tree flowers using ultrasound-assisted water extraction

Flowers of Delonix regia trees from Ivory Coast are traditionally macerated in water to prepare beverages with beneficial health properties mainly due to their polyphenolic contents. Different maceration procedures, mimicking the traditional process, were compared on the basis of polyphenol content followed by HPLC-DAD analysis. Under optimized maceration ratio ( R = plant sample weight/maceration media volume), plant extractions were compared, including acidified-water-based media and assisted-ultrasound or stirring extraction procedures. Diffusion kinetics of polyphenol families (anthocyanins, flavonols and phenolic acids) were followed by HPLC and lead to find optimum ratio ( R = 1/100). Flavonol contents were 28.5, 31, and 33.5 μmol g −1 (expressed as quercetin equivalent), using acidified-water (0.01N) media with sulphuric or citric acids. Anthocyanin and phenolic acid contents were within the same range for these water media (5.6 μmol g −1 as cyanidin equiv. and 27.5 μmol g −1 as gallic acid (GA) equiv., respectively). Ultrasound-assisted procedure shortened maceration time (three times shorter) but did not show higher level of total polyphenol than stirring-assisted procedure (39 μmol g −1 GA equiv.). This eco-friendly and low-cost extraction process will provide to African people, with safer quality and longer availability, polyphenol-rich bio-products.

Composition and bioactivity of tea flower polysaccharides obtained by different methods

The effects of different extraction methods on the composition and bioactivity of tea flower polysaccharides (TFPS) were investigated. Traditional water extraction (TWE), microwave-assisted water extraction (MAE), and ultrasound-assisted water extraction (UAE) were compared to extract TFPS. TWE was found to be the optimal method with highest yield of TFPS and highest neutral and acid saccharides contents in TFPS. TFPS obtained by TWE mainly consisted of two kinds of polysaccharides with the molecular weight of 31 kDa and 5000 Da. TFPS obtained by MAE and UAE generally had very low inhibitory effects on α-glucosidase. TFPS (2 mg/mL) obtained by TWE exhibited a strong inhibitory effect on α-glucosidase with the inhibitory rate of 83.3%. TFPS obtained by TWE had stronger proliferation effect on lymphocyte at the concentration of 3.0 μg/mL than that of tea leave polysaccharides (TPS).