Decaffeination of tea extracts by using poly(acrylamide-co-ethylene glycol dimethylacrylate) as adsorbent

Poly(acrylamide-co-ethylene glycol dimethacrylate) was synthesized by thermal polymerization. The adsorption properties of the polymers for catechins and caffeine were studied. Adsorption kinetics showed the polymers preferred to adsorb the catechins rather than caffeine, and adsorption of catechins and caffeine onto the polymers could be described by the pseudo-second-order model. Isothermal equilibrium curves of catechins and caffeine showed a good fit with Langmuir model. The maximum monolayer adsorption capacity (Q_m) of total catechins (192.85–171.11 mg g⁻¹) was 3.9–5.2-folds of caffeine. Adsorption of catechins and caffeine was spontaneous and exothermic process as the change in free energy and enthalpy were negative. Lower temperature was favorable for the adsorption process. Caffeine and catechins were well separated and recovered by eluting polymers-packed column with gradient ethanol, i.e., 30% ethanol elution for separating caffeine, and 80% ethanol elution for recovering catechins. Thus, the synthetic poly(acrylamide-co-ethylene glycol dimethacrylate) could be used as a new adsorbent candidate for producing the decaffeined catechins.     

Preparation of tea catechins using polyamide

An adsorption separation method using Polyamide-6 (PA) as an adsorbent was developed to separate catechins from green tea extract. The adsorption capacity of total catechins for PA was 193.128 mg g⁻¹ with an adsorption selectivity coefficient K_A^B of total catechins over caffeine 21.717, which was better than macroporous resin model HPD 600. The Langmuir model and the pseudo-second order mode were primely fitted to describe its equilibrium data and adsorption kinetics, respectively. PA column separation by two-step elution using water and 80% (v/v) aqueous ethanol was established to prepare catechins complex which contained 670.808 mg g⁻¹ total catechins and 1.828 mg g⁻¹ caffeine. It is considered that PA was a promising adsorbent for selective isolation of catechins.     

Comparison of extraction and isolation efficiency of catechins and caffeine from green tea leaves using different solvent systems

Catechins from green tea (Camellia sinensis L.) have received considerable attention due to their beneficial effects on human health, such as antioxidant and anticancer activities. Optimisation of extraction conditions of the catechins from green tea leaves was performed using different solvents (ethanol or distilled water), different extraction methods (ultrasound‐assisted, room temperature or reflux extractions) and various extraction times (0.5–24 h). The optimal extraction conditions were determined using 40% ethanol with ultrasound‐assisted extraction method for 2 h at 40 °C. In addition, two isolation methods for the recovery of catechins from green tea extracts were compared using different solvent combinations (chloroform/ethyl acetate versus ethyl acetate/dichloromethane). The results showed that the ethyl acetate/dichloromethane system could achieve much higher content of catechins than the other isolation approaches, indicating the method that extract catechins first with organic solvent such as ethyl acetate before removing caffeine is much effective than removing caffeine first when organic solvents are used for the recovery of catechins without caffeine from green tea extracts.     

LP-8大孔树脂制备高含量酯型儿茶素茶多酚

结合当前茶学中酯型儿茶素研究热点和工业生产中差异化茶多酚产品需求,对LP-8大孔树脂分离制备高含量酯型儿茶素茶多酚开展研究。先经静态吸附和洗脱实验表明LP-8大孔树脂对茶多酚（含酯型儿茶素）和咖啡碱具有较大的吸附选择性差异,用体积分数70%乙醇溶液洗脱即可获较理想的茶多酚回收率,因此确定LP-8树脂具有分离制备高含量酯型儿茶素茶多酚的可行性。再经静态吸附动力学和等温吸附实验,结合Langmuir拟合方程推算,25 ℃下LP-8大孔树脂的饱和吸附量为70.9 mg/g。经动态吸附实验,确定了最佳吸附条件为上样流速1 BV/h、上样质量浓度30 mg/mL,利用不同体积分数的乙醇溶液对饱和吸附样进行梯度洗脱,40%～60%洗脱合并液中酯型儿茶素占茶多酚比例达78.0%（表没食子儿茶素没食子酸酯占茶多酚总量的61.0%）,即利用LP-8大孔树脂获得了高含量酯型儿茶素茶多酚。     

Microbial inhibitory and radical scavenging activities of cold‐pressed terpeneless Valencia orange (Citrus sinensis) oil in different dispersing agents

BACKGROUND: Due to their low solubility in water, oil‐based bioactive compounds require dispersion in a surface‐active agent or appropriate solvents to ensure maximum contact with microorganisms. These combinations, however, may change their physical and/or chemical characteristics and consequently alter the desired functionality. The objective of this study was to determine the impact of selected dispersing agents, ethanol, dimethyl sulfoxide (DMSO), and Tween‐80, on cold‐pressed terpeneless (CPT) Valencia orange oil to function as a free radical scavenger and an antimicrobial food additive. RESULTS: When dissolved in ethanol or DMSO, the orange oil fraction had similar minimum inhibitory concentrations (MIC) for Listeria monocytogenes ATCC 19 115 (0.3% and 0.25% v/v respectively), which were significantly lower (P ≤ 0.5) than the MIC for Salmonella typhimurium ATCC 14 028 (1% v/v). Both ethanol and DMSO oil dispersion systems exhibited an intermediate MIC (0.75% v/v) for Lactobacillus plantarum WCFS1. The orange oil (up to 3%) in an aqueous solution of 0.1% Tween‐80 yielded no inhibitory activities against any of the test bacteria. However, the 1% natural orange oil dispersed in Tween‐80 exhibited 56.86% 2,2‐diphenyl‐1‐picryl hydrazyl (DPPH) radical inhibition versus 18.37% and 16.60% when the same level of orange oil was dissolved in DMSO or ethanol, respectively. At the same orange oil concentration, the oil/Tween‐80 suspension yielded 57.92% neutralization of hydroxyl radicals. This represents 71.37% of the mannitol antioxidant activity, which was used as a positive control. CONCLUSIONS: These findings suggest that Tween‐80 is an appropriate dispersing agent only if the antioxidant functionality is desired. If both antimicrobial and antioxidant properties are needed, the CPT Valencia orange oil should be dispersed in either DMSO or ethanol. Copyright © 2010 Society of Chemical Industry     

Tea extraction methods in relation to control of epimerization of tea catechins

Effect of water temperature and ethanol concentration on epimerization and extractability of tea catechins was investigated. The results showed that epigallocatechin gallate (EGCG) and epicatechin gallate (ECG) were partially epimerized into gallocatechin gallate (GCG) and catechin gallate (CG), respectively, when tea catechins extract was heated in water solution at 100 °C for 2 h or dry tea was extracted in water at 100 °C. The epimerization of the catechins was inhibited if the tea catechins extract was heated as solid powder and the dry tea was extracted in 50% (v/v) ethanol or in water at 80 °C or below. When the dry tea was extracted in water, the extractability of catechins increased with the increase of extraction temperature up to 100 °C, but there was no statistically significant difference in total catechins between 80 °C and 100 °C. When teas were extracted using ethanol solutions, the highest extractability of total catechins was obtained in 50% (v/v) ethanol for dry tea and in 75% (v/v) ethanol for fresh tea leaf. In order to reveal the real profiles of tea catechins in teas to be tested, dry tea should be extracted in 50% (v/v) ethanol for 10 min, while fresh tea leaf should be extracted in 75% (v/v) ethanol for 10 min. For commercial extraction, temperature should be controlled at 80 °C if water is used as the solvent. Copyright © 2007 Society of Chemical Industry     

柱色谱分离制备无酯儿茶素

目的:探索制备无酯儿茶素的工艺。方法:在前人研究的基础上,以绿茶碎末为原料,用乙醇树脂法制备无酯儿茶素产品。先用80%乙醇,按照料液比1:20、浸提50min、温度70℃的浸提工艺对茶叶进行浸提,并在树脂筛选实验和柱效实验的基础上,设计动态吸附及解吸实验,优化动态吸附与解吸儿茶素的工艺条件。结果:在该浸提条件下,儿茶素的提取率为20.16%;筛选出聚酰胺树脂来纯化儿茶素,纯化的最佳工艺条件为:上样流速1BV/h、料液浓度为20mg/mL;解吸流速为1BV/h,分别用1.2BV的水、1BV25%的乙醇以及1BV80%的乙醇溶液进行梯度洗脱;制得的无酯儿茶素其儿茶素总量≥80%、EGCG≥60%、CAF≤0.5%、得率≥7%。结论:通过本实验的最佳工艺条件制备的无酯儿茶素完全符合无酯儿茶素的要求。     

Extraction of active ingredients from green tea (Camellia sinensis): Extraction efficiency of major catechins and caffeine

The effect of different extraction set-ups that influence the extraction efficiency of catechins and caffeine from green tea leaves (variety Fanning Belas, China) were studied using different aqueous and pure solvents (acetone, ethanol, methanol, acetonitrile, water), different temperatures (60, 80, 95 and 100 °C) and times (5–240 min). Raw extracts were analysed for contents of major catechins (EC, EGC, ECG, EGCG), caffeine, proanthocyanidins and flavonols (myricetin, caempherol, quercetin). Starting material was found to contain 191 g major catechins/kg material, 36 g caffeine/kg material and 5.2 g flavonols/kg material on a dry mass basis. The content of major catechins in green tea extracts varied from approximately 280–580 g/kg dry extract, with extraction efficiencies of major catechins varying from 61% to almost 100%. Content of caffeine in extract was in the range of 75 g/kg, where its extraction efficiency varied from 62% to 76%. Average extraction yield was 30% with exceptions when using pure acetone and acetonitrile, where extraction yield was about 3%. Contents of flavonols and proanthocyanidins were in the ranges 6–20 and 12–19 g/kg, respectively. Different extraction procedures with water were also investigated and optimal conditions determined: maximum achieved extraction efficiency of catechins with water was obtained at 80 °C after 20 min (97%) and at 95 °C after 10 min of extraction (90%). Degradation of catechins was observed at higher extraction temperatures and with prolonged extraction times. Using a lower ratio of solvent to material, extraction efficiencies were increased by applying a multi-step extraction procedure. Optimal extraction procedure was then performed using decaffeinated green tea leaves, which were obtained by high-pressure extraction with CO₂, when 98% of caffeine was selectively isolated without significant impact on valuable catechins.     

酒花中原花青素的提取纯化研究

建立了酒花中原花青素的初步提取方法。以乙醇为萃取剂的有机溶剂萃取最佳条件为:pH为4.0～4.2,萃取剂乙醇浓度为50%,萃取温度85℃(沸腾),萃取时间2h,料液比为1:20。得到酒花中原花青素粗提液,用大孔吸附树脂(φ10×200mm)为填料的层析柱进一步分离提纯。从国产ADS-8、ADS-17、ADS-21、AB-8和D101五种不同大孔吸附树脂中选择分离效果最好的AB-8树脂,进行原花青素粗提液的层析柱动态吸附实验,得到最佳大孔树脂吸附分离条件为:柱体积为14.5mL,酒花粗提液原花青素浓度为1.8mg/mL时,上样量为3mL,上样流速为20mL/h,洗脱剂乙醇浓度为100%,洗脱流速为60mL/h,洗脱剂用量为70mL。     

Effects of cosolvents on the decaffeination of green tea by supercritical carbon dioxide

Due to the adverse effects of the caffeine in a variety of plant products, many methods have been explored for decaffeination, in efforts to remove or reduce the caffeine contained in plant materials. In this study, in order to remove caffeine from green tea (Camellia sinensis) leaves, we have employed supercritical carbon dioxide (SC–CO₂), which is known to be an ideal solvent, coupled with a cosolvent, such as ethanol or water. By varying the extraction conditions, changes not only in the amount of caffeine, but also in the quantities of the principal bioactive components of green tea, including catechins, such as epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG) and epicatechin (EC), were determined. The extraction conditions, including temperature, pressure and the cosolvent used, were determined to affect the efficacy of caffeine and catechin extraction. In particular, the type and concentration of a cosolvent used constituted critical factors for the caffeine removal, combined with minimal loss of catechins, especially EGCG. When the dry green tea leaves were extracted with SC–CO₂ modified with 95% (v/v) ethanol at 7.0 g per 100 g of CO₂ at 300 bar and 70 °C for 120 min, the caffeine content in the decaffeinated green tea leaves was reduced to 2.6% of the initial content. However, after the SC–CO₂ extraction, a substantial loss of EGCG, as much as 37.8% of original content, proved unavoidable.     

Extraction behaviors of caffeine and chlorophylls in supercritical decaffeination of green tea leaves

The decaffeination of green tea using supercritical carbon dioxide (SC-CO₂) was optimized by response surface methodology (RSM) for the maximal removal of caffeine, and the coextration of chlorophylls was also monitored during decaffeination. The experimental conditions for the SC-CO₂ extraction of caffeine were set up according to the Box-Behnken design of RSM. The relationships between the extraction yield of caffeine and various parameters used for the SC-CO₂ extraction such as pressure, temperature and concentration of ethanol were studied at a fixed CO₂ flow rate. The extraction yields of caffeine and total chlorophyll were significantly influenced by extraction pressure, temperature and concentration of cosolvent, and their extraction yields behaved almost in parallel at different extraction conditions that were obtained by varying pressure, temperature and ethanol cosolvent concentration. At the optimal decaffeination conditions such as 3.0 g of 95% (v/v) ethanol cosolvent per 100 g of CO₂, 23 MPa, 63 °C and an extraction duration of 120 min for 10 g of green tea leaves, the extraction yields for caffeine and catechins were 96.60% (w/w) and 40.61% (w/w), respectively, and the substantial coextraction of total chlorophyll (43.09% of the total amount) was also observed during the decaffeination process.     

大孔树脂分离提取发酵液中灵芝三萜类物质

利用大孔树脂富集提取发酵液中灵芝三萜。通过比较4种大孔树脂对灵芝三萜的吸附和解吸性能，发现AB-8树脂最适合灵芝三萜的提取。结果表明：控制体积流量为2mL／min、pH值2，AB-8树脂的饱和吸附量达到最大，为8．837mg／g（以干树脂质量计）。确立了最佳洗脱方案，依次用水、体积分数20％、40％、95％乙醇溶液分段洗脱。     

Bioactive components and antioxidant properties of γ-aminobutyric acid (GABA) tea leaves

Various ethanolic concentrations (0–95%, v/v) and temperatures (25–95 °C) were used to extract γ-aminobutyric acid (GABA) tea leaves. Extraction yields, and contents of total phenols, various catechins, GABA, theanine, and antioxidant properties of extracts were determined. The 50% (v/v) ethanol at 50–95 °C gave higher yields (32.05–32.56 g dried extract/100 g dried tea leaves). The bioactive components and antioxidant properties of extracts were affected by the ethanolic concentrations and temperatures. Among catechins, epigallocatechin gallate was the main catechin in all extracts, followed by epigallocatechin, epicatechin, epicatechin gallate, gallocatechin and gallocatechin gallate. The 50–75% (v/v) ethanol at 75–95 °C gave higher contents of ester type (102.92–104.54 mg/g extract) and non-ester type (61.75–63.55 mg/g extract) catechins. Water at 50–75 °C gave higher GABA and theanine contents and higher chelating ability of extracts. The 75% (v/v) ethanol at 25–75 °C gave higher scavenging ability and reducing power of extracts. Based on dried tea extracts or leaves results obtained, the optimal extraction conditions to maintain the total contents of various catechins, GABA and theanine in the maximum level were 50% ethanol (v/v) and 75–95 °C.     

Analysis of tea catechins in vegetable oils by high‐performance liquid chromatography combined with liquid–liquid extraction

In this study, a method was developed for the determination of various tea catechins in vegetable oils. Firstly, vegetable oils including tea seed oil, sunflower seed oil and soya bean oil were extracted by methanol/water (40:60, v/v), and then, a high‐performance liquid chromatography (HPLC) method was developed for the simultaneous determination of GA, caffeine, EGC, EGCG, EC, ECG, GC, GCG, C and CG. For the compounds detected in tested vegetable oils, LODs were in the range of 0.05–1.65 ng, both intraday and interday relative standard deviations (RSDs) were <5.0%, and the recovery rates were in the range of 96.2–100.5% with RSD <3.7%. The results showed in vegetable oils which declared to had added tea catechins in, the concentrations of tea catechins were less than that showed in package label, and the content of EGCG was the highest in all samples. Therefore, the advancement made in our study will facilitate studies of tea catechins in oil industry.     

Stop for tea? Enzyme inhibitors from tea – what good are they?

Tea possesses many bioactive components including polyphenols, theanine and caffeine. Inhibitory effect of these components on the various enzymes involved in some chronic diseases was reviewed in this study. Many studies revealed that anti‐obesity of tea was mainly ascribed to the polyphenols which could inhibit the activity of the enzymes related to diet metabolism such as α‐amylase, α‐glucosidase and lipase. Inhibitory effect of catechins and caffeine against β‐ and γ‐secretase, acetylcholinesterase, protein kinase C and histone deacetylase might be responsible for the prevention from nervous system diseases. Cytochrome P450 enzymes, cytosolic sulfotransferases, cyclooxygenase‐2 and phosphoinositide‐3‐kinase could be efficiently suppressed by catechins, which would decrease the risk of cancer initiation and proliferation; theanine could lower the activity of some anticarcinogen‐activated enzymes and alleviate the adverse effect of cancer cure. Catechins and caffeine exhibited significant inhibition against the matrix metalloproteinases, histidine decarboxylase and many kinases related to inflammation. Thus, catechins, theanine and caffeine might be employed as inhibitors of the enzymes associated with these chronic diseases.     

A dark brown roast coffee blend is less effective at stimulating gastric acid secretion in healthy volunteers compared to a medium roast market blend

Coffee consumption sometimes is associated with symptoms of stomach discomfort. This work aimed to elucidate whether two coffee beverages, containing similar amounts of caffeine, but differing in their concentrations of ^βN‐alkanoyl‐5‐hydroxytryptamides (C5HTs), chlorogenic acids (CGAs), trigonelline, and N‐methylpyridinium (N‐MP) have different effects on gastric acid secretion in healthy volunteers. The intragastric pH after administration of bicarbonate with/without 200 mL of a coffee beverage prepared from a market blend or dark roast blend was analyzed in nine healthy volunteers. Coffee beverages were analyzed for their contents of C5HT, N‐MP, trigonelline, CGAs, and caffeine using HPLC‐DAD and HPLC‐MS/MS. Chemical analysis revealed higher concentrations of N‐MP for the dark brown blend (87 mg/L) compared to the market blend coffee (29 mg/L), whereas concentrations of C5HT (0.012 versus 0.343 mg/L), CGAs (323 versus 1126 mg/L), and trigonelline (119 versus 343 mg/L) were lower, and caffeine concentrations were similar (607 versus 674 mg/mL). Gastric acid secretion was less effectively stimulated after administration of the dark roast blend coffee compared to the market blend. Future studies are warranted to verify whether a high ratio of N‐MP to C5HT and CGAs is beneficial for reducing coffee‐associated gastric acid secretion.     

Preparative separation and purification of phenolic compounds from Canarium album L. by macroporous resins

BACKGROUND: Canarium album L. (also called Chinese olive) is a traditional medicine material in China, and phenolic compounds from C. album possess great pharmacological activities. To obtain high‐purity phenolics from C. album, a crude extract of C. album phenolics was prepared by ethanol extraction. The use of macroporous resins for further separation and purification of phenolics in the extract was studied. RESULTS: Through static adsorption and desorption tests, AB‐8 resin was chosen for the separation of phenolics because of its higher adsorption capacity and desorption ratio than other resins. Then, dynamic adsorption and desorption experiments were carried out on an AB‐8 resin packed column to obtain optimal separation parameters. The highest adsorption capacity of AB‐8 was achieved when variables including initial concentration (C₀), feed flow rate and feed volume were 10 mg mL^?1, 2 mL min^?1 and 9 bed volumes (BV), respectively, and saturated resin was first washed with 5 BV of water to remove impurities, then a purified product containing more than 85% of C. album phenolics was obtained by desorbing the resin with 2.5 BV of 70% (v/v) aqueous ethanol at flow rate of 1 mL min^?1, and the recovery of phenolics was up to 75%. In addition, five phenolic compounds in the product were identified as gallic acid, ellagic acid, corilagin, hyperin and kaempferol‐3‐glucopyranoside by UV and LC–ESI–MS analysis. CONCLUSION: The results in this study could provide scientific references for the large‐scale production of phenolics from C. album. Copyright © 2007 Society of Chemical Industry     

Combination Inhibition Activity of Nisin and Ethanol on the Growth Inhibition of Pathogenic Gram Negative Bacteria and Their Application as Disinfectant Solution

Nisin and ethanol have been used as antimicrobial agents in food industry. However, nisin alone could not inhibit the growth of gram‐negative bacteria, except in combination with a chelating agent, EDTA, or organic acid. This research aimed to study the survival of Escherichia coli O157: H7, Salmonella Typhimurium TISTR 292 and Salmonella Enteritidis DMST 17368 after treatment with nisin at 100, 200, 300, 500, 800, or 1000 IU/mL and ethanol at 70%, 50%, 30%, 20%, or 10% (v/v) alone and in combination. None of all nisin concentrations could reduce the growth of target strains. While 20% ethanol (v/v) having no negative effect on human health, could slightly reduce the growth of target strains. However, the combination of nisin at 500, 800 or 1000 IU/mL and 20% ethanol displayed significant growth reduction at 15 min were below 1 log CFU/mL. Thus, the minimum inhibitory concentration of nisin and ethanol was 500 IU/mL and 20% (v/v), respectively. The release of fatty acid, genetic materials and scanning electron microscope suggested that nisin‐ethanol treated cells have altered permeability causing bacterial growth inhibition. Comparison treatment of combined solution and commercial chloride based sanitizer were done for all target strains on stainless steel surface. Survivals of three target strains were below 1 log CFU/mL. The result suggested that combined solution of nisin and ethanol may be a beneficial sanitizer for food industry to inhibit the growth of E. coli O157:H7 and Salmonella sp.     

Effects of single dose and regular intake of green tea (Camellia sinensis) on DNA damage,DNA repair,and heme oxygenase‐1 expression in a randomized controlled human supplementation study

Regular intake of green tea (Camellia sinensis) lowers DNA damage in humans, but molecular mechanisms of genoprotection are not clear. Protection could be via direct antioxidant effects of tea catechins, but, paradoxically, catechins have pro‐oxidant activity in vitro, and it is hypothesized that mechanisms relate to redox‐sensitive cytoprotective adaptations. We investigated this hypothesis, focusing particularly on effects on the DNA repair enzyme human oxoguanine glycosylase 1 (hOGG1), and heme oxygenase‐1, a protein that has antioxidant and anti‐inflammatory effects. A randomized, placebo‐controlled, human supplementation study of crossover design was performed. Subjects (n = 16) took a single dose (200 mL of 1.5%, w/v) and 7‐days of (2 × 200 mL 1%, w/v per day) green tea (with water as control treatment). Lymphocytic DNA damage was ～30% (p < 0.001) lower at 60 and 120 min after the single dose and in fasting samples collected after 7‐day tea supplementation. Lymphocytic hOGG1 activity was higher (p < 0.0001) at 60 and 120 min after tea ingestion. Significant increases (p < 0.0005) were seen in hOGG1 activity and heme oxygenase‐1 after 7 days. Results indicate that molecular triggering of redox‐sensitive cytoprotective adaptations and posttranslational changes affecting hOGG1 occur in vivo in response to both a single dose and regular intake of green tea, and contribute to the observed genoprotective effects of green tea.     

Presence of two forms of methylated (–)‐epigallocatechin‐3‐gallate in green tea

Crude catechins extract from Chinese green tea were fractionated using Sephadex LH‐20 column chromatography. The fraction containing (–)‐epigallocatechin‐3‐gallate (EGCG) was then subjected to a semipreparative high‐performance liquid chromatography (HPLC). Using a mobile phase of water : dimethyl formamide : methanol : acetic acid (157 : 49 : 2 : 1 v/v/v/v( the mixture of two methylated catechins was separated and isolated. According to mass spectrometry (MS) and nuclear magnetic resonance (¹H‐NMR) date, these compounds were identified as (–)‐epigallocatechin‐3‐(3‐O‐methylgallate) and (–)‐epigallocatechin‐3‐(4‐O‐methylgallate).