茶叶浸提液微波辅助萃取过程中溶剂选择的差异

研究了绿茶中活性成分儿茶素单体在不同性质的溶剂(甲醇、乙醇、水、乙酸乙酯)下,微波辅助萃取的效率和选择性差异。实验结果发现,酯型儿茶素单体(L-EGCG和L-ECG)用甲醇或乙醇萃取较用水萃取效率高,其他三种简单儿茶素单体(L-EGC,D,L-C,L-EC)则是以纯水作为萃取溶剂萃取效率为佳。乙酸乙酯对儿茶素各单体的浸出量相对水、甲醇和乙醇都大幅减少。适当增加萃取溶剂的离子浓度,会有利于微波辅助萃取效率的提高,但溶剂的离子浓度过大时,会降低儿茶素各单体的浸出量。     

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.     

Novel oil extraction technologies: Process conditions,quality parameters,and optimization

Conventional techniques of extracting oil using organic solvents pose health, safety, and environmental concerns. In modern extraction methods, green solvents such as water, ethanol, ethyl acetate, carbon dioxide, ionic liquids, and terpenes are currently gaining prominence. These green solvents present no signs of pollution and remain in liquid form over a temperature range of 0 to 140 °C. Other techniques covered in this review include microwave‐assisted enzymatic extraction, ultrasound‐assisted extraction, supercritical fluid technology, high pressure–assisted extraction, and pulse electric field–assisted extraction. These techniques are considered environmentally friendly because they exhibit less hazardous chemical synthesis, use renewable feedstock, and reduce the chemical load and emissions generated by organic solvents. Aqueous enzymatic extraction is a novel technique that uses enzymes as the medium for extraction of oil. Selection of the enzymes solely depends on the structure of the oilseed and the composition of the cell wall. Studies reveal an enzyme to substrate ratio of 1% to 8%, the temperature of 40 to 55 °C, and a pH of 4 to 8 to be typical for enzymatic extraction of oil from different oilseeds. Microwave‐assisted extraction has proven to impart significant effects on mass transfer and offers high throughput and extraction efficiency. A microwave power of 275 to 1,000 W and a temperature range of 30 to 60 °C are noticed in the different studies. The review presents a comprehensive account of the modern extraction techniques, the parameters responsible for yield and quality, and their industrial applications. Besides, the review highlights the optimized parameters for oil extraction from different oil‐bearing materials.     

Phenolic content and antioxidative capacity of green and white tea extracts depending on extraction conditions and the solvent used

The efficiencies of different solvents in the extraction of phenolics from bagged and loose leaves of white and green tea, after different extraction times, as well as the antioxidative capacity of the obtained extracts, were investigated. The developed HPLC method has the potential to separate and determinate 17 phenolics widely distributed in plants, but in investigated tea extracts only four catechins and traces of three flavonols and one flavone were separated and detected based on comparison with authentic standards. The extraction efficiency of phenolics depended strongly on the time of extraction and the solvents used. The extraction of catechins from green tea was significantly affected by the form (bagged or loose) of the tea, whereas this effect was shown not to be statistically significant for white tea. Green tea was a richer source of phenolics than was white tea. The extraction of phenolics from white tea by water could be accelerated by the addition of lemon juice. Aqueous ethanol (40%) was most effective in the prolonged extraction of catechins. The antioxidative capacity of the investigated tea extracts correlated with their phenolic content.     

溶剂法提取分蘖葱头有机硫化合物及其GC-MS分析

为研究有机溶剂对分蘖葱头中有机硫化合物提取及成分的影响,采用二氯甲烷、乙酸乙酯、正己烷3种溶剂提取分蘖葱头中有机硫化合物,并利用顶空固相微萃取和气相色谱-质谱联用技术对不同溶剂提取到有机硫化合物进行比较分析。结果表明:二氯甲烷提取分蘖葱头中有机硫化合物的最佳工艺条件为浸提时间4 h、料液比1∶4(g/m L)、搅拌速率250 r/min,在此条件下有机硫化合物得率为(0.413 3±0.007)%。乙酸乙酯、正己烷有机硫化合物得率分别为(0.273 3±0.011)%、(0.288 9±0.009)%。3种溶剂共提取分离出45种组分,均检测出9种有机硫化合物,其中相对含量较高的均为噻吩类和硫醚类。另外,以二氯甲烷为溶剂提取出独有的有机硫化合物12种;以乙酸乙酯为溶剂提取出独有的有机硫化合物3种;以正己烷为溶剂提取出独有的有机硫化合物8种。     

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.     

Green ultra-high pressure extraction of bioactive compounds from Haematococcus pluvialis and Porphyridium cruentum microalgae

Microalgae are considered prolific sources of bioactive compounds that can be useful for nutraceuticals. In this study, the potential of ultra-high pressure extraction (UHPE) for the simultaneous cell disruption and extraction of bioactives from two microalgae species, Haematococcus pluvialis and Porphyridium cruentum, was evaluated. The variables studied to extract carotenoids for H. pluvialis were pressure (100–600 MPa) and number of cycles (1 and 3 cycles) whereas the variables studied to obtain bioactives such as B-phycoerythrin, carotenoids, and PUFAs for P. cruentum were pressure (100–600 MPa) and different extraction solvents (water, ethanol, ethyl acetate or ethanol/d-limonene), generally recognized as safe (GRAS). The UHPE results showed significant increase on the extraction of carotenoids (109.74–119.34 mg per g extract) from H. pluvialis using 1 cycle of 20 min regardless of the pressure used. For P. cruentum, an UHPE with water provided extracts enriched in B-phycoerythrin (up to 144.43 mg per g extract), while subsequent UHPE using ethanol, ethyl acetate or ethanol/d-limonene 1:1 (v/v) provided extracts enriched in carotenoids (up to 65.05 mg per g extract) and polyunsaturated fatty acids (mainly eicosapentanoic acid and linoleic acid). Therefore, UHPE proved to be a viable green alternative for the recovery of bioactives from microalgae biomass.Industrial relevance: Microalgae are promising sources of bioactives such as B-phycoerythrin, carotenoids and polyunsaturated fatty acids. The potential of ultra-high-pressure extraction (UHPE) has been demonstrated as a fast and viable eco-friendly alternative using GRAS solvents (water, ethanol, ethyl acetate or ethanol/d-limonene) for the simultaneous cell disruption and extraction of these bioactives from Haematococcus pluvialis and Porphyridium cruentum. The bioactives obtained with one step or two step-UHPE process can be used in an array of food, cosmetic and pharmaceutical applications.     

Column-chromatographic extraction and separation of polyphenols, caffeine and theanine from green tea

A highly efficient column-chromatographic extraction (CCE) followed by sequential adsorption to extract and separate bioactive compounds from green tea was developed. Tea powder was loaded into columns with 4-fold solvents and eluted through a cyclic CCE. High-quality tea extracts with greater than 90% extraction efficiencies of polyphenols, epigallocatechin-3-gallate, caffeine, theanine and polysaccharides were obtained with 4-fold water circulated five times among different columns at 70 °C. Similar results, except for low polysaccharide extraction (35.5%), were obtained with 4-fold 30% ethanol circulated three times at room temperature. The highly concentrated water extraction was directly passed through columns of polyamide, DM130 macroporous and 732 ion exchange resins, resulting in high-purity polyphenols (99%), caffeine (98%) and theanine (98%) after simple purification of the eluates from each column. This method uses simple equipment, minimum solvents and can be used for both quantitative analysis and continuous preparation of high-quality tea extracts and bioactive compounds.     

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。     

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.     

The protective effect of green and black teas (Camellia sinensis) and their identified compounds against murine sepsis

Several compound classes could be identified in the infusion of green tea (GTI) and black tea (BTI) from Camellia sinensis, mainly catechins and their gallate derivatives in GTI and their oxidation products, theaflavins and theasinensins, in BTI. We also managed to identify other components, such as proanthocyanidins, flavonoid glycosides, alkaloids, hydroxybenzoic and hydroxycinnamic acids and saponins. The infusions were fractionated and the ethyl acetate fractions [green tea ethyl acetate fraction (GEAF) and black tea ethyl acetate fraction (BEAF)] have concentrated the catechins, theaflavins and caffeine. So, the infusions, fractions and major compounds identified from both teas were assayed against murine sepsis, in order to assess whether they are effectively protecting from this pathology. The infusions at 70 mg/kg resulted in a decrease of sepsis mortality in 43% (GTI) and 40% (BTI), respectively. The ethyl acetate fractions were also efficient, allowing a survival rate of 50% (GEAF) and 66.6% (BEAF) at concentrations of 30 and 70 mg/kg, respectively. The main components from GEAF and BEAF were also assayed; epigallocatechin gallate (10 mg/kg), theaflavins (9 mg/kg) and caffeine (18 mg/kg) showed a survival rate of 50%, 40% and 20%, respectively. This protective effect can be explained, at least in part, by some of these compounds' ability to modulate some important inflammatory parameters, such as neutrophil influx, avoiding its accumulation in lungs, depletion of the pro-inflammatory cytokines (TNF-α and IL-6), increase the anti-inflammatory cytokine (IL-10) and, also, a significant decrease in tissue expression of iNOS and COX-2.     

Optimal extraction conditions for simultaneous determination of catechins and caffeine in green tea leaves

The amount of catechins and caffeine in green tea are considered a standard of quality evaluation for green tea. The objectives of this study were to investigate the optimal conditions for simultaneous extraction of catechins and caffeine and to compare their quantity and composition within the exotic tea varieties. Moreover, 8 tea varieties of exotic origin were tested with the optimal extraction conditions found in this study. Regarding the caffeine and catechins contents, a 2 h room temperature extraction using a 2% phosphoric acid-40% EtOH solution was the most suitable simultaneous extraction method. The total catechins and caffeine contents of the tea leaves ranged 44.25–64.80 and 9.26–13.11 mg/g, respectively. The optimal extraction method of catechins and caffeine in tea leaves may be used for further studies and breeding of high quality tea plants.     

普洱熟茶不同溶剂萃取层中儿茶素及黄酮醇类化合物差异的研究

目的 探索普洱熟茶在不同溶剂(乙酸乙酯和正丁醇)萃取中儿茶素和黄酮醇类化合物的组成及含量的差异,构建一种有效提取普洱熟茶中儿茶素及黄酮醇类物质的方法.方法 以普洱熟茶(2008年生产)的水提物为研究对象,分别用乙酸乙酯和正丁醇溶剂萃取的萃取层为分析供试样,采用高效液相色谱法(high performance liqui...     

Quantitative and Qualitative Portrait of Green Tea Catechins (Gtc) Through Hplc

Green tea (Camellia sinensis) is a prosperous source of polyphenols, especially catechins. In the current research, an effort was made to optimize the extraction conditions for maximum yield of catechins from the local green tea Qi-Men. For the purpose, three different solvents were used, i.e., aqueous ethanol (50%), aqueous methanol (50%), and water at different time intervals (20, 40, and 60 min). Green tea catechins were quantified through HPLC using a C18 column and UV detector. The antioxidant activity of green tea catechins was measured through in vitro tests including DPPH radical scavenging ability and antioxidant activity. Results showed that extraction through aqueous ethanol resulted in maximum yield of green tea catechins (17400 ± 0.19 mg/100 g green tea leaves. Moreover, epigallocatechin, epigallocatechin gallate, epicatechin gallate, and epicatechin ranged from 4.26 ± 0.09 to 6.4 ± 0.2, 12.1 ± 0.123 to 17.7 ± 0.3, 1.32 ± 0.03 to 1.81 ± 0.02, 5.48 ± 0.099 to 8.6 ± 0.2 g/100 g of dry-extract, respectively. Furthermore, highest antiradical (80.65 ± 3.69%) and antioxidant activity (67.12 ± 3.08%) were observed in catechins extracted through aqueous ethanol.     

Extraction and analysis of antioxidant components from Origanum dictamnus

Three alternative extraction procedures were carried out in order to separate the antioxidant components and isolate an efficient extract from Origanum dictamnus. Procedure A included sequential extractions with petroleum ether (PE), diethyl ether (DE) and ethanol; procedure B sequential extractions with PE and ethyl acetate (EAc); procedure C a single step extraction with ethanol. The most efficient radical scavengers, according to the DPPH method, were isolated in ethanol extract of procedure A (mainly rosmarinic acid), followed by ethanol extract of procedure C. However, both ethanol extracts had low solubility in oil and could not protect it. EAc and DE extracts, containing mainly apigenin and epirosmanol ethyl ether, presented lower radical scavenging activity but were very effective against autoxidation of cottonseed oil (a concentration of 200 ppm was adequate to stabilize it). PE extract protected the oil effectively at concentration of 350 ppm, while being the least active against DPPH.Industrial relevanceThis study examines Origanum dictamnus as a potential antioxidant additive for edible oils and fats. Three different extraction procedures of the raw material with non-toxic organic solvents were used to recover the sum of the extractable compounds and specific fractions respectively. The extraction procedures, accompanied with analytical techniques, led to the characterization of the antioxidant properties and the composition of the plant as well as the isolation of very efficient oil-soluble antioxidant fractions.     

Toxicity and repellent action of Coffea arabica against Tribolium castaneum (Herbst) adults under laboratory conditions

Coffea arabica parchment extracts and caffeine isolated from the plant were evaluated randomly against 1-week-old adults of red flour beetle, Tribolium castaneum for fumigant toxicity and repellent action under laboratory conditions. The effects on detoxification enzymes and neuroenzyme was also determined. Among the various extracts prepared sequentially using hexane, dichloromethane, ethyl acetate and methanol as solvents, the dichloromethane extract did repel insects on contact (EC₅₀ = 4380.65 ppm). The repellence was more prominent when an olfactory response was measured (EC₅₀ = 2571 ppm). The active ingredient isolated from dichloromethane extract was identified as caffeine which showed very strong repellency as compared to the extract. In terms of toxicity of this extract, a significant mortality was recorded in fumigation assay (LC₅₀ = 5555 and 791 ppm, 24 and 48 h post-treatment, respectively). However, caffeine did not induce similar toxicity as the dichloromethane extract. The studies on the impact on detoxification enzymes of T. castaneum showed that dichloromethane extract inhibited carboxyl esterase activity, which possibly led to high toxicity. However, caffeine inhibited glutathione-s-transferase and induced carboxylesterase enzymes. It was, therefore, obvious that C. arabica parchment crude extracts have dual effects against T. castaneum adults, i,e, fumigant toxicity and repellent effects. However, the active compounds responsible for the two activities are surely different as caffeine could only induce repellent action against the beetles and the toxic compound needs to be identified, which is presently being investigated.     

Effects of aqueous brewing solution pH on the extraction of the major green tea constituents

The pH of the aqueous brewing solution was maintained at values ranging from 1 to 9 during the green tea extraction and the effects on the tea's extracted constituents were studied. The epistructured catechins were stable under acidic conditions but epimerized or degraded at pH ≥ 6. The extractable solids contained more epistructured catechins at pHs 3–5 but more non-epistructured catechins at pHs 6–7. More tea cream was obtained at pH 1 but the concentration of catechins, caffeine and theanine was low in this fraction. Therefore, to maximize the extraction of the epistructured catechins and to minimize their epimerization and degradation and to maximize the extraction of caffeine and theanine, the results suggest that the pH should be maintained between 3 and 5.3 during the aqueous brewing process.     

Digestive stability and absorption of green tea polyphenols: Influence of acid and xylitol addition

The objective of this study was to determine the effect of sugar substitute and acid on digestive stability and intestinal uptake of catechins in Ready-To-Drink (RTD) green tea. Green tea extracts formulated with prescribed amounts of sucrose (200, 500, and 1000 mg), glucose (280, 700, and 1400 mg), and xylitol (200, 500, and 1000 mg) in combination with citric acid (10 mg) or vitamin C (10 mg) were subjected to an in vitro digestion model coupled with Caco-2 cells. Green tea extracts only showed a poor digestive recovery (5.3%) of total catechins and EGC and EGCG significantly decreased with the digestive recovery of 4.6% and 6.1%, respectively. However, measured amount of EGC, EGCG, or ECG in digestive fluids and caco-2 human intestinal cell significantly increased by adding citric acid or vitamin C. There was remarkable increase of digestive recovery of total catechins in green tea with xylitol/citric acid and xylitol/vitamin C by 1.7–2.5 times and 3 times, respectively, with different amounts of xylitol. It was also determined that intestinal uptake of total catechins significantly increased 6 and 11 times in green tea with xylitol/citric acid and xylitol/vitamin C, respectively, compared to green tea only.     

HPLC Analysis of Catechins, Theaflavins, and Alkaloids in Commercial Teas and Green Tea Dietary Supplements: Comparison of Water and 80% Ethanol/Water Extracts

ABSTRACT:  To help meet the needs of consumers, producers of dietary tea supplements, and researchers for information on health-promoting tea compounds, we compared the following conditions for the extraction of tea leaves and green tea-containing dietary supplements: 80% ethanol/water at 60 °C for 15 min and boiled water for 5 min. The following 7 catechins, 4 theaflavins, and 3 alkaloids were separated in a 70-min single HPLC analysis: (−)-epigallocatechin, (−)-catechin, (+)-epicatechin, (−)-epigallocatechin-3-gallate, (−)–gallocatechin-3-gallate, (−)-epicatechin-3-gallate, (−)-catechin-3-gallate, theaflavin, theaflavin-3-gallate, theaflavin-3'-gallate, theaflavin-3,3'-digallate, caffeine, theobromine, and theophylline. The following ranges of concentrations of flavonoids (catechins plus theaflavins) in the tea leaves extracted with 80% ethanol were observed (in mg/g): in 32 black teas, 19.8 to 115.1; in 24 green teas, 12.3 to 136.3; in 14 specialty teas, 4.9 to 118.5; in 7 herbal teas, 0 to 46.0. Total alkaloids in all teas ranged from 0 to 32.6 mg/g. Significantly greater amounts of flavonoids were extracted from the tea leaves with aqueous ethanol than with boiled water. Levels of tea catechins in 10 capsules sold as dietary supplements were about 50 to 75% lower than the amounts listed on the labels. Catechin content of 4 commercial green tea extracts ranged from 96 to 696 mg/g. The results make it possible to maximize the extraction of tea compounds to better relate the flavonoid and alkaloid content of teas and dietary tea supplements to their health-promoting effects.     

核桃青皮提取物的抑真菌活性研究

核桃青皮中含有种类较为丰富对供试真菌具有抑菌活性的次生代谢物质。以核桃青皮为原料,乙醇、石油醚、正丁醇、乙酸乙酯以作为提取剂进行浸提,得到核桃青皮的提取液,选取酵母菌、青霉、木霉、马拉色菌、脚气真菌作为供试菌种,通过实验观察不同溶剂提取液对供试菌种的抑制作用,研究核桃青皮提取物对真菌的抑制作用。核桃青皮中含有胡桃醌、多糖、黄酮等多种活性成分,利用分光光度法测定黄酮、胡桃醌、多糖的吸光值,通过吸光值计算提取物中各成分的质量浓度。结果表明：核桃青皮不同极性溶剂的浸提液对酵母菌、青霉、木霉均有抑制效果。核桃青皮95%乙醇浸提液对脚气真菌的抑制效果显著,抑菌率为59.64%;正丁醇核桃青皮浸提液对脚气真菌、马拉色菌有抑制效果。通过核桃青皮不同极性溶剂浸提液抑菌率的比较,和核桃青皮中所含三种活性物质的浓度与抑菌机制可知,核桃青皮不同极性溶剂的浸提液中主要起抑菌作用的是胡桃醌。