Microwave-assisted Extraction Of Polyphenols Research Articles

Microwave-Assisted Extraction of Polyphenols from Bitter Orange Industrial Waste and Identification of the Main Compounds.

In this work, the extraction of phenolic compounds from orange waste (OW) obtained after the industrial extraction of neohesperidin from bitter oranges (Seville oranges) was assayed by microwave-assisted extraction (MAE) and Soxhlet extraction (SE). The extraction agents were ethanol and acetone. For SE, aqueous solutions of both extraction agents were used at 50%, 75%, and 100% (v/v). For MAE, a design of experiments was applied to determine the conditions that maximize the extraction yield. The independent variables were temperature (from 20 to 75 °C), process time (between 10 and 20 min), and percentage of extraction agent (v/v) in the extraction solution (50%, 75%, and 100%). Following that, the extracts were analyzed by ultra-high-performance liquid chromatography to identify the main phenolic compounds extracted. Results showed that 50% (v/v) ethanol or acetone was the extraction agent concentration that maximized the extraction yield for both SE and MAE, with the yields of MAE being higher than those of SE. Thus, the highest extraction yields on a dry basis achieved for MAE were 16.7 g/100 OW for 50% acetone, 75 °C, and 15 min, and 20.2 g/100 OW for 50% ethanol, 75 °C, and 10.8 min, respectively. Finally, the main phenolic compounds found in the orange waste were naringin, hesperidin, neohesperidin, and naringenin (i.e., flavonoids).

Microwave-Assisted Extraction of Polyphenols from Eucalyptus Bark—A First Step for a Green Production of Tannin-Based Coagulants

Tannins are natural polyphenolic compounds widely found in plants. The production of natural coagulants for water treatment is one of their new applications. Polyphenols extraction is the first step for synthesizing tannin-based coagulants. Eucalyptus globulus bark (EGB), an abundant by-product of the pulp and paper industry, usually applied as fuel for energy production, was used in this work as a tannin source. The extraction of polyphenols from EGB was studied using water as a solvent. Extraction assays employing different extraction techniques were conducted. Microwave-assisted extraction showed superior performance and was further optimized. The influence of irradiation time, water-to-bark ratio, and temperature were evaluated using Response Surface Methodology. The extraction yield and the total phenolic content of the extract were modeled as function of the extraction conditions. The overall best conditions that maximize both responses were obtained through multi-response optimization. Optimized values (15% of extraction yield and a phenolic content of 354 mg of gallic acid equivalents per gram of extract) were predicted for an extraction time of 15 s, a liquid-to-solid ratio of 48.5 mL/g, and 141 °C. The extract generated under these conditions presented a condensed tannin content of 645 mg/g, expressed in terms of catechin equivalents. EGB presented good tannin-extractable contents to produce natural coagulants.

Microwave-Assisted Extraction of Polyphenols from Blackcurrant By-Products and Possible Uses of the Extracts in Active Packaging.

The design of experiment (DoE) approach was used to optimize the extraction of polyphenols from blackcurrant by-products with microwave-assisted extraction and deionized water as a green solvent. Three factors (microwave power, extraction time, and solvent/matrix ratio) were evauated, and a central composite orthogonal design (CCO) was applied in order to reduce experimental runs. Empirical models relating the response and process parameters were developed. The validity of the models was tested using an analysis of variance (ANOVA). The optimal extraction conditions were found using the highest value of microwave power (780–800 W) and the lowest extraction time (60 min) and solvent/matrix ratio (10 m/g). Compared with conventional solvent extraction, the polyphenol yield increased by 25% after applying the optimized MAE process. The obtained extract was used to realize a sustainable active maltodextrin (Glucidex 2) pad using an electrospinning technique. The antimicrobial and antioxidant activities of the pads were tested on the post-harvest storage of raspberries. Two set of experiments were carried out. The recorded results showed that the pad had antimicrobial activity on the tested fruit samples and implied the possibility of using it to extend the shelf-life of the fruits.

Optimization of conventional solid-liquid extraction and microwave-assisted extraction of polyphenols and antioxidant compounds of blueberry (Vaccinium corymbosum) pomace through response surface methodology

BACKGROUND: Blueberries contain large amounts of phenolic compounds as well as a higher concentration of anthocyanins than other berries. The peel of these fruits contains most of the anthocyanins and therefore pomace is left with the largest quantity of valuable phenolic compounds. Extraction is the most critical step to obtain such compounds. OBJECTIVE: This study aims to optimize the extraction of polyphenols and antioxidant compounds from blueberry pomace by solid-liquid extraction (SLE) and microwave-assisted extraction (MAE). METHODS: A Pareto chart was used to confirm the factor with the highest impact, response surface for analyzing the effect of extraction conditions on total phenol content (TPC) (through Folin-Ciocalteu), total anthocyanin content (TAC) (through differential pH), antioxidant capacity (AC) (through DPPH assay) and the Box-Behnken matrix to determine the optimal conditions for marc extraction with each method. RESULTS: Ethanol concentration is an impact factor for both methods, as well as irradiation method, radiation power for MAE and temperature for SLE. Regarding SLE and MAE extraction, under optimal conditions, a TCP content of 335.95 and 426.19 (mg GAE/100 g), TAC 272.69 and 389.64 (mg Cyn-3-glu/100 g), and CA 528.96 and 654.11 (mg TE/100 g) was obtained, respectively. CONCLUSIONS: The performance of phenolic compound extraction via MAE method is better than that of SLE.

The role of heating step in microwave-assisted extraction of polyphenols from spent coffee grounds

Microwave-assisted extraction is currently one of the most studied techniques for biomolecule recovery from natural sources, due to its favorable features for the treatment of thermo-sensitive compounds. In this work, the kinetic of antioxidant extraction from spent coffee grounds was investigated, focusing the attention on the effects of initial thermal ramp on the total polyphenol concentration, total solids and antiradical power of the final product. The hydro-alcoholic extracts demonstrated to be very rich of antioxidants with high antiradical power (from 0.45 to 0.88μTroloxequivalent/g dried spent coffee grounds), and their quality was significantly affected by the investigated variables. Peleg’s model, was successfully used to describe extraction kinetics, whose investigation revealed that 10min of heating time at 423K provided the highest concentration of polyphenols, and resulted as a good compromise to perform a fast extraction with high extraction yields (43mgCaffeic Acid Equivalent/g dried spent coffee grounds after 60min of extraction).

Microwave-Assisted Extraction and Antioxidant Activities of Polyphenols from Camellia Fascicularis Leaves

A microwave-assisted extraction method was established and optimized for extracting polyphenols from the leaves of Camellia fascicularis, which possess antioxidant properties. Microwave-assisted extraction of polyphenols from C. fascicularis leaves was optimized using response surface methodology. The influential factors, including ethanol concentration, ratio of liquid to raw material, and microwave power, were studied to optimize the extraction process, while setting the irradiation time to 20 s. The optimum process parameters, namely, ethanol concentration of 50%, the ratio of liquid to raw material of 32 mL/g, and microwave power of 160 W, contributed to the highest polyphenol yield of 106.1 mg GAE/g dw. The crude polyphenols were purified through an HP-20 macroporous adsorption resin column to obtain purified C. fascicularis polyphenols. Antioxidant assay demonstrated that purified polyphenols from C. fascicularis showed significant antioxidant activities in a concentration-dependent manner for scavenging hydroxyl, 2,2-diphenyl-1-picrylhydrazyl, and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) radicals. Thus, microwave-assisted extraction was an effective method of extracting polyphenols from C. fascicularis leaves, which might be an excellent food material with potential antioxidant properties.

Optimisation of microwave-assisted extraction parameters for antioxidants from waste Achillea millefolium dust

Microwave-assisted extraction of polyphenols and flavonoids from waste Achillea millefolium (yarrow) dust was optimised using the response surface methodology. The influence of the extraction time (13–47s), ethanol concentration (53–87%), liquid/solid ratio (13–47mL/g) and microwave power (170 and 340W) was studied. The optimised conditions for the maximal recovery of polyphenols and flavonoids were as follows: 33s of extraction time, 70% of ethanol concentration, 40mL/g of liquid/solid ratio and 170W of microwave power. Under the optimal conditions, 237.74±2.08mg of gallic acid equivalents per g of extract dry matter of total polyphenols, and 42.95±1.32mg of quercetin equivalents per g of extract dry matter of total flavonoids were extracted. The optimal extract strongly reduced the diphenylpicrylhydrazyl radical (IC50 7.89μg/mL). The antioxidant activity of the obtained extracts was in correlation to the total polyphenol content in yarrow extracts. Compared to the conventional extractions (solid–liquid extraction (24h) and maceration (48h)) microwave-assisted extraction yielded extracts with higher polyphenol and flavonoid content and higher antioxidant activity in very short time (33s).

Microwave-assisted extraction of polyphenols from Clinacanthus nutans Lindau medicinal plant: Energy perspective and kinetics modeling

Clinacanthus nutans Lindau (C. nutans, “snake grass”) is a well-known medicinal plant in South-East Asia that recently has attracted attention for its high polyphenol content and its medical and nutraceutical applications. In this work, polyphenols have been recovered from C. nutans by microwave-assisted extraction (MAE). The influence of the main process parameters has been analyzed: ethanol concentration in the extraction solvent mixture, microwave energy applied and solvent-to-feed ratio. Model results have been correlated with mathematical models of the extraction process, that allow linking the observed variations in extraction curves with modifications of mass transfer and equilibrium parameters. Moreover, in order to assess the energy efficiency of the process, results were studied and explained in view of the specific energy absorbed during the microwave treatment (J/g). Results indicate that microwave pre-treatment improves extraction rate by a factor of 2–5, yielding the best results when a water–ethanol solvent mixture with 50%vol of ethanol is used at a solvent-to-feed ratio (S/F) of 14mL/g.

Microwave-assisted extraction of polyphenols from Camellia oleifera fruit hull.

The abundant fruit hulls of tea-oil tree (Camellia oleifera) are still underutilized and wastefully discaded to pollute the environment. In order to solve this problem and better utilize the fruit hulls of C. oleifera, a microwave-assisted extraction system was used to extract their polyphenols using water as the extraction solvent. A central composite design (CCD) was used to monitor the effects of three extraction processing parameters – liquid:solid ratio (mL/g), extraction time (min) and extraction temperature (°C) – on the polyphenol yield (%). The results showed that the optimal conditions were liquid:solid ratio of 15.33:1 (mL/g), extraction time of 35 min and extraction temperature of 76 °C. Validation tests indicated that under the optimized conditions the actual yield of polyphenols was 15.05 ± 0.04% with RSD = 0.21% (n = 5), which was in good agreement with the predicted yield. Phenolic compounds in the extracts were analysed by HPLC, and gallic acid was found to be the predominant constituent. The total flavonoid content in the extracts was determined and high total flavonoid content was revealed (140.06 mg/g dry material).

Study on the microwave-assisted extraction of polyphenols from tea

This study demonstrated a promising method for quickly extracting tea polyphenol (TP) by microwave-assisted extraction (MAE) technology. Some influential parameters, including MAE temperature, microwave power, concentration of extraction solvent, MAE time and the solid/liquid ratio, were investigated. The optimum condition of MAE was obtained by dual extraction with 60% ethanol (v/v) and the solid/liquid ratio 1:12 g/mL at 80°C for 10 minutes under the microwave power 600W. The yield of TP was 96.5% under the described condition. Compared with traditional methods, including hot reflux extraction (HRE), ultrasound-assisted extraction (UAE) and supercritical fluid extraction (SFE), the extraction time was saved 8 times than that of HRE, and the yield was increased by 17.5%. The extraction time at comparable levels of production was saved 2 times, and the energy consumption was one fourth that of UAE. The extraction time was saved 5 times than that of SFE, and the yield of TP was increased by 40%. Moreover, compared with MAE of TP studied by others, it decreased the solid/liquid ratio from 1: 20 to 1: 12 g/mL without 90-min pre-leaching time, and the yield of TP was increased by 6%–40%.