Optimisation of microwave‐assisted extraction of phenolic compounds from broccoli and its antioxidant activity

The effect of independent variables of microwave‐assisted extraction (MAE), extraction temperature (50–90 °C), microwave power (100–200 W), solvent concentration (methanol/water, 50–90%, v/v) and extraction time (1–27 min) on total phenolics and flavonoids contents as well as antioxidant activity of broccoli extracts was investigated. Response surface methodology was successfully applied for optimisation and the high correlation of the mathematical model indicated that a quadratic polynomial model could be used for optimisation of investigated responses. Considering the maximum amount of extracted total phenolics, total flavonoids and antioxidant activity expressed as ORAC value, the optimal conditions for all three investigated responses were obtained (temperature ?71.11 °C; microwave power ?167.03 W; solvent concentration ?75.95%; and extraction time 16.34 min), which is in agreement with optimal conditions obtained for each investigated responses. The development of simultaneously MAE methods for total phenolics, total flavonoids and antioxidant activity of broccoli extracts might simplify assessment of broccoli as valuables source of antioxidants.     

Subcritical water extraction of phenolic compounds from flaxseed meal sticks using accelerated solvent extractor (ASE)

Subcritical water extraction (SWE) is a technique based on the use of water as an extractant, at temperatures between 100 and 374 °C and at a pressure high enough to maintain the liquid state. SWE provides higher selectivities, low cost, and shorter extraction times. In this study, phenolic compounds in flaxseed (Linum usitatissimum L.) meal sticks were extracted with subcritical water using accelerated solvent extractor. For this aim, the interactions between temperature (160, 170, and 180 °C) and extraction time (5, 15, 30, and 60 min) for subcritical water extraction of SDG lignan, total phenolics, and total flavonoids from flaxseed meal sticks were investigated. The highest extraction yield of SDG lignan (77.01 %) in subcritical water extracts was determined at 160 °C for 60 min. However, high extraction yields were obtained as 70.67 and 72.57 % at 170 and 180 °C for 15 min, respectively. Also, the highest extraction yield of total phenolics (70.82 %) and total flavonoids (267.14 %) were determined at 180 °C for 15 min. Besides, high correlations between SDG lignan–total phenolics, SDG lignan–total flavonoids, and total phenolics–total flavonoids were obtained from 0.86 to 1 in water extracts.     

Studies on retention of antioxidant activity,phenolics and flavonoids in high pressure processed black grape juice and their modelling

The effect of high pressure processing on total antioxidant activity, phenolic and flavonoid content of black grapes juice was studied. Response surface methodology (RSM) was used for designing the experiment keeping high pressure (400–600 MPa), temperature (40–60 °C) and processing time (2–4 min) as independent variables. The data obtained were analysed using multiple regression technique and quadratic models were found to fit well (R², 85.61–96.65%) in describing the effect of high pressure, temperature and time on total antioxidant activity, phenolics and flavonoids. The optimum levels were found to be 550 MPa, 44 °C and 2 min for pressure, temperature and processing time, respectively (desirability, 95.00) for getting the maximum retention of total antioxidant activity, phenolics and flavonoids in the juice. The experimental and predicted valued of responses showed high correlation (R², 99.26–99.90%) at the optimised levels of the variables.     

Optimization of Ultrasound-Assisted Extraction Procedure to Determine Total Isoflavones in Chinese Soybean Cheese by Box–Behnken Design

Isoflavones from Chinese soybean cheese were extracted with aqueous ethanol. Single-factor experiment design was employed to optimize the solid-to-liquid ratio (in grams per milliliter), ethanol concentration (in percent), extraction time (in hours), and extraction temperature (in degrees Celsius). The solid-to-liquid ratio was 1.5:10 (g/mL), and ethanol concentration (50 %–90 %), extraction time (2–3 h), extraction temperature (50–70 °C) were used for further optimization of extraction conditions. The optimal conditions for the ultrasound-assisted extraction of total isoflavones from Chinese soybean cheese were determined using response surface methodology (RSM) by Box–Behnken design. Three variables “ethanol concentration, extraction time and extraction temperature” were regarded as factors in the optimization study. The optimal conditions for total isoflavone extraction in Chinese soybean cheese were: ethanol concentration of 65.43 %, extraction temperature of 65.38 °C, and extraction time of 2.51 h. The verification experimental OD value was 0.534, which agreed with the predicted value, thus indicating suitability of the model employed and the suitability of RSM in optimizing the extraction conditions.     

Response surface optimisation for the extraction of phenolics and flavonoids from a pink guava puree industrial by‐product

Pink guava puree industry produces huge amount of by‐products that have potential as sources for polyphenols. Response surface methodology was implemented to optimise the extraction conditions for phenolics (Y₁) and flavonoids (Y₂) from a by‐product of the guava industry. A three‐factor inscribed central composite design was employed to determine the effects of three independent variables, namely pH (X₁: 2–6), temperature (X₂: 40–60 °C) and time (X₃: 1–5 h), on the response variables. The corresponding predicted values for phenolics and flavonoids were 336.30 and 427.35 mg 100 g^?1, respectively. Predicted values for extraction rates of phenolics agreed well with experiment values; R² of 0.902. However, the model derived for flavonoids extraction was less reliable; R² of 0.983. Increase in time and temperature was found significant in increasing the extraction rate. The optimum conditions for extracting phenolics by ethanolic solvent occurred at a pH of 2 and 60 °C for a 5‐h extraction.     

响应面法优化超声波辅助提取胡桃楸种仁壳总黄酮工艺

为确定胡桃楸种仁壳总黄酮超声波辅助提取的最佳工艺条件,以总黄酮得率和总还原力为指标,进行单因素实验,并在此基础上,选取超声波功率、超声波时间、料液比为影响因素,采用响应面法进行优化并得到回归模型。结果表明:最优工艺条件为超声波功率250W,超声波时间31min,料液比1:31(g/mL)。回归模型预测的黄酮得率理论值为6.70mg/g,经验证实验,RSD为1.47%,该回归方程与实际情况拟合较好。     

Influence of different extraction temperatures and methanol solvent percentages on the total phenols and total flavonoids from the heartwood and bark of Acacia auriculiformis

Acacia auriculiformis heartwood and bark were obtained, dried under shelter for 2 weeks and pulverized into powdered form to be extracted with the following extraction temperatures of 35, 55 and 75 °C and methanol solvent percentages of 55, 65 and 75 % for 3 h in a water bath. The material ratio used was 1:20 (pulverized samples: solvent). The total phenolics and flavonoids yield was determined by using a Thermo Scientific Genesys 10 UV–Visible Spectrophotometer. The optimum total phenolics and flavonoids yield were achieved by extraction with an extraction temperature of 75 °C and a methanol solvent percentage of 75 % for both the heartwood [75.44 % (total phenolics) and 36.64 % (total flavonoids)] and bark [87.18 % (total phenolics) and 99.10 % (total flavonoids)] of A. auriculiformis trees.     

Optimization of Supercritical Fluid Extraction of Phenolics from Date Seeds and Characterization of its Antioxidant Activity

Supercritical fluid extraction (SFE) was utilized for the first time to extract phenolics in date seeds. Orthogonal array design (OA₉ (3⁴)) was applied to optimize extraction variables including extraction temperature, extraction pressure, extraction time, and number of extraction. Optimum values of extraction variables were analyzed and number of extractions was found to have a significant effect on total phenolics content (TPC). Optimal SFE conditions for maximum yield of TPC were 50 °C, 350 bar, and two repeated extractions, each for 2 h. Under optimal condition, the TPC was increased to 441.57 mg gallic acid equivalents/100 g fresh weight. Several phenolic compounds were detected in date seeds including chlorogenic acid, rutin, ellagic acid, quercetin, and two unidentified compounds of phenolic acids. In addition, phenolics of date seeds showed a higher antioxidant activity than ascorbic acid at the same concentration in the range of 1.0–8.0 mg/L.     

Antioxidant activities of onion (Allium cepa L.) peel extracts produced by ethanol,hot water,and subcritical water extraction

Onion (Allium cepa L.) peels were extracted by ethanol, hot water and subcritical water (SW) extraction and their antioxidant activities were evaluated. Extraction yields of SW extraction were 4-fold higher than ethanol extraction. However, the ethanol extraction increased the total phenolics contents (327.5 mg GAE/g extract) and flavonoids contents (183.95 mg QE/g extract) in the onion peel extract. The onion peel extracts by ethanol extraction showed greater DPPH radical scavenging activities and greater antioxidant activities determined by ferric thiocyanate assay than those by hot water extraction and SW extraction at 165°C. Antioxidant activity of onion peel extract by SW extraction at 110°C was similar to that of ethanol extraction. HPLC profiles revealed that SW extraction at lower temperature (110°C) increased the concentration of quercetin. These results demonstrated that the onion peel extracts produced by SW extraction technique have great potential as a source for useful antioxidant.     

Antioxidant Extraction from Mustard (Brassica juncea) Seed Meal Using High‐Intensity Ultrasound

Brassicaceae oilseeds provide feedstocks for the biofuels industry, but value‐added coproducts are necessary to supply financial incentives for increased production. Our objective was to use high‐intensity ultrasound to optimize extraction of antioxidants from mustard (Brassica juncea) seed meal. The ultrasound‐assisted extraction (UAE) variables included temperature, solvent‐to‐material ratio, sonication duration, and EtOH concentration. Extracts were analyzed for total phenolics content (TPC), antioxidant activity, and sinapine content. Conventional extraction using water and 70% EtOH (v/v) at 80 °C for 3×30 min yielded 7.83 ± 0.07 and 8.81 ± 0.17 mg sinapic acid equivalents (SAE)/g meal, respectively. UAE extraction at 40 °C for 30 min yielded similar phenolics content (8.85 ± 0.33 mg SAE/g meal) as conventional hot ethanolic extraction, but required less time and lower temperature. The highest TPC (13.79 ± 0.38 mg SAE/g meal) was in the 7‐d aqueous extracts. Sonicated solutions of pure sinapine and sinapic acid showed 1st‐order reaction kinetics with greater degradation of isolated compounds than those present in extracts. Sinapine contained in extracts showed insignificant (P < 0.05) degradation after 30 min of sonication. Our research indicates that ultrasound treatment can assist the extraction of antioxidants from B. juncea meal by reducing both the temperature and time requirement without significant degradation of the primary antioxidants present.     

Ultrasound-assisted extraction of bioactive compounds from <Emphasis Type="Italic">Malva sylvestris</Emphasis> leaves and its comparison with agitated bed extraction technique

The effects of ultrasound-assisted extraction (UAE) variables—namely extraction temperature (40–60 °C), ultrasonic power (50–150 W), and sonication time (40–60 min)—on the extractive value (EV) of bioactive phenolics from Malva sylvestris leaves were investigated and optimized using Response surface methodology. The effects of extraction solvents (ethanol, ethyl acetate, and n-hexane) on EV, free radical scavenging activity (FRSA), total phenolic content (TPC), and major bioactive phenolics were studied using agitated bed extraction (ABE), and the results were compared with the UAE findings. Under the optimal UAE conditions (48 °C, 110.00 W, and 48.77 min) the experimental EV was 279.89 ± 0.21 mg/g with 71.12 ± 0.15% DPPH_sc, 73.35 ± 0.11% ABTS_sc, and a TPC of 152.25 ± 0.14 mg GAE/g. Ethanolic ABE results in higher EV (320.16 ± 0.25 mg g^?1) compared to UAE, while the FRSA and TPC values were reduced. HPLC analysis revealed that the concentration of bioactive phenolics increased significantly (p < 0.05) under the optimal UAE conditions.     

Extraction of antioxidants and flavonoids from yuzu (<Emphasis Type="Italic">Citrus junos</Emphasis> Sieb ex Tanaka) peels: a response surface methodology study

In the present investigation, extraction of antioxidants and flavonoids from the peels of yuzu fruit using a single factor experiment and a response surface methodology (RSM) based on central composite design was studied. Four independent variables were evaluated at five levels with total 29 experimental runs, including ethanol concentration (EtOH), ratio of liquid to material (L/S), extraction temperature (T), and extraction time (t). The total phenolic content (TPC), total flavonoids content (TFC), two indicators of antioxidant capacity (FRAP and DPPH), and three individual major flavonoids in yuzu (hesperidin, naringin, and phloretin) served as the response functions. Quadratic polynomial equations were obtained by multiple regression analysis to predict the optimal extraction conditions. The regression analysis showed that >95?% of variations were explained by the models of different responses considered. The responses were significantly influenced by all studied factors. The Multiresponse optimized conditions targeted at maximizing all the responses were found to be EtOH?=?65.550?%; T?=?43.864?°C; t?=?119.673 min; and L/S?=?37.168 ml/g, with a desirability of 0.950. At the optimized conditions, the experimental values of FRAP (964.9?±?23.1 mgTE/g DW), DPPH (453.0?±?5.2 mgTE/g DW), TPC (1161.2?±?25.2 mgGAE/g DW), (TFC393.4?±?mgQE/g DW), hesperidin (337.2?±?4.0 mg/g DW), naringin (244.9?±?1.1 mg/g DW), and phloretin (43.9 mg/g DW) were in a reasonable agreement with the predicted values. The extraction method was applied successfully to extract antioxidants and flavonoids from yuzu peels. It also allows a fast and cost-saving process for extraction of the studied phytochemicals, in addition to improvement of the quantity of the targeted extract.     

Extraction of inulin from Burdock root (Arctium lappa) using high intensity ultrasound

Burdock root could be a source of inulin, but scarce studies about its extraction exist. To optimise conventional and ultrasound‐assisted extraction of inulin, various combinations were used. The independent variables for ultrasound extraction were sonication amplitude (20–100%), sonication temperature (20–60 °C) and sonication time (5–25 min) while for conventional extraction the following variables were water to solid ratio (5–15 v/w), temperature (40–90 °C) and time (5–40 min). For each response, a second‐order polynomial model was developed using multiple linear regression analysis. The use of high intensity ultrasound significantly improves the extraction of inulin contained within the body of Burdock root. It was shown that increasing the amplitude (from 20% to 85%) and extraction time increased the extraction yield; however, the effect of temperature was minor. Optimum extraction condition was found to be sonication time: 25 min, sonication amplitude 83.22% and temperature: 36.76 °C.     

响应面分析法优化竹节草黄酮提取工艺

研究超声波辅助法提取竹节草黄酮工艺。利用响应面分析法对影响竹节草黄酮得率的4个主要因素(提取时间、提取功率、乙醇体积分数和固液比)进行研究。结果表明：最佳的竹节草黄酮提取工艺参数为提取时间39min、提取功率70W、乙醇体积分数65%、固液比1:21(g/mL)。在此条件下黄酮得率实测值为20.07mg/g,实测值与回归模型预测值(20.29mg/g)相对误差为1.1%,说明采用响应面法优化得到的提取条件可靠。     

Optimizing the Tyrosinase Inhibitory and Antioxidant Activity of Mango Seed Kernels with a Response Surface Methodology

This study describes the optimization of polyphenol extraction from mango seed kernels by using response surface methodology (RSM). In the solid-to-liquid selection, the extraction yield, total phenolic content (TPC), antioxidant activity, and tyrosinase inhibitory activity are all significantly increased with a decrease in the solid-to-liquid ratio (P?<?0.05). Between the Nam-Dok-Mai kernel (NDK) and the Tong-Dam kernel (TDK), the TDK was chosen for RSM with a fixed ratio of 1:30 solid-to-liquid. The variables in the independent processing were the concentrations of ethanol, the temperature, and the time applied to RSM. Ethanol concentration, temperature, and duration had significant individual and interactive effects on phenolic yield and antioxidant activities (P?<?0.05). The optimized condition that maximized the extraction yields, TPC, and antioxidant activities from TDK was an ethanol concentration of 62 %, a temperature of 63 °C, and a duration of 150 min. The obtained and validated optimized model could be used to describe the effect of these variables on the extraction of phenolic compounds from mango seed kernels.     

Optimisation of extraction conditions for recovering carotenoids and antioxidant capacity from Gac peel using response surface methodology

The peel of Gac fruit is regarded as waste product in the processing of Gac although it contains high level of carotenoids and possesses a significant antioxidant capacity. This study optimised the extraction yields of carotenoids and antioxidant capacity from Gac peel. Different organic solvents were examined to determine the most suitable solvent for the extraction. The extraction conditions including time, temperature and solvent–solid ratio were then optimised for maximising extraction yields of carotenoids and antioxidant capacity from Gac peel using response surface methodology. Ethyl acetate was identified as the most suitable solvent. The optimal extraction time, temperature and solvent–solid ratio were 150 min, 40.7 °C and 80 mL g^?1, respectively. The carotenoid extraction yield and the antioxidant capacity extraction yield were 271 mg/100 g DW and 737 μm TE/100 g DW, respectively. Thus, the extraction using ethyl acetate with the ratio of 80:1 (mL solvent per g Gac peel) for 150 min at 40.7 °C is suggested for recovering carotenoids and antioxidant capacity from Gac peel.     

Optimization of phenolic compound recovery and antioxidant activity of light and dark dried fig (Ficus carica L.) varieties

The optimum conditions for extraction of total phenolic contents (TPC) and for enhancing the antioxidant activity from light and dark dried figs were determined. The effects of the solvent nature (acetone, ethanol, methanol, or water), solvent concentration (20–80%), acetic acid concentration (0–2%), extraction temperature (25–70°C), extraction time (0.5–4 h), sample to solvent ratio (1/25–1/100), and number of extractions (1, 2, and 3) were determined. The TPC was used to identify antioxidant compounds. 2,2-diphenyl-1-picrylhydrazyl (DPPH) was used to evaluate antioxidant activity. All extraction parameters had significant effects (p<0.05) on the TPC and the antioxidant activities. The best conditions were obtained with double extraction using 60% acetone without acidification, at 40°C for 120 min, and with a 1/75 solid to solvent ratio. These conditions resulted in TPC concentrations of 469.46 (light variety) and 399.79 mg of gallic acid (GAE)/100 g (dark variety), and antioxidant activities of 96.47 and 102.28 mg of GAE/100 g, respectively.     

Optimization of the Process Parameters to Establish the Quality Attributes of DPPH Radical Scavenging Activity,Total Phenolic Content,and Total Flavonoid Content of Apple (Malus domestica) Honey Using Response Surface Methodology

The response surface methodology was used to study the combined effect of temperature (60 to 80°C), time (10 to 15 min), and pH (3 to 6) on the antioxidant activity (1,1-diphenyl-2-picrylhydrazyl-radical scavenging activity, total phenolic content, and total flavonoid content) of apple honey. Statistical analysis revealed that all the responses were significantly (p < 0.05) affected by independent process variables. 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity, total phenolic content, and total flavonoid content increased with the increase in time and temperature due to the formation of browning pigments. The antioxidant properties of apple honey significantly (p < 0.05) decreased with increase in pH from 3 to 6. The thermal treatment of apple honey at 80°C was found to be more effective than at 70 and 60°C. The average increase in 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity, total phenolic content, and total flavonoid content of raw apple honey due to combined effect of three process variables was 9.6% ± 1.9, 13.7 ± 2.5 mg gallic acid equivalent/100 g and 49.3 ± 3.3 mg quercetin/100 g, respectively. The results showed that the most desirable optimum conditions for temperature, time and pH for 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity (92.39%), total phenolic content (133.55 mg gallic acid equivalent/100 g of honey), and total flavonoid content (25.82 mg quercetin/100 g of honey) were 80°C, 15 min and 3.01, respectively. The results demonstrated that thermal treatment significantly increased the antioxidant activity of apple honey.     

响应面法优化葛根总黄酮的超声辅助提取工艺

为提高葛根总黄酮的得率,采用响应面试验设计优化超声辅助提取葛根总黄酮的工艺条件。在单因素试验基础上确定以超声时间、料液比及超声温度为3个主要因素,以总黄酮得率为响应值,根据Box-Behnken原理采用三因素三水平响应面试验设计进行优化。结果表明超声辅助法提取葛根总黄酮的最佳工艺条件为：以蒸馏水作为超声提取溶剂,超声时间43min、料液比1:10(g/mL)、超声温度68℃,总黄酮得率为5.28%,与预测得率5.36%相比,相对误差仅为1.49%。说明该模型可靠,与实际情况拟合较好。     

Monitoring on extraction characteristics of cheonnyuncho (Opuntia fiscus-indica) fruit

Extraction conditions of the fruit of cheonnyuncho (Opuntia ficus-indica) were optimized by using response surface methodology. Accordingly, the extract yield of the cheonnyuncho fruit was maximum when extracted at 85.69°C for 92.89 min using amount of water to sample of 23.46 mL/g. Moreover, the optimum conditions for the maximum yield of effective substances were as follows: flavonoid 89.80°C, 170.81 min, and 17.07 mL/g; phenolics 98.30°C, 96.46 min, and 15.93 mL/g; electron donating ability 71.00°C, 173.58min, and 15.22mL/g; reducing sugars 69.87°C, 68.84 min, and 16.29 mL/g; pectins 96.54°C, 135.28 min, and 20.02 mL/g; and vitamin C 61.80°C, 101.98 min, and 12.14 mL/g, respectively. The optimum extraction condition ranges for obtaining desirable physiochemical properties of cheonnyuncho extracts were 85–100°C for 60–120 min using 18–25 mL/g of amount of water to sample.