Phenolic and flavonoid content and antioxidants capacity of pressurized liquid extraction and perculation method from roots of Scutellaria pinnatifida A. Hamilt. subsp alpina (Bornm) Rech. f.

The extract was separated from roots of Scutellaria pinnatifida using perculation and pressurized liquid extraction (PLE). A circumscribed central composite (CCC) was used to optimize the effective extraction variables. For achieving maximum extraction yield via PLE the temperature, pressure, static time, dynamic time, and the solvent flow rate were adjusted 65.8 °C, 39.2 bar, 12.9 min, 18.9 min, and 0.76 mL/min, respectively. Ferric reducing antioxidant power (FRAP) (mmol/g) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity (mg/mL) were evaluated and the highest antioxidant activity was observed from the PLE extract. The total phenolic and flavonoid content was calculated and a good correlation founded between phenolic content and antioxidant activity. The results indicated the root of this plant is a potential source of natural antioxidants and flavonoids. The PLE method is quicker and it has more extraction yield than perculation.     

Supercritical fluid extraction of Prunus persica leaves and utilization possibilities as a source of phenolic compounds

Mediterranean countries contribute highly on world peach production and tonnes of waste leaves are released due to pruning. The aim of this study was to investigate the utilization possibilities of the leaves by supercritical fluid extraction. A statistical design was used to evaluate the effect of temperature (40–80 °C), pressure (150–300 bar) and concentration of ethanol as co-solvent (6–20%) at a flow rate of 15 g/min and for a duration of 60 min. The most effective variables were found as pressure and co-solvent ratio (p < 0.005). Optimum extraction conditions were elicited as 60 °C, 150 bar and 6% co-solvent yielding a total phenol content of 79.92 mg GAE/g extract, EC₅₀ value of 232.20 μg/ml and a radical scavenging activity of 53.25% which was higher than the value obtained by conventional solvent extraction method (32.23%). Consequently, Prunus persica L. leaves were found as a potential phenolic source for industrial applications.     

Supercritical CO2 and low-pressure solvent extraction of mango (Mangifera indica) leaves: Global yield,extraction kinetics,chemical composition and cost of manufacturing

Low-pressure solvent extraction (LPSE) and supercritical fluid extraction (SFE) were used to obtain extracts from mango (Mangifera indica) leaves. Kinetics curves were determined for both methodologies. The extracts chemical compositions and manufacturing costs were determined for both processes. Global yield isotherms for SFE process were determined at 10–40 MPa and 313–323 K. The highest yield was 2.24% at 30 MPa and 323 K; the LPSE yield (9.3%) was almost three times higher than that of SFE (3.6%). Thin layer chromatography showed that mango leaves extracts have several classes of compounds as alkaloids, flavonoids and terpenoids, recovered by both methods. The cost of manufacturing (COM) mango leaves extracts were US$ 32/kg and US$ 92/kg for LPSE and SFE, respectively.     

Integrated supercritical fluid extraction and subcritical water hydrolysis for the recovery of bioactive compounds from pressed palm fiber

Pressed palm fiber (PPF), a residue obtained from palm oil industry, is a source of bioactive compounds, such as carotenoids, which are used as food additives. It also has cellulose and hemicellulose that can be used to yield fermentable sugars for the production of second generation ethanol. Supercritical fluid extraction (SFE) of pressed palm fiber provides an oil rich in carotenoids while subcritical water hydrolysis (SubWH) produces hydrolysates with high amounts of fermentable sugars. In this work, the effects of pressure (15–30 MPa) and temperature (318 and 328 K) on SFE of carotenoids were investigated. The SFE extract with highest carotenoid content was obtained at 318 K and 15 MPa (2.3% d.b., 0.81 mg β-carotene/g extract). After the extraction, the influence of process temperature (423–633 K), pressure (15 and 25 MPa), solvent:feed ratio (120 and 240), and residence time (1.25–5 min) on SubWH of the extraction residue was studied. At the temperature of 523 K, the highest total reducing sugar yield (11–23 g glucose/100 g carbohydrate) and the highest biomass conversion (40–97%) were obtained for any pressure and solvent:feed ratio. The highest selectivity for saccharide formation was found at 423 K (20–59 mol glucose/mol furfural equivalent). Optimal conditions for high saccharide formation and low sugar degradation product in subcritical hydrolysis were obtained at 523 K, 15 MPa, solvent:feed ratio of 120, residence time of 2.5 min with a total reducing sugar yield of 22.9 g glucose/100 g carbohydrate and a conversion of 84.9%.     

Subcritical water extraction of steviol glycosides from Stevia rebaudiana leaves and characterization of the raffinate phase

The objectives of this work were to obtain steviol glycosides of S. rebaudiana leaves, possessing natural and noncaloric sweetener properties, using subcritical water extraction; to assess optimum extraction conditions; to determine biological activities of Stevia extracts and to characterize the raffinate phase. A Box–“Bhenken” statistical design was used to evaluate the effects of various values of temperature (100–150 °C), time (30–60 min) and flow rate (2–6 ml/min) at a pressure of 230 bar applying a solid/liquid ratio of 1:10 (m:v). The most effective parameter was temperature (p < 0.005). Optimum extraction conditions were elicited as 125 °C, 45 min, 4 ml/min flow rate which yielded 38.67 mg/g stevioside and 35.68 mg/g rebaudioside A. The total phenolic, flavonoid contents and DPPH free radical scavenging activity were found as 48.63 mg gallic acid/g extract, 29.81 mg quercetin/g extract and 92.50%, respectively. After extraction, total chlorophyll, carotenoid contents and dietary fibers were quantified as 31.91 mg/100 g, 5.71 mg/100 g and 4.98% in the raffinate phase. Hence, both extract and raffinate phases of S. rebaudiana leaves can be utilized as sources of natural sweeteners, fibers and coloring agents in the industry.     

A bioactivity based comparison of Echinacea purpurea extracts obtained by various processes

Echinacea species is provided as dietary supplements for various infectious and immune related disorders and has a potential role in cancer prevention. The aim of this study was to optimize the extraction of total flavonoids using different extraction methods and investigate the cytotoxic effects on various cancer cell lines (CaCo-2, MCF-7, A549, U87MG, and HeLa) and VERO (African green monkey) as a non-cancerous cell line. Box-Behnken statistical design was used to evaluate the effect of pressure (100–200 bar), temperature (40–80 °C) and ethanol as co-solvent (6–20 wt%) at a flow rate of 15 g/min for 60 min in supercritical CO₂ extraction and the effect of temperature (60–100 °C), time (5–15 min) and power (300–900 W) in microwave-assisted extraction. Optimum extraction conditions were elicited as 300 bar, 80 °C and 13% co-solvent yielding 0.472 mg rutin equivalent total flavonoids/g extract in SC-CO₂ extraction, whereas 60 °C, 10 min and 300 W yielded the highest (0.202 mg rutin equivalent) total flavonoids in microwave-assisted extraction. Additional trials with subcritical water (0.022 mg/g) and Soxhlet extraction with methanol (0.238 mg/g) yielded lower flavonoid contents. The exposures upto 50 μg/ml of extracts revealed no significant inhibition on the proliferation of both tested cancer cells and healthy VERO cells.     

Cosolvent-modified supercritical carbon dioxide extraction of phenolic compounds from bamboo leaves (Sasa palmata)

This study highlights the possibility of supercritical carbon dioxide for extracting phenolic compounds from bamboo leaves that have shown antioxidant and anticancer activities. The CO₂ extraction solvent was modified by adding ethanol–water mixture cosolvent of different concentrations to allow extraction of both polar and non-polar compounds. Conventional Soxhlet extraction was also done to investigate the advantages of supercritical extraction over the conventional extraction method. For addition of 5% (mol) of a 25:75 (mol:mol) ethanol–water mixture solvent to CO₂, the highest amount of polyphenols (7.31 ± 0.06 mg/g bamboo leaves in catechin equivalents) and radical scavenging activity (3.65 ± 0.05 mg/g bamboo leaves in BHA equivalents) at 20 MPa and 95 °C, could be obtained among the mixture cosolvents studied. For Soxhlet extraction with a 25:75 (mol:mol) ethanol–water mixture, 1.48 times the amount of phenolic compounds (10.85 ± 0.52 mg/g bamboo leaves in catechin equivalents), could be isolated compared with the supercritical extraction method, however, the radical scavenging activity (3.30 ± 0.05 mg/g bamboo leaves in BHA equivalents) was 0.90 times lower than the extract obtained from the supercritical extraction method. The seven major antioxidative compounds identified from the SC-CO₂ extraction method were: (1) dl-alanine, (2) gluconic acid, (3) phosphoric acid, (4) ß-siosterol, (5) β-amyrene, (6) α-amyrin acetate and (7) friedelin.     

Extraction of protocatechuic acid from Scutellaria barbata D. Don using supercritical carbon dioxide

The use of supercritical carbon dioxide (SC⿿CO₂), with water as a modifier, was evaluated in this study as a method to extract protocatechuic acid (PA) from Scutellaria barbata D. Don. The highest extraction yield of PA, 64.094 ± 2.756 μg/g of dry plant, was achieved at 75 °C and 27.5 MPa, with the addition of 15.6% (v/v) water as a modifier. The mean particle size was 0.355 mm, the CO₂ flow rate was 2.2 mL/min (STP) and the dynamic extraction time was 100 min. At pressures of 16.2⿿30.0 MPa and temperatures of 45⿿75 °C, the mole fraction solubilities of PA in SC⿿CO₂ ranged from 2.829 ÿ 10^⿿7 to 9.631 ÿ 10^⿿7. The solubility data for PA fit well in the Chrastil model. It is evident that the SC⿿CO₂ extraction uses less solvent, saves both energy and time and is an environmentally friendly extract technology that can be used in the food, cosmetic and pharmaceutical industries.     

Optimization of subcritical water extraction of antioxidants from Coriandrum sativum seeds by response surface methodology

Subcritical water extraction (SWE) of antioxidants from Coriandrum sativum seeds (CSS) was optimized by simultaneous maximization of the total phenolics (TP) and total flavonoids (TF) yield and antioxidant activity, using IC₅₀ value. Box–Behnken experimental design (BBD) on three levels and three variables was used for optimization together with response surface methodology (RSM). Influence of temperature (100–200 °C), pressure (30–90 bar) and extraction time (10–30 min) on each response was investigated. Experimentally obtained values were fitted to a second-order polynomial model and multiple regression. Analysis of variance (ANOVA) was used to evaluate model fitness and determine optimal conditions. Moreover, three-dimensional surface plots were generated from employed mathematical model. The optimal SWE conditions obtained in simultaneous optimization were temperature of 200 °C, pressure of 30 bar and extraction time of 28.3 min, while obtained values of TP and TF yields and IC₅₀ value at this experimental point would be 2.5452 g GAE/100 g CSS, 0.6311 g CE/100 g CSS and 0.01372 mg/ml, respectively. Moreover, good and moderate linear correlation was observed between antioxidant activity (IC₅₀ value) and total phenolics content (R² = 0.965), and total flavonoids content (R² = 0.709) which indicated that these groups of compounds are responsible for antioxidant activity of C. sativum extracts.     

Optimization of microwave-assisted enzymatic extraction of polyphenols from waste peanut shells and evaluation of its antioxidant and antibacterial activities in vitro

A microwave-assisted enzymatic extraction (MAEE) method was developed and optimized to enhance the polyphenols extraction yield from waste peanut shells. The optimum conditions were as follows: irradiation time 2.6 min, amount of cellulase 0.81 wt.%, a pH of 5.5, and incubation at 66 °C for 2.0 h. Under these conditions, the extraction yield of total polyphenols could reach 1.75 ± 0.06%, which was higher than other extraction methods including heat-refluxing extraction, ultrasonic-assisted extraction and enzyme-assisted extraction. The structural changes of the plant material after different extractions observed by scanning electron microscopy provided visual evidence of the disruption effect. Moreover, the crude extract was then purified by NKA-9 resin, the polyphenols content in the purified extract increased to 62.73%. The antioxidant activities of the crude and purified polyphenols extract were evaluated by DPPH and hydroxyl radicals, reducing power and β-carotene bleaching test. The antibacterial activities of purified extract were also tested using Oxford cup method. The results indicated that the MAEE method was efficient and environment-friendly, and the polyphenols have significant antioxidant and antibacterial activities, which can be used as a source of potential antioxidant and preservative.     

Optimization of multi-stage countercurrent extraction of antioxidants from Ginkgo biloba L. leaves

Multi-stage countercurrent extraction (MCE) as a novel extraction technique was used to extract antioxidants from Ginkgo biloba leaves. Orthogonal array design (OAD) was employed to optimize the ratio of 60% ethanol to raw material (8–16 mL/g), extraction time (30–60 min) and extraction temperature (60–80 °C) to obtain a high yield of antioxidants from G. biloba leaves by MCE. The optimum conditions were a ratio of 60% ethanol to raw material of 16 mL/g and extraction time of 30 min at 80 °C. Under these conditions, the yields of flavonoids and total phenolics were 1.74% and 2.42%, respectively, and DPPH radicals scavenging activity of the extract was 89.97%. Compared with heat-reflux extraction, MCE had obvious advantages of less extraction time and lower solvent and energy consumption. It may be used as a promising technique for the extraction of bioactive compounds from plant materials.     

Application of response surface methodology for the optimization of supercritical carbon dioxide extraction and ultrasound-assisted extraction of Capparis spinosa seed oil

Caper (Capparis spinosa) seed oil growing wild in Iran was extracted using supercritical CO₂ and ultrasound-assisted extraction methods. The experimental parameters of SFE and UAE were optimized using a rotatable central composite design. The highest yield for SFE was obtained at a pressure of 355 bar, temperature of 65 °C, modifier volume of 140 μL, static and dynamic extraction time of 10 and 35 min, respectively, and for UAE was gained at solvent volume of 23 mL, sonication time of 45 min and temperature of 40 °C. This resulted in a maximum oil recovery of 25.1% and 27.9% for SFE and UAE, respectively. The extracts with higher yield from both methods were subjected to transesterification and GC–MS analysis. SFE and UAE processes selectively extracted the fatty oils with high percentage of omega-6 and omega-9-fatty acids. The major components of the extracted oils from both methods were linoleic, oleic, its positional isomer cis-vaccenic and Palmitic acid.     

Supercritical carbon dioxide extraction of squalene and tocopherols from amaranth and assessment of extracts antioxidant activity

Squalene and tocopherols are the most important bioactive constituents in lipophilic amaranth fraction. Therefore, developments of processes of isolation of amaranth extracts enriched with these compounds are of interest. In this study the lipophilic fraction of amaranth seeds was extracted by supercritical fluid extraction with carbon dioxide (SCE-CO₂) under different pressure conditions and by adding 2 and 5% of cosolvent ethanol. The yield of extract varied from 1.37 (15 MPa without cosolvent) to 5.12% (55 MPa and 5% of cosolvent). The highest content of unsaponifiables (21.1%) in the extract was at 55 MPa and 5% of cosolvent; at these conditions the yields of tocopherols and squalene from amaranth seeds were 317.3 mg/kg and 0.289 g/100 g, respectively. Tocopherol isomers in amaranth oil were distributed at the approximate ratio of 1(α-T):27(β-T):6.5(γ-T):5(δ-T). The extract was fractionated in the two separators by gradual decrease of the pressure and it was found that the fraction obtained at ambient conditions contained the highest concentration of tocopherols (up to 7.6 mg/g) and squalene (up to 17.9 g/100 g oil). The highest antioxidant activity measured by the L-ORAC assay possessed the fractions with the highest concentrations of squalene and tocopherols and obtained at 15 MPa with pure CO₂ (235.1 μmol TE/g) and 2% of cosolvent (257.6 μmol TE/g).     

Extraction of phenolic compounds from pitanga (Eugenia uniflora L.) leaves by sequential extraction in fixed bed extractor using supercritical CO2, ethanol and water as solvents

With the goal of maximizing the extraction yield of phenolic compounds from pitanga leaves (Eugenia uniflora L.), a sequential extraction in fixed bed was carried out in three steps at 60 °C and 400 bar, using supercritical CO₂ (non-polar) as solvent in a first step, followed by ethanol (polarity: 5.2) and water (polarity: 9.0) in a second and third steps, respectively. All extracts were evaluated for global extraction yield, concentration and yield of both polyphenols and total flavonoids and antioxidant activity by DPPH method (in terms of EC₅₀). The nature of the solvent significantly influenced the process, since the extraction yield increased with solvent polarity. The aqueous extracts presented higher global extraction yield (22%), followed by ethanolic (16%) and supercritical extracts (5%). The study pointed out that the sequential extraction process is the most effective in terms of global extraction yield and yield of polyphenols and total flavonoids, because it produced the more concentrated extracts on phenolic compounds, since the supercritical ethanolic extract presented the highest phenolics content (240.5 mg GAE/g extract) and antioxidant capacity (EC₅₀ = 9.15 μg/mL). The most volatile fraction from the supercritical extract, which is similar to the essential oils obtained by steam distillation or hydrodistillation, presented as major compounds the germacrenos D and B + bicyclogermacrene (40.75%), selina-1,3,7(11)-trien-8-one + selina-1,3,7(11)-trien-8-one epoxide (27.7%) and trans-caryophyllene (14.18%).     

Extraction of bioactive compounds from peach palm pulp (Bactris gasipaes) using supercritical CO2

Natural compounds with biological activity have recently attracted special interest in the agro-industry as sources of additives in nutraceutical food production and pharmaceutical industries. Herein, we evaluated extracts obtained from peach palm fruit (Bactris gasipaes) using supercritical carbon dioxide, in terms of yield, total phenolic content, total flavonoids, total carotenoids, and antioxidant activity by β-carotene bleaching method. Extractions were performed at 40, 50, and 60 °C and 100, 200, and 300 bar; additionally, Soxhlet (with petroleum ether) and methanol extraction were conducted. The results showed that supercritical CO₂ allows obtaining extracts rich in carotenoids and, although it presents lower yield than conventional extraction (SOX), supercritical CO₂ represents a technique with greater advantages. The best operation condition for supercritical extraction was 300 bar–40 °C, given that the highest concentration of carotenoids was obtained, without the yield being significantly different from that obtained with 300 bar–60 °C, this extract had antioxidant activity comparable to that of commercial caffeic acid.     

Enzyme and high pressure assisted extraction of carotenoids from tomato waste

Enzyme (EA) and high pressure (HP) assisted extraction of carotenoids, especially lycopene, from tomato waste using various organic solvents was examined. Total carotenoid and lycopene extraction yields were increased by the use of pectinase and cellulase enzymes, when compared to the non enzyme treated solvent extraction process. The increase of extraction yield depended on the solvent. Maximum total carotenoid (127 mg/kg d.w.) and lycopene (89.4 mg/kg d.w.) extraction yields were obtained in enzyme treated samples extracted with ethyl lactate (solvent:solid = 10:1 mL:g), corresponding to almost 6-fold and 10-fold increase, respectively, with respect to non enzyme treated samples. HP assisted extraction led to higher extraction yields (from 2 to 64% increase depending on the solvent used) compared to conventional solvent extraction process performed at ambient pressure for 30 min. HP assisted solvent extraction was successfully performed at 700 MPa by using significantly (P < 0.05) lower ratios of solvent:solid (6:1 and 4:1 mL:g) and reduced processing time (10 min), compared to solvent extraction performed at ambient pressure, solvent:solid ratio 10:1 mL:g and 30 min extraction time.     

Ethanol modified supercritical carbon dioxide extraction of flavonoids from Momordica charantia L. and its antioxidant activity

Ethanol modified supercritical carbon dioxide (SC-CO₂) extraction of flavonoids from Momordica charantia L. fruits and its antioxidant activity were performed. The influences of parameters such as temperature, extraction time and pressure on the yield of flavonoids were investigated. The antioxidant activities of flavonoids were assessed by means of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging assay and β-carotene bleaching test. The experimental data obtained indicated that pressure, temperature and time had significant effect on the extraction yield. The optimum extraction conditions, determined by the 3D response surface and contour plots derived from the mathematical models, were as follows: extraction temperature 46 °C, pressure 33.4 MPa, and extraction time 53.2 min. Under these conditions, the experimental value was 15.47 mg/g, which was well matched with value predicted by the model. The antioxidant activity of flavonoids obtained by ethanol modified SC-CO₂ extraction method had higher antioxidant activity than the flavonoids extracted by conventional solvent extraction (CSE) method. The DPPH radical-scavenging ability of flavonoids obtained by ethanol modified SC-CO₂ extraction method reached to 96.14 ± 1.02%, equivalent to the clearance rate of ascorbic acid at 1.2 mg/mL. Results indicated that ethanol modified SC-CO₂ extraction was a suitable approach for the selective extraction of flavonoids from M. charantia L.     

Recovery of betulinic acid from plane tree (Platanus acerifolia L.)

Betulinic acid (3β, hydroxy-lup-20(29)-en-28-oic acid) is a bioactive triterpenic acid which was identified in various botanical sources and in considerable amounts in the bark of plane tree (Platanus acerifolia L.). In this work, the recovery of betulinic acid from plane tree bark was studied using different liquid solvent based extraction methods, namely solid–liquid extraction (SLE), ultrasound assisted extraction (UAE) and pressurized liquid extraction (PLE). Furthermore, preliminary studies of the supercritical fluid extraction (SFE) of plane tree bark are also reported.The liquid solvent based extraction techniques (SLE, UAE and PLE) were carried out using ethanol and ethyl acetate, and produced a recovery of betulinic acid in the range 10–15 mg/g of bark, with concentrations around 25–35% mass. A betulinic acid enrichment in the ethanolic extracts was possible by means of a simple precipitation step adding water. The precipitate contained 42–46% mass of betulinic acid and high recovery (>95%). Increasing the extraction temperature, by means of the PLE assays, has not resulted in an improvement of betulinic acid recovery.The preliminary SFE assays produced lower recoveries of betulinic acid (0.5–8 mg/g) with respect to liquid extraction. The addition of ethanol as cosolvent produced a significant improvement of both betulinic acid recovery and concentration in the SFE extract.     

Supercritical fluid extraction from Priprioca: Extraction yield and mathematical modeling based on phase equilibria between solid and supercritical phases

This study aimed to investigate the supercritical carbon dioxide extraction of Cyperus articulatus L. (Priprioca). Before the experiments were performed, the raw material was cleaned, vacuum packed and maintained at −5 °C. The moisture content of the material was determined using an oven with forced air circulation operating at 105 °C. The material was then ground, and the mean diameter of the resulting particles was determined using a set of standard sieves. Extraction was performed at pressures of 100–300 bar, temperatures of 40–50 °C, and extraction times up to 240 min using supercritical carbon dioxide as the solvent. For each load, approximately 50 g of Priprioca was packed into the extractor. According to the experimental results, the yields of extraction were significantly influenced by pressure and temperature. Additionally, this paper provides a mathematical model of the supercritical extraction of Priprioca. The employed mathematical model was based on the mass conservation law, which included two partial differential equations for the solute concentration in the solid and fluid phases. By applying a novel method, the distribution coefficient of the extract between supercritical fluid and solid phases was obtained using the criterion of equal fugacity at equilibrium. The model-predicted extraction yield was then compared with the corresponding experimental data. Additionally, the reasons for the deviations between the model and the experimental data under certain operational conditions are discussed.     

Supercritical carbon dioxide extraction of Capsicum peppers: Global yield and capsaicinoid content

The objective of this study was to select a variety of pepper with high concentration of capsaicin and subject it to supercritical fluid extraction (SFE), in order to determine the best conditions of temperature (40, 50 and 60 °C) and pressure (15, 25 and 35 MPa) in terms of global yield (X₀) and capsaicinoids content of the extracts. The influence of drying process (freeze and oven drying) on X₀, capsaicin (C) and dihydrocapsaicin (DHC) contents and total phenolics was also analyzed. Capsicum frutescens showed the highest levels of capsaicinoids (1516 μg/g fresh fruit). For the responses C and DHC, the extraction conditions of 15 MPa and 40 °C provided the highest concentrations (C ⿿ 42 mg/g extract and DHC ⿿ 18.5 mg/g extract). The freeze drying process resulted in extracts with the highest concentration of capsaicinoids (61 mg/g extract), but in contrast, the phenolics were less susceptible to different drying processes, with a mean concentration of 35 mg GAE/g extract. The kinetics experiments indicated that the extraction rate of oleoresin was slightly slower than that of capsaicinoids at the operation conditions (40 °C and 15 MPa).