Optimization of extraction of phenolic content from hazelnut shell using response surface methodology

Response surface methodology was applied to predict the optimum conditions for extraction of phenolic compounds in hazelnut shell. The phenolic content in the shell extract was determined spectrophotometrically according to the Folin‐Ciocalteu method and expressed as gallic acid equivalent (mg GAE g^?1). Two central composite designs were used to investigate the effects of two independent variables, namely solvent composition (%) and extraction time (min), on phenolic extraction. In a first series of repeated batch extractions, the solvent consisted of different methanol percentages in distilled water at pH 4, while in a second series methanol was substituted by ethanol. The highest phenolic content (6.67 mg GAE g^?1 of shell) was predicted at the extraction conditions of 55.7% ethanol and 108.7 min. These best conditions, obtained and applied to 13 different cultivars, showed values varying from 9.18 mg GAE g^?1 of shell for Barcelona to 3.00 mg GAE g^?1 of shell for Tonda di Giffoni. Copyright © 2007 Society of Chemical Industry     

A systematic approach for extraction of phenolic compounds using parsley (Petroselinum crispum) flakes as a model substrate

The impact of extraction methodology and polarity of extraction solvents on the assay of phenolic compounds was investigated using parsley (Petroselinum crispum) flakes as a model substrate. This systematic study was undertaken to address substantial variations in the extraction procedures, solvents and conditions as described in the recent literature. Five different extraction procedures [shaking, vortex mixing, sonication, stirring and pressurized liquid extraction (PLE)] and three different solvents (methanol, ethanol and acetone), with five different solvent to water ratios per solvent, were used for extraction. Extracts were analyzed for phenolic content by high‐performance liquid chromatography and Folin–Ciocalteu assays. The yields of phenolic compounds extracted with a pressurized liquid extractor were comparable to or better than those of four classical extraction procedures. Optimum extraction efficiency with PLE was obtained when extractions were performed with four extraction cycles using ethanol–water (50:50, v/v). The amount of apiin (4,5,7‐trihydroxyflavone 7‐apiosylglucoside) and malonylapiin (apigenin malonylapiosylglucoside) isolated from parsley varied with the composition of extraction solvent. Apiin extractability was found to be a maximum when the solvent (ethanol, methanol or acetone) to water ratio was 30:70 (v/v), whereas higher amounts of malonylapiin were isolated with a reverse solvent to water ratio (70:30, v/v). Malonylapiin was not detected when parsley samples were extracted with organic solvent to water ratios of 10:90 (v/v) and 30:70 (v/v). Published in 2006 by John Wiley & Sons, Ltd     

Bioactive compounds extracted by liquid and supercritical carbon dioxide from citrus peels

This work investigated the extraction of bioactive compounds from citrus peels, an agri-food waste. Carbon dioxide (CO₂), an eco-friendly solvent, was used under liquid and supercritical conditions to perform the extractions from orange, tangerine and lemon peels. The possibility of using ethanol as a cosolvent at small percentages up to 20% was also studied. The extraction yield, total polyphenolic content, individual polyphenolic profile, antiradical activity and volatile organic compounds of the extracts were evaluated. The highest yields were obtained when 20% ethanol was used as a cosolvent in both liquid (at 20 MPa and 20 °C) and supercritical (at 30 MPa and 60 °C) CO₂ extraction. In addition, the extracts obtained with liquid CO₂ + 20% ethanol showed the highest content of naringin (35.26, 44.05 and 19.86 mg g^-1 in orange, tangerine and lemon peel extracts, respectively) and terpenes, in particular limonene. This type of extract also showed the highest antiradical activity (31.78–59.51 µmolTE g^-1) as measured by both ABTS·+ and DPPH·. These findings show that the extraction with a liquid CO₂ and ethanol mixture could be a valid alternative to traditional solvent extraction using 80% less organic solvent and producing extracts with high antiradical capacity and rich in volatile organic compounds.     

Waste from peach (Prunus persica) processing used for optimisation of carotenoids ethanolic extraction

The processing of peaches to produce fruit pulp generates solid and liquid wastes rich in phytochemicals, such as carotenoids; thus, the objective of this work was to study the use of this waste for carotenoid extraction based on a complete experimental design and using response surface methodology. The parameters studied were the amount of solvent (20–50 mL), the number of extractions (1–5) and the extraction time (10–30 min). The extracts were analysed by spectrophotometry and the optimised conditions by HPLC. The optimised results were four extractions of 10 min using 38.5 mL of ethanol, which presented a yield of 168.59 μg g^?1 DW of total carotenoids of which 67.55 μg g^?1 corresponds to β‐carotene, 86.75 μg g^?1 to cryptoxanthin, 12.08 μg g^?1 to zeaxanthin and 2.2 μg g^?1 to lutein, which representing 66% of extraction pigments relative to the total content of carotenoids present in the peach waste.     

Comparative evaluation of microwave‐assisted extraction and preheated solvent extraction of bioactive compounds from a plant material: a case study with cabbages

Preheated solvent extraction (PSE) was evaluated via the analysis of the extraction kinetics, microstructure of extracted samples and energy consumption as alternative to microwave‐assisted extraction (MAE). Cabbage outer leaves and ethanol were used as test material and extraction solvent, respectively. MAE was first optimised in terms of glucosinolates and phenolics yields; total antioxidant activity of the extracts was also assessed. MAE at a specific absorbed power of 0.37 W g^?1 for 9 min was selected as optimum condition to extract glucosinolates and phenolics, while PSE was optimised at 6 min of the extraction. The highest normalised total glucosinolates and phenolic contents as well as antioxidant activities of the extracts obtained via MAE were not significantly different from those obtained via PSE. Confocal laser scanning microscopy revealed no significant differences in cabbage cell damages rendered by MAE and PSE. PSE nevertheless exhibited slightly higher specific energy consumption than MAE.     

Effect of solvent type on the extractability of bioactive compounds,antioxidant capacity and colour properties of natural annatto extracts

This study was conducted to obtain annatto extracts with both high antioxidant capacity and colour potential using solvents of different polarities (water, ethanol/water, ethanol, ethanol/ethyl acetate and ethyl acetate). The highest levels of total phenolic compounds were found in the water, ethanol/water and ethanol extracts (0.5 mg GAE mL^?1), and the highest level of bixin was found in the ethanol/ethyl acetate extract (5.2 mg mL^?1), which was characterised as the reddest and the most vivid one (a* = 40.5, h° = 46.1, C* = 58.4). The ethanol/ethyl acetate extract also showed the highest antioxidant activity (4.7 μm TEAC mL^?1) and the highest percentage of tryptophan protection against singlet oxygen (63.6%). On the other hand, ethyl acetate and ethanol/water were the least effective solvents for the extraction of phenolic compounds and bixin, respectively. According to the multivariate statistical analysis, ethanol/ethyl acetate and ethyl acetate were the most promising solvents to obtain annatto extracts with both antioxidant and colour properties.     

Extraction of phenolics from Vitis vinifera wastes using non-conventional techniques

Polyphenols, the well known naturally occurring antioxidants, are the most abundant secondary metabolites in grape wastes. Herein we investigate several non-conventional extraction methods vs classic solid–liquid extraction (SLE) to obtain phenolic compounds from grape seeds and skins. We compared SLE, ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE) and high pressure and temperature extraction (HPTE) in term of extraction yield and antioxidant power of the extract. Solvent of choice between methanol and ethanol was the former, both for skins and seeds. Quali-quantitative analyses were performed using colorimetric and HPLC methods. The highest content in total polyphenols, o-diphenols and flavonoids, both for seeds (108.3, 47.0 mg_GAE g_DW⁻¹, 47.2 mg_CE g_DW⁻¹) and skins (34.2, 10.1 mg_GAE g_DW⁻¹, 21.6 mg_CE g_DW⁻¹) was obtained with HPTE working in a Parr reactor. While the highest antiradical power was determined in seeds extracts from MAE (78.6 μl_extract μg_DPPH⁻¹). Prolonged extraction times (over 30 min) further increased the amount of total polyphenols, while progressively decreased the amount of flavonoids and the antiradical power.     

Pulsed electric fields- and ultrasound-assisted green extraction of valuable compounds from Origanum vulgare L. and Thymus serpyllum L.

This work compared the effects of pulsed electric fields (PEF) and ultrasound (US) technologies on the extent of cell disintegration of two Mediterranean herb tissues (Origanum vulgare L., Thymus serpyllum L.), as well as on the extractability of phenolic compounds during the subsequent hydroalcoholic extraction (0%–50% ethanol in water, v/v) for up to 4 h. The rate of phenolic compounds extraction decreased with time and was predicted rather satisfactorily (R² = 0.898–0.989) by the Peleg’s model. The application of either PEF or US treatment prior to solid–liquid extraction (SLE) has the potential to reduce duration and concentration of ethanol to achieve the same recovery yield of phenolic compounds. Under optimised PEF (3 kV cm⁻¹, 10 kJ kg⁻¹) and US (400 W, 20 min) treatment conditions, the extracts obtained from either PEF or US pretreated herb samples showed higher total phenolic yield (36% on average) and antioxidant activity (FRAP) (36% on average) as compared to the control extraction, especially when 25% ethanol was used as a solvent. GC/MS analyses revealed no evidence of degradation of individual phenolics due to either PEF or US application.     

Phenolic and antioxidant potential of olive oil mill wastes

Olive oil mill waste was subjected to conventional liquid solvent extraction and supercritical fluid extraction using different solvents and carbon dioxide, respectively. The optimum solvent extraction conditions of phenols were 180 min using ethanol, at a solvent to sample ratio 5:1 v/w, and at pH 2. Solvent and SFE extracts were tested for their antioxidant activity by the DPPH radical scavenging method and by determination of peroxide value on virgin olive oil and sunflower oil. The ethanol extract exhibited the highest antiradical activity, and no correlation was found between antiradical activity and phenol content. The SFE extract exerted good antioxidant capacity although its phenolic yield was not quite high. Moreover, the ethanol extract appeared to be a stronger antioxidant than BHT, ascorbyl palmitate and vitamin E by the Rancimat method on sunflower oil. HPLC analysis of the extracts showed that the predominant phenolic compound was hydroxytyrosol. Various phenolic acids and flavonoids were also identified.     

Extraction,optimisation and characterisation of phenolics from Thymus vulgaris L.: phenolic content and profiles in relation to antioxidant,antidiabetic and antihypertensive properties

The objectives of this study were to examine varying extraction conditions of Thymus vulgaris L. as related to phenolic content and profiles of the extracts and their antioxidant, antihypertensive and antidiabetic properties. Phenolics were extracted under various conditions pertaining to free and bound phenolics, solvent type and combination of extraction time and temperature, and these extracts were evaluated in terms of their antioxidant activities and inhibitory activities of angiotensin‐converting enzyme (ACE), α‐glucosidase and α‐amylase. The acetone–water solvent mixture (1:1; v/v) produced the extract with the greatest phenolic content, antioxidant activity and inhibitory activities of ACE and α‐glucosidase. The optimal extraction temperature for maximum phenolic content and antioxidant activity associated with methanol extraction was 60 °C, whereas a lower temperature at 40 °C was required to maximise inhibitory activities for ACE, α‐glucosidase and α‐amylase. An inverse relationship was seen between antioxidant and glucosidase inhibitory activities vs. the ACE and α‐amylase inhibitory activities, which suggests the need for extractions to be directed to specific bioactivities of thyme extracts. Generally, the results indicate major differences in phenolic profiles among the tested extraction conditions with thymol as the predominant phenolic seen in most extractions, while gallic acid, rosmarinic acid or diosmin also predominated in other extracts. Extracts with the same predominant phenolic compound and similar phenolic content showed major disparities in their ACE, glucosidase and α‐amylase inhibitory activities, indicating that the major phenolic profiles of thyme extracts may not be necessarily related to the degree of inhibition of ACE, glucosidase and α‐amylase enzymes.     

A comparative study on the polyphenolic content,antibacterial activity and antioxidant capacity of different solvent extracts of Brassica oleracea vegetables

Brassica vegetables are rich in polyphenols, flavonoids and glucosinolates. Investigation was undertaken to optimise the best solvents among 60% ethanol, acetone and methanol for the extraction of polyphenols from Brassica vegetables. Furthermore, different properties such as antibacterial activity and antioxidant capacity were also investigated. Results showed that a 60% methanolic extract showed the highest total phenolic content which was 23.6, 20.4 and 18.7 mg gallic acid equivalents (GAE) g^?1 extract for broccoli, Brussels sprouts and white cabbage, respectively. The hydroxybenzoic acid content of various solvent extracts ranged from 5.86 to 8.91 GAE g^?1 extract for broccoli, 2.70 to 5.44 GAE g^?1 extract for Brussels sprouts and 3.69 to 4.86 GAE g^?1 extract for white cabbage, while the hydroxycinnamic acid content ranged from 0.78 to 1.26 chlorogenic acid equivalents (CAE) g^?1 extract for broccoli, 1.41 to 3.45 CAE g^?1 extract for Brussels sprouts and 0.49 to 1.14 CAE g^?1 extract for white cabbage. A concentration‐dependent antioxidative capacity was confirmed for different reactive oxygen species, and moderate antibacterial activity was observed against a number of Gram‐negative and Gram‐positive food spoilage and food pathogenic bacteria. Solvents significantly affected polyphenolic content and its different properties, and the methanol was found to be the best solvent for the extraction of polyphenols from studied Brassica vegetables.     

Characterisation of phenolic extracts from olive pulp and olive pomace by electrospray mass spectrometry

Methanol extracts of olive pomace (two‐phase olive oil extraction) and olive pulp were analysed by reverse phase HPLC and the eluted fractions were characterised by electrospray ionisation mass spectrometry. This technique allowed the identification of some common phenolic compounds, namely, verbascoside, rutin, caffeoyl‐quinic acid, luteolin‐4‐glucoside and 11‐methyl‐oleoside. Hydroxytyrosol‐1′‐β‐glucoside, luteolin‐7‐rutinoside and oleoside were also detected. Moreover, this technique enabled the identification, for the first time in Olea europaea tissues, of two oleoside derivatives, 6′‐β‐glucopyranosyl‐oleoside and 6′‐β‐rhamnopyranosyl‐oleoside, and of 10‐hydroxy‐oleuropein. Also, an oleuropein glucoside that had previously been identified in olive leaves was now detected in olive fruit, both in olive pulp and olive pomace. With the exception of oleoside and oleuropein, the majority of phenolic compounds were found to occur in equivalent amounts in olive pulp and olive pomace. Oleoside was the main phenolic compound in olive pulp (31.6 mg g^?1) but was reduced to 3.6 mg g^?1 in olive pomace, and oleuropein (2.7 mg g^?1 in the pulp) almost disappeared (<0.1 mg g^?1 in the pomace). Both these phenolic compounds were degraded during the olive oil extraction process. Copyright © 2004 Society of Chemical Industry     

Optimum aqueous extraction conditions for preparation of a phenolic‐enriched Davidson's plum (Davidsonia pruriens F. Muell) extract

This study aimed to optimise aqueous extraction conditions for total phenolic compounds (TPC) from Davidson's plum (Davidsonia pruriens F. Muell) and to assess the physicochemical and antioxidant properties of the phenolic‐enriched extract. The results showed that temperature, time and ratio significantly affected the extraction of TPC. Optimization of extraction conditions was performed using response surface methodology (RSM) utilising a Box–Behnken design. Optimal extraction conditions were determined to be temperature: 90 °C, extraction time: 30 min and solvent to mass ratio: 20:1 mL g^?1. The extracted solid obtained under these conditions had low‐moisture content, high water solubility and contained 45 mg GAE g^?1 of TPC, 22 mg RUE g^?1 of flavonoids, 3.2 mg CAE g^?1 of proanthocyanidins, 2 mg CGE g^?1 of anthocyanidins and 56 mg ACE g^?1 vitamin C. The extract possessed potent antioxidant capacity, but was comparatively lower than those of vitamin E and BHT. Thus, Davidson's plum should be further investigated for its potential health promoting benefits and utilisation in the nutraceutical and food industries.     

Red clover (Trifolium pratense L.) isoflavones: root phenolic compounds affected by biotic and abiotic stress factors

BACKGROUND: Phenolic compounds have recently received considerable attention for their ability to protect plant and human cells from oxidative stress‐induced damage. Red clover (Trifolium pratense L.) is a rich source of isoflavonoids with multiple potential protective functions. The aim of this study was to identify and characterise phenolic compounds in red clover roots by high‐performance liquid chromatography and mass spectrometry and to study the effects of stress factors and growth stage on root phenolics. RESULTS: A total of 28 phenolic compounds were tentatively identified in red clover roots. The most abundant phenolics in pot‐grown roots were formononetin glycoside malonate (G‐M) (1.51–4.26 mg g^?1), formononetin (2.21–3.57 mg g^?1) and biochanin A (1.73–2.17 mg g^?1), whereas field‐grown roots were rich in formononetin‐G‐M (3.90–4.27 mg g^?1), maackiain‐G‐M (2.35–3.02 mg g^?1) and pseudobaptigenin‐G‐M (1.80–2.58 mg g^?1). Concentrations were affected by the growth stage. Ozone exposure slightly affected the total phenolic content in roots and also had minor effects on individual compounds. CONCLUSION: Elevated ozone, cultivation regime and growth stage affected the levels of phenolics in red clover roots, suggesting sensitivity of root phenolics to biotic and abiotic stress conditions. The high levels of phenolics found in roots even in late autumn may be utilised in many applications. Copyright © 2009 Society of Chemical Industry     

Optimization and economic evaluation of pressurized liquid extraction of phenolic compounds from jabuticaba skins

The optimization of the extraction of anthocyanins and other phenolic compounds from jabuticaba skins, a promising Brazilian source of these compounds, was studied using pressurized liquid extraction (PLE). An optimization study was performed using ethanol as a solvent and with extraction pressure (5-10 MPa), temperature (313-393 K) and static extraction time (3-15 min) as independent variables. The optimum PLE conditions for all response variables were estimated; however, PLE conditions resulting in the highest recovery of anthocyanins (5 MPa, 553 K and 9 min of static extraction time) were chosen for comparison with a conventional low-pressure solvent extraction (LPSE). The attributes compared were yield, content of anthocyanins and phenolic compounds and economic feasibility. Similar extraction yields were obtained by LPSE and PLE under optimized conditions; however 2.15 and 1.66-fold more anthocyanins and total phenolic compounds, respectively, were extracted using PLE, while the cost of manufacturing (COM) obtained for the PLE extract was 40-fold lower.     

Extraction of Total Phenolic Content from Garcinia mangostana Linn. hull. I. Effects of Solvents and UV–Vis Spectrophotometer Absorbance Method

The effect of solvents with different polarity on the extraction of total phenolic content from mangosteen hull was investigated. The Folin–Ciocalteu (FC) method, expressed in equivalent to gallic acid concentration was used to quantify total phenolic content. Methanol was the most effective solvent in giving the highest recovery (p?<?0.05) of phenolic compounds, compared to ethanol, acetone, isopropanol, ethyl acetate and distilled water. Regression analysis was performed to evaluate the relationship between the direct absorbance method and the FC method for total phenolic contents determination. Strong coefficients of determinations (R ²?≥?0.990) were obtained for the absorbance of acetone, ethanol, and methanol extracts suggesting the regression equations obtained can be used to determine the total phenolic contents without using the FC method.     

Selection of the Solvent and Extraction Conditions for Maximum Recovery of Antioxidant Phenolic Compounds from Coffee Silverskin

The extraction of antioxidant phenolic compounds from coffee silverskin (CS) was studied. Firstly, the effect of different solvents (methanol, ethanol, acetone, and distilled water) on the production of antioxidant extracts was evaluated. All the extracts showed antioxidant activity (FRAP and DPPH assays), but those obtained with methanol and ethanol had significantly higher (p?<?0.05) DPPH inhibition than the remaining ones. Due to the lower toxicity, ethanol was selected as extraction solvent, and further experiments were performed in order to define the solvent concentration, solvent/solid ratio, and time to maximize the extraction results. The best condition to produce an extract with high content of phenolic compounds (13 mg gallic acid equivalents/g CS) and antioxidant activity [DPPH?=?18.24 μmol Trolox equivalents/g CS and FRAP?=?0.83 mmol Fe(II)/g CS] was achieved when using 60 % ethanol in a ratio of 35 ml/g CS, during 30 min at 60–65 °C.     

Activated Carbon and Ion Exchange Treatments for Removing Phenolics and Phytate from Peanut Protein Products

Commercial defatted peanut flour and laboratory defatted peanut meal contained 1.5 and 1.7% phytate, 1756 and 2033 μg g^?1 total phenolic acids and 50 and 120 μg g^?1 neutral phenolics, respectively. Laboratory peanut protein isolate contained undetectable amounts of neutral phenolics, 810 μg g^?1 total phenolic acids and about 1% phytate. The ion exchange treatment removed ≥85% of the phytate and the ion exchange and activated carbon treatments removed 92 and 82%, respectively, of the total phenolic acids from peanut protein isolate. p-Coumaric acid was the major phenolic acid, accounting for 40–68% of the total phenolic acids in all peanut protein products.     

Microwave‐assisted extraction of secoisolariciresinol diglucoside from flaxseed hull

Microwave‐assisted extraction (MAE) of secoisolariciresinol diglucoside (SDG) from defatted flaxseed hull (DFH) was studied. The effects of pre‐soaking methods and extraction parameters (ethanol concentration (0–100%, v/v), microwave energy input (50–390 W), liquid to solid ratio (5:1 to 40:1, mL g^?1) and irradiation time (10–330 s)) on the SDG yield were investigated. Response surface methodology (RSM) was applied to optimise the MAE conditions as irradiation time 90.5 s, ethanol concentration 40.9% (v/v), liquid to solid ratio 21.9:1 (mL g^?1) and microwave power 130 W. The SDG recovery from DFH with MAE was 11.7 g SECO kg^?1 DFH (on dry‐weight basis), which was significantly higher than that of stirring extraction (10.0 g SECO kg^?1 DFH) and Soxhlet extraction (7.60 g SECO kg^?1 DFH). Compared with stirring extraction and Soxhlet extraction, MAE showed its superiority in improving SDG yield and saving time and energy. Copyright © 2007 Society of Chemical Industry     

Effects of high-pressure treatment on the extraction yield, phenolic content and antioxidant activity of litchi (Litchi chinensis Sonn.) fruit pericarp

As a promising technique, high-pressure extraction (HPE) method was used to extract bioactive compounds from litchi fruit pricarp. The study involved in different experimental factors such as solvent, ethanol concentration (35-95, v/v), material to solvent ratio (1:25-1:100, w/v), acidic medium, extraction pressure (200-500 MPa), time (2.5-30 min) and temperature (30-90 °C). The extraction yield, total phenolic contents, 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity and superoxide anion scavenging capability of the HPE sample were examined and then compared with those of ultrasonic extraction and conventional extraction samples. The application of HPE obtained higher extraction yield compared to other extraction methods. However, there were no significant differences ( P  >   0.05) in the total phenolic content and the antioxidant activities among these various extractions. Compared with some conventional extraction method, the HPE exhibited higher extraction efficiency in terms of higher extraction yield and extraction time.