Antioxidant and anticancer activities of high pressure-assisted extract of longan (Dimocarpus longan Lour.) fruit pericarp

Longan fruit pericarp was extracted with 50% ethanol employing high pressure (500 MPa) and conventional extraction methods. Total phenolic contents of high pressure-assisted extract of longan (HPEL) and conventional extract of longan (CEL) were 20.8 and 14.6 mg gallic acid equivalents/g dry weight, respectively. Subsequently, the antioxidant activities of these extracts were analyzed employing various antioxidant model systems including 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, superoxide anion radical scavenging activity, total antioxidant capacity, and lipid peroxidation inhibitory activity. In addition, anticancer activity was also tested using HepG2, A549, and SGC 7901 cancer cell lines. HPEL showed excellent antioxidant and anticancer activities and were higher than CEL. Three phenolic compounds, namely gallic acid, corilagin, and ellagic acid, were identified and quantified by external standard methods. Compared with CEL, HPEL exhibited higher extraction effectiveness in terms of higher extraction yield, higher phenolic content, and higher antioxidant and anticancer activity with shorter extraction time.

Industrial relevance

This study was focused to evaluate the antioxidant and anticancer activity of longan fruit pericarp by high-pressure treatment. The high-pressure treatment provided a better way of utilizing longan fruit pericarp as a readily accessible source of the natural anticancer and antioxidant in food and pharmaceutical 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.     

Ultrahigh pressure extraction as a tool to improve the antioxidant activities of green tea extracts

In this study, the effect of ultrahigh pressure extraction at pressures of 150 MPa, 250 MPa, 350 MPa and 450 MPa on the total phenolic contents, the extraction yields and the antioxidant activities of green tea were investigated. The antioxidant activities of these extracts were analyzed using DPPH radical scavenging activity and total antioxidant capacity. The results showed that the phenolic contents and the antioxidant activities of extracts were greatly influenced by high pressure. The total phenolic contents and the antioxidant activities of ultrahigh pressure extraction at 450 MPa were higher than those of other ultrahigh pressure extraction and conventional extraction. The high content of phenolic compounds in the green tea leaves could account for the antioxidant activity. This study indicated that this new technology can benefit the food and pharmaceutical industries.     

Total phenolic content and antioxidant capacity of extracts obtained from six important fruit residues

The extracts from kinnow peel, kinnow seeds, litchi pericarp, litchi seeds, grape seeds, and banana peel were screened for total phenolic content (TPC), trolox equivalent antioxidant capacity (TEAC), 1,1 diphenyl-2-picryl hydrazyl (DPPH) radical scavenging activity, as well as reducing power. Kinnow peel extract exhibited the highest reducing power, TEAC, and DPPH free radical scavenging activity, whereas, the phenolic content of 37.4 mg GAE/g-dw was highest for grape seed extract. Banana peel extract with a low TPC showed the lowest reducing power, TEAC as well as DPPH free radical scavenging activity among the fruit residue extracts examined in the present study. Correlation analysis between the reducing power and DPPH radical scavenging ability; reducing power and ABTS radical scavenging activity; and ABTS and DPPH radical scavenging abilities showed a high degree of correlation (r² = 0.85-0.91). However, r² of 0.36, 0.66, and 0.49 between TPC and DPPH radical scavenging activity; TPC and reducing power; and TPC and ABTS radical scavenging ability, respectively, indicated that some non-phenolic compounds also contributed to the total antioxidant activity in fruit residue extracts examined in this study. To the best of our knowledge, this is the first paper presenting comprehensive data on TPC, reducing power, and antioxidant activity for the six fruit residues. This study demonstrated that kinnow peel, litchi pericarp, litchi seeds, and grape seeds, can serve as potential sources of antioxidants for use in food and pharmaceutical industry.     

Antioxidant and tyrosinase inhibitory activity of mango seed kernel by product

The antioxidant and tyrosinase inhibitory properties of extracts of mango seed kernel (Mangifera indica L.), which is normally discarded when the fruit is processed, were studied. Extracts contained phenolic components by a high antioxidant activity, which was assessed in homogeneous solution by the 2,2-diphenyl-1-picrylhydrazyl radical and 2,2′-azinobis (3-ethylbenzothialozinesulfonic acid) radical cation-scavenging assays and in an emulsion with the ferric thiocyanate test. The extracts also possessed tyrosinase inhibitory activity. Drying conditions and extraction solvent were varied, and optimum conditions for preparation of mango seed kernel extract were found to be sun-drying with ethanol extraction at room temperature. Refluxing in acidified ethanol gave an increase in yield and the obtained extract had the highest content of total phenolics, and also was the most effective antioxidant with the highest radical-scavenging, metal-chelating and tyrosinase inhibitory activity. The extracts did not cause acute irritation of rabbit skins. Our study for the first time reveals the high total phenol content, radical-scavenging, metal-chelating and tyrosinase inhibitory activities of the extract from mango seed kernel. This extract may be suitable for use in food, cosmetic, nutraceutical and pharmaceutical applications.     

Integration of pressurized liquids and ultrasound in the extraction of bioactive compounds from passion fruit rinds: Impact on phenolic yield,extraction kinetics and technical-economic evaluation

Passion fruit rind is a by-product rich in bioactive compounds that can be recovered by high pressure extractions and ultrasound using nontoxic solvents in shorter process times. This work investigated Pressurized Liquid Extraction (PLE) and its combination with ultrasound (Ultrasound-Assisted Pressurized Liquid Extraction, UAPLE) to intensify the recovery of phenolic compounds from passion fruit rinds. The influences of process parameters such as temperature, pressure, ultrasonic intensity and solvent mass flow rate on the global yield (X₀), total phenolic content (TPC) and antioxidant capacity were evaluated. The major phenolics were determined by UHPLC-QE HRMS. Kinetic extraction curves adjusted by the Spline and two-site models showed that in UAPLE (60 °C, 10 MPa and 360 W/cm²) with solvent flow rate of 10 g/min, 100% of TPC was recovered in 68.54 min of extraction. This condition also provided the greatest economic viability concerning total phenolics, with the lowest estimated manufacturing cost.Industrial relevanceSynthetic compounds in processed food have been increasingly rejected by consumers, who look for natural compounds that promote health benefits and are obtained with sustainable technologies. The bioactive compounds found in passion fruit rinds can meet this industrial demand as potential colorants, additives and natural preservatives in foods or beverages, incorporated in cosmetics, functional food and pharmaceutical supplements. In order to successfully recover bioactive compounds, it is recommended to apply selective extraction techniques in the target compound, thus providing final products with greater added value. In addition, the process optimization is crucial to achieve optimal extraction conditions to maximize the yield of the targent compounds. Given this context, searching for a more sustainable destination of the passion fruit agroindustrial waste and to increase its commercial value, this work proposes the combination of two extraction techniques, Ultrasound and Pressurized Liquid Extraction (UAPLE), to intensify the recovery of bioactive compounds from passion fruit rinds. The findings of this work reveal that UAPLE can enhance the extraction of phenolic compounds from passion fruit rinds even at moderate temperatures, thus encouraging the application of this technique for other agroindustrial by-products. Moreover, the economic evaluation of the UAPLE at the optimal conditions indicates its viability for industrial scale application.     

Optimization of Supercritical Carbon Dioxide Extraction of Xanthones from Mangosteen Pericarp by Response Surface Methodology

Mangosteen fruit pericarp is one of the important sources of bioactive compound xanthone. Supercritical carbon dioxide (SC-CO₂) extraction was employed to extract xanthones from mangosteen fruit pericarp at three different levels of pressure (200–300 bar), temperature (40–60 °C) and solvent to material ratio (100–300 kg/kg). The optimal conditions for the total xanthone yield and the influence of parameters were determined by response surface methodology (RSM) using Box–Behnken design. In our study, the increase in total xanthone yield in SC-CO₂ fluid extraction depends more on the solute’s vapor effect. From response surface plots, pressure, temperature and solvent to material ratio exhibited independent and interactive effects on the extraction of xanthones. A regression equation for predicting the total xanthone yield was derived by statistical analysis, and a model with predictive ability of 0.99 was obtained. Maximum xanthone yield of 8.01% was predicted by RSM at 60 °C, 300 bar and a solvent to material ratio of 300 kg/kg while experimentally a yield of 7.56% was achieved. HPLC analysis was carried out for the optimum conditions for the identification and quantification of the xanthones. The antioxidant activities of the extracts were investigated by ferric reducing antioxidant power (FRAP) and the results showed that the extracts were enriched with antioxidant compound.     

Optimisation of pressurised liquid extraction for antioxidative polyphenolic compound from Momordica charantia using response surface methodology

Pressurised liquid extraction (PLE) of antioxidant compounds from bitter gourd fruits (Momordica charantia) in aqueous ethanolic solvent was investigated using response surface methodology at laboratory scale to understand key impact of extraction variables. Extraction efficiency was optimised by measuring the yield of extraction, total phenolic content (TPC), total flavonoid content (TFC), ferric reducing/antioxidant power assay (FRAP) and radical scavenging activity (RSA). The optimal extraction conditions were reached at 80% ethanol concentration, 10‐min extraction time and at 160 °C. Under these extraction conditions, values of TPC (5.40 ± 0.30 g GAE per 100 g), TFC (1.50 ± 0.10 g QE per 100 g), FRAP (778.55 ± 10 μmol eq Fe (II) g^?1), yield (178.50 ± 5.50 mg g^?1 dc) and RSA (75.50 ± 4.50%) were achieved. Furthermore, statistical analysis revealed that antioxidative attributes of bitter gourd extract were strongly and positively correlated with extraction temperature and ethanol concentration rather than processing time. This study illustrated that PLE has the potential to extract antioxidant compounds from tropical fruit vegetables in an accelerated manner. Furthermore, influential parameters affecting the process could be optimised for further industrial intake.     

茉莉酸甲酯处理对采后龙眼果皮褐变的影响

本实验以10、50、100μmol/L MeJA处理‘储良’龙眼(Dimocarpus longan Lour.)果实,研究其对(20±1)℃、85%相对湿度贮藏条件下的龙眼果皮褐变的影响。结果表明：与对照组相比,MeJA处理可有效降低‘储良’龙眼采后果皮褐变指数、果皮细胞膜透性和果肉自溶指数,而且MeJA浓度越高,抑制效果越明显。与对照组相比,100μmol/L MeJA处理龙眼果实能够保持较高的果皮总酚和类黄酮含量,降低果皮多酚氧化酶活力,有效提高果皮过氧化物酶和苯丙氨酸解氨酶活力;另一方面,MeJA处理可以有效降低超氧阴离子自由基产生速率以及H₂O₂含量,有效增强抗氧化酶(超氧化物歧化酶、过氧化氢酶)活力以及1,1-二苯基-2-三硝基苯肼自由基清除能力,提高果皮抗氧化能力。综上,100μmol/L MeJA处理可抑制龙眼果实采后部分酚类物质代谢,增强其抗氧化能力,从而延缓龙眼采后果皮褐变的发生,延长贮藏保鲜期。     

A process for turning pomegranate peels into a valuable food ingredient using ultrasound-assisted extraction and encapsulation

A new method for pomegranate peel application in food industries was developed based on the ultrasound-assisted extraction of phenolic compounds and their subsequent encapsulation by spray drying. The effects of various parameters on extraction yield, on encapsulation efficiency/yield, and on the main physical properties of the microcapsules (moisture content, bulk density, rehydration ability) were studied. Ultrasound was found to increase extraction yield, but mainly to shorten the treatment time by over 20 times. The maximum encapsulation efficiency was 99.80% and the optimum operating conditions were found to be: wall material, maltodextrin/whey protein isolate (50:50); inlet air temperature, 150 °C; drying air flow rate, 17.5 m³/h; ratio of wall to core material, 9/1; feed solid concentration, 30% (w/w). The encapsulated phenolic extract was found efficient in improving the shelf life of hazelnut paste, in spite of the limited solubility of the crude extract in such a high lipid content matrix.Industrial relevancePomegranate peels, a by-product of pomegranate juice and concentrate industries, present a wide range of pharmaceutical and nutraceutical properties. Therefore, the peels could have more beneficial applications in food industries instead of being used as animal feed or in commercial cosmetic products. In this work, a new method for pomegranate peel application was developed based on the ultrasound-assisted extraction of phenolics and their subsequent encapsulation by spray drying.     

Effects of extraction solvent on wheat bran antioxidant activity estimation

Significant levels of antioxidant activities and phenolic components have been detected in wheat and wheat-based food products, indicating that wheat may serve as an excellent dietary source of natural antioxidants for disease prevention and health promotion. Several solvent systems have been used to prepare antioxidant extracts from wheat and wheat-based food products. This makes it difficult to compare and understand the antioxidant activities of wheat reported from different research groups. The purpose of this study was to evaluate the effects of four selected solvent systems at ambient temperature for 15 h and Soxhlet extraction with absolute ethanol on antioxidant activity measurements. The four solvent systems included 50% acetone (v/v), 70% methanol (v/v), 70% ethanol (v/v), and ethanol, and antioxidant activities were tested using ORAC, radical scavenging activities against stable DPPH^• and cation ABTS^•+, and total phenolic content. The results showed that the extracting solvent significantly altered the antioxidant property estimations of wheat bran, and 50% acetone is a recommended solvent for extracting phenolic antioxidants from wheat bran for analytical purpose.     

Optimisation of ethanol modified supercritical carbon dioxide on the extract yield and antioxidant activity from Garcinia mangostana L.

Xanthones are an important class of secondary metabolites present in mangosteen fruit pericarp. Herein we have used supercritical fluid technology to extract the active constituents from mangosteen pericarp. Ethanol was added (5% w/w) as a co-solvent to increase the polarity of the CO₂, thus favouring the extraction of xanthones. The maximum extraction yield of 15 wt.% was achieved at a pressure of 280 bar, temperature of 50 °C and a time of 8 h, while without co-solvent the yield was 7.5 wt.%. Conditions for antioxidant activity as measured by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging assay was 280 bar at 50 °C and 5 h. Box–Behnken design was used to study the efficiency of extraction pressure (180, 280, and 380 bar), temperature (40, 50, and 60 °C) and time (2–8 h) on the total extraction yields and their radical scavenging activity. Experimental results of the total extract yield and radical scavenging activity were close to the predicted values calculated from the polynomial response surface models equations (R² = 0.99 and 0.98).     

Valorization of Pinus taeda bark: source of phenolic compounds,tannins and fuel

Pine bark is a byproduct of wood processing which is usually burnt for energy. This article analyzes the liquid–solid extraction of Pinus taeda bark to obtain phenolic compounds by using response surface methodology to determine extraction conditions. The independent variables studied were temperature, ethanol concentration and solid–liquid ratio, and the variables to be optimized were total extractives yield, phenolic content, antioxidant capacity and condensed tannins yield. In addition, the extract was characterized by Fourier transform infrared spectroscopy and UV–Vis spectroscopy. Furthermore, extraction kinetics were modeled, and mass transfer mechanisms were studied. The extraction condition that maximizes extraction yields was defined at 50 °C, with a solid–liquid ratio of 1/10 and with an ethanol concentration of 50%. The condensed tannins yield was 4.01 g catechin equivalent (CE)/100 g pine bark dry base (d.b.), the total extractive yield was 9.83 g extract/100 g pine bark d.b. and the Stiasny number was 77. The extract showed a FRAP antioxidant concentration of 20.89 mmol ascorbic acid equivalent (AAE)/100 g pine bark d.b and 0.35 mmol trolox (TRE)/g pine bark d.b. for ABTS assay. The results showed that extended Fick’s law was adequate to describe the extraction kinetics. The extraction did not significantly affect the calorific value of bark (21 kJ/g d.b.). After extraction, the ashes were reduced by 13% and potassium (K) by 48%. The extraction of Pinus taeda to obtain phenolic content is technically feasible, and this paper provides the scientific ground for further scaling the process.

     

On the extraction and antioxidant activity of phenolic compounds from winery wastes

Winery waste (from red winemaking, variety Agiorgitiko) was extracted under various conditions using different solvents. The minimum time required for ensuring maximum extraction of phenols was 180 min at a solvent to sample ratio 9:1 v/w and at pH 1.5. The antioxidant activity of solvent extracts was investigated by DPPH radical scavenging method, by determination of peroxide value on virgin olive oil and by the Rancimat method on sunflower oil. Ethanol extract exhibited the highest antioxidant activity compared to the other solvent extracts, to synthetic food antioxidants BHT, ascorbyl palmitate and to the natural food antioxidant, vitamin E. No correlation was found between antioxidant activity and total phenol content. HPLC analysis of the extracts showed that gallic acid, catechin and epicatechin were the major phenolic compounds in winery waste. Hydroxytyrosol, tyrosol, cyanidin glycosides and various phenolic acids such as caffeic, syringic, vanillic, p-coumaric and o-coumaric acids were also identified.     

Phenolics, betacyanins and antioxidant activity in Opuntia joconostle fruits

Sour prickly pears (xoconostles) are fruits from Opuntia joconostle cactus, which are cultivated in the central Mexico area. Phenolic and pigment content in various parts of O. joconostle fruits were analyzed. The antioxidant activity of a methanolic extraction and different semi-purified fractions were also evaluated by the DPPH⁺ method. Xoconostle fruits were obtained from a commercial orchard in Mexico State. Fruits were analyzed as whole fruit and each fruit part including pericarp, mesocarp and endocarp. Samples were homogenized and kept at 4 °C until sample preparation. Total phenolic content and total flavonoid content varied among the different parts of the fruit. The highest amount of phenolic compounds and total flavonoids content were found in pericarp 2.07 mg gallic acid equivalents (GAE)/g fresh weight (FW) and 0.46 mg(+)-catechin equivalents (CE)/g FW respectively. Seven phenolics were identified as protocatechuic, 4-hydroxybenzoic, caffeic, vanillic and syringic acids, rutin, and quercetin. The color of the fruit parts was mainly due to the presence of betacyanins. The betacyanin concentration was higher in the endocarp (23.03 mg betanin equivalents/100 g fresh weight) than in the pericarp and mesocarp. Betacyanins were identified by HPLC-PDA-MS as betanin, isobetanin, betanidin, isobetanidin, and phyllocactin. Methanolic extracts and semi-purified fractions A (phenolics and flavonols) and B (betacyanins) of xoconostle showed high antioxidant activity mainly in the pericarp. These results suggest that xoconostle is a rich source of antioxidant compounds such as phenolic compounds and betacyanins.     

Phenolic composition,antioxidant and antimicrobial activities of free and bound phenolic extracts of Moringa oleifera seed flour

Phenolic compounds, antioxidant and antibacterial activities of defatted Moringa oleifera seed flour (DMF) were investigated. The total phenolic and flavonoid contents were measured using colorimetric methods. Free phenolic acid and flavonoid profiles were analyzed by high performance liquid chromatography, while antioxidant capacities were evaluated using scavenging assays of 1,1-diphenyl-2-picrylhydrazyl radical (DPPH), ferric reducing antioxidant power and total antioxidant capacity. The results showed that extractability of phenolic compounds was significantly higher (p < 0.05) in bound phenolic extract (4173.00 ± 32.22 mg gallic acid equivalents (GAE)/100 g) than in free phenolic extract (780.00 ± 14.2 mg GAE/100 g) and it showed higher antioxidant and antimicrobial activities. The IC₅₀ value for DPPH radical scavenging activity was 0.9 ± 0.05 and 14.9 ± 0.07 mg/mL for bound phenolic and free phenolic extracts, respectively. Bound phenolic extract was more effective (minimum inhibitory concentration (MIC), 0.06–0.157%) than free phenolic extract (MIC, 0.117–0.191%) against tested bacteria. Ten phenolic compounds (gallic acid, p-coumaric acid, ferulic acid, caffeic acid, protocatechuic acid, cinnamic acid, catechin, epicatechin, vanillin and quercetin) were identified and quantified in both extracts. These natural plant phenolics from Moringa seeds could be a good source of antioxidants and antibacterials for food and pharmaceutical industries.     

Stability and antioxidant potential of purified olive mill wastewater extracts

A purified olive extract (POE) rich in phenolic and oleosidic compounds was prepared from olive mill wastewaters by adsorption onto an amphoteric polymer resin with the yield of 2.2% (w/v). In addition to complex and simple phenolic compounds found in the POE, the highly hydrophilic elenolic acid and DEDA (dialdehydic form of decarboxymethyl elenolic acid, a non-phenolic secoiridoids) were also present in high concentration (45%, w/w). Among the phenolic constituents, the major compounds are hydroxytyrosol and its glucoside, DEDA linked to hydroxytyrosol (Hy-DEDA), p-coumaric acid and caffeic acid, verbascoside and some flavonoids. The high content (23%, w/w in gallic acid equivalent) and structural diversity of these phenolic compounds confer superior antioxidant potential of POE with an IC₅₀ less than 8.5 μg/ml determined by DPPH assay. The stability of bioactive components during storage of the extract and changes in antioxidant properties were studied under different conditions. Determination of kinetics of degradation revealed that air/oxygen is the determinant factor which influences the stability of POE under low temperature storage conditions, while exposure to sunlight did not have significant effect on their stability. Whilst an increase in storage temperature decreased the total content of phenolic compounds (20-24% reduction) and non-phenolic secoiridoid aglycons, a high antioxidant capacity was still observed particularly in the nitrogen-protected POE samples (93-95% of the initial value). This was believed to be due to the transformation of hydroxytyrosol-containing complex phenols, especially the secoiridoid ester Hy-DEDA, into free phenolic monomer. This contributed significantly to the maintenance of a high antioxidant potency of the whole extract during storage. The high antioxidant, radical scavenging activity and stability of the extract suggest potential applications in the food and pharmaceutical industries.     

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.     

Antioxidant properties of various solvent extracts of potato peel,sugar beet pulp and sesame cake

BACKGROUND: Growing interest in the replacement of synthetic food antioxidants by natural ones has fostered research on vegetable sources and screening of raw materials to identify new antioxidants. The food‐processing industry generates substantial quantities of phenolic‐rich by‐products that could be valuable natural sources of antioxidants. In this study the antioxidant properties and total phenolic, flavonoid and flavonol contents of three industrial by‐products, sugar beet pulp, sesame cake and potato peel, extracted with various solvents were examined. Since different antioxidant compounds have different mechanisms of action, several methods were used to assess the antioxidant efficacy of extracts. RESULTS: Among the six solvents tested, methanol gave the highest extract yield of potato peel and sugar beet pulp, while diethyl ether gave the highest extract yield of sesame cake. Methanol exhibited the highest extraction ability for phenolic compounds, with total phenolics amounting to 2.91, 1.79 and 0.81 mg gallic acid equivalent g^?1 dry weight in potato peel, sugar beet pulp and sesame cake extracts respectively, and also showed the strongest antioxidant capacity in the three assays used. All three methods proved that potato peel extract had the highest antioxidant activity owing to its high content of phenolic compounds and flavonoids. CONCLUSION: On the basis of the results obtained, potato peel, sugar beet pulp and sesame cake extracts could serve as natural antioxidants owing to their significant antioxidant activity. Therefore they could be used as preservative ingredients in the food and/or pharmaceutical industries. Copyright © 2009 Society of Chemical Industry     

Influence of pressurised liquid extraction and solid–liquid extraction methods on the phenolic content and antioxidant activities of Irish macroalgae

The efficiencies of pressurised liquid extraction (PLE) and a traditional solid–liquid extraction (SLE) at extracting antioxidant polyphenols from Irish macroalgae Ascophyllum nodosum, Pelvetia canaliculata, Fucus spiralis and Ulva intestinalis were compared. PLE was more effective for extracting polyphenols with acetone/water (80:20); however, when food‐friendly solvents of ethanol/water (80:20) and water were employed, SLE resulted in higher phenolic content in brown macroalgal extracts. For example, the Fucus spiralis SLE water and ethanol/water extracts displayed total phenolic contents (TPCs) of 130.58 ± 2.78 and 142.81 ± 1.77 μg phloroglucinol equivalents (PGE) mg^?1 sample, respectively, compared with TPCs of 90.79 ± 1.16 and 124 ± 6.54 μg PGE mg^?1 sample for the corresponding PLE extracts. All SLE aqueous ethanolic macroalgal extracts possessed higher DPPH radical scavenging abilities (RSA) and ferric reducing antioxidant power (FRAP) than their PLE equivalents . This study indicates that the application of high extraction temperatures (50–200 °C) and pressures (500–3000 psi) used in PLE does not enhance the antioxidant activities of macroalgal extracts relative to SLE extraction. The ability to produce antioxidant food‐friendly macroalgal extracts using SLE could represent significant cost reductions on an industrial scale further enhancing the potential of macroalgal polyphenols to be used in functional food preparations.