Influence of ethanol/water ratio in ultrasound and high‐pressure/high‐temperature phenolic compound extraction from agri‐food waste

The valorisation and management of agri‐food waste are currently hot investigation topics which probe the recovery of valuable compounds, such as polyphenols. In this study, high‐pressure/high‐temperature extraction (HPTE) and ultrasound‐assisted extraction (UAE) have been used to study the recovery of phenolic compounds from grape marc and olive pomace in hydroalcoholic solutions. The main phenolic compounds in both extracts were identified by HPLC‐DAD. Besides extraction yield (total polyphenol and flavonoid content) and the antiradical power, polyphenol degradation under HPTE and UAE has also been studied. HPTE with ethanol 75% gave higher phenolic extraction yields: 73.8 ± 1.4 mg of gallic acid equivalents per gram of dried matter and 60.0 mg of caffeic acid equivalents per gram of dried matter for grape marc and olive pomace, respectively. In this study, the efficient combination of ethanol/water mixture with HPTE or UAE has been used to enhance the recovery of phenolic compounds from grape marc and olive pomace. HPLC‐DAD showed that UAE prevents phenolic species degradation damage because of its milder operative conditions.     

Optimization of extraction process for phenolic acids from black cohosh (Cimicifuga racemosa) by pressurized liquid extraction

An investigation to optimize the extraction of phenolic acids from black cohosh using a pressurized liquid extractor system was studied with the aim of developing a generalized approach for sample preparation of phenolic compounds from plant matrices. Operating parameters such as solvent composition, solid‐to‐solvent ratio, temperature, particle size distribution, and number of extraction cycles were identified as main variables that influence extraction efficiency. A mixture of methanol and water (60:40 v/v) was found to be the best solvent for total phenolics (TP) and individual phenolic acids. The four phenolic acids extracted from black cohosh were identified by HPLC and LC‐MS as caffeic acid, ferulic acid, sinapic acid and isoferulic acid. Over 96% of the measured phenolics were extracted in first two cycles. The extraction efficiency for black cohosh with MeOH:H₂O (60:40 v/v) was found to be maximum at a solid‐to‐solvent ratio of 80 mg ml^?1. TP content of the extract was found to increase with temperature up to 90 °C. Particle size was found to have a large impact on extraction efficiency of TP. Samples with particle size between 0.25 mm and 0.425 mm provided optimum extraction of phenolics from black cohosh. Published in 2005 for SCI by John Wiley & Sons, Ltd.     

Comparative content of some phytochemicals in Spanish apples,peaches and pears

Dietary fibre, total polyphenols and phenolic acids in Spanish apples, peaches and pears were analysed and compared with their total radical‐trapping antioxidative potential (TRAP). There were no significant differences in the content of dietary fibre among the studied fruits. The content of total polyphenols was 2.4 ± 0.4, 2.1 ± 0.3 and 6.9 ± 0.7 g kg^?1 in peeled fruits and 4.7 ± 0.4, 4.5 ± 0.4 and 11.1 ± 1.2 g kg^?1 in their peels for peaches, pears and apples respectively. The contents of dietary fibre, total polyphenols, caffeic, p‐coumaric and ferulic acids and the TRAP values were significantly (P < 0.05) higher in peels than in peeled fruits. The contents of all studied compounds and the TRAP values were significantly higher in peeled apples and their peel than in peaches and pears. We observed a strong correlation between the contents of total polyphenols and phenolic acids and the total radical‐trapping antioxidative potential in all three fruits. The relatively high content of dietary fibre, the highest contents of total polyphenols, caffeic, p‐coumaric and ferulic acids and the highest value of TRAP make apples preferable among the studied fruits for dietary prevention of atherosclerosis and other diseases. © 2002 Society of Chemical Industry     

Pressurised water extraction of polyphenols from pomegranate peels

Pomegranate peels are one of the most valuable by-products of the food industry in terms of polyphenols which are conventionally extracted from plant materials by organic solvents, especially with methanol. Pressurised water extraction was investigated for the extraction of polyphenols from pomegranate peels. The most important factors affecting the extraction results were found to be particle size, temperature, and static time. The results indicated that pressurised water extraction was as effective as conventional methanol extraction for the recovery of polyphenols from pomegranate peels. Total phenolic contents of pomegranate peels obtained by pressurised water extraction at optimised conditions and conventional solid–liquid methanol extraction were determined as 264.3 and 258.2 mg/g tannic acid equivalents, respectively. Hydrolyzable tannins were the predominant polyphenols of pomegranate peels corresponding to 262.7 mg/g tannic acid equivalents. Punicalagin content of pomegranate peels by pressurised water extraction was found to be 116.6 mg/g on dry matter basis.     

Effect of in vitro‐simulated gastrointestinal digestion on the stability and antioxidant activity of blueberry polyphenols and their cellular antioxidant activity towards HepG2 cells

In this study we investigated the influence of in vitro‐simulated gastrointestinal digestion on the bioaccessibility and antioxidant activity of polyphenols from blueberries (Vaccinium spp.). Total phenolic, anthocyanin, and flavonoid content was determined, and extract and digesta compositions were analysed by HPLC‐ESI‐MS/MS. The phenolic compounds were relatively stable under a gastric environment, whereas polyphenols and anthocyanins were unstable under an intestinal environment. The bioaccessibility of polyphenol, anthocyanin, and flavonoid was greatly decreased after the intestinal digestion, and the recoveries were only 13.93%, 1.95%, and 15.68% (the IN sample), respectively. Polyphenolic profile alteration occurred during in vitro‐simulated gastrointestinal digestion. Changes of phenolic compound antioxidant activity during digestion correlated with polyphenol, flavonoid, and caffeic acid concentrations. Digested extract cellular antioxidant activity was lower than non‐digested extract activity (P < 0.05). Polyphenol dose–response correlations with cellular antioxidant activity were observed. These results indicated that in vitro‐simulated gastrointestinal digestion significantly impact polyphenols and their antioxidant activity.     

Preparation of free, soluble conjugate, and insoluble-bound phenolic compounds from peels of rambutan (Nephelium lappaceum) and evaluation of antioxidant activities in vitro

The soluble phenolic compounds of rambutan peels (RP) were extracted by microwave-assisted extraction (MAE) and the operating parameters were optimized. The optimal conditions obtained were ethanol concentration of 80.85%, extraction time of 58.39 s, and the ratio of liquid to solid of 24.51:1. The soluble phenolic content by MAE was 213.76 mg GAE/g DW. The free, soluble conjugate, and insoluble-boaund phenolic compounds were prepared by alkaline hydrolysis, and the contents of 3 fractions were 185.12, 27.98 and 9.37 mg GAE/g DW, respectively. The contents of syringic acid and p-coumaric acid were high in the free fraction, showing 16.86 and 19.44 mg/g DW, and the soluble conjugate and insoluble-bound phenolics were mainly composed of gallic acid and caffeic acid. Furthermore, the antioxidant activities of 3 fractions were evaluated in 5 model systems. Results indicated that the free fraction had high antioxidant activities, compared with the soluble conjugate and insoluble-bound fractions.     

An Alternative Method for the Determination of Some of the Antioxidant Phenolics in Varietal Turkish Red Wines

The concentration of eight biologically important phenolic compounds (β‐coumaric acid, gallic acid, ferulic acid, caffeic acid, trans‐resveratrol, quercetin, (+)‐ catechin and (?)‐ epicatechin) of red wines produced on a pilot plant scale were determined using gas chromatography with mass spectrometric detection in the selective ion monitoring mode (GC/MS‐SIM). The procedure involved an easy fractionation and liquid‐liquid extraction method. For derivatization, BSA [N,O‐bis‐trimethylsilyl aceta‐mide] / TMCS was used. The results showed that the p‐coumaric acid, gallic acid, ferulic acid, caffeic acid, trans‐resveratrol, quercetin, (+)‐ catechin and (?)‐epicatechin levels in the wine samples ranged between 2.05 and 4.21 mg/L; 21.78 and 60.83 mg/L; 0.33 and 0.82 mg/L; 1.50 and 4.06 mg/L; 0.96 and 3.93 mg/L; 2.66 and 3.14 mg/L; 8.72 and 11.30 mg/L; 5.50 and 9.58 mg/L, respectively. Although the quercetin and trans‐resveratrol levels of Turkish red wines were similar to previously reported values, (+)‐ catechin and (?)‐ epicatechin levels were lower than the values of red wines originating from other countries.     

Effect of commercial enzymatic preparation with pectolytic activities on conventional extraction and ultrasound‐assisted extraction of oil from grape seed (Vitis vinifera L.)

Conventional solvent extraction (CE) and ultrasound‐assisted extraction (UAE) in hexane for oil from untreated and enzyme‐treated grape seeds were investigated and compared. Among the output power tested (50, 100 and 150 W) in UAE on untreated seeds, UAE at 150 W for 30 min with liquid‐to‐solid ratio 8:1 (v/w) gave oil extraction yield comparable to CE (ca. 14% w/w) for 6 h with liquid‐to‐solid ratio 12:1 (v/w). CE and UAE at 150 W did not influence the fatty acid profiles of oil. CE oil was found to be the most oxidised. The enzymatic treatments (2, 4 and 6 g per 100 g seeds of Rapidase^® Expression) prior to CE enhanced by 2.5% of the oil yield. Enzymatic treatments higher than 2 g per 100 g seeds increased relative value of some fatty acids both in CE and UAE. Enzymatic pretreatment from 2 to 4 g per 100 g seeds significantly improved some physicochemical parameters of oil quality when extracted by CE, but not by UAE.     

UHPLC-DAD-ESI-MS/MS法分析紫山药块根和茎叶中酚类物质

本文采用微波辅助法,以80%甲醇作为溶剂提取经冻干后紫山药块根和地上茎叶中的多酚类物质,提取物经超高效液相色谱分离、电喷雾串联三重四级杆质谱正和负离子方式检测分析。根据液相保留时间、紫外吸收、相对分子质量和二级碎片离子等信息,结果表明,紫山药块根和茎叶中酚类物质主要为酚酸、花色苷及黄酮类化合物。分析得到的29种酚类化合物中,5-O-咖啡酰奎宁酸、阿魏酰奎宁酸(tR:12.289)、迷迭香酸、芦丁和槲皮素为块根和茎叶共有组分,块根中另含有芥子酸、芥子酸葡萄糖苷、丁香酸衍生物、香豆酸衍生物、阿魏酸衍生物、芥子酸二葡萄糖苷和花色苷等11种酚类物质。茎叶中除5种共有组分,还含有咖啡酸、咖啡酰奎宁酸甲酯、咖啡酰莽草酸、对香豆酰奎宁酸、香豆酰奎宁酸甲酯、山奈酚-3-O-芦丁糖苷与迷迭香酸甲酯等13种酚类化合物。     

Comparison between ultra-homogenisation and ultrasound for extraction of phenolic compounds from teff (Eragrostis tef (Zucc.))

This study investigated the effect of the solvent composition on the extraction of phenolic compounds from teff grains and compared the efficiency between the techniques homogeniser-assisted extraction (HAE) and ultrasound-assisted extraction (UAE). The solvents used were water, ethanol and methanol, and the response analysed was the total phenolic content (TPC). The quantitative profile of polyphenols extracted was also determined by ultra-performance liquid chromatography–tandem mass spectrometry (UPLC-TQD). According to the optimisation, the maximum response was estimated at solvent ratios of 51:40:9 and 49:26:25 (water/ethanol/methanol, v/v/v) for HAE and UAE, respectively. Under optimal conditions, the extraction technique did not significantly influence the TPC extracted, but the TFC (total flavonoid content) and the antioxidant capacity were significantly higher when UAE was used. The phenolic acids p-coumaric and protocatechuic and the flavonoids quercetin, rutin and myricetin were the main polyphenols extracted. Both techniques studied were efficient in extracting polyphenols from whole teff grains.     

超声辅助提取瑭溪蜜柚皮中酚酸的研究

利用20kHz的超声波辅助提取琯溪蜜柚皮中的酚酸,主要研究了超声参数(超声时间、温度、超声功率)对琯溪蜜柚皮中的7种酚酸(咖啡酸、对香豆酸、阿魏酸、芥子酸、原儿茶酸、对羟基苯甲酸、香草酸)和黄酮糖苷(柚皮苷)的影响。结果表明:柚皮苷和酚酸的含量都随着超声时间和温度的增加而增加。超声功率对柚皮苷含量的影响较小,但对7种酚酸有不同程度的影响。确定了超声提取琯溪蜜柚皮中柚皮苷和酚酸的最佳提取条件:柚皮苷,超声30 min、超声温度40℃、超声功率8 W;酚酸,超声30 min、超声温度30℃、超声功率30 W。     

Comparison of enzyme‐assisted and ultrasound‐assisted extraction of vitamin C and phenolic compounds from acerola (Malpighia emarginata DC.) fruit

This article describes a comparative study of enzyme and ultrasound techniques for the simultaneous extraction of vitamin C and phenolic compounds from acerola fruit. Ultrasound‐assisted extraction (UAE) took only 6 min to achieve the highest level of vitamin C and phenolic compounds as well as antioxidant activity of acerola juice, while enzyme‐assisted extraction (EAE) took up to 120 min to obtain the maximal values. On the basis of kinetic model of second‐order extraction, the extraction rate constant of vitamin C and phenolics in UAE increased approximately 3.1 and 2.7 times, respectively, in comparison with that in EAE. In addition, the maximal level of vitamin C, phenolics and the antioxidant activity evaluated by 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH), and 2,2′‐azinobis‐(3‐ethylbenzothiazoline‐6‐sulphonic acid) (ABTS) methods in UAE was 4.6%, 3.5%, 4.6% and 3.3%, respectively, higher than those in EAE. Obviously, UAE is a useful method for the extraction of antioxidants from plant materials.     

Bioactive compounds present in the Mediterranean sofrito

Sofrito is a key component of the Mediterranean diet, a diet that is strongly associated with a reduced risk of cardiovascular events. In this study, different Mediterranean sofritos were analysed for their content of polyphenols and carotenoids after a suitable work-up extraction procedure using liquid chromatography/electrospray ionisation-linear ion trap quadrupole-Orbitrap-mass spectrometry (LC/ESI-LTQ-Orbitrap-MS) and liquid chromatography/electrospray ionisation tandem triple quadrupole mass spectrometry (LC/ESI-MS-MS). In this way, 40 polyphenols (simple phenolic and hydroxycinnamoylquinic acids, and flavone, flavonol and dihydrochalcone derivatives) were identified with very good mass accuracy (<2 mDa), and confirmed by accurate mass measurements in MS and MS² modes. The high-resolution MS analyses revealed the presence of polyphenols never previously reported in Mediterranean sofrito. The quantification levels of phenolic and carotenoid compounds led to the distinction of features among different Mediterranean sofritos according to the type of vegetables (garlic and onions) or olive oil added for their production.     

Green method for determination of phenolic compounds in mung bean (Vigna radiata L.) based on near‐infrared spectroscopy and chemometrics

Mung bean grains exhibit high level of antioxidant activity due the presence of phenolic compounds. Near‐infrared spectroscopy (NIRS), in conjunction with chemometrics, was used to develop a rapid, nondestructive, chemical free and easy‐to‐use method to determine these compounds in sixty genotypes of mung bean. NIRS calibration curve with high‐performance liquid chromatography (HPLC) as reference method was used to determine phenolic compounds (catechin, chlorogenic acid, caffeic acid, p‐coumaric acid, t‐ferulic acid, vitexin, isovitexin, myricetin, quercetin and kaempferol). It was observed that partial least square regression (PLSR) model in the wavelength range of 1600–2500 nm with standard normal variate (SNV) and linear baseline correction (LBC) as preprocessing techniques can measure phenolic compound accurately (R² > 0.987) with root‐mean‐square error less than 1.82%. This study shows that NIRS along with chemometrics is an accurate method to estimate the phenolic compounds rapidly and nondestructively.     

HPLC–DAD–ESI–MS Analysis of Phenolic Compounds During Ripening in Exocarp and Mesocarp of Tomato Fruit

Identification of phenolic compounds was done by means of liquid chromatography (HPLC) coupled to mass spectrometry (MS) using the electrospray ionization interface (ESI). Quantification of phenolic compounds was carried out by using HPLC with diode array detector (DAD) in exocarp and mesocarp of tomato fruit at 6 different ripeness stages (mature‐green, breakers, turning, pink, light‐red, and red). Several phenolic compounds were identified including chlorogenic acid, caffeic acid, p‐coumaric acid, ferulic acid, and rutin and some combined phenolic acids were tentatively identified, mainly glycosides, such as caffeoyl hexose I, caffeoyl hexose II, caffeoylquinic acid isomer, dicaffeoylquinic acid, p‐coumaroyl hexose I, p‐coumaroyl hexose II, feruloyl hexose I, feruloyl hexose II, siringyl hexose, and caffeoyl deoxyhexose hexose. Fruit exocarp had higher quantities of total soluble phenolics (TSP) compared to mesocarp. During ripening, TSP increased in both exocarp and mesocarp, mainly in exocarp. While rutin increased, chlorogenic acid decreased in both tissues: exocarp and mesocarp.     

Optimisation of the microwave‐assisted extraction process for six phenolic compounds in Agaricus blazei murrill

An efficient microwave‐assisted extraction (MAE) technique was employed in the extraction of phenolic compounds from Agaricus blazei murrill, and phenolic compounds were quantified by High‐performance liquid chromatography (HPLC). The MAE procedure was optimised, validated and compared with other conventional extraction techniques. MAE gave the best result because of the highest extraction efficiency within the shortest extraction time. The optimal conditions of MAE were 60% ethanol, ratio of solid/liquid 1:30, temperature 110 °C, irradiation power 500 W and three extraction cycles, each 5 min. This is the first report on combining MAE with HPLC for the extraction and quantification of phenolic compounds in A. blazei murrill. The developed MAE method provided a good alternative for the extraction of phenolic compounds in A. blazei murrill as well as other materials.     

The use of an enzymatic extraction procedure for the enhancement of highland barley (Hordeum vulgare L.) phenolic and antioxidant compounds

A multistep enzymatic extraction method was compared with a conventional chemical extraction process to evaluate the phenolic content and antioxidant activity of highland barley (Z2, Zangqing 25; CHQK, Changheiqingke). The main phenolic compound extracted was (+)‐catechin, followed by ferulic acid, p‐coumaric acid, caffeic acid and chlorogenic acid. The multi‐enzymatic digestion yielded a higher retrieval of (+)‐catechin compared to the conventional chemical extraction procedure (P < 0.05). Compounds obtained from the multi‐enzymatic digestion process exhibited significantly higher (P < 0.05) antioxidant activities determined by oxygen radical absorbance capacity (ORAC) and cellular antioxidant activity (CAA) when compared to chemical extracts. These results suggest that highland barley subjected to in vitro multi‐enzymatic digestion exhibits a higher phenolic content and antioxidant activity than the chemical extraction, and this multi‐enzymatic digestion coupled with the CAA assay may be a valuable tool to evaluate the antioxidant potential of wholegrains and fruits, as well as vegetables.     

红薯叶不同溶剂提取物抗氧化性及活性成分鉴定

研究不同极性溶剂对红薯叶中酚类化合物的提取以及提取物抗氧化性的影响,并鉴定提取物中的主要抗氧化成分组成。分别采用极性不同的7 种溶剂（蒸馏水、甲醇、无水乙醇、丙酮、正丁醇、乙酸乙酯和氯仿）从红薯叶中提取多酚,并评价提取物中总酚、总黄酮和花青素的含量,以及对1,1-二苯基-2-三硝基苯肼（1,1-diphenyl-2-picrylhydrazyl,DPPH）自由基清除能力和还原能力,最后运用高效液相色谱-串联质谱（high performance liquidchromatography tandem mass spectroscopy,HPLC-MS/MS）技术分析抗氧化活性最好的提取物中多酚的主要组成成分。结果表明：提取溶剂的极性对红薯叶中多酚类化合物的提取效率和提取物抗氧化活性有很大的影响,水提物具有最高的粗提物得率（（37.13±1.60）%）,而甲醇提取物中总酚含量（13.80 mg GAE/g）和总黄酮含量（（5.68±0.35）mg QE/g）最高,且具有最好的DPPH自由基清除能力（IC50为0.32 mg/mL）与还原能力（ρ0.5为0.95 mg/mL）。采用HPLC-MS/MS从红薯叶甲醇提取物中鉴定9 种、初步鉴定3 种酚类化合物,鉴定的化合物为咖啡酸、对羟基苯甲酸、1-咖啡酸奎宁酸、3-咖啡酸奎宁酸、异绿原酸A、异绿原酸B、异绿原酸C、3,4,5-三咖啡酰奎尼酸和金丝桃苷。     

Evaluation of the extraction efficiency for polyphenol extracts from by‐products of green kiwifruit juicing

The health benefits of fruits are attributable in part to their bioactive components such as phenolics and pectic polysaccharides. By‐products derived from kiwifruit processing can be a good source of such bioactive compounds. Extracts were produced using different concentrations of ethanol in water (0%, 30%, 50%, 74% and 96% v/v) from by‐products (skin, residue and pulp) of the green‐fleshed kiwifruit (Actinidia deliciosa‘Hayward’) juicing process. The amounts of phenolic compounds and uronic acid (UA) as well as the phenolic composition in each extract were determined. Results show that different by‐products contained different concentrations of phenolics and pectic polysaccharides. Based on total phenolic contents, 96% v/v ethanol appeared to be the best extraction medium. The 30% or 74% ethanolic dilution was the second best medium for phenolic extraction from skin and pulp/residue, respectively. Water was a good medium for extracting satisfactory quantities of phenolics as well as the highest concentration of pectic polysaccharides. Phenolic profiling by high‐performance liquid chromatography (HPLC) was used to detect individual phenolic compounds in an extract. Results using HPLC showed that alkali pre‐treatment has improved the extraction efficiency of phenolics as a function of alkali concentration, fruit tissue type, extraction media, by‐product preparation method, and class of polyphenols. As a result more efficient methods for both extraction and characterisation of polyphenols could be evaluated.     

Recovery of phenolic compounds from peach pomace using conventional solvent extraction and different emerging techniques

The study compared high-pressure, microwave, ultrasonic, and traditional extraction techniques. The following extraction conditions were implemented: microwave-assisted extraction (MAE) at 900 W power for durations of 30, 60, and 90 s; ultrasonic-assisted extraction (UAE) at 100% amplitude for periods of 5, 10, and 15 min; and high-pressure processing (HPP) at pressures of 400 and 500 MPa for durations of 1, 5, and 10 min. The highest yield in terms of total phenolic content (PC) was obtained in UAE with a value of 45.13 ± 1.09 mg gallic acid equivalent (GAE)/100 g fresh weight (FW). The highest PC content was determined using HPP-500 MPa for 10 min, resulting in 40 mg GAE/100 g, and MAE for 90 s, yielding 34.40 mg GAE/100 g FW. The highest value of antioxidant activity (AA) was obtained by UAE in 51.9% ± 0.71%. The PCs were identified through the utilization of Fourier transform infrared (FTIR) spectroscopy and high-performance liquid chromatography (HPLC). Utilizing multivariate analysis, the construction of chemometric models were executed to predict AA or total PC of the extracts, leveraging the information from IR spectra. The FTIR spectrum revealed bands associated with apigenin, and the application of HPP resulted in concentrations of 5.41 ± 0.25 mg/100 g FW for apigenin and 1.30 ± 0.15 mg/100 g FW for protocatechuic acid. Furthermore, HPLC analysis detected the presence of protocatechuic acid, caffeic acid, p-coumaric acid, and apigenin in both green extraction methods and the classical method. Apigenin emerged as the predominant phenolic compound in peach extracts. The highest concentrations of apigenin, p-coumaric acid, and protocatechuic acid were observed under HPP treatment, measuring 5.41 ± 0.25, 0.21 ± 0.04, and 1.30 ± 0.15 mg/kg FW, respectively.