Optimization of Microwave-Assisted Extraction of Curcumin from Curcuma longa L. (Turmeric) and Evaluation of Antioxidant Activity in Multi-Test Systems

Turmeric (Curcuma longa L.) is a medicinal plant, and its biological activities mainly arise from the main constituent, known as diferuloylmethane or curcumin. In the present paper, microwave-assisted extraction (MAE) was investigated for the recovery of curcumin from turmeric in comparison to conventional heat-assisted extraction (CHAE) technique. Various experimental conditions, such as solvent concentration (0-100%, v/v), MAE temperature (30-130 degrees C) and MAE time (0-20 min) were investigated to optimize the extraction of curcumin from turmeric. The identification and quantification of curcumin in extracts were performed by HPLC-DAD system. Antioxidant potential and radical scavenging abilities of microwave-assisted extract and conventional heat-assisted extract of turmeric (MAET and CHAET) were evaluated using different systems including total phenolic content (TPC), total antioxidant capacity (TAC), and radical scavenging activities. MAET and CHAET showed high antioxidant activity in all test systems, but the antioxidant properties of MAET were stronger than those of CHAET

Development of a Low-Cost Optical Sensor for Cupric Reducing Antioxidant Capacity Measurement of Food Extracts

A low-cost optical sensor using an immobilized chromogenic redox reagent was devised for measuring the total antioxidant level in a liquid sample without requiring sample pretreatment. The reagent, copper(II) neocuproine (Cu(II)-Nc) complex, was immobilized onto a cation-exchanger film of Nafion, and the absorbance changes associated with the formation of the highly colored Cu(I)-Nc chelate as a result of reaction with antioxidants was measured at 450 nm. The sensor gave a linear response over a wide concentration range of standard antioxidant compounds. The trolox equivalent antioxidant capacity (TEAC) values of various antioxidants reported in this work using the optical sensor-based "cupric reducing antioxidant capacity" (CUPRAC) assay were comparable to those of the standard solution-based CUPRAC assay, showing that the immobilized Cu(II)-Nc reagent retained its reactivity toward antioxidants. Common food ingredients like oxalate, citrate, fruit acids, and reducing sugars did not interfere with the proposed sensing method. This assay was validated through linearity, additivity, precision, and recovery, demonstrating that the assay is reliable and robust. The developed optical sensor was used to screen total antioxidant capacity (TAC) of some commercial fruit juices without preliminary treatment and showed a promising potential for the preparation of antioxidant inventories of a wide range of food plants

Antioxidant/antiradical properties of microwave-assisted extracts of three wild edible mushrooms

A microwave-assisted extraction (MAE) process for polyphenols from three wild edible mushrooms was studied. The optimal extraction conditions were found to be methanol concentration of 80%, extraction temperature of 80 degrees C, and extraction time of 5 min. Different antioxidant assays (i.e., total antioxidant capacity (TAC) and total phenolic content (TPC)) were utilized to evaluate the antioxidant capacity of the methanolic extracts of Terfezia boudieri Chatin, Boletus edulis, and Lactarius volemus. The reactive species scavenging activities of these extracts were also investigated in vitro. High contents of phenolic and flavonoid compounds may be the major contributors to the observed high antioxidant activities of these extracts. B. edulis showed the higher TAC and TPC; highest inhibitory effect on DPPH and on other studied reactive oxygen species (ROS). MAE showed obvious advantages of high extraction efficiency with lower solvent consumption in terms of high antioxidant capacity/activity of extracts achieved within the shortest time. (C) 2014 Elsevier Ltd. All rights reserved

Polyphenolic contents of natural dyes produced from industrial plants assayed by HPLC and novel spectrophotometric methods

Polyphenolic compounds are abundantly found in natural dyes. The cupric reducing antioxidant capacity assay originally developed in our laboratories was utilized to estimate the total polyphenolic content of natural dyes (i.e., Rubia tinctorum L, Curcuma longa L., Alkanna tinctoria, Matricaria chamomilla, Dactylopius coccus Costa) for the first time. The polyphenolic compounds such as ellagic acid, gallic acid, quercetin, rutin, fisetin, myricetin, kaempferol, luteolin, apigenin, and morin were all capable of reducing the Cu(II)-neocuproine reagent to the Cu(I)-neocuproine chelate showing maximum absorbance at 450 nm, and the responses of synthetic mixture components were additive in accordance with Beer's law. As a comparative reference method, the AlCl3/potassium acetate spectrophotometric method was applied to total flavonoid assay of these dyes. The results of the proposed and reference methods were correlated with high performance liquid chromatography (HPLC) findings expressed in the units of quercetin (QR) equivalent polyphenolic concentration. The individual phenolic constituents of dye extracts were identified and quantified by HPLC on a C18 column (alizarin, curcumin, carminic acid, etc.). The method of standard additions was applied to the solutions of these dyes by adding standard increments of QR and measuring the resulting absorbances. (C) 2010 Elsevier B.V. All rights reserved

Novel Optical Fiber Reflectometric CUPRAC Sensor for Total Antioxidant Capacity Measurement of Food Extracts and Biological Samples

A novel fiber optic sensor was developed for screening the total antioxidant capacity (TAC) based on the use of cupricneocuproine (Cu(II)Nc) immobilized onto a Nafion cation-exchange membrane with reflectance spectrometric measurement. The reflectance change associated with the formation of the highly colored Cu(I)Nc chelate on the membrane as a result of reaction with antioxidants was measured at 530 nm by using a miniature reflectance spectrometer. The calibration graph of trolox (TR) was linear with a slope of 3.40 x 10(3) L mol(-1) mm(-1). The limit of detection (LOD) and limit of quantification (LOQ) for TR in the reflectometric cupric reducing antioxidant capacity (CUPRAC) method were found as 0.53 and 1.76 mu M, respectively. The trolox equivalent antioxidant capacities (TEAC) of various antioxidant compounds using the proposed method were comparable to those of the main CUPRAC assay. This assay was validated through linearity, additivity, precision, and recovery. The developed reflectance sensor was used to screen the TAC of some commercial fruit juices and mice tissue homogenates without preliminary treatment. The method is rapid, inexpensive, versatile, and nonlaborious, uses stable reagents on the sensor, and enables the in situ estimation of antioxidant capacity of food extracts and biological samples

A novel hypobromous acid scavenging activity assay using p-cresol as a spectrofluorometric probe

In this study, a novel spectrofluorometric assay based on p-cresol (4-methyl phenol) probe is developed for the measurement of HOBr scavenging activity. It is the first study involving the use of a p-cresol probe for the determination of the HOBr scavenging activity of biothiols. While the p-cresol probe (lambda(ex) = 260 nm, lambda(em) = 305 nm) has fluorescence characteristics, its brominated derivatives emerging at the end of the oxidation reaction with HOBr do not show fluorescence. The initial fluorescence intensity of the p-cresol probe is decreased in the presence of the brominating agent, HOBr, and this decrease is lower in the presence of HOBr scavenging antioxidants. The scavenging activities of biothiols tested with respect to the developed method decrease in the following order: penicillamine > N-acetyl cysteine > L-glutathione (reduced) > cysteamine > homocysteine > glutathione ethyl ester > cysteine > 1,4-dithiothreitol > lipoic acid > methionine. Penicillamine (IC50 = 10.12 mu M) was the most effective HOBr-scavenger among the tested biothiols. The results obtained with the developed method for biothiols and some pharmaceutical samples were statistically compared (using ANOVA) to those found by the reference methods (KI/taurine and UPLC). The advantage of the proposed method over the KI/taurine assay was demonstrated

The main and modified CUPRAC methods of antioxidant measurement

The antioxidant activity/capacity levels of biological fluids and foods are measured for the diagnosis and the treatment of oxidative stress-associated diseases in clinical biochemistry, and for meaningful comparison of the antioxidant content of foods. Currently, there is no "total antioxidant" as a nutritional index available for food labeling and biological fluids due to the lack of standardized quantitative methods

Synthesis, characterization and antioxidant capacity of naringenin-oxime

The recognition of the benefits of polyphenolic antioxidants is eliciting increasing interest in the search for new polyphenolic derivatives with improved antioxidant activity. Since naringenin (4'5,7-trihydroxyflavanone) (NG) is one of the most abundant citrus and grapefruit polyphenolics and flavanone oximes were used in the synthesis of anticancer and radioprotector compounds having antiradical activity, the corresponding oxime of NG, naringenin oxime (NG-Ox), was synthesized and investigated. The structure of NG-Ox was characterized by FT-IR, (1)H NMR, elemental analysis, and the synthesized compound was screened for its antioxidant capacity by using the cupric reducing antioxidant capacity (CUPRAC) method. Trolox equivalent antioxidant capacity (TEAC) of NG-Ox was measured to be higher than that of the parent compound, NG. Other parameters of antioxidant activity (scavenging effects on center dot OH, O(2)(center dot-) and H(2)O(2)) of NG-Ox were also determined. (C) 2011 Elsevier B.V. All rights reserved