An LCEC method for the analysis of synthetic amino acids in fruit juices

Summary A fast and simple HPLC-method for the determination of synthetic amino acids in adulterated orange juice has been developed. The amino acid enantiomers were derivatized with a chiral reagent and the derivatives separated on a 3 m particle size C₁₈ column. An electrochemical detector operating in the oxidative mode was used for detection. The potential at which the derivatives are oxidized was determined by cyclic voltammetry.By using selective (electrochemical) detection it is possible to reduce the sample clean-up to simple centrifugation and filtration steps.     

Chemical composition,antioxidant and cytotoxic activities of extracts from the leaves of Smilax brasiliensis Sprengel (Smilacaceae)

The antioxidant and cytotoxic activities of petroleum ether and methanol extracts, fatty acids and methyl esters from leaves of Smilax brasiliensis were evaluated, and the composition of the extracts was determined. Palmitic, linoleic and linolenic acids were major components of the extracts. For antioxidant activity, all samples exhibited IC₅₀ values lower than BHT (2,6-di-tert-butyl-4-methylphenol). The extracts, fatty acids and methyl esters from S. brasiliensis presented no toxicity to larvae of the brine shrimp, Artemia salina. Among the purified substances, only methyl linolenate showed toxicity (LD₅₀ = 21.47 μg/mL). This study showed, for the first time, the composition of petroleum ether and methanol extracts from S. brasiliensis leaves, as well as the antioxidant and cytotoxic activities of extracts, fatty acids and methyl esters.     

Novel ninhydrin adduct of catechin with potent antioxidative activity

The reaction of ninhydrin with (+)-catechin in the presence of TMSOTf resulted in condensation product 1, which consists of a 2:1 mixture of epimers at the C-2 position. The antioxidative radical-scavenging activity of 1 against the galvinoxyl radical, acting as an oxyl radical, was significantly enhanced compared to (+)-catechin. Our results offer a new method for chemical modification of a natural phenolic antioxidant.     

Determination of carotenoids in tomato juice by liquid chromatography

A high-performance liquid chromatography method was developed to determine the various carotenoids in tomato juice. A C30 column and a mobile phase of acetonitrile-1-butanol (7:3, v/v) (A) and methylene chloride (B) with the following gradient elution were used: 99% A and 1% B intitally, increased to 4% B in 20 min, 10% B in 50 min and returned to 1% B in 55 min. Sixteen carotenoids, including all-trans-lutein, all-trans-beta-carotene, all-trans-lycopene and their 13 cis isomers were identified and resolved within 52 min with flow-rate at 2.0 ml/min and detection at 476 nm. Of the various extraction solvent systems, the best extraction efficiency of carotenoids in tomato juice was achieved by employing ethanol-hexane (4:3, v/v). Lycopene was found to be present in largest amount in tomato juice, followed by beta-carotene and lutein.     

GC–MS analysis of phytoconstituents present in Trigonella foenumgraecum L. seeds extract and its antioxidant activity

Trigonella foenumgraecum L. (TF) is a medicinal herb, belonging to the family Legumes. It has shown positive results in remedying hypo-cholesterolemic, anti-inflammatory, antibacterial, antioxidant, anti-lipidemia, antilithigenic, hepatoprotective, antiulcer, anticarcinogenic, antifungal and other miscellaneous pharmacological effects of fenugreek. The n-hexane extract of Trigonella foenumgraecum L. Seeds (TF) was analysed by gas chromatography-mass spectroscopy for identification and characterization of its therapeutic claim by traditional system. DPPH method was used to determine the antioxidant activity of Trigonella foenumgraecum L-seeds extract using UV spectrophotometer at a wavelength of 518 nm as it is one of the most sorted methods for antioxidant activity. The major compounds discovered in Trigonella foenumgraecum L. seeds extract are Linoleic acid (48.01%); 9,12-Octadecadienoic acid (Z,Z)-, 2,3-dihydroxypropyl ester (24.65%); 2-[4-Methyl-6-(2,6,6-trimethylcyclohex-1-enyl)hexa-1,3,5-trienyl]cyclohex-1-en-carboxaldehyde(1.88%); Nonane dioic acid, bis (2-ethylhexyl) ester (1.09%); Bis (2-ethylhexyl) ester of azelaic acid (11.97%); Elemicin (0.51%); cis-Linoleic acid methyl ester (0.76%); Linoleic acid chloride(0.57%); Ethyl oleate(0.18%); Isopropyl linoleate (0.38%); Dihydrovallesiachotamine (0.06%); 4-(2,2-Dimethyl-6-methylenecyclohexyl) butanal(0.12%); Citronellyl myristate (0.09%); Rhaphidecursinol B(0.25%); 5-Methoxygalbelgin (0.07%); Vitamin E (0.31%); 1,1,1,5,5,5-hexafluoro-4-{[3-(trifluoromethyl) phenyl]imino}-2-pentanone (0.76%); γ-Sitosterol (0.66%); 1-(1,5-Dimethylhexyl)-3a,12a-dimethyltetradecahydro-1H-cyclopenta[a]cyclopropa[e]phenanthren-7-ol (0.16%) and (9Z)-9-Octadecenyl (9Z)-9-hexadecenoate (1.57%). The results showed potential antioxidant activity of n-hexane extract of Trigonella foenumgraecum L. seeds by showing significant reduction in free radical against DPPH. The hexane extract of Trigonella foenumgraecum L. seeds comprises various non-water-soluble (nonpolar) constituents. These compounds were established qualitatively via GC-MS evaluation. The free radical scavenging activity of the plant extract was established owning to the presence of compounds such as terpenes, vitamin E, and unsaturated fatty acids.     

Estimation of antioxidant capacity against peroxynitrite and hypochlorite with fluorescein

Peroxynitrite and hypochlorite are oxidants relevant in many pathological situations. We propose a simple spectrofluorometric assay to determine antioxidant capacity against hypochlorite and peroxynitrite based on protection against fluorescein bleaching. The assay can be performed on a microplate and requires minute amounts of material. Standard antioxidants show different reactivities for both oxidants. Antioxidant capacity of fruit bodies of edible mushrooms, tea, coffee and wine estimated as exemplary biological material point to considerable differences in the scavenging capacity of various biological material against hypochlorite, peroxynitrite and peroxyl radicals.     

Radical scavenging and in vitro antifungal activities of Cu(II) and Co(II) complexes of the t-butylphenyl derivative of porphyrazine

Co(II) and Cu(II) complexes and metal-free t-butylphenyl peripherally substituted porphyrazine (Pz) have been screened for in vitro antifungal (Aspergillus niger) and antioxidant (free radical scavenging, superoxide radical scavenging, and reducing power) activities. The results were compared with synthetic antioxidants, e.g., butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), trolox, or α-tocopherol. The free radical scavenging activity of H₂Pz was higher than the CuPz complex. However, CuPz complex showed higher superoxide radical scavenging activity than BHA, BHT, and trolox while H₂Pz and CoPz showed weaker activity than BHA, BHT, and trolox. The reducing power of all complexes was similar to that of BHT and α-tocopherol on a per molar basis. The ligand and complexes have antifungal activity against A. niger. The compounds have significant superoxide radical scavenging activity against various antioxidant systems in vitro.     

Effects of electron-withdrawing substituents on DPPH radical scavenging reactions of protocatechuic acid and its analogues in alcoholic solvents

The DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity of protocatechuic acid (3,4-dihydroxybenzoic acid) and its related catechols was examined. Compounds possessing strong electron-withdrawing substituents showed high activity. NMR analysis of the reaction mixtures of catechols and DPPH radical in methanol showed the formation of methanol adducts. The results suggest that high radical scavenging activity of catechols in alcohol is due to a nucleophilic addition of an alcohol molecule on o-quinones, which leads to a regeneration of a catechol structure. Furthermore, the radical scavenging activity in alcohols would largely depend on the electron-withdrawing/donating substituents, since they affect the susceptibility toward nucleophilic attacks on o-quinone.     

Modified cupric reducing antioxidant capacity (CUPRAC) assay for measuring the antioxidant capacities of thiol-containing proteins in admixture with polyphenols

Proteins are not considered as true antioxidants but are known to protect antioxidants from oxidation in various antioxidant activity assays. This study aims to investigate the contribution of proteins, especially thiol-containing proteins, to the observed overall antioxidant capacity measured by known methods. To determine the antioxidant properties of thiol-containing proteins, the CUPRAC method of antioxidant assay using the oxidizing reagent Cu(II)-neocuproine previously used for simultaneous analysis of cystine and cysteine was adopted. While the CUPRAC method is capable of determining all antioxidant compounds including thiols in complex sample matrices, the Ellman method of thiol quantitation basically does not respond to other antioxidants. The antioxidant quantities in the selected samples were assayed with the ABTS and FRAP methods as well as with the CUPRAC method. In all applied methods, the dilutions were made with a standard pH 8 buffer used in the Ellman method by substituting the Na₂EDTA component of the buffer with sodium citrate. On the other hand, the standard CUPRAC protocol was modified by substituting the pH 7 ammonium acetate buffer (at 1 M concentration) with 8 M urea buffer adjusted to pH 7 by neutralizing with 6 M HCl. Urea helps to partly solubilize and denaturate proteins so that their buried thiols be oxidized more easily. All methods used in the estimation of antioxidant properties of proteins (i.e., CUPRAC, Ellman, ABTS, and FRAP) were first standardized with a simple thiol compound, cysteine, by constructing the calibration curves. The molar absorptivities of these methods for cysteine were: ?_CUPRAC = 7.71 × 10³, ?_Ellman = 1.37 × 10⁴, ?_ABTS = 2.06 × 10⁴, and ?_FRAP = 2.98 × 10³ L mol⁻¹cm⁻¹. Then these methods were applied to various samples containing thiols, such as glutathione (reduced form:GSH), egg white, whey proteins, and gelatin. Additionally, known quantities of selected antioxidants were added to these samples to show the additivity of responses.     

Thin-layer chromatography applied in quality assessment of beverages derived from fruits

ABSTRACT

The analysis of food products is important for the assessment of food quality and authenticity, the control of a technological process, the determination of nutritional values, and the detection of compounds which could exert beneficial or toxic effects on human health. Techniques which are usually chosen for these purposes must provide accurate and reliable results, being relatively simple and inexpensive to perform. The aim of this paper is to give a brief overview of the thin-layer chromatography methods for the analysis of different compounds (polyphenols, dyes, carboxylic acids, biogenic amines, and vitamin C), used for quality assessment and authentication of non-fermented or fermented beverages derived from fruits, namely fruit juices and wines.     

Antioxidant capacity and antibacterial activity from Annona cherimola phytochemicals by ultrasound-assisted extraction and its comparison to conventional methods

In recent years, the food, pharmacy, and cosmetic industries have focused on the search of natural compounds with antimicrobial and antioxidant properties; commonly, these compounds are obtained from Kingdom plantae. The aim of the present work is comparing antibacterial and antioxidant capacity of Annona cherimola Mill leaves, using different extraction methods. The ultrasound assisted extraction technique (UAE) was compared with conventional techniques: Soxhlet and maceration. Water and ethanol were used as solvents for leaves extractions performed with these three methods. The main acetogenins reported in Annona cherimola Mill and Annona muricata L. species were simulated using the functional hybrid B3LYP and to confirm its presence, analysis of the compound composition was performed using FT-IR, UV–Vis and HPLC. Total phenolics (TP) and flavonoids (TF) were determined by spectroscopy techniques and novel Differential Pulse Voltammetry (DPV) electrochemical technique. Total Antioxidant Capacity (TAC) of the extracts was measured, using the DPPH, FRAP and CUPRAC techniques. The highest antioxidant content was found in the Soxhlet water extracts; even so, the UAE technique presented an attractive alternative due to considerable reduction in extraction time, which was greater than 99%, and possible selectivity in compounds extraction. Finally, antibacterial activity of the extracts was evaluated, obtaining the best results against gram-positive bacteria using UAE water extract. In this way, the UAE technique presents an excellent extraction option due to the considerable reduction in time and energy, as well as the increase in antibacterial activity.     

Crystal structures,electrochemical properties,antioxidant screening and in vitro cytotoxic studies on four novel Cu(II) complexes of bidentate Schiff base ligands derived from 2-methoxyethylamine

Four novel Schiff base ligands and their copper(II) complexes, [Cu(L¹)₂] (1), [Cu(L²)₂] (2), [Cu(L³)₂] (3), and [Cu(L⁴)₂] (4), were synthesized and characterized by elemental analyses, FT-IR, and UV–Vis spectroscopy. The ligands were synthesized from the condensation of 2-methoxyethylamine with various salicylaldehyde derivatives (x-salicylaldehyde for HLⁿ, x = H (n = 1), 5-Br (n = 2), 3-OMe (n = 3), and 4-OMe (n = 4)). The molecular structures of 1, 2, and 3 were determined by the single crystal X-ray diffraction technique. The redox behavior studies of the complexes in acetonitrile display the electronic effects of the groups on the redox potential. The antioxidant activity of the Schiff base ligands and their Cu(II) complexes was evaluated using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging method and FRAP assay. Furthermore, the in vitro anticancer activity of compounds was screened, including MTT and migration assays against gastric cancer cell line (MKN-45). The results show that all ligands and complexes have antioxidant and anticancer activity in a concentration-dependent way.     

Polymethacrylate Colorimetric Sensor for Evaluation of Total Antioxidant Capacity

A new colorimetric 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, Fe(III) – 1,10-phenanthroline (Fe(III)-phen), was immobilized into a polymethacrylate matrix (PMM), and the absorbance changes associated with the formation of the highly colored Fe(II)-phen chelate as a result of reaction with antioxidants was measured at 510 nm. The developed optical sensor was used to screen total antioxidant capacity of some black and green teas, red and white wines.     

An Improved On-Line HPLC-DPPH Method for the Screening of Free Radical Scavenging Compounds in Water Extracts of Lamiaceae Plants

An on-line HPLC-1,1-diphenyl-2-picrylhydrazyl (DPPH*) method has been improved for the detection of polar and nonpolar radical scavenging compounds from complex plant extracts. Eight water extracts were prepared from steam-distilled essential oil-extracted Lamiaceae plants (Origanum vulgare L., O. Onites L., O. Minutiflorum O. Schwartz et P. H. Davis, O. Syriacum L., Satureja cuneifolia Ten., Thymbra spicata L., Coridothymus capitatus (L.) Reichb. f., Majorana hortensis Moench). After the components within each extract had been separated by reverse phase chromatography using 10% to 100% methanol with 2% acetic acid as a mobile phase, analytes capable of scavenging a citric acid-sodium citrate buffered methanolic DPPH* solution were detected by post-column derivatization at 517 nm. The HPLC-DPPH* on-line method was applied to the qualitative and quantitative analysis of these Lamiaceae plant extracts. There was a strong correlation between the scavenging (negative) peak area and the concentration of the radical scavenging reference substances used. The radical scavenging compounds within the extracts were determined as benzoic acid and hydroxycinnamic acid derivatives, flavonoids and diterpenoids according to their retention time and UV spectral data. Rosmarinic acid and carnosic acid were identified as the dominant radical scavengers in these extracts by this method.     

Characterization and Bioavailability of Vitamin C Nanoliposomes Prepared by Film Evaporation-Dynamic High Pressure Microfluidization

Vitamin C nanoliposomes were prepared by combining a conventional method (film evaporation) with dynamic high pressure microfluidization. Their physicochemical characterizations (antioxidant activity, particle size, entrapment efficiency, morphology, in vitro drug release, and storage stability) and skin permeation behavior were investigated. The results showed that vitamin C nanoliposomes, having equivalent DPPH (2, 2-diphenyl-1-picrylhydrazyl) free radical scavenging capacity of pure vitamin C solution without loss of their biological activity, exhibited better storage stability at 37°C for 24 hours and at 4°C for 60 days, a more excellent sustained drug release as well as higher skin penetration rate than vitamin C liposomes.