Simultaneous Determination of Phenolic Compounds in Red Wines by HPLC‐UV

A photoelectrochemical enzyme biosensor based on functionalized hematite microcubes for rutin determination by square-wave voltammetry

A photoelectrochemical biosensing strategy for the highly sensitive detection of the flavonoid rutin was developed by synergizing the photoelectrocatalytic properties of hematite (α-Fe₂O₃) decorated with palladium nanoparticles (PdNPs) and the biocatalysis towards laccase-based reactions. The integration of α-Fe₂O₃.PdNPs with a polyphenol oxidase as a biorecognition element yields a novel biosensing platform. Under visible light irradiation, the photoactive biocomposite can generate a stable photocurrent, which was found to be directly dependent upon the concentration of rutin. Under the optimal experimental conditions, the cathodic photocurrent, measured at 0.33 V vs. Ag/AgCl, from the square-wave voltammograms presented a linear dependence on the rutin concentration within the range of 0.008-30.0 × 10^-8 mol L^-1 (sensitivity: 1.7 μA·(× 10^-8 M^-1)·cm^-2), with an experimental detection limit (S/N = 3) of 8.4 × 10^-11 mol L^-1. The proposed biosensor device presented good selectivity towards rutin in the presence of various organic compounds and inorganic ions, demonstrating the potential application of this biosensing platform in complex matrices. This bioanalytical device also exhibited excellent operational and analytical properties, such as intra-day (standard deviation, SD = 0.21%) and inter-day (SD = 1.30%) repeatability, and long storage stability (SD = 2.80% over 30 days).Graphical abstract.

An Approach of the Madeira Wine Chemistry

Madeira wine is a fortified Portuguese wine, which has a crucial impact on the Madeira Island economy. The particular properties of Madeira wine result from the unique and specific winemaking and ageing processes that promote the occurrence of chemical reactions among acids, sugars, alcohols, and polyphenols, which are important to the extraordinary quality of the wine. These chemical reactions contribute to the appearance of novel compounds and/or the transformation of others, consequently promoting changes in qualitative and quantitative volatile and non-volatile composition. The current review comprises an overview of Madeira wines related to volatile (e.g., terpenes, norisoprenoids, alcohols, esters, fatty acids) and non-volatile composition (e.g., polyphenols, organic acids, amino acids, biogenic amines, and metals). Moreover, types of aroma compounds, the contribution of volatile organic compounds (VOCs) to the overall Madeira wine aroma, the change of their content during the ageing process, as well as the establishment of the potential ageing markers will also be reviewed. The viability of several analytical methods (e.g., gas chromatography-mass spectrometry (GC-MS), two-dimensional gas chromatography and time-of-flight mass spectrometry (GC×GC-ToFMS)) combined with chemometrics tools (e.g., partial least squares regression (PLS-R), partial least squares discriminant analysis (PLS-DA) was investigated to establish potential ageing markers to guarantee the Madeira wine authenticity. Acetals, furanic compounds, and lactones are the chemical families most commonly related with the ageing process.

Characteristics, Biological Properties and Analytical Methods of Trans-Resveratrol: A Review

Trans-resveratrol (TR) is the biological active isomer of resveratrol and the one responsible for therapeutic effects; both molecules are non-flavonoid phenolics of the stilbenes class found mainly in berries and red grapes. TR biological properties lie in modulation of various enzymatic classes. It is a promising candidate to novel drugs due its applications in pharmaceutical and cosmetic industries, such as anticarcinogenic, antidiabetic, antiacne, antioxidant, anti-inflammatory, neuroprotective, and photoprotector agent. It has effects on bone metabolism, gastrointestinal tract, eyes, kidneys, and in obesity treatment as well. Nevertheless, its low solubility in water and other polar solvents may be a hindrance to its therapeutic effects. Various strategies been developed to overcome these issues, such as the drug delivery systems. The present study performed a research about methods to identify TR and RESV in several samples (raw materials, wines, food supplements, drug delivery systems, and blood plasma). Most of the studies tend to analyze TR and RESV by high performance liquid chromatography (HPLC) coupled with different detectors, even so, there are reports of the use of capillary electrophoresis, electron spin resonance, gas chromatography, near-infrared luminescence, UV-Vis spectrophotometer, and vibrational spectrophotometry, for this purpose. Thus, the review evaluates the biological activity of TR and demonstrates the currently used analytical methods for its quantification in different matrices.

Targeted phenolic profiling of Sauvignon blanc and Shiraz grapes grown in two regions of India by liquid chromatography-tandem mass spectrometry

The phenolic compounds play an important role in production of quality grapes and wines. The current investigation focused on optimization of an extraction method for targeted analysis of 33 phenolic compounds in grapes by liquid chromatography tandem mass spectrometry (LC-MS/MS). The optimized method was successfully used for phenolic profiling of two wine grape varieties, Sauvignon blanc (white) and Shiraz (red) originated from Pune and Nasik regions of Maharashtra State, India. The optimized sample preparation procedure involved liquid-liquid extraction with acidified methanol by vortexing for 2 min followed by analysis on LC-MS/MS. The limit of quantification of the targeted compounds was in the range of 29 to 411 µg/L. The results indicated that skin of both varieties contained the highest amount of flavonols (69.47 ± 14.74 mg/kg in Sauvignon blanc and 129.47 ± 10.05 mg/kg in Shiraz) compared to pulp. The highest amounts of flavan-3-ols were present in grape seed collected from the Pune region (2016.84 ± 14.73 mg/kg in Sauvignon blanc and 1945.06 ± 32.69 mg/kg in Shiraz). The concentration of stilbenes was the highest in grape skin (0.13 ± 0.52 to 5.78 ± 5.45 mg/kg) compared to seed and pulp of both varities. Hydroxybenzoic acid (vanillin), hydroxycinnamic acid (p-coumaric acid) and anthocyanins (oenin, malvidin, cyanidin and kuromanin) were found only in Shiraz variety. The results of antioxidant activity (FRAP and DPPH assay) indicated the highest scavenging activity in seed (978.64 ± 56.23 to1133.38 ± 143.65 µMol TE/g DW FRAP and 594.93 ± 37.94 to 631.94 ± 56.45 µMol TE/g DW in DPPH). The phenolic contents in Sauvignon blanc and Shiraz grapes between Pune and Nasik regions did not have any significant difference.

Extraction and evaluation of natural occurring bioactive compounds and change in antioxidant activity during red winemaking

Phenolic composition of red wines from Stanušina, a grape variety indigenous of the Republic of Macedonia, was compared with the regional Vranec and the international Cabernet Sauvignon. The extent of skin contact (i.e. maceration time) on levels of phenolic compounds and antioxidant activity of wines was evaluated. A total of 19 phenolic compounds were identified and quantified. Among these malvidin-3-glucoside and its derivatives were the major compounds, while caftaric acid was the predominant cinnamic acid derivative, followed by catechin, the main flavan-3-ol. The concentration of hydroxycinnamic acids, anthocyanins and (+)-catechin ranged from 224 to 511 mg/L, 22 to 360 mg/L and 26 20 to 375 mg/L, respectively and peaked at 3rd, 6th and 9th day of maceration, respectively. However, prolong maceration slightly decreased their concentration. Stanušina wines presented high levels of hydroxycinnamic acids and antioxidant activity.

Voltammetric Determination of Dinonyl Diphenylamine and Butylated Hydroxytoluene in Mineral and Synthetic Oil

A method is reported for the determination of diphenylamine and butylated hydroxytoluene in mineral and synthetic oil. The procedure used differential pulse voltammetry with a glassy carbon electrode. This method was then used for determining these antioxidants in supporting electrolyte consisting of dilute sulfuric acid and sodium dodecyl sulfonate in ethanol. Anodic peaks were obtained for both analytes. Oxidation peaks at 250 mV were observed from a mixture of butylated hydroxytoluene and dinonyl diphenylamine, allowing their simultaneous determination. This approach was successfully used for the determination of dinonyl diphenylamine and butylated hydroxytoluene in fortified mineral and synthetic oils with good accuracy and precision.

Determination of polyphenols in Spanish wines by capillary zone electrophoresis. Application to wine characterization by using chemometrics

A capillary zone electrophoresis (CZE) method for the simultaneous determination of 20 polyphenols in wine was developed. The separation was performed using fused-silica capillaries of 75 μm i.d. and a 30 mM sodium tretraborate buffer solution at pH 9.2 with 5% isopropanol as a background electrolyte. A capillary voltage of +25 kV with pressure-assisted (3.5 kPa) separation from minute 18 was applied, thus achieving a total analysis time of <25 min. Instrumental quality parameters such as limits of detection (LOD, values between 0.3 and 2.6 mg/L), linearity (r(2) > 0.990), and run-to-run and day-to-day precisions (RSD values lower than 6.5 and 15.7%, respectively) were established. Three different calibration procedures were evaluated for polyphenol quantitation in wines: external calibration using standards prepared in Milli-Q water, standard addition, and pseudomatrix-matched calibration using wine as a matrix. For a 95% confidence level, no statistical differences were observed, in general, between the three calibration methods (p values between 0.11 and 0.84), whereas for some specific polyphenols, such as cinnamic acid, syringic acid, and gallic acid, results were not comparable when external calibration was used. The CZE method using pseudomatrix-matched calibration was then proposed and applied to the analysis of polyphenols in 49 Spanish wines, showing satisfactory results and a wide compositional variation between wines. Electrophoretic profiles and other compositional data (e.g., peak areas of selected peaks) were considered as fingerprints of wines to be used for characterization and classification purposes. The corresponding data were analyzed by principal component analysis (PCA) to extract information on the most significant features contributing to wine discrimination according to their origins. Results showed that a reasonable distribution of wines depending on the elaboration areas was found, tyrosol and gallic, protocatechuic, p-coumaric, and caffeic acids being some representative discriminant compounds.

Development and validation of an analytical method for the determination of trans- and cis-resveratrol in wine: analysis of its contents in 186 Portuguese red wines

A simple procedure based on solid-phase extraction and high performance liquid chromatography coupled to diode array detector has been developed and validated for the qualitative and quantitative analysis of cis- and trans-resveratrol in wines. The method was linear from 0.025 (lower limit of quantitation, LLOQ) to 15 μg/mL for trans-resveratrol and from 0.023 (LLOQ) to 0.92 μg/mL for cis-resveratrol, with correlation coefficients higher than 0.99 for both isomers. Intra- and interday precision and accuracy were in conformity with the criteria normally accepted in method validation, that is, CVs inferior to 15% and mean relative errors within a ±14% interval. The extraction presented mean efficiencies close to 100% for both analytes. The validated methodology was applied to 186 Portuguese red wines from different regions, grape varieties and vintage. The results obtained showed that the content of trans-resveratrol in red wines ranged from 0.05 to 10.9 μg/mL, while the concentrations of cis-resveratrol ranged from 0.04 to 8.71 μg/mL.