Simultaneous determination of 15 phenolic compounds and caffeine in teas and mate using RP-HPLC/UV detection: method development and optimization of extraction process

Development of Phaleria macrocarpa (Scheff.) Boerl Fruits Using Response Surface Methodology Focused on Phenolics, Flavonoids and Antioxidant Properties

In this study, the optimal conditions for the extraction of antioxidants from the Buah Mahkota Dewa fruit (Phaleria macrocarpa) was determined by using Response Surface Methodology (RSM). The optimisation was applied using a Central Composite Design (CCD) to investigate the effect of three independent variables, namely extraction temperature (°C), extraction time (minutes) and extraction solvent to-feed ratio (% v/v) on four responses: free radical scavenging activity (DPPH), ferric ion reducing power assay (FRAP), total phenolic content (TPC) and total flavonoid content (TFC). The optimal conditions for the antioxidants extraction were found to be 64 °C extraction temperature, 66 min extraction time and 75% v/v solvent to-feed ratio giving the highest percentage yields of DPPH, FRAP, TPC and TFC of 86.85%, 7.47%, 292.86 mg/g and 3.22 mg/g, respectively. Moreover, the data were subjected to Response Surface Methodology (RSM) and the results showed that the polynomial equations for all models were significant, did not show lack of fit, and presented adjusted determination coefficients (R²) above 99%, proving that the yield of phenolic, flavonoid and antioxidants activities obtained experimentally were close to the predicted values and the suitability of the model employed in RSM to optimise the extraction conditions. Hence, in this study, the fruit from P. macrocarpa could be considered to have strong antioxidant ability and can be used in various cosmeceutical or medicinal applications.

Development of an immunoaffinity chromatography and LC-MS/MS method for the determination of 6 zearalenones in animal feed

A novel and simple method for detecting 6 zearalenones in animal feed using liquid chromatography coupled with triple quadrupole mass spectrometry (LC-MS/MS) and immunoaffinity columns (IAC) was developed. The chromatographic peaks of the 6 zearalenones were successfully identified by comparing their retention times and mass spectrum with reference standards. The mobile phase was composed of mobile phase A (water) and B (0.5% formic acid in ACN). Method validation was performed with linearity, sensitivity, selectivity, accuracy and precision. The limits of detection (LODs) for the instrument used to study zearalenones ranged from 0.3 to 1.1 μg/kg, and the limits of quantification (LOQs) ranged from 1.0 to 2.2 μg/kg. Average recoveries of the 6 zearalenones ranged from 82.5% to 106.4%. Method replication resulted in intra-day and inter-day peak area variation of <3.8%. The developed method was specific and reliable and is suited for the routine analysis of zearalenones in animal feed.

Microbial diversity and component variation in Xiaguan Tuo Tea during pile fermentation

Xiaguan Tuo Tea is largely consumed by the Chinese, but there is little research into the microbial diversity and component changes during the fermentation of this tea. In this study, we first used fluorescence in situ hybridization (FISH), next-generation sequencing (NGS) and chemical analysis methods to determine the microbial abundance and diversity and the chemical composition during fermentation. The FISH results showed that the total number of microorganisms ranges from 2.3×10² to 4.0×10⁸ cells per gram of sample during fermentation and is mainly dominated by fungi. In the early fermentation stages, molds are dominant (0.6×10²~2.8×10⁶ cells/g, 0~35 d). However, in the late stages of fermentation, yeasts are dominant (3.6×10⁴~9.6×10⁶ cells/g, 35~56 d). The bacteria have little effect during the fermentation of tea (10²~10³ cells/g, <1% of fungus values). Of these fungi, A. niger (Aspergillus niger) and B. adeninivorans (Blastobotrys adeninivorans) are identified as the two most common strains, based on Next-generation Sequencing (NGS) analysis. Peak diversity in tea was observed at day 35 of fermentation (Shannon–Weaver index: 1.195857), and lower diversity was observed on days 6 and 56 of fermentation (Shannon–Weaver index 0.860589 and 1.119106, respectively). During the microbial fermentation, compared to the unfermented tea, the tea polyphenol content decreased by 54%, and the caffeine content increased by 59%. Theanine and free amino acid contents were reduced during fermentation by 81.1 and 92.85%, respectively.

Antioxidant and Cytoprotective Effects of Tibetan Tea and Its Phenolic Components

Tibetan tea (Kangzhuan) is an essential beverage of the Tibetan people. In this study, a lyophilized aqueous extract of Tibetan tea (LATT) was prepared and analyzed by HPLC. The results suggested that there were at least five phenolic components, including gallic acid, and four catechins (i.e., (+)-catechin, (−)-catechin gallate (CG), (−)-epicatechin gallate (ECG), and (−)-epigallocatechin gallate). Gallic acid, the four catechins, and LATT were then comparatively investigated by four antioxidant assays: ferric reducing antioxidant power, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide radical (PTIO•) scavenging, 1,1-diphenyl-2-picryl-hydrazl radical scavenging, and 2,2′-azino-bis(3-ethylbenzo-thiazoline-6-sulfonic acid) radical scavenging assays. In these assays, LATT, along with the five phenolic components, increased their antioxidant effects in a concentration-dependent manner; however, the half maximal scavenging concentrations of ECG were always lower than those of CG. Gallic acid and the four catechins were also suggested to chelate Fe²⁺ based on UV-visible spectral analysis. Ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UPLC−ESI−Q−TOF−MS/MS) analysis suggested that, when mixed with PTIO•, the five phenolic components could yield two types of radical adduct formation (RAF) products (i.e., tea phenolic dimers and tea phenolic-PTIO• adducts). In a flow cytometry assay, (+)-catechin and LATT was observed to have a cytoprotective effect towards oxidative-stressed bone marrow-derived mesenchymal stem cells. Based on this evidence, we concluded that LATT possesses antioxidative or cytoprotective properties. These effects may mainly be attributed to the presence of phenolic components, including gallic acid and the four catechins. These phenolic components may undergo electron transfer, H⁺-transfer, and Fe²⁺-chelating pathways to exhibit antioxidative or cytoprotective effects. In these effects, two diastereoisomeric CG and ECG showed differences to which a steric effect from the 2-carbon may contribute. Phenolic component decay may cause RAF in the antioxidant process.

Detection and determination of undeclared synthetic caffeine in weight loss formulations using HPLC-DAD and UHPLC-MS/MS

Caffeine is present in products marketed for weight loss, with the purpose of increasing thermogenesis and lipid metabolism. The dosage declared by the product manufacturer, or even its presence, is not always correctly described on the label. This work aimed to investigate the undeclared synthetic caffeine in weight loss formulations by a high-performance liquid chromatography with diode array detection (HPLC-DAD) method. From one hundred products purchased through Brazilian e-commerce, seventeen contained caffeine, either naturally or synthetically added to formulation. The caffeine-containing samples were confirmed by an ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method, and adulteration was clearly proven in five products. The content highest caffeine contained 448.8 mg per dose. Other irregularities were also found; nevertheless, the most serious was the addition of synthetic drugs without asking the consumers. Additional drugs expose the consumer to more possible side-effects as well as deleterious drug interactions. Intentional adulteration with any unlabeled substance is typically motivated by a desire to increase or alter the claimed effect of the marketed product to gain a commercial advantage.

Microwave-Assisted Extraction of Cannabinoids in Hemp Nut Using Response Surface Methodology: Optimization and Comparative Study

Hemp nut is commonly incorporated into several food preparations; however, most countries set regulations for hemp products according to their cannabinoid content. In this study, we have developed an efficient microwave-assisted extraction (MAE) method for cannabinoids (i.e., Δ9-tetrahydrocannabinol, cannabidiol, and cannabinol) in hemp nut. Optimization of the MAE procedure was conducted through single factor experiments and response surface methodology (RSM). A comparative study was also conducted to determine the differences in the extraction yields and morphology of hemp nut between MAE and reference extraction methods, namely heat reflux extraction (HRE), Soxhlet extraction (SE), supercritical fluid extraction (SFE), and ultrasound-assisted extraction (UAE). Among the independent variables in RSM, the temperature was the most significant parameter. The optimal conditions of MAE were as follows: extraction solvent of methanol, microwave power of 375 W, temperature of 109 °C, and extraction time of 30 min. Compared with reference extraction methods, MAE achieved the highest extraction yields of total cannabinoids in hemp nut (6.09 μg/g for MAE; 4.15 μg/g for HRE; 5.81 μg/g for SE; 3.61 μg/g for SFE; 3.73 μg/g for UAE) with the least solvent consumption and shortest time. Morphological observations showed that substantial cell rupturing occurred in the microstructure of hemp nut after MAE, indicating enhanced dissolution of the target compounds during the extraction process. The MAE method is thus a rapid, economic, and environmentally friendly extraction method that is both effective and practical for industrial applications.

Methylxanthines and catechines in different teas (Camellia sinensis L. Kuntze) - influence on antioxidant properties

In general, there are four basic types of tea: green (not fermented), black (fermented), oolong and white tea (partially fermented). The differences among these types are in the processing technology, which is largely reflected in their chemical composition. The most influential factor that significantly affects the quality and quantity of substances (biologically active) is the processing temperature, which causes changes in the composition (isomerization and/or transformation). The present paper focuses on monitoring content of three methylxanthines - alkaloids (caffeine, theophylline and theobromine), and seven flavan-3-ols - catechins ((+)-catechin (C), (-)-catechin-3-gallate (C-3-G), (-)-epicatechin (EC), (-)-epicatechin-3-gallate (EC-3-G), (-)-epigallocatechin-3-gallate (EGC-3-G), (-)-gallocatechin (GC) and (-)-gallocatechin-3-gallate (GC 3-G)), which are characteristic for tea. Attention was also given to the assessment of selected antioxidant parameters using spectrophotometric procedures (ABTS - radical cation decolorization assay and Phosphomolybdenum reducing antioxidant power assay) in relation to the determined substances using RP-HPLC/DAD analysis. Based on the results obtained, it can be concluded that a type of tea clearly affects the quality and quantity of the substances that have a positive impact on the consumer's health, significantly reflected in the levels of antioxidant active substances determined by the spectrophotometric procedures. The highest content of methylxanthin, catechins, polyphenols and antioxidant substances was recorded in the green tea sample GT3. The highest content of flavonoids and phenolic acids was recorded in the Pu-erh tea sample PT 5.

Rapid High Performance Liquid Chromatography Determination and Optimization of Extraction Parameters of the α-Asarone Isolated from Perilla frutescens L

Response surface methodology (RSM), based on a central composite design, was used to determine the best liquid-to-raw material ratio (10:3–15 mL/g), extraction time (1–3 h), and ethanol concentration (50%–100%) for maximum content of α-asarone from Perilla frutescens (PF) extract. Experimental values of α-asarone were 9.51–46.36 mg/g; the results fitted a second-order quadratic polynomial model and correlated with the proposed model (R² > 0.9354). The best conditions were obtained with extraction time of 1.76 h, liquid-to-raw material ratio of 10:13.5 mL/g, and ethanol concentration of 90.37%. Under these conditions, the model predicted extraction content of 40.56 mg/g, while experimental PF content of α-asarone was 43.84 mg/g dried plant. Optimized conditions determined for maximum content of α-asarone were similar to the experimental range. Experimental values agreed with those predicted, thus validating and indicating suitability of both the model and the RSM approach for optimizing extraction conditions. In addition, a reliable, reproducible and accurate method for the quantitative determination of α-asarone by High Performance Liquid Chromatography (HPLC) analysis was developed with limit of detection (LOD), limit of quantitation (LOQ) values of 0.10 and 0.29 µg/mL and excellent linearity (R² > 0.9999).

Simultaneous Determination of β-Cypermethrin and Its Metabolite 3-Phenoxybenzoic Acid in Microbial Degradation Systems by HPLC-UV

The wide use of pesticides in agriculture is necessary to guarantee adequate food production worldwide. However, pesticide residues have caused global concern because of their potential health risk to consumers. In this study, we could identify β-cypermethrin (β-CY) and its degradation product 3-phenoxybenzoic acid (3-PBA) by liquid chromatograph-mass spectrometry. Few studies on the simultaneous determination of β-CY and its metabolites have been carried out so far; hence, we established a high-performance liquid chromatography method to determine the concentrations of both β-CY and 3-PBA simultaneously in microbial degradation systems. In this study, a novel β-CY degrading strain, Bacillus licheniformis B-1, was isolated from a tea garden soil, utilizing β-CY as a growth substrate. Good linear relationships between β-CY and 3-PBA were observed and the concentrations of reference solutions were between 0.50 and 60.00 µg/mL. Satisfactory stability and intra- and interday precision were obtained. The limits of detection were 0.06 and 0.13 µg/mL for β-CY and 3-PBA, respectively, and the corresponding limits of quantification were 0.21 and 0.34 µg/mL, respectively. Spiking recoveries for β-CY varied from 98.38 to 105.80%, with relative standard deviations (RSDs) varying from 1.49 to 3.93%. Spiking recoveries for 3-PBA varied from 99.59 to 101.20%, with RSDs varying from 0.58 to 3.64%. The proposed method has advantages of simplicity, rapidity, high accuracy, good separation and reproducibility; thus, it is ideally suitable for simultaneous determination of β-CY and 3-PBA in microbial degradation systems.

Simultaneous extraction and determination of free and conjugated phytosterols in tobacco

Acid hydrolysis and alkaline saponification were incorporated into a microwave-assisted extraction process for the simultaneous extraction of free and conjugated phytosterols from tobacco. The crude extract of the microwave-assisted extraction was purified by C18 solid-phase extraction and then determined by high-performance liquid chromatography. Phytosterols of cholesterol, ergosterol, stigmasterol, campesterol, and β-sitosterol were determined by chromatographic quantification. The multiple parameters of microwave-assisted extraction were optimized by a uniform design method. The optimal ratio of extraction ethanol solvent to tobacco mass was 30 mL/g. The microwave-assisted extraction acid hydrolysis was carried out in sulfuric acid medium by heating for 10 min at 55°C. The microwave-assisted extraction alkaline saponification was performed after adding excessive sodium hydroxide by heating another 10 min. The repeatability of the proposed method was acceptable with recoveries from 69.68 to 88.17% for the phytosterols. Five target phytosterols were all found in the tobacco samples, and the contents were significantly different in samples from different producing areas.

Optimization of pancreatic lipase inhibitory and antioxidant activities of Ilex paraguariensis by using response surface methodology

Response surface methodology (RSM) using a Box-Behnken design was used to optimize the extraction conditions for obtaining pancreatic lipase inhibitory and antioxidant principles from Ilex paraguariensis leaves. Three influencing factors: extraction time (min), the liquid-solid ratio, and ethanol concentration (%, v/v) were investigated in the ultrasonic extraction process. Optimization of the extraction conditions to obtain a product with minimum PL activity, maximum antioxidant activity, and maximum yield was performed using RSM by focusing on the three target influencing factors. The optimum conditions were established as the ethanol concentration (54.8 %), liquid-solid ratio (35.4), and extraction time (70.0 min). Under these conditions, the 2,2-diphenyl-1-picrylhydrazyl scavenging activity, PL activity, extraction yield were 59.3 ± 3.5, 35.3 ± 3.0, and 34.4 ± 0.4 %, respectively, similar to the theoretical predicted values of 59.7, 35.2, and 34.3 %, respectively.

In vitro antioxidant and anti-inflammatory properties of Limonium algarvense flowers' infusions and decoctions: A comparison with green tea (Camellia sinensis)

This work reports the in vitro antioxidant and anti-inflammatory activities and toxicity of infusions and decoctions of Limonium algarvense flowers, and green tea. The total contents in different phenolic groups and the quantification of individual phenolics by HPLC are also reported. L. algarvense and green tea had similar antioxidant properties, except for hydroxyl radical-scavenging activity, higher on green tea, and iron chelating potential, higher on L. algarvense. The later species also had the uppermost anti-inflammatory potential. Green tea decoction had the highest content of phenolic groups, but the infusion of L. algarvense had higher amounts of salicylic, gallic and coumaric acids. L. algarvense was not toxic, whereas green tea was toxic for S17 cells. Under our experimental conditions, infusions and decoctions of L. algarvense flowers had similar or higher antioxidant and anti-inflammatory properties than green tea, and thus, may be useful for alleviating symptoms associated with oxidative and inflammatory-related diseases.

Evaluation of seven different drying treatments in respect to total flavonoid, phenolic, vitamin C content, chlorophyll, antioxidant activity and color of green tea (Camellia sinensis or C. assamica) leaves

The effect of seven drying treatments (sun, shade, oven 60 °C, oven 80 °C, oven 100 °C, microwave and freeze-drying) were evaluated with respect total flavonoid (TFC), phenolic (TPC), antioxidant activity, vitamin C and color characteristics of green tea. In general, drying increased antioxidant activity, TPC, TFC and chlorophyll content, while it led to a decrease in vitamin C. The highest TPC (209.17 mg Gallic acid/gdw) and TFC (38.18 mg Quercitin/gdw) were obtained in oven drying at 60 and 100 °C, respectively. Among methods, oven drying at 60 °C revealed the highest radical scavenging activity (IC50 = 167.166 μg/ml), while microwave showed the lowest one (IC50 = 505.5 μg/ml). Similar trend was also observed in reducing power assay. The highest vitamin C (16.36 mg/100gDM) and Chlorophyll a (17.35 mg/l) were obtained in freeze drying. Finally, sun and freeze drying methods were considered as the least and the most desirable drying methods, respectively the final color of green tea leaves.

Effects of alternative steeping methods on composition, antioxidant property and colour of green, black and oolong tea infusions

Cold water steeping is reported to maximise tea health benefits, but requires long infusion time. In this work, the employment of a brief hot infusion step followed by ice addition was evaluated. The comparison of this innovative method with hot and cold steeping was investigated on green, black and oolong teas. Catechins, xanthines and gallic acid content, antioxidant power, total phenolics and colour analysis were evaluated. Hot infusion shown rapid extractive power, but relevant compound degradation. On the contrary, cold infusion extracted higher level of healthy molecules with slow kinetic. The innovative method achieved in short time similar properties of cold infusion in terms of antioxidant power. As for bioactive compounds, such as gallic acid and epigallocatechin gallate, highest values, about double than in hot infusion, were recorded for green and black teas. This steeping method may represent an alternative approach for industrial beverage preparation.

Antioxidants: Characterization, natural sources, extraction and analysis

Recently many review papers regarding antioxidants from different sources and different extraction and quantification procedures have been published. However none of them has all the information regarding antioxidants (chemistry, sources, extraction and quantification). This article tries to take a different perspective on antioxidants for the new researcher involved in this field. Antioxidants from fruit, vegetables and beverages play an important role in human health, for example preventing cancer and cardiovascular diseases, and lowering the incidence of different diseases. In this paper the main classes of antioxidants are presented: vitamins, carotenoids and polyphenols. Recently, many analytical methodologies involving diverse instrumental techniques have been developed for the extraction, separation, identification and quantification of these compounds. Antioxidants have been quantified by different researchers using one or more of these methods: in vivo, in vitro, electrochemical, chemiluminescent, electron spin resonance, chromatography, capillary electrophoresis, nuclear magnetic resonance, near infrared spectroscopy and mass spectrometry methods.

Water-compatible magnetic imprinted nanoparticles served as solid-phase extraction sorbents for selective determination of trace 17beta-estradiol in environmental water samples by liquid chromatography

Endocrine disrupting compounds (EDCs) are a potential risk for wildlife and humans for their existence in water. The efficient extraction and clean-up steps are required before detection of low concentration levels of EDCs. In this work, a novel water-compatible magnetic molecularly imprinted nanoparticles is synthesized for the selective extraction of 17β-estradiol (E2) in environmental water samples. The preparation is carried out by introducing aldehyde groups to the surface of amino-functionalized magnetic nanoparticles through a simple one-step modification, followed by copolymerization of functional monomer gelatin and template E2 via surface imprinting technique. The gelatin with abundant active groups could not only act as functional monomer reacting with template, but also assemble covalently at the surface of magnetic nanoparticles. At the same time, gelatin would improve the water-compatibility of imprinted materials for attaining high extraction efficiency. To obtain high imprinting effect, the preparation conditions are optimized in detail using Central composite design-response surface methodology. The resultant polymers have uniform spherical shape with a shell thickness of about 8nm, stable crystalline form, and super-paramagnetic property. Meanwhile, the obtained polymers have high capacity of 12.87mgg(-1) and satisfactory selectivity to template molecule. To testify the feasibility of the magnetic imprinted polymers in sample pretreatment, a method for determination of trace E2 in environmental water samples was set up by combination of solid-phase extraction (SPE) using the prepared polymers as sorbents and HPLC for rapid isolation and determination of E2. The limit of detection of proposed method is 0.04ngmL(-1), the intra- and inter-day relative standard deviations (RSDs) are less than 4.6% and 5.7%, respectively. The recoveries of E2 from environmental water samples are in the range from 88.3% to 99.1% with the RSDs less than 7.2%.