The determination of the caffeic acid derivatives of Echinacea purpurea aerial parts under various extraction conditions by supercritical fluid extraction (SFE)

Development of Promising Flower-like Ag/SrFeO3 Nanosheet Electrode Materials: An Efficient and Selective Electrocatalytic Detection of Caffeic Acid in Coffee and Green Tea

The development of highly efficient electrocatalytic sensors is necessary for detection in various paramedical and industrial applications. Motivated by this concept, we demonstrate flower-like Ag/SrFeO3 nanostructures prepared by a facile route to modify electrocatalyst material for the detection of caffeic acid (CA). The surface morphology, phase structure, particle size, and pore volume were investigated through different physicochemical analytical techniques. The cyclic voltammetry technique was employed to evaluate the electrochemical behavior of both glassy carbon and modified Ag/SrFeO3 electrodes toward CA. The study revealed that the modified electrode shows excellent electrocatalytic activity toward CA compared to the reported values, with a wide linear range of 1-15 nM, a detection limit of 23 nM, good stability, and excellent repeatability. The superior results are attributed to numerous factors such as rapid electron transfer ability, tunable texture, high surface area, and good conductivity. The created Ag/SrFeO3 nanostructure-based electrochemical biosensor is a potential candidate for real-time analytical performance to directly detect CA in commercially available coffee and green tea without any pre-treatment.

Chitosan–Hydroxycinnamic Acids Conjugates: Emerging Biomaterials with Rising Applications in Biomedicine

Over the past thirty years, research has shown the huge potential of chitosan in biomedical applications such as drug delivery, tissue engineering and regeneration, cancer therapy, and antimicrobial treatments, among others. One of the major advantages of this interesting polysaccharide is its modifiability, which facilitates its use in tailor-made applications. In this way, the molecular structure of chitosan has been conjugated with multiple molecules to modify its mechanical, biological, or chemical properties. Here, we review the conjugation of chitosan with some bioactive molecules: hydroxycinnamic acids (HCAs); since these derivatives have been probed to enhance some of the biological effects of chitosan and to fine-tune its characteristics for its application in the biomedical field. First, the main characteristics of chitosan and HCAs are presented; then, the currently employed conjugation strategies between chitosan and HCAs are described; and, finally, the studied biomedical applications of these derivatives are discussed to present their limitations and advantages, which could lead to proximal therapeutic uses.

Supercritical Carbon Dioxide Extraction of Phenolic Compounds from Potato (Solanum tuberosum) Peels

In the last three decades, greener technologies have been used, aiming at extracting phenolic compounds from vegetable matrices due to the inherent advantages compared to organic solvent-based methodologies. In this work, supercritical CO2 was investigated for recovering phenolic acids from potato peels. Following screening runs for assessing the significant extraction parameters, a Central Composite Design of Experiments was carried out aiming at process optimization, with methanol concentration (MeOH, %) and CO2 flow rate (qCO2, g/min) as independent variables. Both parameters were deemed to impart a significant effect on the final response. Although the major phenolic acid in potato peels is chlorogenic acid (CGA), the main compound extracted was caffeic acid (CFA), present at a concentration of 0.75 mg/g dry peel in the extracts. The optimum extraction conditions were 80 °C, 350 bar, MeOH 20%, and flow rate of 18.0 g/min, which enabled a total phenolic recovery of 37% and a CFA recovery of 82%. The antioxidant activity of the supercritical fluid extraction (SFE) extracts was also measured, with the highest scavenging capacity reaching 73%. The need for using mixtures of water and organic solvents as co-solvents in SFE to enable CGA recovery seems necessary, possibly due to its better dissolution in aqueous solutions than in pure solvents.

Selective extraction of bioactive compounds from plants using recent extraction techniques: A review

Plant extraction has existed for a long time and is still of interest. Due to technological improvements, it is now possible to obtain extracts with higher yields. While global yield is a major parameter because it assesses the extraction performance, it can be of interest to focus on the extraction of particular compounds (specific metabolites) to enrich the sample and to avoid the extraction of unwanted ones, for instance the primary metabolites (carbohydrates, triacylglycerols). The objective then is to improve extraction selectivity is then considered. In solid-liquid extraction, which is often called maceration, the solvent has a major impact on selectivity. Its polarity has a direct influence on the solutes extracted, related to the chemical structure of the compounds, and modelling compound/solvent interactions by using various polarity or interaction scales is a great challenge to favor the choice of the appropriate extracting liquid. Technical advances have allowed the development of recent, and sometimes green, extraction techniques, such as Microwave-Assisted Extraction (MAE), Ultrasound-Assisted Extraction (UAE), Pressurized Liquid Extraction (PLE) and Supercritical Fluid Extraction (SFE). This review focuses on the specificity of these recent techniques and the influence of their physical parameters (i.e. pressure, intensity, etc.). In addition to the solvent selection, which is of prime interest, the physical parameters applied by the different techniques influence the extraction results in different ways. Besides, SFE is a versatile and green technique suitable to achieve selectivity for some compounds. Due to its properties, SC-CO₂ allows tailoring conditions to improve the selectivity.

Au-Nitrogen-Doped Graphene Quantum Dot Composites as "On-Off" Nanosensors for Sensitive Photo-Electrochemical Detection of Caffeic Acid

Herein, gold–nitrogen-doped graphene quantum dot (Au/NGQD) composite modified electrodes were fabricated and applied as “on–off” nanosensors for the photo-electrochemical (PEC) detection of caffeic acid under visible-light irradiation. An effective and simple strategy was established for the preparation of Au/NGQD composites by hydrothermal and calcination methods. Owing to the quantum confinement effect of NGQDs, the local surface plasmon resonance (LSPR) effect of Au nanoparticles (NPs), and the synergistic effect between Au and NGQDs NPs, the Au/NGQDs showed excellent PEC performance, with wide linear concentration ranges (0.11 to 30.25 μM and 30.25 to 280.25 μM), a low detection limit (0.03 μM), excellent sensitivity, and high stability. The present study may provide an advanced strategy for the simple design of Au/NGQD composites to allow their effective application for selective and sensitive sensing of small biological molecules.

Re-opening the stage for Echinacea research - Characterization of phylloxanthobilins as a novel anti-oxidative compound class in Echinacea purpurea

BACKGROUND

Phylloxanthobilins are tetrapyrrolic natural products that arise from the degradation of chlorophyll. Phylloxanthobilins have been discovered roughly 10 years ago in the leaves of deciduous trees, and are now considered a compound class with high and still unexplored potential of bioactivities. To date, however, there are no reports on the occurrence of phylloxanthobilins in parts of a medicinal plant used for pharmaceutical preparations.

PURPOSE

The relevance of Echinacea purpurea as medicinal plant is undoubtedly high, and a large variety of pharmaceutical preparations is available on the market, mostly for the treatment of the common cold. Nevertheless, its phytochemical profiling has been limited to analysis for previously characterized substances, and this has not explained all its pharmacological efficacies. We therefore set out to investigate the occurrence of phylloxanthobilins in Echinacea purpurea.

METHODS

Phylloxanthobilins in leaf extracts of Echinacea purpurea were detected using analytical HPLC. Identified phyllobilins were purified from plant material and characterized by UV/Vis, mass spectrometry, MS/MS, and confirmed by co-injections with previously published phyllobilins from different sources. The anti-oxidant activity of selected isolated phylloxanthobilins was assessed by an in vitro ferric reducing antioxidant power (FRAP) assay; in addition, the ability to scavenge ROS in cells caused by hydrogen peroxide stimulation was determined by measuring H₂DCF-DA fluorescence and by assessing cellular GSH levels.

RESULTS

In extracts of Echinacea purpurea leaves, an unprecedented diversity of phylloxanthobilins was detected; surprisingly, not only in senescent yellow leaves, but also in green leaves with no visible chlorophyll degradation. Six phylloxanthobilins were identified and structurally characterized. The uptake of phylloxanthobilins by human endothelial kidney cells was demonstrated. When investigating the anti-oxidative activity of these natural products, a potent in vitro activity was demonstrated; in addition, phylloxanthobilins possess intracellular ROS scavenging ability and can prevent oxidative stress as assessed by total cellular GSH levels.

CONCLUSION

Phylloxanthobilins are important constituents of Echinacea purpurea extracts, and our first exploratory studies hint towards promising bioactivities of these natural products, which may be relevant for understanding Echinacea efficacies.

Ultra-stable Electrochemical Sensor for Detection of Caffeic Acid Based on Platinum and Nickel Jagged-Like Nanowires

Electrochemical sensors have the high sensitivity, fast response, and simple operation for applications in biological, medical, and chemical detection, but limited by the poor stability and high cost of the electrode materials. In this work, we used PtNi lagged-like nanowire for caffeic acid (CA) electrochemical detection. The removal of outer layer Ni during reaction process contributed to the rehabilitation of active Pt sites at the surface, leading to the excellent electrocatalytic behavior of CA sensing. Carbon-supported PtNi-modified glassy carbon electrode (PtNi/C electrode) showed a broad CA detecting range (from 0.75 to 591.783 μM), a low detection limit (0.5 μM), and excellent stability. The electrode preserved high electrocatalytic performance with 86.98% of the initial oxidation peak current retained after 4000 potential cycles in 0.5 mM caffeic acid solution. It also demonstrates excellent anti-interference capability and is ready for use in the real sample analysis.

Highly selective separation and purification of chicoric acid from Echinacea purpurea by quality control methods in macroporous adsorption resin column chromatography

Chicoric acid is the main phenolic active ingredient in Echinacea purpurea (Asteraceae), best known for its immune-enhancing ability, as well as used as a herbal medicine. To achieve further utilization of medicinal ingredients from E. purpurea, an efficient preparative separation of chicoric acid was developed based on macroporous adsorption resin chromatography. The separation characteristics of several different typical macroporous adsorption resins were evaluated by adsorption/desorption column experiments, and HPD100 was revealed as the optimal one, which exhibited that the adsorbents fitted well to the pseudo-second-order kinetics model and Langmuir isotherm model, and the optimal process parameters were obtained. The breakthrough curves could be predicted and end-point could be determined early. Besides, the optimal elution conditions of chicoric acid can be achieved using the quality control methods. As a result, the purity of chicoric acid was increased 15.8-fold (from 4 to 63%) after the treatment with HPD100. The process of the enrichment and separation of chicoric acid is considerate, because of its high efficiency and simple operation. The established separation and purification method of chicoric acid is expected to be valuable for further utilization of E. purpurea according to product application in pharmaceutical fields in the future.

Natural Antioxidants in Foods and Medicinal Plants: Extraction, Assessment and Resources

Natural antioxidants are widely distributed in food and medicinal plants. These natural antioxidants, especially polyphenols and carotenoids, exhibit a wide range of biological effects, including anti-inflammatory, anti-aging, anti-atherosclerosis and anticancer. The effective extraction and proper assessment of antioxidants from food and medicinal plants are crucial to explore the potential antioxidant sources and promote the application in functional foods, pharmaceuticals and food additives. The present paper provides comprehensive information on the green extraction technologies of natural antioxidants, assessment of antioxidant activity at chemical and cellular based levels and their main resources from food and medicinal plants.

Chemical Analysis of the Herbal Medicine Salviae miltiorrhizae Radix et Rhizoma (Danshen)

Radix Salviae miltiorrhizae et Rhizoma, known as Danshen in China, is one of the most popular traditional Chinese medicines. Recently, there has been increasing scientific attention on Danshen for its remarkable bioactivities, such as promoting blood circulation, removing blood stasis, and clearing away heat. This review summarized the advances in chemical analysis of Danshen and its preparations since 2009. Representative established methods were reviewed, including spectroscopy, thin layer chromatography, gas chromatography, liquid chromatography (LC), liquid chromatography-mass spectrometry (LC-MS), capillary electrophoresis, electrochemistry, and bioanalysis. Especially the analysis of polysaccharides in Danshen was discussed for the first time. Some proposals were also put forward to benefit quality control of Danshen.