Phenolic compounds are well-known phytochemicals found in all plants. They consist of simple phenols, benzoic and cinnamic acid, coumarins, tannins, lignins, lignans and flavonoids. Substantial developments in research focused on the extraction, identification and quantification of phenolic compounds as medicinal and/or dietary molecules have occurred over the last 25 years. Organic solvent extraction is the main method used to extract phenolics. Chemical procedures are used to detect the presence of total phenolics, while spectrophotometric and chromatographic techniques are utilized to identify and quantify individual phenolic compounds. This review addresses the application of different methodologies utilized in the analysis of phenolic compounds in plant-based products, including recent technical developments in the quantification of phenolics.

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Techniques for analysis of plant phenolic compounds.

Extraction of active chemical compounds from natural products is one of the most important research areas for pharmaceutical and chemical industries. Traditional techniques used for the solvent extraction of natural products are associated with longer extraction times and lower yields, use of large amount of organic solvents and poor extraction efficiency. Ultrasound can be effectively used to improve the extraction rate by increasing the mass transfer rates and possible rupture of cell wall due to formation of microcavities leading to higher product yields with reduced processing time and solvent consumption. The present work presents an exhaustive overview of different aspects of ultrasound assisted extraction (UAE) of various natural products. Mechanism of UAE has been discussed and recommendations for optimum operating conditions have been reported for maximizing the yield. An overview of different applications of UAE has been also presented. Possible intensification of UAE by coupling with traditional solvent and supercritical extraction processes has also been discussed. Overall it appears that ultrasonic irradiations can be effectively used for intensification of the extraction of important constituents from natural products.

Intensification of extraction of natural products using ultrasonic irradiations—A review of current status

Flavonoids are major bioactive compounds known to be beneficial against many chronic diseases such as cancer, cardiovascular disorders, and inflammation. Food products obtained from plants are key sources of flavonoids for humans. However, during different food-processing steps, flavonoids are lost in remarkable amounts. Supplementation of flavonoids as a food additive will help in retaining the required health-beneficial amount of flavonoids in the diet, and extraction is an important step in the preparation of food additives. Microwave extraction is one of the most advanced extraction methods, which has the potential of playing a major role in flavonoid extraction and analytical quantification. The present paper reviews the potential application of microwave extraction for flavonoids and the advantage of microwave-assisted process over the other extraction processes generally employed for extraction.

Microwave-Assisted Extraction of Flavonoids: A Review

Herein, we present a survey of the literature covering the development of molecular imprinting science and technology over the years 2004-2011. In total, 3779 references to the original papers, rev ...

Molecular imprinting science and technology: a survey of the literature for the years 2004-2011.

Direct analysis in real time mass spectrometry (DART-MS) has become an established technique for rapid mass spectral analysis of a large variety of samples. DART-MS is capable of analyzing the sample at atmospheric pressure, essentially in the open laboratory environment. DART-MS can be applied to compounds that have been deposited or adsorbed on to surfaces or that are being desorbed therefrom into the atmosphere. This makes DART-MS suitable and well-known for analysis of ingredients of plant materials, pesticide monitoring on vegetables, forensic and safety applications such as screening for traces of explosives, warfare agents, or illicit drugs on luggage, clothes, or bank notes, etc. DART can also be used for analysis of either solid or liquid bulk materials, as may be required in quality control, or to quickly investigate the identity of a compound from chemical synthesis. Even living organisms can be subjected to DART-MS. Driven by different needs in analytical practice, the combination of the DART ionization source and interface can be configured in multiple geometries and with various accessories to adapt the setup as required. Analysis by DART-MS relies on some sort of gas-phase ionization mechanism. In DART, initial generation of the ionizing species is by use of a corona discharge in a pure helium atmosphere which delivers excited helium atoms that, upon their release into the atmosphere, will initiate a cascade of gas-phase reactions. In the end, this results in reagent ions created from atmospheric water or (solvent) vapor in the vicinity of the surface subject to analysis where they effect a chemical ionization process. DART ionization processes may generate positive or negative ions, predominantly even-electron species, but odd-electron species do also occur. The prevailing process of analyte ion formation from a given sample is highly dependent on analyte properties.

Direct analysis in real time—a critical review on DART-MS

Portulaca oleracea L. is a traditional edible and medicinal plant in China. Flavonoids are one of the main active ingredients of this plant. Five extraction technologies of flavonoids from P. oleracea L. were investigated and compared, including microwave-assisted extraction, ultrasonic extraction, reflux extraction, Soxhlet extraction, and marinated extraction. The results showed that microwave-assisted extraction was most suitable for the extraction of flavonoids from P. oleracea L. because of its high effect and short extraction time. The found optimum extraction conditions were that the ethanol concentration was 70% (v/v), solid–liquid ratio was 1:50, extracting temperature was 50 °C and irradiation time was 9 min. Quantification was performed by means of UV–Vis spectrophotometry with chromogenic system of NaNO2–Al (NO3)3–NaOH. Under the optimum conditions, the calibration curve for the analyte was linear with the correlation coefficients greater than 0.9999. The average recovery was 102.6%, and its RSD was 1.13%(n = 5). Eight types of P. oleracea L. according to different habits were investigated. The total content of flavonoids was 7.16, 7.10, 9.38, 6.82, 6.78, 11.36, 5.12, and 1.76 mg g−1, respectively.

Analysis of Flavonoids in Portulaca oleracea L. by UV–Vis Spectrophotometry with Comparative Study on Different Extraction Technologies

Fingerprint profile of active components for Artemisia selengensis Turcz by HPLC–PAD combined with chemometrics

Identification of Portulaca oleracea L. from different sources using GC-MS and FT-IR spectroscopy.

Fingerprint analysis of Radix Aconiti using ultra-performance liquid chromatography–electrospray ionization/ tandem mass spectrometry (UPLC–ESI/MSn) combined with stoichiometry

Hongbin Zhu

Papers

Analysis of Flavonoids in Portulaca oleracea L. by UV–Vis Spectrophotometry with Comparative Study on Different Extraction Technologies

Fingerprint profile of active components for Artemisia selengensis Turcz by HPLC–PAD combined with chemometrics

Identification of Portulaca oleracea L. from different sources using GC-MS and FT-IR spectroscopy.

Fingerprint analysis of Radix Aconiti using ultra-performance liquid chromatography–electrospray ionization/ tandem mass spectrometry (UPLC–ESI/MSn) combined with stoichiometry

Rapid quality assessment of Radix Aconiti Preparata using direct analysis in real time mass spectrometry.