Optimized determination of phenolic compounds in Dendrobium officinale stems by reverse-phase high performance liquid chromatography

Separation and determination of phenolic compounds using novel deep eutectic solvent-in-water microemulsion electrokinetic chromatography

BACKGROUND

Microemulsion electrokinetic chromatography (MEEKC) is a mode of capillary electrophoresis with a wide range of applications in which microemulsion is utilized as background electrolyte to achieve the separation of analytes. Microemulsions are composed of oil droplets, aqueous buffer, surfactant, and co-surfactant. Currently, conventional organic reagents act as the most commonly used oil phase in microemulsions, which are unfriendly to the environment. Recently, deep eutectic solvent (DES) has become a new type of eco-friendly solvent due to its non-toxicity. Therefore, it is of great value to establish a new MEEKC method by replacing conventional organic reagents as the oil phase with DES.

RESULTS

The novel DES/W MEEKC method was established for phenolic compounds in Senecio scandens samples. Single-factor experiments and response surface methodology were performed to systematically optimize the crucial parameters for the method, including the type and content of the oil phase, surfactant content, concentration of borax buffer, and pH of the background solution. Under the optimized conditions, satisfactory regression curves were established for all standard analytes with correlation coefficients ≥0.9990. The method featured high sensitivity and favorable accuracy, with the instrumental detection limit in the range of 0.22-1.04 μg/mL, and intraday and interday precision for migration time expressed as relative standard deviations of 0.18-0.82% and 1.25-2.50%, respectively. The DES/W MEEKC method was successfully applied to Senecio scandens with good recoveries of 87.72-106.99%. In conclusion, the newly established DES/W MEEKC method is highly efficient, green and environmentally friendly.

SIGNIFICANCE

DES is considered a green and efficient solvent. The DES/W MEEKC method is highly efficient and environmentally friendly. Actually, the method provides a novel and effective analytical tool for the simultaneous separation and determination of multiple phenolic compounds, especially in complex plant matrices. In the future, the DES/W MEEKC method still has the prospect of being widely used in the separation of other complex phytochemicals.

Simultaneous determination of nine phenolic compounds in imitation wild Dendrobium officinale samples using ultrahigh-performance liquid chromatography-tandem mass spectrometry

Dendrobium officinale Kimura et Migo (D. officinale), one of the nine everlasting types of grass, has gained increasing attention owing to its important roles in alternative medicines and drug discovery. Due to its natural resources being in danger of being extinct, imitation wild planting is becoming increasingly common. To assess the product's quality completely, an efficient ultrahigh performance liquid chromatography-triple quadrupole tandem mass spectrometry (UHPLC-QQQ-MS/MS) method was established to simultaneously quantify nine phenolic compounds in D. officinale samples. The extraction parameters, including solvent, solvent concentration, solid-liquid ratio, and extraction time, were systematically optimized with the single-factor test. The results demonstrated that extraction with a 1:200 solid-to-liquid ratio of 80% methanol for 1.5 h was the most efficient condition for the extraction of flavonoids. Satisfactory retention times and resolution of the nine analytes were acquired on the Thermo Scientific Hypersil GOLD column with multiple reaction monitoring in negative ion scanning mode. The method was validated to demonstrate its selectivity, linearity, precision, accuracy, and robustness. Thus, the verified UHPLC-QQQ-MS/MS method was successfully applied to the quantification of phenolic components present in D. officinale samples. The results indicated that the quantity and composition of phenolic components in D. officinale from various provenances were significantly different. This work provides a theoretical foundation for the cultivation and assessment of wild D. officinale quality.

A review of the polyphenols extraction from apple pomace: novel technologies and techniques of cell disintegration

Apple pomace, a solid waste produced during industrial processing of apple juice or cider, is a rich source of high value-added compounds such as polyphenols. This review summarizes present studies on the qualitative and quantitative methods, including Folin-Ciocalteu colorimetric, high pressure liquid chromatography (HPLC) and fluorescence spectrum, as well as enhanced extraction methods of polyphenols in apple pomace by different traditional and novel technologies, including ultrasounds (US), microwave (MW), pulsed electric fields (PEF), high voltage electrical discharges (HVED) and enzyme. The principles and characteristics of different effective enhanced extraction technologies of polyphenols in apple pomace were compared. In addition, the different cell disruption analysis methods, such as destructive detection method (electrical conductivity disintegration index, Zc), image analysis method (including scanning electron microscopy, SEM, and confocal laser scanning microscopy, CLSM), and nondestructive method (such as magnetic resonance imaging, MRI) are presented in this review. The study proved that there was a correlation between destructive detection method and image analysis method. However, each of the technologies reviewed in this study has some disadvantages to overcome, and some mechanisms need to be further substantiated. Therefore, more competitive techniques for polyphenols extraction and analysis of cell disintegration are needed to emerge in the future.

HPLC coupled with electrospray ionization multistage MS/MS and TLC analysis of flavones-C-glycosides and bibenzyl of Dendrobium hercoglossum

Dendrobium hercoglossum Rchb. f. (D. hercoglossum), as one of the origins of medicinal Dendrobium, has been widely used as a health food and nutrient source promoting fluid production. Due to a lack of quality control, it is often counterfeited or mixed with other Dendrobium. In this study, a high-performance liquid chromatography characteristic chromatogram method is established for the quality evaluation of D. hercoglossum. Based on the high-performance liquid chromatography characteristic chromatogram, D. hercoglossum is divided into two classes, each with different flavone peaks. These flavone peaks were identified using high-performance liquid chromatography coupled with electrospray ionization multistage tandem mass spectrometry. Among them, the acylated (3-hydroxy-3-methylglutaryl, p-coumaroyl, feruloyl, or sinapoyl) flavones-C-glycosides are first found in D. hercoglossum in this study. In addition, one unique band was found in D. hercoglossum by thin-layer chromatography, which can be used to distinguish it from other Dendrobium species as a characteristic marker of this plant. Combining the high-performance liquid chromatography characteristic chromatogram and high-performance liquid chromatography coupled with electrospray ionization multistage tandem mass spectrometry, the unique band was identified as 4,5-dihydroxy-3,3'-dimethoxybibenzyl. These analysis methods can be applied for the quality control and identification of D. hercoglossum as well as providing reference for the identification of similar constituents in other Dendrobium species.