Simultaneous preconcentration and analysis of anthraquinones based on ultrasound emulsification ionic liquid microextraction

Recent advances in green solvents-based liquid-phase microextraction techniques for chromatographic analysis of active components in traditional Chinese medicine

Traditional Chinese medicine (TCM) is a treasure of China and a crucial part of traditional medicine in the world, particularly in many oriental countries. TCM is the core and basis of traditional medicine in clinical practice for numerous diseases, and performs important function in nutraceuticals and dietary supplements. However, it is extremely difficult to extract each active ingredient from TCM to elucidate the mechanism of TCM clinical efficacy due to numerous compounds in TCM, especially trace compounds. Consequently, liquid-phase microextraction (LPME) techniques, one of the main extraction methods of active ingredients in TCM, have attracted a considerable attention from researchers. In recent years, many novel green solvents based-LPME methods have been reported, such as single-drop microextraction (SDME), hollow-fiber liquid-phase microextraction (HF-LPME), dispersive liquid-liquid microextraction (DLLME), and electro-membrane extraction (EME). Therefore, in this review, we present an up-to-date and comprehensive summary of various LPME techniques, novel green solvents, and their applications in the analysis of active ingredients within the complex TCM samples. We provide a detailed overview of the fundamental principles, modes, and the critical process parameters of the LPME techniques. In addition, we compare different types of green solvents (i.e., deep eutectic solvents, ionic liquids, magnetic ionic liquids, supramolecular solvents, switchable solvents, among others), and the advantages and disadvantages of these solvents are critically evaluated, highlighting their suitability for various applications. Finally, we elucidate the merits and demerits of different LPME methods, discuss their practical applications, and explore their future research directions. This review aims to provide a valuable resource for researchers and practitioners in the field of TCM, promoting research development and application of the advanced and environmentally friendly sample pretreatment techniques.

Simultaneous Estimation of Rhein and Aloe-Emodin in Traditional and Ultrasound-Based Extracts of Rheum palmatum L. (Rhubarb) Using Sustainable Reverse-Phase and Conventional Normal-Phase HPTLC Methods

The greenness indices of literature analytical procedures for the simultaneous measurement of rhein and aloe-emodin have not been determined. As a consequence, the first goal of this study was to design and validate a sensitive and sustainable reverse-phase high-performance thin-layer chromatography (HPTLC) method for the simultaneous estimation of rhein and aloe-emodin in a traditional extract (TE) and ultrasound-based extract (UBE) of commercial Rhubarb and Rhubarb plant extracts in comparison to the conventional normal-phase HPTLC method. The second goal was to determine the greenness indices for both methods using the AGREE approach. For the sustainable reverse-phase HPTLC approach, the method was linear in the 50–1000 ng/spot range for rhein and 25–1000 ng/spot range for aloe-emodin. However, for the conventional normal-phase HPTLC approach, the method was linear in the 50–600 ng/spot range for rhein and 100–600 ng/spot range for aloe-emodin. The limit of detection (LOD) for rhein and aloe-emodin was 16.81 ng/spot and 8.49 ng/spot, respectively, using the sustainable analytical method. However, the LOD for rhein and aloe-emodin was 18.53 ng/spot and 39.42 ng/spot, respectively, using the conventional analytical method. For the simultaneous determination of rhein and aloe-emodin, the sustainable analytical method was more sensitive, accurate, precise, and robust than the conventional analytical method. The amount of rhein and aloe-emodin was higher in the UBE of commercial Rhubarb and Rhubarb plant extract over their TE. For the simultaneous quantification of rhein and aloe-emodin in the TE and UBE of marketed Rhubarb and Rhubarb plant extract, the sustainable analytical method was superior to the conventional analytical method. The AGREE index for the sustainable reverse-phase and conventional normal-phase HPTLC methods was determined to be 0.78 and 0.49, respectively, indicating an excellent greenness profile of the sustainable reverse-phase HPTLC method over the conventional normal-phase HPTLC approach. The sustainable analytical method was found to be superior to the conventional analytical method based on these results.

Ballpoint connector-protected salt-oil-salt liquid phase microextraction for concentration and enrichment of trace anthraquinone compounds in rhubarb

This study proposed a new ballpoint connector-protected salt-oil-salt liquid phase microextraction for extraction and enrichment of trace rhein and chrysophanol in rhubarb prior to determination of the analytes by high performance liquid chromatography. In this study, a handy ballpoint connector (between ballpoint tip and ink chamber) was used as extraction device, in which its cavity was filled with n-octanol, and the bare n-octanol in its two opening ends was covered with a thin layer of sodium chloride film. The design subtly assembled salt film onto ballpoint connector for extraction and enrichment, which greatly improved the enrichment factors of the target analytes. Moreover, the novel procedure and its extraction mechanism were described and analyzed, and several crucial parameters reflecting the extraction effect were investigated and optimized. Under optimum conditions, high enrichment factors (247 and 127), good linearities with r ≥ 0.9998, limits of detection (0.6-1.1 ng/mL), relative standard deviations of intra- and interday (2.2-8.8% and 4.3-8.9%), and average recoveries (97.6-98.1%), were obtained, respectively. The proposed method can not only eliminate the negative effects from viscosity and ion strength at high salt concentration of sample phase, but also make salting-out effect be focused on small area so as to maximize the extraction effect.

Screening for Natural Inhibitors of Topoisomerases I from Rhamnus davurica by Affinity Ultrafiltration and High-Performance Liquid Chromatography-Mass Spectrometry

Topoisomerase I (Topo I) catalyzes topological interconversion of duplex DNA during DNA replication and transcription, and has been deemed as important antineoplastic targets. In this study, the fraction R.d-60 from ethyl acetate extracts of Rhamnus davurica showed higher inhibitory rates against SGC-7901 and HT-29 compared with the R.d-30 fraction in vitro. However, the specific active components of R.d-60 fraction remain elusive. To this end, a method based on bio-affinity ultrafiltration and high performance liquid chromatography/electrospray mass spectrometry (HPLC- ESI-MS/MS) was developed to rapidly screen and identify the Topo I inhibitors in this fraction. The enrichment factors (EFs) were calculated to evaluate the binding affinities between the bioactive constituents and Topo I. As a result, eight ligands were identified and six of which with higher EFs showed more potential antitumor activity. Furthermore, antiproliferative assays in vitro (IC₅₀ values) with two representative candidates (apigenin, quercetin) against SGC-7901, HT-29 and Hep G2 cells were conducted and further validated. Finally, the structure-activity relationships revealed that flavones contain a C2-C3 double bond of C ring exhibited higher bio-affinities to Topo I than those without it. This integrated method combining Topo I ultrafiltration with HPLC-MS/MS proved to be very efficient in rapid screening and identification of potential Topo I inhibitors from the complex extracts of medicinal plants, and could be further explored as a valuable high-throughput screening platform in the early drug discovery stage.

Analysis of Flavonoids in Rhamnus davurica and Its Antiproliferative Activities

Rhamnus davurica Pall. (R. davurica) has been used as a traditional medicinal herb for many years in China and abroad. It has been well documented as a rich source of flavonoids with diversified structures, which in turn results in far-ranging biological activities, such as anti-inflammation, anticancer, antibacterial and antioxidant activities. In order to further correlate their anticancer potentials with the phytochemical components, the fingerprint profile of R. davurica herb from Dongbei was firstly investigated using HPLC-ESI-MS/MS. Thirty two peaks were detected and identified, 14 of which were found in R. davurica for the first time in this work. Furthermore, a total of 23 peaks were resolved as flavonoids, which are the major components found in R. davurica. Meanwhile, the antiproliferative activities against human cancer cells of HT-29 and SGC-7901 in vitro exhibited distinct inhibitory effects with IC50 values at 24.96 ± 0.74 and 89.53 ± 4.11 μg/mL, respectively. Finally, the general toxicity against L-O2 cells displayed a much higher IC50 at 229.19 ± 8.52 μg/mL, which suggested very low or no toxicity on hepatic cell viability. The current study revealed for the first time the correlations between the flavonoids of R. davurica with their antiproliferative activities, which indicated that the fingerprint profile of flavonoids and their anticancer activities could provide valuable information on the quality control for herbal medicines and their derived natural remedies from this valuable medicinal plant.