Preparative isolation of 1,1-diphenyl-2-picrylhydrazyl inhibitors from Ribes himalense using medium-pressure and two-dimensional reversed-phase/reversed-phase liquid chromatography guided by an online HPLC-1, 1-diphenyl-2-picrylhydrazyl assay

Screening Antioxidant Components in Different Parts of Dandelion Using Online Gradient Pressure Liquid Extraction Coupled with High-Performance Liquid Chromatography Antioxidant Analysis System and Molecular Simulations

Utilizing online gradient pressure liquid extraction (OGPLE) coupled with a high-performance liquid chromatography antioxidant analysis system, we examined the antioxidative active components present in both the aerial parts and roots of dandelion. By optimizing the chromatographic conditions, we identified the ferric reducing-antioxidant power system as the most suitable for online antioxidant reactions in dandelion. Compared to offline ultrasonic extraction, the OGPLE method demonstrated superior efficiency in extracting chemical components with varying polarities from the samples. Liquid chromatography-mass spectrometry revealed twelve compounds within the dandelion samples, with nine demonstrating considerable antioxidant efficacy. Of these, the aerial parts and roots of dandelion contained nine and four antioxidant constituents, respectively. Additionally, molecular docking studies were carried out to investigate the interaction between these nine antioxidants and four proteins associated with oxidative stress (glutathione peroxidase, inducible nitric oxide synthase, superoxide dismutase, and xanthine oxidase). The nine antioxidant compounds displayed notable binding affinities below -5.0 kcal/mol with the selected proteins, suggesting potential receptor-ligand interactions. These findings contribute to enhancing our understanding of dandelion and provide a comprehensive methodology for screening the natural antioxidant components from herbs.

Gain deeper insights into traditional Chinese medicines using multidimensional chromatography combined with chemometric approaches

Traditional Chinese medicines (TCMs) possess a rich historical background, unique theoretical framework, remarkable therapeutic efficacy, and abundant resources. However, the modernization and internationalization of TCMs have faced significant obstacles due to their diverse ingredients and unknown mechanisms. To gain deeper insights into the phytochemicals and ensure the quality control of TCMs, there is an urgent need to enhance analytical techniques. Currently, two-dimensional (2D) chromatography, which incorporates two independent separation mechanisms, demonstrates superior separation capabilities compared to the traditional one-dimensional (1D) separation system when analyzing TCMs samples. Over the past decade, new techniques have been continuously developed to gain actionable insights from complex samples. This review presents the recent advancements in the application of multidimensional chromatography for the quality evaluation of TCMs, encompassing 2D-gas chromatography (GC), 2D-liquid chromatography (LC), as well as emerging three-dimensional (3D)-GC, 3D-LC, and their associated data-processing approaches. These studies highlight the promising potential of multidimensional chromatographic separation for future phytochemical analysis. Nevertheless, the increased separation capability has resulted in higher-order data sets and greater demands for data-processing tools. Considering that multidimensional chromatography is still a relatively nascent research field, further hardware enhancements and the implementation of chemometric methods are necessary to foster its robust development.

Rapid screening and evaluation of natural antioxidants from leaf, stem, and root of Artemisia argyi by online liquid microextraction combined with HPLC-based antioxidant assay system coupled with calibration quantitative analysis

To reveal the utilization value of leaf, stem, and root of Artemisia argyi, a rapid online liquid microextraction combined with a high-performance liquid chromatography coupled with 2,2-nitrogen-di (3-ethyl-benzothiazole-6-sulfonic acid) diammonium salt antioxidant assay system was established for analysis of antioxidants in the leaf, stem, and root of A. argyi, and a calibration quantitative method of antioxidant activity with equivalent chlorogenic acid was proposed. Thirty-three positive peaks were identified; among them, 12 compounds were found that possess good antioxidant activity including eleven organic acids (components 2-4, 8, 11-14, 17, 19, and 21) and one flavonoids (component 22). The proposed calibration quantitative method avoided the influence of content of compound and compared the extent of radical scavenging capacity of five antioxidant compounds, which were ranked as follow: 3,5-dicaffeoylquinic acid > 3,4-dicaffeoylquinic acid ≈ 4,5-dicaffeoylquinic acid > 1,4-dicaffeoylquinic acid > chlorogenic acid. In conclusion, this study provided composition and biological potential for the future development of the leaf, stem, and root of A. argyi. It is believed that the online liquid microextraction combined with high-performance liquid chromatography based antioxidant assay system can be widely used for the rapid screening of natural antioxidant components in the different parts of natural products.

Separation of Antioxidants from Trace Fraction of Ribes himalense via Chromatographic Strategy and Their Antioxidant Activity Supported with Molecular Simulations

Antioxidants from natural sources have long been of interest to researchers. In this paper, taking the traditional Tibetan medicine Ribes himalense as an example, an integrated approach was used to identify and isolate its chemical composition with free-radical-scavenging properties from its ethanol extract. First, the ethanol extract of Ribes himalense was pretreated using polyamide medium-pressure liquid chromatography (polyamide-MPLC), and the target fraction (Fr4) was obtained. Then, a combined HPLC mode was utilized to purify antioxidants in Fr4 under the guidance of an online HPLC-1,1-diphenyl-2-picrylhydrazyl (HPLC-DPPH) activity screening system. Finally, three antioxidants (3-caffeoylquinic acid methyl ester, rutin, and myricetin-3'-α-L-rhamnopyranoside) were isolated, and this is the first report of their presence in R. himalense. Further molecular docking studies showed that the antioxidants exhibited good binding with HO-1, Nrf2, and iNOS. In conclusion, this comprehensive approach is capable of extracting high-purity antioxidants from trace fractions of Ribes himalense and holds promise for future applications in the exploration of the chemical compositions and bioactivity of natural products.

An Integrated Strategy for Investigating Antioxidants from Ribes himalense Royle ex Decne and Their Potential Target Proteins

Natural products have been used extensively around the world for many years as therapeutic, prophylactic, and health-promotive agents. Ribes himalense Royle ex Decne, a plant used in traditional Tibetan medicine, has been demonstrated to have significant antioxidant and anti-inflammatory properties. However, the material basis of its medicinal effects has not been sufficiently explored. In this study, we established an integrated strategy by online HPLC-1,1-diphenyl-2-picrylhydrazyl, medium-pressure liquid chromatography, and HPLC to achieve online detection and separation of antioxidants in Ribes himalense extracts. Finally, four antioxidants with quercetin as the parent nucleus were obtained, namely, Quercetin-3-O-β-D-glucopyranoside-7-O-α-L-rhamnopyranoside, Quercetin-3-O-β-D-xylopyranosyl(1-2)-β-D-glucopyranoside, Quercetin-3-O-β-D-glucopyranoside, and Quercetin-3-O-β-D-galactoside. Until now, the four antioxidants in Ribes himalense have not been reported in other literatures. Meanwhile, the free-radical-scavenging ability of them was evaluated by DPPH assay, and potential antioxidant target proteins were explored using molecular docking. In conclusion, this research provides insights into the active compounds in Ribes himalense which will facilitate the advancement of deeper studies on it. Moreover, such an integrated chromatographic strategy could be a strong driver for more efficient and scientific use of other natural products in the food and pharmaceutical industries.

Efficient Production of Antioxidants from Rape Pollen via a Chromatographic Strategy

Rape pollen has always been considered as a research hotspot in health foods and pharmaceuticals due to its abundance of natural active ingredients. In this work, a compound with antioxidant activity was directly isolated from the methanol extract of rape pollen using a two-step procedure, under the supervision of online HPLC−1,1-diphenyl-2-picrylhydrazyl (HPLC-DPPH) detection. Firstly, online HPLC−DPPH detection was used to identify the active peaks in the methanol extract of rape pollen, and then the methanol extract was pretreated via medium-pressure liquid chromatography (MPLC) to obtain the target fraction 3 (Fr3). Fr3 was further purified using HPLC to finally obtain the target fraction 3-1, which was identified as kaempferol 3,4′-di-O-β-D-glucopyranoside through NMR and mass spectrometry. To further explore the free radical scavenging activity of this compound, its DPPH scavenging ability was determined, and two proteins related to the antioxidant pathway were used for molecular docking. The results revealed that the chromatographic strategy used in this study was efficient and reliable in separating high−purity antioxidants from rape pollen. A strategy such as this, meanwhile, also holds promise for qualitatively identifying and specifically isolating active compounds from other natural products.

Targeted isolation of 1,1-diphenyl-2-picrylhydrazyl inhibitors from Saxifraga atrata and their antioxidant activities

Saxifraga atrata is an important traditional Tibetan medicine used to treat cough and pneumonia, and has tremendous medicinal potential. In this study, we devised a technique to separate 1,1-diphenyl-2-picrylhydrazyl inhibitors from a methanol extract of Saxifraga atrata. The material was first processed using MCI GEL® CHP20P medium-pressure liquid chromatography, yielding 1.1 g of the target fraction Fr2. Subsequently, online hydrophilic interaction liquid chromatography-1,1-diphenyl-2-picrylhydrazyl assay was used to identify prospective 1,1-diphenyl-2-picrylhydrazyl inhibitors, and two 1,1-diphenyl-2-picrylhydrazyl inhibitor fractions (Fr24 and Fr25) were identified from Fr2. Then, medium-pressure preparation was continued using an XIon column to separate two 1,1-diphenyl-2-picrylhydrazyl inhibitor fractions (Fr24 and Fr25). The target compound was concentrated in fractions Fr24 and Fr25 using reverse-phase liquid chromatography during further separation procedures. Finally, the purity, structure, and 1,1-diphenyl-2-picrylhydrazyl inhibitory activity of the isolated 1,1-diphenyl-2-picrylhydrazyl inhibitors were determined. Two 1,1-diphenyl-2-picrylhydrazyl inhibitors (adenosine with the half maximal inhibitory concentration of 66.87 ± 14.33 μM and (-)-4-O-(E)-Caffeoyl-L-threonic acid with the half maximal inhibitory concentration of 59.06 ± 5.02 μM) were isolated with purities exceeding 95%. The results showed that this technology is effective in the targeted separation of antioxidants from natural products. This article is protected by copyright. All rights reserved.

Preparation and Antioxidant Activities of Phenylethanoids from Dracocephalum heterophyllum

The health benefits of Dracocephalum heterophyllum are widely reported in traditional Tibetan medicines, but the reported chemical composition is limited, probably due to difficulties in separating and purifying compounds. In this study, antioxidative phenylethanoids were isolated from an extract of Dracocephalum heterophyllum using medium- and high-pressure liquid chromatography, coupled with on-line HPLC–1,1-diphenyl-2-picrylhydrazyl recognition. Firstly, crude samples (1.3 kg) of Dracocephalum heterophyllum were pretreated via silica gel medium-pressure liquid chromatography to yield 994.0 g of Fr2, of which 10.8 g was then pretreated via MCI GEL®CHP20P medium-pressure liquid chromatography. The resulting Fr23 and Fr25 were further separated and purified using high-pressure liquid chromatography, and yielded 8.08 mg of Fr2391, 9.76 mg of Fr2551, 16.09 mg of Fr2581, and 8.75 mg of Fr2582. Furthermore, analysis of the purity and structures of the phenylethanoids suggested that Fr2391, Fr2551, Fr2581, and Fr2582 corresponded to decaffeoylverbascoside, rosmarinic acid, acteoside, and 2′-O-acetylplantamajoside, respectively, with all being over 95% pure. Finally, the antioxidant potential of the compounds was explored based on their ability to scavenge 1,1-diphenyl-2-picrylhydrazine, as well as through molecular docking of proteins related to antioxidant pathways. Altogether, our findings revealed that the proposed method is promising for separating pure antioxidative phenylethanoids from other natural compounds.

Three new dihydroflavonols with free radical scavenging activity from Ribes himalense Royle ex Decne

Ribes himalense Royle ex Decne, a small shrub, is widely used as a Tibetan medicine in Chinese folk. In this study, three novel 1,1-diphenyl-2-picrylhydrazyl inhibitors named Rihimaside A, Rihimaside B, and Rihimaside C, as well as one known 1,1-diphenyl-2-picrylhydrazyl inhibitor, dihydromyricetin, were isolated from the leaves and stems of Ribes himalense Royle ex Decne using online high performance liquid chromatography-1,1-diphenyl-2-picrylhydrazyl activity screening system combined with medium and high-pressure liquid chromatography. All four 1,1-diphenyl-2-picrylhydrazyl inhibitors are dihydroflavonols. The 1,1-diphenyl-2-picrylhydrazyl scavenging activity and IC₅₀ values of three novel 1,1-diphenyl-2-picrylhydrazyl inhibitors were determined using 1,1-diphenyl-2-picrylhydrazyl methods. Rihimaside A, Rihimaside B, and Rihimaside C exhibited IC₅₀ values of 9.58 μg/mL, 12.57 μg/mL and 387 μg/mL, respectively.

A Method to Separate Two Main Antioxidants from Lepidium latifolium L. Extracts Using Online Medium Pressure Chromatography Tower and Two-Dimensional Inversion/Hydrophobic Interaction Chromatography Based on Online HPLC-DPPH Assay

Free radicals, including 1,1-diphenyl-2-picrylhydrazyl, mediate oxidative stress to cause many chronic diseases (including cardiovascular diseases, diabetes and cancer). The extract of traditional Tibetan medicine Lepidium latifolium L. (L. latifolium) was reported to have free radical inhibition ability. Therefore, a system method was established to separate the ethanol extract of L. latifolium to prepare two main antioxidant compounds. First of all, silica gel and a medium-pressure liquid chromatography tower were used for pre-treatment of the ethanol extract of L. latifolium to obtain the main antioxidant active component fraction 4 through online high-performance liquid chromatography-1,1-diphenyl-2-picrylhydrazyl (HPLC-DPPH) assay. Then, fraction 4-1 was obtained by one-dimensional preparation using Megres C18 chromatographic column, and two active compounds with IC50 values 59.9 and 71.3 μg/mL were obtained by two-dimensional preparation using Click XIon chromatographic column. Through the study of the chemical components and separation methods of L. latifolium, the combination of HPLC-DPPH assay and two-dimensional preparative liquid chromatography was realized, providing a reference for the separation of active compounds from L. latifolium.

Comprehensive screening and separation of cyclooxygenase-2 inhibitors from Pterocephalus hookeri by affinity solid-phase extraction coupled with preparative high-performance liquid chromatography

Pterocephalus hookeri, a classical Tibetan herb, is mainly used to treat rheumatoid arthritis (RA) and contains various constituents potentially with cyclooxygenase-2 (COX-2) selective inhibition. A novel strategy for screening and target separating COX-2 inhibitors from the extracts of P. hookeri based on affinity solid-phase extraction (ASPE) column combined with preparative high-performance liquid chromatography (pre-HPLC) was successfully developed. The potential COX-2 inhibitors of P. hookeri were screened and recognized by the ASPE-HPLC system, which strategy is to analyze the compounds isolated by the ASPE column. Then, the active compounds were targeted separated by pre-HPLC according to real-time chromatograms. The control drugs celecoxib and glipizide were analyzed to verify the specificity and accuracy of the developed method. As a result, two pure compounds with COX-2 binding affinities were successfully separated from P. hookeri. They were characterized as swertisin and scopoletin using ¹H- and ¹³C NMR spectroscopy, and the in vitro COX-2 inhibitory activities were verified. Compounds with COX-2 inhibitory activities could be screened and targeted separated from crude extracts by this strategy, which indicated that the proposed method was feasible, robust and effective for rapid separation of COX-2 inhibitors from natural products.

Preparative isolation of antioxidative gallic acid derivatives from Saxifraga tangutica using a class separation method based on medium-pressure liquid chromatography and reversed-phase liquid chromatography

Saxifraga tangutica is widely used as a medicinal herb to treat hepatic diseases. Here, we developed a class separation method to separate gallic acid derivatives 1,1-diphenyl-2-picrylhydrazyl inhibitors from the methanol extract of Saxifraga tangutica. Firstly, an MCI GEL CHP20P medium-pressure liquid chromatography was used to pretreat the crude extract from Saxifraga tangutica (500 g) and the target sample (fraction Fr1, 1.7 g) was obtained. Then, an online reversed-phase liquid chromatography-1,1-diphenyl-2-picrylhydrazyl assay was employed for recognizing potential 1,1-diphenyl-2-picrylhydrazyl inhibitors and six 1,1-diphenyl-2-picrylhydrazyl inhibitors fractions were recognized from fraction Fr1. Subsequently, the six 1,1-diphenyl-2-picrylhydrazyl inhibitors fractions were isolated via a ReproSil-Pur C18 AQ preparative column. During the separation process, the hydrophilic liquid chromatography was used to enrich the target compounds (Fr1-3-1-1 and Fr1-3-1-2) from the fraction Fr1-3, which were hardly isolated only by one step reversed-phase liquid chromatography. Finally, six gallic acid derivatives were obtained and identified as gallic acid (Fr1-1-1), gallic acid 3-O-β-D-glucoside (Fr1-1-2), protocatechuic acid (Fr1-2), 4-O-galloyl-(-)-shikimic acid (Fr1-3-1-1), 5-O-galloyl-(-)-shikimic acid (Fr1-3-1-2), and 3-O-galloyl-shikimic acid (Fr1-4), respectively. Thus, the present study indicated that this method was highly efficient for the preparative separation of gallic acid derivatives 1,1-diphenyl-2-picrylhydrazyl inhibitors from natural products.