Enantiomeric analysis of γ(δ)-lactones by reversed phase high performance liquid chromatography using amylose tris(5-chloro-2-methylphenylcarbamate) as stationary phase.

A Chiralpak AY-3R column was investigated for analytical enantiomeric separation of twelve racemic γ(δ)-lactones using reversed phase high performance liquid chromatography. Main influence factors, including organic modifier, flow rate and column temperature, were optimized. Five kinds of γ(δ)-lactones were successfully enantioseparated using the established method: γ-nonanolactone, δ-decalactone, δ-undecalactone, δ-dodecalactone and δ-tetradecalactone. Under optimized conditions, enantiomeric peak resolution (Rs) for the five γ(δ)-lactones reached more than 1.09, 1.08, 1.54, 1.43, and 1.11, respectively. Their chromatographic elution behavior was investigated using Van't Hoff equation and Van Deemter equation. It was found that an exothermic process occurred during enantiomeric separation of γ(δ)-lactones using this chromatographic column, and it showed a typical Van Deemter curve. Finally, this method was applied in enantiomeric ratio analysis of γ(δ)-lactones contents for purchased butter samples, and results confirmed the predominant content of the (R)-configuration of δ-dodecalactone in natural animal butter, while in margarine, an equal proportion of (R/S)-configuration of δ-dodecalactone was detected.

Application of two-dimensional reversed phase countercurrent chromatography × high-performance liquid chromatography to bioactivity-guided screening and isolation of α-glucosidase inhibitors from Rheum palmatum L.

In the present work, comprehensive two-dimensional reversed-phase countercurrent chromatography × reversed-phase liquid chromatography combined (2D RPCCC × RPLC) with 2D microfraction bioactive evaluation was employed to screen and isolate α-glucosidase inhibitors from Rheum palmatum L. Countercurrent chromatography was employed to improve 2D analysis and preparative separation. A selected biphasic solvent system composed of petroleum ether/ethyl acetate/methanol/water with gradient elution mode was used for the first dimension RPCCC separation (1D RPCCC). Solid-phase extraction was applied to eliminate interfering polar compounds before the second dimension analysis (2D RPLC). 76 components were shown in 2D contour plot in UV 280 nm. 11 Candidates were separated by a scaled-up CCC and identified by 1H NMR and 13C NMR, including anthraquinones, flavonoids, stilbenes, phenols, and glucoside derivatives. In addition, it was found that two components, resveratrol-4'-O-(6″-galloyl)glucoside (36) and lyciumaside (43) were identified as natural α-glucosidase inhibitors in Rheum palmatum L. for the first time.

Screening and identification of antibacterial components in Artemisia argyi essential oil by TLC-direct bioautography combined with comprehensive 2D GC × GC-TOFMS.

One of the primary components that contribute to Artemisia argyi 's effectiveness is essential oil, which has an exceptional antibacterial effect that has been well documented. The actual cause of its antibacterial activity and associated mechanism, however, are still not completely understood. For the first time, comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (2D GC × GC-TOFMS) and thin-layer chromatography-direct bioautography (TLC-DB) were employed to investigate its antibacterial components. The antibacterial properties of A. argyi essential oil were investigated, and the antibacterial activity of six compounds was evaluated, using Staphylococcus aureus (S. aureus) and Escherichia coli (E. coil) as test microorganisms. TLC-direct bioautography was used to screen two bioactive clusters. Following 2D GC × GC-TOFMS identification of bioactive clusters, six compounds were evaluated for in vitro antibacterial activity verification. All the components tested displayed antibacterial action. Results showed that α-terpineol and eugenol had high potent antibacterial activity (MIC＜0.62 mg/mL, IC50＜2.00 mg/mL). For complex essential oils from traditional Chinese medicine, this method is efficient for quick screening and identifying antibacterial compounds.

Efficient screening of pancreatic lipase inhibitors from Rheum palmatum by affinity ultrafiltration-high-performance liquid chromatography combined with high-resolution inhibition profiling.

INTRODUCTION: Pancreatic lipase is one of the most important key targets in the treatment of obesity. Inhibition of pancreatic lipase can effectively reduce lipid absorption and treat obesity and other related metabolic disorders. OBJECTIVES: The goal of this study is the efficient screening of pancreatic lipase inhibitors in the root and rhizome of Rheum palmatum using affinity ultrafiltration-high-performance liquid chromatography (AUF-HPLC) combined with high-resolution inhibition profiling (HRIP). METHODS: Potential pancreatic lipase ligands and pancreatic lipase inhibitors in ethyl acetate fraction of R. palmatum were screened using AUF-HPLC and HRIP, respectively. All screened compounds were identified by HPLC- quadrupole time-of-flight (Q-TOF)/MS. Eight compounds were screened out by both AUF-HPLC and HRIP, and six compounds were screened out by either AUF-HPLC or HRIP alone. The pancreatic lipase inhibitory activities of all screened compounds were verified by enzyme inhibition assay and molecular docking. RESULTS: Five new potent pancreatic lipase inhibitors were discovered, namely procyanidin B5 3,3'-di-O-gallate (IC50 = 0.06 ± 0.01 µM), 1,6-di-O-galloyl-2-O-cinnamoyl-ß-D-glucoside (IC50 = 12.83 ± 0.67 µM), 1-O-(1,3,5-trihydroxy)phenyl-2-O-galloyl-6-O-cinnamoyl-ß-D-glucoside (IC50 = 17.84 ± 1.33 µM), 1,2-di-O-galloyl-6-O-cinnamoyl-ß-D-glucoside (IC50 = 18.39 ± 1.52 µM), and 4-(4'-hydroxyphenyl)-2-butanone-4'-O-ß-D-(2"-O-galloyl-6"-O-cinnamoyl)-glucoside (IC50 = 2.91 ± 0.40 µM). It was found that procyanidin B5 3,3'-di-O-gallate showed higher pancreatic lipase inhibitory activity than the positive control orlistat (IC50 = 0.12 ± 0.02 µM). CONCLUSION: The combination of affinity ultrafiltration-high-performance liquid chromatography (AUF-HPLC) and high-resolution inhibition profiling (HRIP) could reduce the risk of false-negative screening and missed screening and could achieve more efficient screening of bioactive compounds in complex natural products.

Expanding the ubiquitin code in pancreatic cancer.

The ubiquitin-proteasome system (UPS) is a fundamental regulatory mechanism in cells, vital for maintaining cellular homeostasis, compiling signaling transduction, and determining cell fates. These biological processes require the coordinated signal cascades of UPS members, including ubiquitin ligases, ubiquitin-conjugating enzymes, deubiquitinases, and proteasomes, to ubiquitination and de-ubiquitination on substrates. Recent studies indicate that ubiquitination code rewriting is particularly prominent in pancreatic cancer. High frequency mutation or aberrant hyperexpression of UPS members dysregulates ferroptosis, tumor microenvironment, and metabolic rewiring processes and contribute to tumor growth, metastasis, immune evasion, and acquired drug resistance. We conduct an in-depth overview of ubiquitination process in pancreatic cancer, highlighting the role of ubiquitin code in tumor-promoting and tumor-suppressor pathways. Furthermore, we review current UPS modulators and analyze the potential of UPS modulators as cancer therapy.

[Off-line comprehensive two-dimensional countercurrent chromatography-liquid chromatography separation of Curcuma volatile oil].

The chemical constituents of volatile oils used in traditional Chinese medicine are highly complex. Thus, achieving the complete separation of volatile oils by one-dimensional chromatography is difficult owing to the low peak capacity of the technique. Although comprehensive two-dimensional gas chromatography provides an efficient means for separating volatile oils, it cannot be used to screen bioactive components because of its limitations. Therefore, developing a new method to separate volatile oils based on liquid chromatography is of great significance in efforts to obtain new approaches to screen bioactive components in volatile oil. The objectives of the present study are to establish an efficient method for separating the chemical constituents of Curcuma volatile oil using off-line comprehensive two-dimensional countercurrent chromatography-liquid chromatography (CCC-LC) and to investigate the two-dimensional peak capacity, orthogonality, and spatial coverage of this method. Both CCC and LC conditions were optimized. A biphasic n-hexane-methanol-water solvent system was selected via the colorimetric method, and the lower phase was used as the mobile phase in gradient-elution mode: 0-55 min, n-hexane-methanol-water (5∶2∶3 v/v/v); 55-170 min, n-hexane-methanol-water (5∶3∶2, v/v/v); 170-290 min, n-hexane-methanol-water (5∶4∶1, v/v/v). After gradient elution, elution-extrusion elution mode was applied within 290-375 min. Good resolution was achieved by the CCC separation process. The HPLC separation process was carried out with gradient elution using a mobile phase composed of acetonitrile (A)-water (B): 0-10 min, 50%A-65%A; 10-14 min, 65%A; 14-21 min, 65%A-85%A; 21-25 min, 85%A-95%A; 25-30 min, 95%A-55%A; 30-40 min, 55%A. Curcuma volatile oil was separated under the above optimized two-dimensional separation conditions, and the data obtained were drawn into a two-dimensional contour map using Matlab software. The calculated total peak capacity exceeded 954, which was 10 times more than that of one-dimensional chromatography. High orthogonality (r=0.17) and spatial coverage factor (68.1%) were also obtained. Our research provides a new methodology for separating volatile oils used in traditional Chinese medicine as well as an approach for evaluating the quality of traditional Chinese medicinal herbs using two-dimensional chromatographic fingerprints.

Coumarins from Jinhua Finger Citron: Separation by Liquid-Liquid Chromatography and Potential Antitumor Activity.

In this paper, liquid-liquid chromatography was introduced for the first time for the separation of fingered citron (Citrus medica L. var. sarcodactylis Swingle). The fingered citron cultivated in Jinhua is of significant industrial and medicinal value, with several major coumarin compounds detected in its extract. Therefore, further separation for higher purity was of necessity. A preparative liquid-liquid chromatographic method was developed by combining two elution modes (isocratic and step-gradient) with selection according to different polarities of the target sample. Five coumarin derivatives-5,7-dimethoxycoumarin (52.6 mg, 99.6%), phellopterin (4.9 mg, 97.1%), 5-prenyloxy-7-methoxycoumarin (6.7 mg, 98.7%), 6-hydroxy-7-methoxycoumarin (7.1 mg, 82.2%), and byakangelicol (10.5 mg, 90.1%)-with similar structures and properties were isolated on a large scale from 100 mg of petroleum ether (PE) extract and 100 mg of ethyl acetate (EA) extract in Jinhua fingered citron. The productivity was much improved. The anti-growth activity of the isolated coumarins was evaluated against three cancer cell lines (HeLa, A549, and MCF7) with an MTT assay. The coumarins demonstrated potential anti-tumor activity on the HeLa cell line, with 5,7-dimethoxycoumarin in particular exhibiting the best anti-growth activity (IC50 = 10.57 ± 0.24 µM) by inhibiting proliferation. It inhibited colony formation and reduced the size of the tumor sphere in a concentration-dependent manner. The main mechanism was confirmed as inducing apoptosis. This work was informative for further studies aimed at exploring new natural-product-based antitumor agents.

Matrix solid-phase dispersion combined with micro-fractionation bioactivity evaluation screening polymethoxylated flavones from Citrus peels.

Polymethoxyflavones were a unique class of natural and safe flavonoids containing two or more methoxy groups, which were also the most abundant edible part in Citrus peel. The optimum condition in the process of selective extraction of polymethoxylated flavones from Citrus peel by matrix solid-phase dispersion (MSPD) was as follows: SBA-15 as adsorbent, ethyl acetate as eluent, the mass ratio of adsorbent to sample 1:1, and the mixture of sample and adsorbent was ground for 3 min. Twelve antioxidants were successfully screened by micro-fractionation bioactivity evaluation assay, in which four of them were flavonoid glycosides, seven of them were polymethoxylated flavones, and one was phenylpropanoid. 1-sinapoly-ß-D-glucopyranoside (1) was reported for the first time in Citrus peel. And antioxidant capacity of 1-sinapoly-ß-D-glucopyranoside, 5, 7, 8, 3', 4', 5'-hexamethoxyflavone (6), hexamethoxyflavone (11), and 5, 6, 7, 4'-tetramethoxyflavone (7) were reported for the first time. Nobiletin (compound 8), 3, 5, 6, 7, 8, 3', 4'-heptamethoxyflavone (9) and tangeretin (10) were isolated and purified by countercurrent chromatography combined with preparative liquid chromatography. Antioxidant activity evaluation indicated that the three isolated polymethoxylated flavones owned similar antioxidant activity. This study indicated that MSPD combined with micro-fractionation bioactive evaluation was efficient in screening bioactive compounds for rapid extraction and effective pinpointing bioactive substances in natural products.

Recent progress on chiral extractants for enantioselective liquid-liquid extraction.

As the demand for enantiopure compounds increases, chiral separation has become increasingly important in many fields. Enantioselective liquid-liquid extraction is an up-and-coming technology for enantiomeric separation because it is highly efficient and easy to be scaled up. The key factor for enantioselective liquid-liquid extraction is the development of novel chiral extractants with high enantiorecognition performance. With successful studies on catalytically active metal complexes as chiral extractants, novel chiral extractants can be screened and designed from the field of asymmetric catalysis. Chiral ionic liquids, sulfobutylether-ß-cyclodextrins bonded magnetic nanoparticles and 2,2',3,3'-tetrahydro-1,1'-spirobi[indene]-7,7'-diol (SPINOL) based phosphoric acid host show unique potential ability in enantioselective liquid-liquid extraction and they deserve further study. Brief principles, extraction equipment and solvent systems in enantioselective liquid-liquid extraction are presented in the present paper, and recent progress in development of new chiral extractants in the past decade is mainly reviewed, including metal complexes, cyclodextrins, ionic liquids, tartrate acids and crown ethers.

Retention correlation and orthogonality between reversed phase countercurrent chromatography and liquid chromatography based on solvent strength.

Correlation of elution performance between reversed phase countercurrent chromatography and liquid chromatography was investigated using five selected natural components. Theoretical guidance for orthogonality of two-dimensional countercurrent chromatography and liquid chromatography was proposed. The difference in retention behavior between countercurrent chromatography and liquid chromatography was studied when the mobile phase was composed of methanol and water by measuring the partition behavior of five selected compounds in two typical biphasic solvent systems composed of n-hexane-ethyl acetate-methanol-water and chloroform-methanol-water. An orthogonal diagram between countercurrent chromatography and liquid chromatography was obtained by normalized treatment of the measured partition coefficients and capacity factors. The experimental results showed that each biphasic solvent system used for countercurrent chromatography had a high orthogonality with liquid chromatography when a specific volume ratio was used.

Enantioseparation of two antifungal azole drugs by analytical countercurrent chromatography using sulfobutyl ether-ß-cyclodextrin as chiral selector.

This study reports a successful enantioseparation of two antifungal drugs, Ketoconazole and Voriconazole, using countercurrent chromatography (CCC) with synthesized sulfobutyl ether-ß-cyclodextrin (SBE-ß-CD) as chiral selector. Two biphasic solvent systems composed of dichloromethane: 0.1 mol L-1 of phosphate buffer solution (pH 3.0) (1:1, v/v) and n-hexane: ethyl acetate: 0.1 mol L-1 phosphate buffer solution (pH 3.0) (1.5:0.5:2, v/v/v) were selected. Influence factors were investigated, including degree of substitution of SBE-ß-CD, concentration of SBE-ß-CD, equilibrium temperature, and pH of aqueous phase. Under optimized separation conditions, a large enantioseparation factor of α ≥ 3.26 and a high peak resolution Rs= 1.82, was achieved for enantioseparation of Voriconazole by countercurrent chromatography, and purity of two azole stereoisomers collected from CCC separation reached 98.5%, as determined by HPLC. Molecular docking was employed to investigate the formation of inclusion complex.

Miniaturized matrix solid-phase dispersion and solid-phase clear-up combined with capillary electrophoresis for efficient determination of trace bioactive components in complicated sample matrix: Take Wubi Shanyao Pill as an example.

Accurate quantitative analysis of trace analytes in a complicated matrix is a challenge in modern analytical chemistry. An appropriate analytical method is considered to be one of the most common gaps during the whole process. In this study, a green and efficient strategy based on miniaturized matrix solid-phase dispersion and solid-phase extraction combined with capillary electrophoresis was first proposed for extracting, purifying and determining target analytes from complicated matrix, using Wubi Shanyao Pill as an example. In detail, 60 mg of samples were dispersed on MCM-48 to obtain high yields of analytes, then the extract was purified with a solid-phase extraction cartridge. Finally, four analytes in the purified sample solution were determined by capillary electrophoresis. The parameters affecting the extraction efficiency of matrix solid-phase dispersion, purification efficiency of solid-phase extraction and separation effect of capillary electrophoresis were investigated. Under the optimized conditions, all analytes demonstrated satisfactory linearity (R2 >0.9983). What's more, the superior green potential of the developed method for the determination of complex samples was confirmed by the Analytical GREEnness Metric Approach. The established method was successfully applied in the accurate determination of target analytes in Wubi Shanyao Pill and thus provided reliable, sensitive, and efficient strategy support for its quality control.

A comprehensive strategy for prediction and quality evaluation of standardized planting herbs based on plant metabolomics coupled with extreme learning machine: Astragali Radix as an example.

INTRODUCTION: Standardizing the planting process is an effective way to control the quality stability of herbal resources, which are susceptible to external environmental factors (e.g., moisture, soil, etc.). However, how to scientifically and comprehensively assess the effects of standardized planting on plant quality and quickly test unknown samples has not been addressed. OBJECTIVE: The aim of this study was to determine and compare the metabolite levels of herbs before and after standardized planting, to quickly distinguish their sources, and to evaluate their quality, using the typical herb Astragali Radix (AR) as an example. METHODS: In this study, an efficient strategy using liquid chromatography-mass spectrometry (LC-MS) based on plant metabolomics combined with extreme learning machine (ELM) has been developed to efficiently distinguish and predict AR after standardized planting. Moreover, a comprehensive multi-index scoring method has been developed for the comprehensive evaluation of the quality of AR. RESULTS: The results confirmed that AR after standardized planting was significantly differentiated, with a relatively stable content of 43 differential metabolites, mainly including flavonoids. An ELM model was established based on LC-MS data, and the accuracy in predicting unknown samples could reach more than 90%. As expected, higher total scores were obtained for AR after standardized planting, indicating much better quality. CONCLUSION: A dual system for evaluating the impact of standardized planting on the quality of plant resources has been established, which will significantly contribute to innovation in the quality evaluation of medicinal herbs and support the selection of optimal planting conditions.

High-resolution monophenolase/diphenolase/radical scavenging profiling for rapid screening of natural whitening candidates from Rosa rugosa cv. 'Plena'.

Antioxidants and tyrosinase inhibitory components were successfully screened and separated from Rosa rugosa cv. 'Plena' by high-performance liquid chromatography microfractionation bioactive screening combined with several separation and purification methods. Ethyl acetate extract of Rosa rugosa cv. 'Plena' showed high antioxidant activity and tyrosinase inhibitory activity. High-speed countercurrent chromatography, silica gel column chromatography, and semi-preparative high-performance liquid chromatography were used for the preparative separation of four bioactive components from ethyl acetate extract. Two tyrosinase-inhibiting active substances, flavogallonic acid, and N1 -N5 -N10 -tri-4-p-coumaroylspermidine, were isolated from Rosa rugosa cv. 'Plena', and they showed great monophenolase inhibition activity (half-maximal inhibitory concentration: 664.60 and 23.77 µg/ml, respectively) and excellent diphenolase inhibition activity (half-maximal inhibitory concentration: 23 614.61 and 16.80 µg/ml, respectively). Meanwhile, gallic acid, flavogallonic acid, and ellagic acid were shown to have excellent 1,1-diphenyl-2-picryl-hydrazyl antioxidant activity (half maximal inhibitory concentration: 6.66, 20.17, and 13.45 µg/ml), and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) antioxidant activity (half maximal inhibitory concentration: 3.53, 3.83, and 2.78 µg/ml). Molecular docking revealed that flavogallonic acid and N1 -N5 -N10 -tri-4-p-coumaroylspermidine had a strong binding affinity (-9.3 and -10 kcal/mol, respectively) to tyrosinase through hydrogen bonding and hydrophobic interactions.

Phytochemistry and pharmacology of natural prenylated flavonoids.

Prenylated flavonoids are a special kind of flavonoid derivative possessing one or more prenyl groups in the parent nucleus of the flavonoid. The presence of the prenyl side chain enriched the structural diversity of flavonoids and increased their bioactivity and bioavailability. Prenylated flavonoids show a wide range of biological activities, such as anti-cancer, anti-inflammatory, neuroprotective, anti-diabetic, anti-obesity, cardioprotective effects, and anti-osteoclastogenic activities. In recent years, many compounds with significant activity have been discovered with the continuous excavation of the medicinal value of prenylated flavonoids, and have attracted the extensive attention of pharmacologists. This review summarizes recent progress on research into natural active prenylated flavonoids to promote new discoveries of their medicinal value.

Comprehensive two-dimensional countercurrent chromatography × gas chromatography characterization of Artemisia argyi essential oil.

A comprehensive two-dimensional (2D) countercurrent chromatography (CCC) × gas chromatography (GC) was investigated for characterization of chemical constituents of Artemisia argyi essential oil, and orthogonality for the 2D chromatographic system was evaluated. A solvent system composed of n-hexane/acetonitrile/methanol (2:2:1, v/v/v) was selected for first dimensional separation of Artemisia argyi essential oil. Then all CCC fractions were analyzed by GC, which provided a wealth of information regarding the composition of the essential oil. Visualization of chemical compositions obtained from the comprehensive 2D CCC × GC separation was achieved by creation of a 2D contour plot map. Total peak capacity was evaluated and approximately 1392 peaks were obtained through a comprehensive 2D CCC × GC separation. A high spatial coverage and a low linear correlation coefficient were achieved. Meanwhile, all compounds were identified by GC-MS. The obtained 2D contour plot could be divided into six zones to show the characteristic chemical compositions. Six zones could be divided into different component groups, including monoterpenes, sesquiterpenes, monoterpene alcohols, phenols, aldehydes, ketones and esters, which could be used to identify compounds that have not been reported, and to predict the structure of unknown compounds in Artemisia argyi essential oil and comprehensively characterize fingerprint peak.

Cucurbitane-type triterpenoids from the fruits of Citrullus colocynthis.

A phytochemical investigation of the fruits of Citrullus colocynthis resulted in the isolation of 21 structurally diverse cucurbitane triterpenoids, including 9 previously undescribed ones, colocynins A-I (1-9). Their absolute configurations were elucidated by means of quantum chemical electronic circular dichroism (ECD) calculations, CD exciton chirality method, and single-crystal X-ray crystallography. Colocynins A-C (1-3) represent the first examples of nonanorcucurbitane-type triterpenoids. An anti-acetylcholinesterase activity assay showed that 6, 10, 13, 18, and 20 exhibited inhibitory activities, with IC50 values ranging from 5.0 to 21.7 µM. In addition, 18 and 21 showed significant cytotoxicity against PACA, A431, and HepG2 cells, with IC50 values ranging from 0.042 to 0.60 and 3.6-14.4 µM, respectively.

Degree and distribution of substitution of hydroxypropyl-ß-cyclodextrin in enantioselective liquid-liquid extraction and countercurrent chromatographic enantioseparation.

Nine types of hydroxypropyl-ß-cyclodextrin (HP-ß-CD) with different degrees and distributions of substitution were synthesised, and nine racemates were selected to investigate the effect of different degrees and distributions of substitution of HP-ß-CD on the enantioseparation factor. 1H NMR and GC/MS were used to characterise the synthesised HP-ß-CD. The degree and distribution of substitution had a significant influence on enantioselective liquid-liquid extraction and enantioseparation by countercurrent chromatography. For most of the tested racemates, increasing both the degree of substitution and distribution of substitution at the C-2 position for HP-ß-CD would lead to an increasing enantioseparation factor; the optimal enantioseparation factor of 2-phenylbutyric acid, tropic acid, 2,3-diphenylpropionic acid, 2-(4-hydroxylphenyl) propanoic acid, and naproxen was increased to 1.77, 1.53, 1.67, 1.61, and 1.75, respectively. The enantioseparation of racemic naproxen, 2-(4-hydroxylphenyl) propanoic acid, and 2,3-diphenylpropionic acid by countercurrent chromatography was optimised using HP-ß-CD with a degree of substitution of 16.5, and peak resolution was significantly improved to 1.03, 1.35, and 1.01, respectively.

High-performance liquid chromatography micro-fraction bioactive evaluation combined with countercurrent chromatographic separation of antioxidants from Citrus peel and their tyrosinase inhibition activities.

In the present study, high-performance liquid chromatography micro-fraction bioactive evaluation and high speed countercurrent chromatography were performed on screening, identification and isolation of antioxidants from Citrus peel. Three compounds were screened as antioxidants and tyrosinase inhibitors using 2,2'-azino-bis (3-ethyl-benzothiazoline-6-sulfonic acid) radical cation scavenging assay and tyrosinase activity test, then they were identified as eriocitrin, narirutin and hesperidin. Moreover, the solvent system ethyl acetate-n-butanol-water (6:4:10, v/v/v) was used for separation of ethyl acetate extract of Citrus peel by high speed countercurrent chromatography. In total, 0.45 mg of eriocitrin with 87.10% purity, 2.04 mg of narirutin with 95.19% purity and 1.35 mg of hesperidin with 95.19% purity were obtained from 20 mg of ethyl acetate extract of Citrus peel in a single run and then each component was subjected to 2,2'-azino-bis (3-ethyl-benzothiazoline-6-sulfonic acid) radical cation scavenging assay and tyrosinase inhibition assay. Eriocitrin showed great antioxidant activity (the half-maximum concentration: 3.65 µM) and tyrosinase inhibition activity (the half-maximum concentration: 115.67 µM), while narirutin and hesperidin exhibited moderate activity. Tyrosinase inhibition activity for eriocitrin in vitro was reported for the first time. Furthermore, molecular docking between eriocitrin and mushroom tyrosinase was also studied.

Analytical enantioseparation of N-alkyl drugs by reversed-phase liquid chromatography with carboxymethyl-ß-cyclodextrin as mobile phase additive.

Carboxymethyl-ß-cyclodextrins (CM-ß-CDs) with five kinds of degrees of substitution were synthesized and characterized. Analytical enantioseparation of six basic drugs containing N-alkyl groups, including pheniramine, chlorpheniramine, labetalol, propranolol, venlafaxine, and trans-paroxol, was achieved by reversed-phase high-performance liquid chromatography (RP-HPLC) using the synthesized CM-ß-CD as chiral mobile phase additives. Key influence factors were optimized, including organic modifier, pH value, CM-ß-CD with different degrees of substitution, and concentration of CM-ß-CD. The mobile phase was composed of methanol and 10 mmol L-1 of phosphate buffer pH 4.0 containing 10 mmol L-1 of CM-ß-CD. Peak resolution for six racemic drugs was gradually increased with an increasing degree of substitution of the synthesized CM-ß-CD. The stoichiometric ratio and binding constants for the inclusion complex formed by CM-ß-CD and enantiomer were determined, which showed that the stoichiometric ratio for each inclusion complex was 1:1.