Junxi Liu

Cytotoxic Diarylheptanoids from the Pericarps of Walnuts (Juglans regia)

Two new diarylheptanoids, juglanin A (1) and B (2), together with 15 known compounds, were isolated from the extract of the seed husks of walnuts (Juglans regia L.). The structures of 1 and 2 were elucidated by various spectroscopic methods including intensive 2D-NMR techniques, HR-ESI-MS, and X-ray single-crystal diffraction analysis, and the cytotoxic activities of 1, 2, and 10 against human hepatoma (Hep G2) cells was reported.

Simultaneous determination of three diarylheptanoids and an α-tetralone derivative in the green walnut husks (Juglans regia L.) by high-performance liquid chromatography with photodiode array detector

By optimizing extraction, separation and analytical conditions, a reliable and accurate high-performance liquid chromatographic (HPLC) method coupled with photodiode array detector (DAD) at room temperature is developed for simultaneous determination of three diarylheptanoids (juglanin A, juglanin B, rhoiptelol) and an alpha-tetralone derivative (regiolone) in methanol extracts from the green walnut husks (Juglans regia L.) The sample pretreatment process involved the reflux extraction using methanol as the extract with a ratio of liquor to sample of 15 mL/g. The separation was achieved on a SinoChrom ODS-AP C(18) column with gradient elution using acetonitrile and 2% (v/v) acetic acid in water. The intra-day and inter-day precision (RSD%) for the analytes ranged from 1.08 to 1.51 and 0.60 to 1.13, respectively. The average recoveries obtained were from 88.4% to 96.2% for the analytes with RSDs below 3.13%. The correlation coefficients of the calibration curve exceeded 0.999. The detection limits were 0.51, 0.25, 0.32 and 0.35 ng at a signal-to-noise ratio of 3, respectively. Quantitative analyses of the samples from different grown sites and in obtained different months showed that the contents of the analytes varied significantly. The method was then successfully applied for the detection and isolation of a new diarylheptanoid derivative in the green walnut husks (J. regia L.). The structure of the new compound was elucidated by various spectroscopic methods including 2D NMR techniques (COSY, HMQC, HMBC), HR-ESI-MS and X-ray single-crystal diffraction analysis.

Structural and Mechanistic Bases of the Anticancer Activity of Natural Aporphinoid Alkaloids

Aporphinoid alkaloids, which encompass a large number of complicated structures, are an important group of natural products. The anticancer activity of aporphinoid alkaloids has become a hot pharmaceutical research area in recent years. Recent studies on the anticancer activity of these compounds are reviewed. The structure activity relationships (SARs) and anticancer mechanisms of aporphinoid alkaloids, as well as simple aporphine, oxoaporphine, dehydroaporphine and dimeric aporphine, have been summarized. The presence of a 1,2-methylenedioxy group and methylation of nitrogen are key features to the cytotoxicity of aporphinoid alkaloids. Oxidation and dehydrogenation of C7 could improve the anticancer activity. The contributions of chirality of hydrogen at C6a and the substitution pattern of other positions about aporphinoid alkaloids for anticancer activity remain unknown. Induced cancer cells apoptosis, prevention of cell proliferation, DNA topoisomerase inhibition, reducing the drug-resistant cellular side population (SP) or cancer stem cells (CSCs) and inhibition of epidermal growth factor receptor (EGFR) tyrosine kinase seem to play important roles in the molecular mechanisms of anticancer activity about aporphinoid alkaloids.

Simultaneous determination of the content of isoquinoline alkaloids in Dicranostigma leptopodum (Maxim) Fedde and the effective fractionation of the alkaloids by high-performance liquid chromatography with diode array detection.

A simple and efficient method was developed for the simultaneous determination of eight isoquinoline alkaloids in methanol extracts of Dicranostigma leptopodum (Maxim) Fedde and the effective fractionation of the alkaloids of D. leptopodum by high-performance liquid chromatography with diode array detection. The chromatographic conditions were optimized on a SinoChrom ODS-BP column to obtain a good separation of the four types of alkaloid analytes, including two aporphines (isocorydine, corydine), two protopines (protopine and allocryptopine), a morphine (sinoacutine), and three quaternary protoberberine alkaloids (berberrubine, 5-hydroxycoptisine, and berberine). The separation of these alkaloids was significantly affected by the composition of the mobile phase, and particularly by its pH value. Acetonitrile (A) and 0.2% phosphoric acid solution adjusted to pH 6.32 with triethylamine (B) were selected as the mobile phase with a gradient elution. With this method, a new quaternary protoberberine alkaloid was isolated and the two structural isomers (isocorydine and corydine) were baseline separated. The appropriate harvest period for D. leptopodum was also recommended based on our analysis. The method for the effective fraction of the alkaloids of D. leptopodum was optimized under this method with regard to the varying significant pharmacological activities of the alkaloids.

Capillary zone electrophoresis for separation and analysis of four diarylheptanoids and an α-tetralone derivative in the green walnut husks (Juglans regia L.)

A fast capillary zone electrophoresis (CZE) method for the simultaneous determination of four cyclic diarylheptanoids (rhoiptelol, RH; juglanin A, JA; juglanin B, JB; juglanin C, JC) and an alpha-tetralone derivative (sclerone, SC) in the extract of the green walnut husks (Juglans regia L.) was developed. The optimized buffer was composed of 25 mM sodium tetraborate at pH 10.3. The applied voltage was 20 kV and the capillary temperature was kept constant at 20 degrees C. The detection wavelength was set at 220 nm using a photodiode array detection. The effects of several CE parameters, including pH value, buffer concentration, applied voltage and separation temperature on the separation were investigated systematically. Regression equations showed good linear relationships (correlation coefficients: 0.9996-0.9999) between the peak area of each compound (RH, JA, JB, JC and SC) and its concentration accordingly. The relative standard deviations (R.S.D.) of the migration time and peak area were less than 0.57 and 3.44% (intra-day), and 0.97 and 3.71% (inter-day), respectively. The contents of the five active compounds in the green walnut husks (J. regia L.) from different origins were determined with satisfactory repeatability and recovery.

Regiolone from the pericarps of Juglans regia L.

Regiolone [(4RS)-4,8-dihydrxadoxy-3,4-dihydroxadnaphthalen-1(2H)-one], C10H10O3, isolated from the pericarps of Juglans regia L., is confirmed as a racemate.

Three-phase solvent systems for the comprehensive separation of a wide variety of compounds from Dicranostigma leptopodum by high-speed counter-current chromatography.

A three-phase solvent system was efficiently applied for high-speed counter-current chromatography to separate secondary metabolites with a wide range of hydrophobicity in Dicranostigma leptopodum. The three-phase solvent system of n-hexane/methyl tert-butyl ether/acetonitrile/0.5% triethylamine (2:2:3:2, v/v/v/v) was selected for high-speed counter-current chromatography separation. The separation was initiated by filling the column with a mixture of intermediate phase and lower phase as a stationary phase followed by elution with upper phase to separate the hydrophobic compounds. Then the mobile phase was switched to the intermediate phase to elute the moderately hydrophobic compounds, and finally the polar compounds still retained in the column were fractionated by eluting the column with the lower phase. In this research, 12 peaks were eluted out in one-step operation within 110 min, among them, eight compounds with acceptable purity were obtained and identified. The purities of β-sitosterol, protopine, allocryptopine, isocorydione, isocorydine, coptisine, berberrubine, and berberine were 94.7, 96.5, 97.9, 86.6, 98.9, 97.6, 95.7, and 92.8%, respectively.

Cerebroside and ceramide from the pollen of Brassica napus L.

The new cerebroside 1-O-(β-D-glucopyranosyl)-(2S, 3S, 4R, 8E)-2-[(2R)-2-hydroxytetracosenoilamino]-8-octadecene-1,3,4-triol (1) and ceramide (2S, 3S, 4R, 8E)-2-[(2R)-2-hydroxytetracosenoilamino]-8-octadecene-1,3,4-triol (2) were isolated from the ethyl acetate extract of the pollen of Brassica napus L. The structures of 1 and 2 were elucidated on the basis of chemical and spectroscopic method. Two new compounds were evaluated for activity in vitro assays for the cytotoxic activities against human tongue squamous carcinoma cell line (Tca8113).

Design, synthesis, and anticancer properties of isocorydine derivatives

Isocorydine (ICD), an aporphine alkaloid, is widely distributed in nature. Its ability to target side population (SP) cells found in human hepatocellular carcinoma (HCC) makes it and its derivative 8-amino-isocorydine (NICD) promising chemotherapeutic agents for the treatment of HCC. To improve the anticancer activity of isocorydine derivatives, twenty derivatives of NICD were designed and synthesized through chemical structure modifications of the aromatic amino group at C-8. The anti-proliferative activities of all synthesized compounds against human hepatocellular (HepG2), cervical (HeLa), and gastric (MGC-803) cancer cell lines were evaluated using an MTT assay. The results showed that all the synthetic compounds had some tumor cell growth inhibitory activity. The compound COM33 (24) was the most active with IC50 values under 10u202fμM (IC50 for HepG2u202f=u202f7.51u202fµM; IC50 for HeLau202f=u202f6.32u202fμM). FICD (12) and COM33 (24) were selected for further investigation of their in vitro and in vivo activities due to their relatively good antiproliferative properties. These two compounds significantly downregulated the expression of four key proteins (C-Myc, β-Catenin, CylinD1, and Ki67) in HepG2 cells. The tumor inhibition rate of COM33 (24) in vivo was 73.8% after a dose 100u202fmg/kg via intraperitoneal injection and the combined inhibition rate of COM33 (24) (50u202fmg/kg) with sorafenib (50u202fmg/kg) was 66.5%. The results indicated that these isocorydine derivatives could potentially be used as targeted chemotherapy agents or could be further developed in combination with conventional chemotherapy drugs to target cancer stem cells (CSCs) and epithelial-to-mesenchymal transition (EMT), the main therapeutic targets in HCC.

Total content determination for the effective fraction of the alkaloids in Dicranostigma leptopodum (Maxim.) Fedde by HPLC and ultraviolet-visible spectrophotometry

For the quality control and the rational use of the effective fraction of the alkaloids (EFA) in Dicranostigma leptopodum (Maxim.) Fedde (DLF), extraction and determination methods for EFA were developed in the present study. The purification of EFA was carried out on the D101 macroporous resin. The high-performance liquid chromatography with the diode-array detection (HPLC-DAD) method was established to determine the total alkaloid content of EFA. In this method, 0.4% ionic liquid (1-butyl-3-methylimidazole tetrafluoroborate) was added into the mobile phase as the tailing-suppression reagent. 5-hydroxy-coptisine, isocorytuberine, protopine, allocryptopine, coptisine, berberine, corydine, and isocorydine were selected as reference standards for the determination, and the total alkaloid content was calculated as their sum in EFA. The results suggested that the total alkaloid content of EFA was 19.04 ± 1.23% (n = 3). Since corresponding reference standards for the alkaloids of DLF are lacking, ultraviolet-visible (UV-Vis) spectrophotometry was also developed for the determination of the total alkaloid content of EFA. In this method, isocorydine was selected as the reference compound for the determination of the total alkaloid content and the results suggested that the total alkaloid content of EFA was 65.92 ± 1.33% (n = 3). These newly established methods were rapid and accurate with high repeatability, and can be applied for the further use of EFA in DLF.