Tertiary Alkaloids Research Articles

Species difference in toxicokinetics and safety assessment of senecionine N-oxide in a UDP-glucuronosyltransferase 1A4 humanized mouse model

Pyrrolizidine alkaloids (PAs) are naturally occurring hepatotoxins, and herbs containing PAs are of high concern. PAs are normally found in tertiary amines and N-oxide forms (PA N-oxides), yet the latter are less evaluated for their toxicokinetics. As a continuation of our investigation into the safety assessment of PA-containing herbal medicines, the toxicity and toxicokinetic characteristics of senecionine N-oxide (a representative toxic PA N-oxide) were investigated by using the UDP-glucuronosyltransferase 1A4 humanized mouse model (hUGT1A4 mouse model) and compared with those in wild-type mice simultaneously. Results show that the toxicity caused by senecionine N-oxide exposure was evidently decreased in hUGT1A4 mice as approved by pathology and biochemistry assays. In addition, a N-glucuronidation conjugate was exclusively found in hUGT1A4 mice but not in wild-type (WT) mice. In vitro studies proved that senecionine N-oxide initially reduced to the corresponding tertiary amine alkaloid (senecionine) and then underwent N-glucuronidation via human UGT1A4. The variation in toxicokinetic characteristics was also observed between hUGT1A4 mice and WT mice with a notably enhanced clearance of senecionine N-oxide and senecionine, and accordingly less formation of pyrrole–protein adducts in hUGT1A4 mice, which finally led to the detoxification of senecionine N-oxide exposure in hUGT1A4 mice. Our results provided the first in vivo toxicity data and toxicokinetic characteristics of senecionine N-oxide in a humanized animal model and revealed that human UGT1A4 plays an important role in the detoxification of senecionine N-oxide.

Bisbenzylisoquinoline Alkaloids of Cissampelos Sympodialis With in Vitro Antiviral Activity Against Zika Virus.

In search of new antiviral compounds against Zika virus we conducted a bioassay-guided fractionation of bisbenzyilisoquinoline alkaloids isolated from Cissampelos sympodialis (Menispermaceae), a medicinal plant species endemic to Brazil. Six subfractions were obtained from a tertiary alkaloidal fraction of the rhizomes (TAFrz) using preparative high-performance liquid chromatography. All the subfractions were tested against Zika virus-infected Vero cells as the cellular model to evaluate cytotoxicity and antiviral effective concentrations. The results showed that three of the six TAFrz subfractions tested were active. The most active ones were the subfraction 6 (that consisted of the alkaloids methylwarifteine and warifteine present as a mixture at a ratio of 8.8:1.2 respectively) and the subfraction 5, that was later identified as warifteine, the major tertiary alkaloid of this species. Warifteine was able to significantly reduce virus titer in Zika virus-infected Vero cells with an IC50 of 2.2 μg/ml and this effect was selective (selectivity index, SI = 68.3). Subfraction 6 had an IC50 = 3.5 μg/ml and was more cytotoxic than pure warifteine, with SI = 6.14. Fraction 5 and fraction 6 were more potent in decreasing the viral titer of Zika virus-infected Vero cells than 6-methylmercaptopurine riboside (IC50 = 24.5 μg/ml and SI = 11.9), a mercaptopurine riboside with ZIKV antiviral activity used as a positive control. Our data demonstrate that alkaloids of the bisbenzylisoquinoline type may be explored as new antiviral agents or as an useful pharmacophore for investigating ZIKV antiviral activity.

Rapid determination of seven bioactive components in rat plasma by UPLC―MS/MS and its application to pharmacokinetic compatibility study of Jinlingzi San

Jinlingzi San (JLZS), composed of Fructus Toosendan (FT) and Rhizoma Corydalis (RC), is a classical traditional Chinese medicine prescription for regulating Qi to relieve pain. The present study investigated the pharmacokinetic compatibility of FT and RC in JLZS. A fast, selective and sensitive UPLC―MS/MS method for simultaneous determination of one limonoid (toosendanin), four tertiary alkaloids (corydaline, tetrahydropalmatine, tetrahydrocoptisine, tetrahydroberberine) and two quaternary alkaloids (palmatine, dehydrocorydaline) in rat plasma was established and fully validated. The plasma samples were pretreated by a fast protein precipitation and chromatographed using a 1.7-μm C18 column and 0.1 % formic acid―water and acetonitrile via gradient elution with a run time of 3.7 min. Multiple reaction monitoring mode with positive electrospray ionization was adopted to detect the analytes and internal standard (diphenhydramine). The lower limits of quantification were 0.08―3.09 ng/mL using only 50 μL of plasma sample. Using the proposed method, the pharmacokinetic differences of seven bioactive components in rats after administration of JLZS and the single herb (FT or RC) were investigated. The results showed that the elimination of toosendanin and alkaloids decreased significantly in the JLZS group (p < 0.05) compared with the single herb group, and the exposure of the alkaloids increased in some degree. The study demonstrated the synergistic effect of combining FT with RC on the pharmacokinetics of seven bioactive components and provided new information for a better understanding of the compatibility mechanism of JLZS.

Antibacterial Activity of Different Extract of Medicinal Plant Antirrihnum Orontium.

Antirrhinum Orontium is belonging to the family Plantaginacea commonly known as lesser snapdragon which is a flowering plant belong to genus Antirrhinum. It was traditionally used in treatment of Tumor, Eye inflammation and Ulcer. Antirrhinum Orontium is contain mostly tertiary alkaloids bases one of them is identified as 4-methyl-2, 6-naphthyridine and Choline is identified as quaternary base. The recent study is to investigate the antibacterial activity of Ethyl acetate, Dichloromethane, Hexane and Water extracts of Antirrhinum Orontium, against the pathogen like Escherichia coli and Staphylococcus aureus. Both the Soxhlet and Maceration water extract were found most active from the other extract against Escherichia coli and Staphylococcus aureus by using agar well diffusion method. The measured zone of inhibition for Soxhlet water extract is 21±0.05mm and Maceration water extract is 20±0.05mm against gram positive Staphylococcus aureus, while for gram negative Escherichia coli 23±0.05mm is measured for Soxlet and 21±0.05mm measured for Maceration water extracts

Antibacterial activity of different extract of medicinal plant Antirrihnum Orontium.

Antirrhinum Orontium is belonging to the family Plantaginacea commonly known as lesser snapdragon which is a flowering plant belong to genus Antirrhinum. It was traditionally used in treatment of Tumor, Eye inflammation and Ulcer. Antirrhinum Orontium is contain mostly tertiary alkaloids bases one of them is identified as 4-methyl-2, 6-naphthyridine and Choline is identified as quaternary base. The recent study is to investigate the antibacterial activity of Ethyl acetate, Dichloromethane, Hexane and Water extracts of Antirrhinum Orontium, against the pathogen like Escherichia coli and Staphylococcus aureus. Both the Soxhlet and Maceration water extract were found most active from the other extract against Escherichia coli and Staphylococcus aureus by using agar well diffusion method. The measured zone of inhibition for Soxhlet water extract is 21±0.05mm and Maceration water extract is 20±0.05mm against gram positive Staphylococcus aureus, while for gram negative Escherichia coli 23±0.05mm is measured for Soxlet and 21±0.05mm measured for Maceration water extracts

Direct preparation of unprotected aminimides (R3N+-NH-) from natural aliphatic tertiary alkaloids (R3N) by [Mn(TDCPP)Cl]-catalysed N-amination reaction.

A panel of natural aliphatic tertiary alkaloids (R3N) were directly converted to R3N+-NH- (without the need to prepare protected aminimides R3N+-NR'- followed by deprotection) by [Mn(TDCPP)Cl]-catalysed N-amination reaction, with O-(2,4-dinitrophenyl)hydroxylamine as the nitrogen source, in up to 98% yields under mild reaction conditions.

Purification of tertiary and quaternary alkaloids from Rhizoma Corydalis using reversed-phase/weak cation-exchange mixed-mode class separation combined with preparative C18 and silica based strong cation-exchange chromatography

A new optimization strategy for purification of alkaloids from Rhizoma Corydalis using preparative liquid chromatography was developed, featuring a selective separation of different types of alkaloids into different parts by a reversed-phase/weak cation-exchange mixed-mode column (named C18WCX) at first. The total alkaloids of Rhizoma Corydalis were divided into four fractions with fraction III and IV corresponding to the tertiary type medium bases and the quaternary type strong bases, respectively. For fraction III, a conventional C18 column was used to isolate tertiary alkaloids using acetonitrile and 0.1% phosphoric acid (adjusted with triethylamine to pH 6.0) as mobile phases. High selectivity and symmetrical peak shapes of tertiary alkaloids were obtained, resulting in six main tertiary alkaloids isolated in a single run. As strong bases, quaternary alkaloids often suffer from serious peak tailing problem on conventional C18 columns. Therefore, a silica-based strong cation-exchange (SCX) column was used for purification of fraction IV. On the SCX column, good peak shapes in high sample loading were achieved. Five main quaternary alkaloids were isolated and identified from the fraction in one-step. The procedures presented effective for the preparative isolation and purification of alkaloids from Rhizoma Corydalis.

Hypepontine, a new quaternary alkaloid with antimicrobial properties

New isoquinoline alkaloid hypepontine (1) together with a five known compounds, were identified in Hypecoum ponticum Velen, the partial synonym of Hypecoum procumbens L. The structure of the new substance was elucidated based on spectroscopic evidence. The tertiary and quaternary alkaloid mixtures as well as the isolated alkaloids were evaluated for their antibacterial and antifungal activity. The result revealed that the crude alkaloid mixture containing quaternary isoquinoline alkaloids showed potent antifungal and antibacterial activity.

Development and Validation of a HPLC-ESI-MS/MS Method for Simultaneous Quantification of Fourteen Alkaloids in Mouse Plasma after Oral Administration of the Extract of Corydalis yanhusuo Tuber: Application to Pharmacokinetic Study.

The tuber of Corydalis yanhusuo is a famous traditional Chinese medicine and found to have potent pharmacological effects, such as antinociceptive, antitumor, antibacterial, anti-inflammatory, and anti-depressive activities. Although there are several methods to be developed for the analysis and detection of the bioactive ingredients’ alkaloids, so far, only few prominent alkaloids could be quantified, and in vitro and in vivo changes of comprehensive alkaloids after oral administration are still little known. In this study, we first developed a simple and sensitive high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS/MS) method to quantify the comprehensive alkaloids of extracts of C. yanhusuo in mouse plasma, using nitidine chloride as an internal standard. As results, at least fourteen alkaloids, including an aporphine (oxoglaucine), a protopine (protopine), five tertiary alkaloids (corydaline, tetrahydroberberine, tetrahydropalmatine, tetrahydrocolumbamine, and tetrahydrocoptisine) and seven quaternary alkaloids (columbamine, palmatine, berberine, epiberberine, coptisine, jatrorrhizine, and dehydrocorydaline) could be well quantified simultaneously in mouse plasma. The lower limits of quantification were greater than, or equal to, 0.67 ng/mL, and the average matrix effects ranged from 96.4% to 114.3%. The mean extraction recoveries of quality control samples were over 71.40%, and the precision and accuracy were within the acceptable limits. All the analytes were shown to be stable under different storage conditions. Then the established method was successfully applied to investigate the pharmacokinetics of these alkaloids after oral administration of the extract of Corydalis yanhusuo in mice. To the best of our knowledge, this is the first document to report the comprehensive and simultaneous analyses of alkaloids of C. yanhusuo in mouse plasma. It was efficient and useful for comprehensive pharmacokinetic and metabolomic analyses of these complex alkaloids after drug administration.

Reactive Species Metabolism and Cytotoxicity of Tribulus terrestris L. Alkaloid Extracts in Leukemic Cell Line

The present communication dealt with cytotoxic and free radical scavenging potential of tertiary and quaternary alkaloid extracts of Tribulus terrestris fruits. Tertiary and quaternary alkaloid extracts were found to be cytotoxic to leukemic cells (Jurkat E6-1) with LC50 values of 100 and 42 µg/ml, respectively. Compared to the control, reactive oxygen species and reactive nitrogen species were significantly reduced in the cells treated with lower concentrations of tertiary and quaternary alkaloid extracts. Cells treated with tertiary alkaloid extract demonstrated significantly elevated levels of peroxidise, catalase and superoxide dismutase-like activities, whereas cells treated with quaternary alkaloid extracts showed insignificant elevations of the tested enzyme activities, compared to the control cells. The antioxidant activity of tertiary alkaloid (100 µg/ml) extract was 46.78 and 14.92 µg/ml of ascorbic acid equivalent as estimated in ferric reducing antioxidant potential and total antioxidant assays. Quaternary alkaloid extract displayed an IC50 value of 159 µg/ml in the nitric oxide mitigation assay. Cells treated with quaternary alkaloid extracts showed 1.4-fold increase in superoxide dismutase-like activity compared to the control cells. These results suggest that tertiary and quaternary alkaloid extracts possessed cytotoxic and free radical scavenging potential against leukemic cells.

Computational Chemistry Study of Natural Alkaloids and Homemade Databank to Predict Inhibitory Potential Against Key Enzymes in Neurodegenerative Diseases.

Cissampelos sympodialis Eichl is used in folk medicine for the treatment of various inflammatory diseases; several alkaloids have been isolated from this species and some of them have anti-allergic, immunomodulatory and spasmolytic activities. Treatment of rats with the total tertiary alkaloid fraction showed an antidepressant effect. One of the depression causes can be the deficiency of monoamines, which is a factor displayed in patients with Alzheimer's disease. Theoretical studies using in silico methods have aided in the process of drug discovery. From this perspective, we applied ligand-based-virtual associated with structure-based-virtual screening of alkaloids from C. sympodialis Eichl and 101 derivatives proposed by us are promising leads against some important targets (BACE, GSK-3β and MAO-A). From the ChEMBL database, we selected a diverse set of 724, 1898 and 1934 structures, which had been tested against BACE, GSK-3β and MAO-A, to create Random Forest (RF) models with good overall prediction rate, over 78%, for cross-validation and test set. Compounds 24 and 47 presented activity against GSK-3β and MAO-A simultaneously. The natural alkaloids roraimine and simpodialine-β-N-oxide presented activity against BACE and liriodenine against MAO-A. The top 20 compounds with best docking performance per enzyme were selected and validated through the RF model. All 9 compounds classified as active in RF model for BACE are bisbenzylisoquinoline alkaloids and were present in the top docking scoring, demonstrating a consensus on results. Affinities of bisbenzylisoquinoline alkaloids, including two secondary metabolites (roraimine and simpodialine-β-N-oxide), with BACE suggest that this skeleton can be used as a model to design new antagonists of this enzyme.

Acetylcholinesterase Inhibitory Activity of Alkaloids Isolated from Stephania venosa

Stephania venosa (Blume) Spreng or "Sa-Bu-Leud" is a Thai medicinal plant used for treatment of cancer and diabetes, and as a blood-tonic and aphrodisiac. This plant .ontains alkaloids as its major components and has been of interest for its acetylcholinesterase (AChE) inhibitory activity. Phytochemical screening - of S. venosa was made using HPLC analysis and showed the chemical variation between the same species from different provenances. Fractionation of .S..venosa extract yielded three alkaloids, namely, dicentrine, crebanine, and tetrahydropalmatine. AChE inhibitory potential of the isolated alkaloids was evaluated using Ellman's AChE inhibition assay. Dicentrine, crebanine, and tetrahydropalmatine inhibited-AChE activity with IC(50) values of 93.5, 86.6, and 168.6 μg/mL, respectively. The AChE inhibitory activity of the tertiary protoberberine alkaloid, tetrahydropalriiatine, was lower than that of the aporphine alkaloids, dicentrine and crebanine, whereas the quaternary protoberberine alkaloid, berberine, showed a higher AChE inhibitory effect than the others.

Cellular distribution of alkaloids and their translocation via phloem and xylem: the importance of compartment pH

The physico-chemical background of alkaloid allocation within plants is outlined and discussed exemplarily for pyrrolizidine alkaloids (PAs) and nicotine. The trigger for this discourse is the finding that, for example, PAs, which are taken up from the soil, are translocated in the xylem, whereas - when genuinely present in plants - they are allocated as N-oxides via phloem. Special emphasis is put on the impact of different pH values in certain compartments, as this entails significant changes in the relative lipophilic character of alkaloids: tertiary alkaloids diffuse readily through biomembranes, while the corresponding protonated alkaloids are retained in acidic compartments, i.e. vacuoles or xylem. Therefore, this phenomenon, well known as the 'ion trap mechanism', is also relevant for long-distance transport of alkaloids. Any efficient allocation of typical tertiary alkaloids within the phloem can thus be excluded. In contrast, due to their strongly increased hydrophilic properties, alkaloid-N-oxides or quarternary alkaloids cannot diffuse through biomembranes and, consequently, would be retained in the acidic xylem during translocation. The major aim of this paper is to sharpen the mind for the chemical peculiarities of alkaloids and to consider them adequately in forthcoming investigations on allocation of alkaloids.

Versatile methods for synthesizing organic acid salts of quaternary berberine-type alkaloids as anti-ulcerative colitis agents

Two versatile methods to synthesize kinds of organic acid salts of quaternary berberine-type alkaloids were investigated in order to determine which is more efficient to improve the liposolubility of the target compounds and to explore the efficacy of the target compounds as anti-ulcerative colitis (UC) agents. Overall evaluation according to the reaction results and yields of the final products indicated that the synthetic method using tertiary (±)-8-acylmethyldihydroberberine-type alkaloids as key intermediates is superior to that of using tertiary dihydroberberine-type alkaloids as intermediates. Ten target compounds were synthesized using quaternary berberine chloride and quaternary coptisine chloride as starting materials, respectively, and the anti-UC activity of some target compounds was evaluated in an in vitro x-box-binding protein 1 (XBP1) transcriptional activity assay using dual luciferase reporter detection. At 10 μM, the tested compounds were found to activate the transcription of XBP1 target at almost the same level as that of quaternary coptisine chloride. The synthesized target compounds were also found to share higher liposolubility than the inorganic acid salts of quaternary berberine-type alkaloid.

Phytochemistry and Pharmacology ofAnamirta cocculusWilld.

Anamirta cocculus is a woody climber of Menispermaceae family remains popular folk remedy in Asia and adjacent regions. It crude drug is officially listed in many Pharmacopoeias. The fruits, especially the seed contain picrotoxin, a very strong poison that was toxic to all vertebrates affecting the CNS, stimulating the respiratory and vagus centres in the medulla and acting on the heart and lungs with diminished pulse. The toxicity results in vomiting, purging, profuse sweating, dimness of vision, unconsciousness and clonic convulsions. Death occurs rapidly due to respiration failure, or slowly from gastro-intestinal symptoms, particularly the medulla oblongata and respiratory centre. In South-East Asia the fruit of Anamirta cocculus is used mainly as a fish poison and as an insecticide. The plant was large-stemmed and, stem and roots contains quaternary alkaloids, such as beriberine, palmatine, magnoflorine, columbamine, oxypalmine, stepharine and the major tertiary alkaloid as 18-oxotetrahydropalmatine. The alkaloids of Anamirta cocculus have antibacterial, antimicrobial, sympatholytical (acetylcholine), and antifertility activities and the isolated alkaloids were confirmed and characterized by UVspectrophotometry, Mass spectroscopy, H1-NMR and C13-NMR spectroscopy.

English

Following the screening of several plant species from an inventory of common medicinal plants from South Africa for medicinal properties, Cissampelos capensis was selected for further investigation due to its interesting and useful ethnomedicinal properties. This study attempts to relate specific constituents present in this plant with its widespread ethnomedicinal uses. Six compounds were isolated and their structures were unambiguously established by spectroscopic methods. The compounds are: 5,6-dehydro-4,5-dihydroxy-1,3,6-trimethoxy-17-methylmorphinan-7-one (1); 1,2-methylenedioxy-3-hydroxy -9,10-dimethoxyaporphine (2); 5,6-didehydro-4-hydroxy-3,6-dimethoxy-17-methylmorphinan-7-one (3); 3,7,8,3'-tetramethoxy- 6 - C-methyl- 5,4'-dihydroxyflavone (6 -C-methylquercetin 3, 3',7, 8 -tetramethyl ether) (4); 5, 7, 8 -trihydroxy-2′, 5′-dimethoxy-3′,4′- methylenedioxyisoflavanone (5); 3 -methoxy-6 -C-methyl-3',4',5,7,8 -pentahydroxyflavone (6 -C- methylquercetin -3-methyl ether) (6). Five of the isolated compounds, (viz., 1,2,4,5 and 6) have, to our knowledge, not been reported previously. The crude fractions and isolates were tested for cytotoxicity using the brine shrimp lethality test and for antimicrobial properties using nine microbes, including three Gram –ve, three Gram +ve bacteria and three fungi. The Gram-negative bacteria were Pseudomonas aeruginosa (NCTC 10332), Proteus vulgaris (NCTC 4175) and Escherichia coli Sero type 1 (NCTC 09001), while the Gram-positive bacteria were Bacillus subtilis (NCTC 8236), Staphylococcus aureus (NCTC 13134) and Bacillus licheniformis (NCTC 01097). The Fungal species used were Candida albicans (ATCC 90028), Candida eropiralis (ATCC 750) and Aspergillus niger (ATCC 10578). The n-Hex fractions were not active while the highest activities were found in the methanolic extracts. The total tertiary alkaloid fraction (TTA) showed the highest activity against the Bacillus substillis. Compounds 1, 2 and 5 appear to be the most promising with regards to the prospects of drug development. Key words: Phytochemistry, Cissampelos capensis, antimicrobial, cytotoxicity, isoflavanone, aporphine, morphinandienone.

Neuraminidase inhibitory activities of quaternary isoquinoline alkaloids from Corydalis turtschaninovii rhizome

Clostridium perfringens is a Gram-positive spore-forming bacterium that causes food poisoning. The neuraminidase (NA) protein of C. perfringens plays a pivotal role in bacterial proliferation and is considered a novel antibacterial drug target. Based on screens for novel NA inhibitors, a 95% EtOH extract of Corydalis turtschaninovii rhizome showed NA inhibitory activity (68% at 30μg/ml), which resulted in the isolation of 10 isoquinoline alkaloids; namely, palmatine (1), berberine (2), coptisine (3), pseudodehydrocorydaline (4), jatrorrhizine (5), dehydrocorybulbine (6), pseudocoptisine (7), glaucine (8), corydaline (9) and tetrahydrocoptisine (10). Interestingly, seven quaternary isoquinoline alkaloids 1–7 (IC50=12.8±1.5 to 65.2±4.5μM) showed stronger NA inhibitory activity than the tertiary alkaloids 8–10. In addition, highly active compounds 1 and 2 showed reversible non-competitive behavior based on a kinetic study. Molecular docking simulations using the Autodock 4.2 software increased our understanding of receptor–ligand binding of these compounds. In addition, we demonstrated that compounds 1 and 2 suppressed bacterial growth.

Influence of vinegar and wine processing on the alkaloid content and composition of the traditional Chinese medicine Corydalis Rhizoma (Yanhusuo).

Corydalis Rhizoma is the dried tuber of Corydalis yanhusuo W.T. Wang which is used in traditional Chinese medicine for pain relief and blood activation. Before being used in the clinics, C. yanhusuo is traditionally processed through dry-frying or frying with vinegar, wine or salt. In this study, eleven alkaloids from Corydalis Rhizoma, namely protopine (1), α-allocryptopine (2), tetrahydrocolumbamine (3), coptisine (4), palmatine (5), berberine (6), dehydrocorydaline (7), d,l-tetrahydropalmatine (8), tetrahydroberberine (9), corydaline (10) and tetrahydrocoptisine (11) were simultaneously quantified using a newly developed high performance liquid chromatography-diode array detector (HPLC-DAD) method. The influence of vinegar and wine processing on the content of the main alkaloids of Corydalis Rhizoma was investigated. For this purpose, two common formulations with clinical application, namely the water decoction of Corydalis Rhizoma and its formula Jin Ling Zi San (combination of Corydalis Rhizoma and Toosendan Fructus) were studied. In the two water decoctions, wine and vinegar processing increased the amount of tertiary alkaloids. The differences were more pronounced for Jin Ling Zi San, in which case the content of all tertiary alkaloids (compounds 1, 2, 3, 8, 9, 10, 11) was increased by wine processing.

Synthesis of Optically Enriched Spirocyclic Benzofuran‐2‐ones by Bifunctional Thiourea‐Base Catalyzed Double‐Michael Addition of Benzofuran‐2‐ones to Dienones

A highly enantioselective catalytic double-Michael addition reaction of substituted benzofuran-2-ones with divinyl ketones promoted by readily accessible tertiary amine-thiourea Cinchona alkaloids has been developed. A number of optically enriched spirocyclic benzofuran-2-ones were prepared in very good yields (up to 99 %), diastereoselectivities (up to 19:1 d.r.), and very good enantioselectivities (up to 92 % ee). Density functional theory (DFT) calculations were performed to investigate the origin of stereoselectivity.

Development and validation of liquid chromatography–tandem mass spectrometry method for simultaneous determination of four tertiary alkaloids in rat plasma and its application to a pharmacokinetic study

A specific and reliable liquid chromatography–electrospray ionization-tandem mass spectrometry method was developed for the simultaneous determination of tetrahydropalmatine (THP), tetrahydroberineper (THB), tetrahydrocoptisine (THC) and corydaline (CDL) in rat plasma using jatrorrhizine as internal standard. Plasma samples were pretreated by protein precipitation with acetonitrile. Chromatographic separation was performed on a Zorbax Eclipse Plus C18 column (3.0mm×100mm, 1.8μm) with gradient elution using acetonitrile–0.1% formic acid water as mobile phase at a flow rate of 0.3mL/min. The detection was carried out by a triple–quadrupole tandem mass spectrometer in multiple-reaction monitoring mode. The mass transition ion-pair was followed as m/z 356.2→192.1, m/z 324.1→176.0, m/z 340.1→176.0, and m/z 370.3→192.1 for THP, THC, THB and CDL. Linear calibration curves were obtained over the range of 0.2–2000ng/mL, and the method limits were 2.0ng/mL for THC, 0.2ng/mL for THB, 1.0ng/mL for THP, and 0.4ng/mL for CDL, respectively. The mean recovery of the analytes ranged from 85.51% to 93.99%. The intra- and inter-day precisions were in the range of 1.21–4.73% and the accuracies were between 92.23% and 98.23%. The validated method was successfully applied to a pharmacokinetic study of THP, THB, THC and CDL in rat plasma following oral administration of Jitai tablet.