Molecularly imprinted polymer solid‐phase microextraction coupled with ultra high performance liquid chromatography and tandem mass spectrometry for rapid analysis of pyrrolizidine alkaloids in herbal medicine

Pyrrolizidine alkaloids are the most widely distributed natural toxins, and pyrrolizidine alkaloid‐containing herbal medicines are probably the most common poisonous plants affecting humans. We reported pyrrolizidine alkaloid‐molecularly imprinted polymer solid‐phase microextraction for the selective adsorption of toxic pyrrolizidine alkaloids from herbal medicine. A sulfonic compound, sodium allylsulfonate, was chosen as the functional monomer to interact with pyrrolizidine alkaloids through strong ionic interaction. To avoid template leakage and for the aim of cost saving, a relatively cheap dummy template was used for the fabrication of molecularly imprinted polymer‐solid‐phase microextraction fibers. The obtained fibers showed selective adsorption ability for four pyrrolizidine alkaloids, including europine, echimidine, lasiocarpine, and heliotrine. The extraction parameters, such as extraction time, extraction temperature, shaking speed, elution solvent and elution time, were optimized. Then ultra high performance liquid chromatography with mass spectrometry coupled with molecularly imprinted polymer‐solid‐phase microextraction method was developed for the fast and efficient analysis of four pyrrolizidine alkaloids from the model herbal plant Farfarae Flos. The established method was validated and exhibited satisfactory accuracy and precision. The present method provides an innovative and fast analytical strategy for the determination of trace toxic pyrrolizidine alkaloids in complicated samples.     

Identification and metabolite profiling of alkaloids in aerial parts of Papaver rhoeas by liquid chromatography coupled with quadrupole time‐of‐flight tandem mass spectrometry

Papaver plants can produce diverse bioactive alkaloids. Papaver rhoeas Linnaeus (common poppy or corn poppy) is an annual flowering medicinal plant used for treating cough, sleep disorder, and as a sedative, pain reliever, and food. It contains various powerful alkaloids like rhoeadine, benzylisoquinoline, and proaporphine. To investigate and identify alkaloids in the aerial parts of P. rhoeas, samples were collected at different growth stages and analyzed using liquid chromatography coupled with quadrupole time‐of‐flight tandem mass spectrometry. A liquid chromatography with mass spectrometry method was developed for the identification and metabolite profiling of alkaloids for P. rhoeas by comparing with Papaver somniferum. Eighteen alkaloids involved in benzylisoquinoline alkaloid biosynthesis were used to optimize the liquid chromatography gradient and mass spectrometry conditions. Fifty‐five alkaloids, including protoberberine, benzylisoquinoline, aporphine, benzophenanthridine, and rhoeadine‐type alkaloids, were identified authentically or tentatively by liquid chromatography coupled with quadrupole time‐of‐flight tandem mass spectrometry in samples taken during various growth stages. Rhoeadine alkaloids were observed only in P. rhoeas samples, and codeine and morphine were tentatively identified in P. somniferum. The liquid chromatography coupled with quadrupole time‐of‐flight tandem mass spectrometry method can be a powerful tool for the identification of diverse metabolites in the genus Papaver. These results may help understand the biosynthesis of alkaloids in P. rhoeas and evaluate the quality of this plant for possible medicinal applications.     

High-performance counter-current chromatography purification and off-line mass spectrometry monitoring and identification of pyrrolizidine alkaloid markers of tropical Ghanaian honey

The nutritional and medicinal properties of honey have been well-documented. However, honey has occasionally been contaminated with hepatotoxic pyrrolizidine alkaloids as a result of bees foraging on the flowers of pyrrolizidine alkaloid plants. This study establishes a simple and rapid method to determine the marker pyrrolizidine alkaloids in honey using high-performance counter-current chromatography and an off-line electrospray ionization-tandem mass spectrometry, in order to identify the botanical sources responsible for the contamination. The honey sample was initially liquid-liquid extracted (sulfuric acid/hexane, 2:3, v/v) to enrich the pyrrolizidine alkaloids and subsequently purified by a semi-preparative high-performance counter-current chromatography using a solvent system, hexane/butanol/1% aqueous ammonia, 1:1:2, v/v, based on partition coefficient measurements of the target alkaloids. The recovered fractions were profiled by injecting them sequentially into an off-line electrospray ionization-tandem mass spectrometry device to monitor the preparative molecular weight based on elution and extrusion modes. The monitored lycopsamine-type pyrrolizidine alkaloids and their N-oxides (m/z 300, 316; lycopsamine, intermedine, rinderine, and echinatine) were used as the phytochemical markers to identify plants like Chromolaena odorata, Ageratum spp., or Heliotropium spp. to be responsible for the pyrrolizidine alkaloid contamination. Identification of these pyrrolizidine alkaloid plants could guide beekeepers in locating their beehives in order to minimize their potential liver damaging effects.     

Simultaneous characterization of pyrrolizidine alkaloids and N‐oxides in Gynura segetum by liquid chromatography/ion trap mass spectrometry

Gynura segetum (Lour.) Merr. (Jusanqi) is a traditional herbal product used for hemostasis and detumescence in Chinese folk medicine. However, its hepatic toxicity should not be ignored. In this study, pyrrolizidine alkaloids (PAs) and their corresponding N‐oxides (PANOs) were extracted from the whole plant of G. segetum and analyzed by high‐performance liquid chromatography coupled to ion trap mass spectrometry (ITMS). Identification of eluted peaks as PANOs was indicated by virtue of their MS and MSⁿ analysis, in addition to the [M+H]⁺ adduct ion, characteristically showed a significant (usually 100% abundance) dimer adduct [2M+H]⁺ that is not observed in the MS of the parent PAs. A total of 20 compounds were identified or tentatively characterized based on their mass spectra and possible biosynthetic pathways, of which three PAs and one PANO, namely seneciphylline, senecionine, seneciphylline and seneciphyllinine N‐oxide, were unequivocally characterized, while other PAs and PANOs were tentatively assigned. Sixteen constituents were reported for the first time from G. segetum and tetrahydrosenecionine has not been previously reported as a natural product. Our results are the first comprehensive analysis of PAs and PANOs in G. segetum constituents and will be helpful for the quality control of the herb of G. segetum and its related preparations. Copyright © 2008 John Wiley & Sons, Ltd.     

Preparative separation of isoquinoline alkaloids from Corydalis impatiens using a middle‐pressure chromatogram isolated gel column coupled with two‐dimensional liquid chromatography

We established a two‐dimensional strong cation exchange/reversed‐phase liquid chromatography protocol to isolate and purify isoquinoline alkaloids from Corydalis impatiens. Isoquinoline alkaloids were first enriched from a C. impatiens extract in which liposoluble components were removed using a medium‐pressure chromatographic tower containing middle chromatogram isolated gel. A strong cation exchange column was employed to separate and obtain 30 fractions. We chose fractions 22–29 for reversed‐phase liquid chromatography purification using characteristic isoquinoline alkaloid ultraviolet absorption spectra. Several isoquinoline alkaloid fractions (22–29) were further separated, and those of low resolution were isolated via two‐dimensional liquid chromatography in the orthogonal plane. A total of eight novel isoquinoline alkaloids with characteristic ultraviolet spectra were obtained from C. impatiens. We thus demonstrate the benefits of off‐line two‐dimensional strong cation exchange/reversed‐phase liquid chromatography to isolate isoquinoline alkaloids from C. impatiens.     

Characterization of tropane and cinnamamide alkaloids from Scopolia tangutica by high‐performance liquid chromatography with quadrupole time‐of‐flight tandem mass spectrometry

Scopolia tangutica is a traditional Chinese medicine used for antispasmodic, anesthesia, analgesia, and sedation. Its medicinal activity is associated to alkaloid constituents, including tropane and cinnamamide types. Low content of alkaloids in plant makes them difficult to be isolated and identified. The present work developed an effective method to quickly characterize alkaloids from Scopolia tangutica by high‐performance liquid chromatography coupled with quadrupole time‐of‐flight tandem mass spectrometry. Thirteen reference compounds were studied for their fragmentation pathways, including five tropane alkaloids and eight cinnamamide ones. Alkaloid constituent was analyzed by an optimized high‐performance liquid chromatography method and mass spectrometry analysis to achieve systematic characterization of alkaloids from Scopolia tangutica. As a result, 53 compounds were identified, including 21 tropane alkaloids (eight new ones), 18 caffeoyl ones (ten new ones) and 14 dicaffeoyl ones (seven new ones). It was important to provide rich information in phytochemical study and structure‐guided isolation of important compounds from this plant.     

Establishment of a search library about benzylisoquinoline alkaloids based on selective separation on the binaphthyl column and standard analysis on C18 column

A search library about benzylisoquinoline alkaloids was established based on preparation of alkaloid fractions from Rhizoma coptidis, Cortex phellodendri, and Rhizoma corydalis. In this work, two alkaloid fractions from each herbal medicine were first prepared based on selective separation on the “click” binaphthyl column. And then these alkaloid fractions were analyzed on C18 column by liquid chromatography coupled with tandem mass spectrometry. Many structure‐related compounds were included in these alkaloids fractions, which led to easy separation and good MS response in further work. Therefore, a search library of 52 benzylisoquinoline alkaloids was established, which included eight aporphine, 19 tetrahydroprotoberberine, two protopine, two benzyltetrahydroisoquinoline, and 21 protoberberine alkaloids. The information of the search library contained compound names, structures, retention times, accurate masses, fragmentation pathways of benzylisoquionline alkaloids, and their sources from three herbal medicines. Using such a library, the alkaloids, especially those trace and unknown components in some herbal medicine could be accurately and quickly identified. In addition, the distribution of benzylisoquinoline alkaloids in the herbal medicines could be also summarized by searching the source samples in the library.     

HPLC‐ESI‐MS/MS of brain neurotransmitter modulator lobeline and related piperidine alkaloids in Lobelia inflata L

There is a renewed interest in lobelia alkaloids because of their activity on the central nervous system. Lobeline, the most active of them, a nicotinic receptor ligand and neurotransmitter transporter inhibitor, is a candidate pharmacotherapy for metamphetamine abuse. In the present work, high‐performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry in positive ion mode was used for investigating the alkaloid profile in Lobelia inflata L. Chromatographic separations were achieved on a Gemini C6‐phenyl reversed‐phase column providing good peak shape and improved selectivity. Being mostly 2,6‐disubstituted piperidines, lobelia alkaloids presented abundant [M + H]⁺ ions with typical fragmentation. Identification was possible from a few specific ions, especially those resulting from excision of one of the substituents. Based on fragmentation pattern of lobeline as reference compound, 52 alkaloids were identified in the aqueous methanolic extract of L. inflata in contrast to the previously known some 20. Structural variability of these alkaloids identified arises basically from their substituents which can be phenyl‐2‐ketoethyl‐ or phenyl‐2‐hydroxyethyl units as well as their methyl‐, ethyl‐ or propyl‐ homologues attached in different combinations. Several propyl homologue lobelia alkaloids and five hydroxypiperidine derivatives were found in the plant at the first time. In addition to 8‐O‐esters of 2‐monosubstituted piperidine alkaloids previously reported by us in L. inflata, a 3‐hydroxy‐3‐phenylpropanoic acid ester of hydroxyallosedamine ring‐substituted was also identified as a new natural product. High‐performance liquid chromatography‐electrospray ionization tandem mass spectrometry can be successfully applied to Lobeliacae plant samples in the routine screening for new and known bioactive constituents, quality control of the crude drug, lobelia herba, alkaloid production studies, breeding and chemotaxonomy. Copyright © 2015 John Wiley & Sons, Ltd.     

Determination of Hepatotoxic Pyrrolizidine Alkaloids in Gynura segetum by MEKC

A novel, rapid and sensitive micellar electrokinetic capillary chromatography method was developed for the separation and determination of two hepatotoxic pyrrolizidine alkaloids in Gynura segetum (Lour.) Merr. (Jusanqi) within 8 min. The method was successfully applied to the simultaneous determination of seneciphylline and senecionine in a Jusanqi sample.     

Diagnostic fragmentation‐assisted mass spectral networking coupled with in silico dereplication for deep annotation of steroidal alkaloids in medicinal Fritillariae Bulbus

Fully understanding the chemicals in an herbal medicine remains a challenging task. Molecular networking (MN) allows to organize tandem mass spectrometry (MS/MS) data in complex samples by mass spectral similarity, which yet suffers from low coverage and accuracy of compound annotation due to the size limitation of available databases and differentiation obstacle of similar chemical scaffolds. In this work, an enhanced MN‐based strategy named diagnostic fragmentation‐assisted molecular networking coupled with in silico dereplication (DFMN‐ISD) was introduced to overcome these obstacles: the rule‐based fragmentation patterns provide insights into similar chemical scaffolds, the generated in silico candidates based on metabolic reactions expand the available natural product databases, and the in silico annotation method facilitates the further dereplication of candidates by computing their fragmentation trees. As a case, this approach was applied to globally profile the steroidal alkaloids in Fritillariae bulbus, a commonly used antitussive and expectorant herbal medicine. Consequently, a total of 325 steroidal alkaloids were discovered, including 106 cis‐D/E‐cevanines, 142 trans‐D/E‐cevanines, 29 jervines, 23 veratramines, and 25 verazines. And 10 of them were confirmed by available reference standards. Approximately 70% of the putative steroidal alkaloids have never been reported in previous publications, demonstrating the benefit of DFMN‐ISD approach for the comprehensive characterization of chemicals in a complex plant organism.     

Two‐dimensional liquid chromatography analysis of all‐trans‐, 9‐cis‐, and 13‐cis‐astaxanthin in raw extracts from Phaffia rhodozyma

An effective two‐dimensional liquid chromatography method has been established for the analysis of all‐trans‐astaxanthin and its geometric isomers from Phaffia rhodozyma employing a C18 column at the first dimension and a C30 column in the second dimension, connected by a 10‐port valve using the photo‐diode array detector. The regression equation of astaxanthin calibration curve was established, and the precision and accuracy values were found to be in the range of 0.32–1.14% and 98.21–106.13%, respectively. By using two‐dimensional liquid chromatography, it was found that day light, ultrasonic treatment, and heat treatment have significant influence on the content of all‐trans‐astaxanthin in the extract from P. rhodozyma due to the transformation of all‐trans‐astaxanthin to cis‐astaxanthin. The day light and ultrasonic treatments more likely transform all‐trans‐astaxanthin to 9‐cis‐astaxanthin, and the thermal treatment transforms all‐trans‐astaxanthin to 13‐cis‐astaxanthin. These results indicate that the two‐dimensional liquid chromatography method can facilitate monitoring astaxanthin isomerization in the raw extract from P. rhodozyma. In addition, the study will provide a general reference for monitoring other medicals and bioactive chemicals with geometric isomers.     

The Double‐Bond Configuration of Corynanthean Alkaloids and Its Impact on Monoterpenoid Indole Alkaloid Biosynthesis

Experimental evidence is provided for the coherence of the double‐bond geometry and the occurrence of “secondary cyclizations” in the biosynthesis of monoterpenoid indole alkaloids. Biosynthetically, akuammiline, C‐mavacurine, and Strychnos alkaloids are proposed to be derived from the corynanthean alkaloid geissoschizine, a key intermediate in the biosynthetic pathway of these monoterpenoid indole alkaloids. This process occurs by so‐called “secondary cyclizations” from geissoschizine or its derivatives. Although corynanthean alkaloids like geissoschizine incorporate E or Z double bonds located at C19–C20, the alkaloids downstream in the biosynthesis exclusively exhibit the E double bond. This study shows that secondary cyclizations preferentially occur with the E isomer of geissoschizine or its derivatives. This is attributed to the flexibility of the quinolizidine system of the corynanthean alkaloids, which can adopt a cis or trans conformation. For the secondary cyclization to take place, the cis‐quinolizidine conformation is required. Experimental evidence supports the hypothesis that the E double bond of geissoschizine induces the cis conformation, whereas the Z double bond induces the trans conformation, which prohibits secondary cyclization of the Z compounds.     

Qualitative screening of absorbed indoloquinazoline alkaloids and their metabolites in rat plasma after the oral administration of Wu‐Zhu‐Yu decoction by high‐resolution mass spectrometry with multiple data mining algorithms

A rapid and sensitive liquid chromatography with high‐resolution mass spectrometry method with multiple data processing algorithms was developed and applied for the metabolite profiling of evodiamine and its analogous alkaloids in rat plasma after the administration of Wu‐Zhu‐Yu decoction. All samples were purified using hydrophilic‐lipophilic balanced solid‐phase extraction cartridges and analyzed by a Sciex TripleTOF 5600⁺ mass spectrometer with a 35 min liquid chromatography gradient elution. High‐resolution full‐scan mass spectrometry and information‐dependent acquisition tandem mass spectrometry data were analyzed using multiple data processing approaches. The results indicated that the detected eight prototype alkaloids could be metabolized to 58 metabolites through both phase I and phase II reactions. Oxidation was demonstrated to be the principle metabolic pathway of the parent compounds. The study contributes to the understanding of the absorption and metabolism of the alkaloids in Wu‐Zhu‐Yu decoction and provides a detailed analysis of scientific data.     

Qualitative and quantitative analysis of pyrrolizidine alkaloids for the entire process quality control from Senecio scandens to Senecio scandens‐containing preparations by high performance liquid chromatography‐tandem mass spectrometry

Senecio scandens as a commonly used traditional Chinese medicine that is used alone or in combination with other herbs in preparations such as QianBai BiYan tablets has attracted much attention because of its hepatotoxic pyrrolizidine alkaloids. Nowadays, most studies for pyrrolizidine alkaloids are only performed on herbs or a preparation, however, production of preparations is a dynamic process, control of toxic impurities for raw materials, or finished products cannot monitor the production process dynamically. Thus, in this study, qualitative and quantitative analysis of pyrrolizidine alkaloids for the entire process quality control from S. scandens to its preparations was carried out with HPLC‐MS/MS for the first time, which was more comprehensive and dynamic than the previous single‐layer analysis. First, the species of pyrrolizidine alkaloids in S. scandens were analyzed, and the characteristic fragmentation rules of pyrrolizidine alkaloids containing common parent nucleus were found, which can be used to identify these components rapidly in the future. Then, a quantitative method for S. scandens to QianBai BiYan tablets and other nine S. scandens‐containing preparations was established, and after the medication safety speculation, all of them met the relevant safety requirements. After that, in order to ensure the stability and controllable of drug quality, the limit of pyrrolizidine alkaloids in preparations was determined according to the safe dosage that is stipulated to be the same as raw materials. Finally, the factors causing the content change of pyrrolizidine alkaloids in S. scandens from different source were studies, which can provide theoretical basis for selecting suitable raw materials for production.     

Identification of metabolites of adonifoline,a hepatotoxic pyrrolizidine alkaloid,by liquid chromatography/tandem and high‐resolution mass spectrometry

Hepatotoxic pyrrolizidine alkaloid (HPA)‐containing plants have always been a threat to human and livestock health worldwide. Adonifoline, a main HPA in Senecio scandens Buch.‐Ham. ex D. Don (Qianli guang), was used officially as an infusion in cases of oral and pharyngeal infections in China. In this study in vivo metabolism of adonifoline was studied for the first time by identifying the metabolites of adonifoline present in bile, urine and feces of rats using liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI‐MSⁿ) (ion trap) as well as liquid chromatography/electrospray ionization high‐resolution mass spectrometry (LC/ESI‐HRMS) (quadrupole‐time of flight). In total 19 metabolites were identified and, among them, retronecine‐N‐oxides were confirmed by matching their fragmentation patterns with their fully characterized synthetic compounds. These metabolites are all involved in both phase I and phase II metabolic processes and the principal in vivo metabolism pathways of adonifoline were proposed. Copyright © 2009 John Wiley & Sons, Ltd.     

Chemical constituents of Meconopsis horridula and their simultaneous quantification by high‐performance liquid chromatography coupled with tandem mass spectrometry

Meconopsis horridula Hook.f. Thoms has been used as a traditional Tibetan medicine to clear away heat, relieve pain, and mobilize static blood. In this study, a reliable method based on high‐performance liquid chromatography with diode array detection and electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry was established for the identification of components in this herb. A total of 40 compounds (including 17 flavonoids, 15 alkaloids, and eight phenylpropanoids) were identified or tentatively identified. Among them, 17 components were identified in the herb for the first time. Compound 39 appears to be a novel compound, which is confirmed as 3‐(kaempferol‐8‐yl)‐2,3‐epoxyflavanone by NMR spectroscopy and mass spectrometry. Moreover, seven major constituents were simultaneously quantified by the developed high‐performance liquid chromatography with tandem triple‐quadrupole mass spectrometry method. The quantitative method was validated and quality parameters were established. The study provides a comprehensive approach for understanding this herbal medicine.     

Anti‐inflammatory bioactive equivalence of combinatorial components β‐carboline alkaloids identified in Arenaria kansuensis by two‐dimensional chromatography and solid‐phase extraction coupled with liquid–liquid extraction enrichment technology

Bioactive equivalent combinatorial components play a critical role in herbal medicines. However, how to discover and enrich them efficiently is a question for herbal pharmaceuticals researchers. In our work, a novel two‐dimensional reversed‐phase/hydrophilic interaction high‐performance liquid chromatography method was established to perform real‐time components trapping and combining for preparation and isolation of coeluting components. Arenaria kansuensis was taken as an example, and solid‐phase extraction coupled with liquid–liquid extraction as a simple and efficient method for enriching trace components, reversed phase column coupled with hydrophilic interaction liquid chromatography XAmide column as two‐dimensional chromatography technology for isolation and preparation of coeluting constituents, enzyme‐linked immune‐sorbent assay as bio‐guided assay, and anti‐inflammatory bioactivity evaluation for bioactive constituents. A combination of 12 β‐carboline alkaloids was identified as anti‐inflammatory bioactive equivalent combinatorial components from A. kansuensis , which accounts for 1.9% w/w of original A. kansuensis . This work answers the key question of which are real anti‐inflammatory components from A. kansuensis and provides a fast and efficient approach for discovering and enriching trace β‐carboline alkaloids from herbal medicines for the first time. More importantly, the discovery of bioactive equivalent combinatorial components could improve the quality control of herbal products and inspire a herbal medicine based on combinatorial therapeutics.     

Rapid screening and identification of lycodine‐type alkaloids in Lycopodiaceae and Huperziaceae plants by ultra‐performance liquid chromatography coupled with quadrupole time‐of‐flight mass spectrometry

Lycodine‐type alkaloids have gained significant interest owing to their unique skeletal characteristics and acetylcholinesterase activity. This study established a rapid and reliable method using ultra‐performance liquid chromatography coupled with electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry (UPLC‐ESI‐Q/TOF‐MS/MS) for comprehensive characterization of lycodine‐type alkaloids for the first time. The lycodine‐type alkaloids were detected successfully from Lycopodiastrum casuarinoides, Huperzia serrata and Phlegmarirus carinatus in seven plants of the Lycopodiaceae and Huperziaceae families, based on the established characteristic MS fragmentation of five known alkaloids. Furthermore, a total of 13 lycodine‐type alkaloids were identified, of which three pairs of isomers were structurally characterized and differentiated. This study further improves mass analysis of lycodine‐type alkaloids and demonstrates the superiority of UPLC with a high‐resolution mass spectrometer for the rapid and sensitive structural elucidation of other trace active compounds. Copyright © 2016 John Wiley & Sons, Ltd.     

Online high‐pH reversed‐phase liquid chromatography × low‐pH reversed‐phase liquid chromatography tandem electrospray ionization mass spectrometry combined with pulse elution gradient in the first dimension for the analysis of alkaloids in Macleaya cordata (willd.) R. Br

An online high‐pH reversed‐phase liquid chromatography× low‐pH reversed‐phase liquid chromatography tandem electrospray ionization mass spectrometry combined with pulse elution gradient in the first dimension was constructed to separate and identify alkaloids from Macleaya cordata (willd.) R. Br. The modulation was performed by using a dual second dimensional columns interface combined with a make‐up dilution pump, which is responsible for dilution and neutralization of the first dimensional effluent, and the dual second dimensional columns integrated the trapping and the separation function to reduce the second dimension system dead volume. Taking advantage of the dissociable characteristics of alkaloids, mobile phases with different pH values were applied in the first dimension (pH 9.0) and the second dimension (pH 2.6) to improve the orthogonality of two‐dimension separation. Besides, the pulse elution gradient in first dimension and second dimensional gradient were carefully optimized and much better separation was achieved compared to the separation with the traditional two‐dimensional liquid chromatography approach. Finally, mass measurement was performed for alkaloids in M. cordata (willd.) R. Br. by coupling proposed two‐dimensional liquid chromatography system with triple quadrupole mass spectrometry, and 39 alkaloids were successfully identified by comparing the obtained result with the former reported results.     

Diastereodivergent Catalysis Using Modularly Designed Organocatalysts: Synthesis of both cis‐ and trans‐Fused Pyrano[2,3‐b]pyrans

Both enantiomers of cis‐ and trans‐fused 3,4,4a,8a‐tetrahydro‐2H,5H‐pyrano[2,3‐b]pyran‐7‐carboxylates have been obtained in high diastereoselectivities and enantioselectivities from the same starting materials using a tandem inverse‐electron‐demand hetero‐Diels–Alder/oxa‐Michael reaction catalyzed by modularly designed organocatalysts (MDOs). Diastereodivergence was achieved in these reactions through the direct control of the stereochemistry of the bridgehead atoms of the fused ring using new MDOs self‐assembled from both enantiomers of proline and cinchona alkaloid thiourea derivatives.