Zhi-Xing Qing

Systematic identification of alkaloids in Macleaya microcarpa fruits by liquid chromatography tandem mass spectrometry combined with the isoquinoline alkaloids biosynthetic pathway.

Alkaloids in Macleaya microcarpa were characterized systematically by combining liquid chromatography tandem mass spectrometry (LC-MS/MS) with the biosynthetic pathway of isoquinoline alkaloids. The mass spectral fragmentation behaviors of 16 references belonging to eight types of alkaloids that exist in the biosynthetic pathway of isoquinoline were investigated in detail. The benzyltetrahydroisoquinoline and aporphine alkaloids were distinguished by characteristic losses of the NHR1R2 (R1 and R2 represent the substituent groups of the nitrogen atom) radical and the fragment ions below m/z 200. Tetrahydroprotoberberine, N-methyltetrahydroberberine and protopine alkaloids were differentiated by the retro-Diels-Alder (RDA) reaction, α-cleavage and the [M-H2O](+) and [M-CH4](+) ions. Discrimination of protoberberine, benzophenanthridine and dihydrobenzophenanthridine-type alkaloids can be realized through the characteristic [fragment ion-2H](+), [M-H2O](+), [M-CH4](+), [M+H-CH3CH2CH2OH](+) and [M+H-CH3COCH3](+) ions. Forty-one alkaloids, including one benzyltetrahydroisoquinoline, one aporphine, nine protopines, seven protoberberines, one tetrahydroprotoberberine, three N-methyltetrahydroprotoberberines, five benzophenanthridines and fourteen dihydrobenzophenanthridines, were separated and identified simultaneously. Thirty-three of these were reported for the first time in M. microcarpa. The benzyltetrahydroisoquinoline, aporphine, tetrahydroprotoberberine and N-methyltetrahydroprotoberberine-type alkaloids have not been reported previously in M. microcarpa. This method can be applied to the analysis of herbal medicines that possess the biosynthetic pathway of isoquinoline alkaloids.

Structural speculation and identification of alkaloids in Macleaya cordata fruits by high‐performance liquid chromatography/quadrupole‐time‐of‐flight mass spectrometry combined with a screening procedure

RATIONALE Alkaloids with significant therapeutic effects are the main active constituents of Macleaya cordata, which is a perennial herb plant in the Papaveraceae family. A systematic and novel method for speculating and identifying the structures of alkaloids in M. cordata fruits by high-performance liquid chromatography/quadrupole-time-of-flight mass spectrometry (HPLC/Q-TOF-MS) with a screening procedure was reported. METHODS Investigation of mass spectral fragmentation of alkaloids was carried out based on the tandem mass spectrometry (MS/MS) data analyses of eight reference substances. The skeletons of alkaloids were determined by their ultraviolet spectra (UV) and MS/MS data. The substituent groups of the alkaloids were acquired through a screening procedure developed in our laboratory and MS/MS data. The substituent linkage sites were deduced by MS/MS fragmentation behavior, as well as biosynthetic pathways of related alkaloids. RESULTS The structures of 21 alkaloids were speculated in this study, 10 of which were reported for the first time in M. cordata. Furthermore, benzyltetrahydroisoquinoline and N-methyltetrahydroprotoberberine-type alkaloids were discovered, which indirectly proved that the biosynthetic pathways of benzophenanthridine alkaloids reported in Eschscholtzia california existed in M. cordata as well. CONCLUSIONS HPLC/Q-TOF-MS combined with a screening procedure was a systematic and reliable method for speculating and elucidating the structures of alkaloids. This study might be useful for the identification of other compounds in herbal medicines.

Synthesis of 5-methyl phenanthridium derivatives: a new class of human DOPA decarboxylase inhibitors.

DOPA decarboxylase (DDC) is responsible for the decarboxylation of l-DOPA and related aromatic amino acids and correlates closely with a number of clinical disorders. Sanguinarine, a natural quaternary benzophenanthridine alkaloid (QBA), was reported to be inhibitor of rat DDC and possessed a different inhibitory mechanism. In this study, several natural QBAs were assayed as human DDC inhibitors for the first time. A series of 5-methyl phenanthridium derivatives that contain the basic core structure of QBAs were also synthesized and evaluated as human DDC inhibitors. The title compounds still possessed DDC inhibitory potential. Among the synthesized compounds, 2-hydroxyl-8-methoxy-5-methylphenanthridinium chloride (11k) showed good inhibitory activity with an IC50 value of 0.12mM. Preliminary structure-activity relationship indicated that DDC inhibitory potential of 5-methyl phenanthridium derivatives correlated with the π-electro densities on CN double bond of iminium cation. The hydroxyl group on compound 11k possibly contributed to the formation of hydrogen bond between DDC and the inhibitor.

Systematic identification of flavonols, flavonol glycosides, triterpene and siraitic acid glycosides from Siraitia grosvenorii using high-performance liquid chromatography/quadrupole-time-of-flight mass spectrometry combined with a screening strategy

&NA; The fruits of Siraitia grosvenorii are considered to be health‐promoting because of the diversity of their bioactive ingredients. In the present study, a screening method, using high‐performance liquid chromatography/quadrupole‐time‐of‐flight mass spectrometry (HPLC‐Q‐TOF‐MS) combined with a screening strategy, has been established. The technology was used to systematically screening the targeted metabolites, primarily from the complex matrix of S. grosvenorii. The compounds were then identified by their exact masses and characteristic fragment ions, in comparison with the fragmentation behaviors of 19 references. Finally, 122 compounds, including 53 flavonols and flavonol glycosides, 59 triterpene glycosides and 10 siraitic acid glycosides, were screened and identified in 10‐, 50‐ and 80‐day fruits, roots, stems and leaves of S. grosvenorii. 98 of them were reported for the first time. Additionally, the distribution of all identified components in different parts of the plant was determined and metabolic networks for flavonol and triterpene glycosides were proposed. Graphical abstract Figure. No caption available. HighlightsA method for systematic screening and identifying metabolites was established.122 Compounds were screened and identified, 98 of them were report for the first time.The fragmentation pathways of flavonol and triterpene glycosides were investigated.The metabolic distribution of all identified compounds were determined.Metabolic network of flavonols and triterpenoids in Siraitia grosvenorii was proposed.

An improved separation method for classification of Macleaya cordata from different geographical origins

In this study, an improved separation method for the metabolomic study of polar and basic secondary metabolites by high-performance liquid chromatography-quadrupole-time-of-flight-mass spectrometry (HPLC-Q-TOF-MS) using an “Xcharge C18” column has been developed. Good retention for the polar compound and perfect peak shape for basic components was achieved. Classification of four different major origins of Macleaya cordata, which is a traditional folk medicine mainly used as a popular natural feed additive (e.g. Sangrovit®) in Europe and Asia since 2002, was performed by principal component analysis (PCA) and partial least square-discriminant analysis (PLS-DA). PCA data showed a clear separation among four different geographical origins. Biomarkers such as N-methyl-7-demethoxylhydrocotarnine and 13-methylcryptopine accountable for variation were tentatively identified by their tandem mass spectrometry (MS/MS) fragmentation behaviors. The proposed analytical method was shown to be a useful tool for the metabolomic study of polar compound and alkaloid containing plants.

Mass spectrometry-guided isolation of two new benzoquinoline alkaloids from Macleaya cordata

Abstract Two new alkaloids, named 2,3-methylenedioxy-7,10-dimethyl-7,8,9,10-tetrahydro-benzoquinoline (1) and 2,3-methylenedioxy-7,10-dimethyl-8-carboxyl-benzoquinoline (2), were detected primarily from the fruits of Macleaya cordata by their different fragmentation pathways. And then isolation of the two compounds was performed by column chromatography and preparative HPLC under the guiding of mass spectrometry. Finally, their structures were determined by spectroscopic analysis. Graphical abstract

23,24-Dihydrocucurbitacin C: a new compound regarded as the next metabolite of cucurbitacin C

Cucurbitacin C, a bitter substance in Cucumis sativus L., was isolated from green leaves by using phytochemical methods. An analytical method using high-performance liquid chromatography (HPLC) was established for the quantification of cucurbitacin C in different parts of the cucumber plant at different growth periods. Cucurbitacin C was detected in the leaves and stems but not in the female flowers, fruits, roots and leafstalks. The level of cucurbitacin C decreased significantly with the process of young leaves turning old. A new compound named 23,24-dihydrocucurbitacin C, regarded as the next metabolite of cucurbitacin C, was determined unambiguously by HPLC-quadrupole-time-of-flight mass spectrometry and nuclear magnetic resonance.

Mass spectrometry-guided isolation of two new dihydrobenzophenanthridine alkaloids from Macleaya cordata

Abstract Two new alkaloids 6-hydroxyethyldihydrochelerythrine (1) and 6-hydroxymethyl-7,8-demethylenedihydrochelerythrine (2) together with two analogues named maclekarpine E (3) and 6-hydroxymethyldihydrosanguinarine (4) were detected primarily from the leaves of Macleaya cordata by their characteristic mass spectrometry (MS) and tandem mass spectrometry (MS/MS). And then isolation of four targeted-compounds was performed by column chromatography and preparation HPLC under the guiding of MS. Finally, their structures were determined by spectrum analysis. Alkaloids 3 and 4 were isolated from this plant medicine for the first time.

Visible light photoredox catalyzed semisynthesis of the analogues of maclekarpine E: a series of 6-vinyl substituted dihydrobenzophenanthridine alkaloids

A visible light promoted vinylation of N-methyl 5,6-dihydrobenzophenanthridine was developed to synthesize the analogues of maclekarpine E. In this photoredox neutral radical coupling reaction, an α-amino C-radical generated at the C-6 of N-methyl 5,6-dihydrobenzophenanthridine was the key intermediate. The subsequent radical addition of vinyl sulfones with the α-amino C-radical followed by elimination of a sulfinyl radical gave the target compounds in moderate to good yields.

Anticancer and reversing multidrug resistance activities of natural isoquinoline alkaloids and their structure-activity relationship

The severe anticancer situation as well as the emergence of multidrug-resistant (MDR) cancer cells has created an urgent need for the development of novel anticancer drugs with different mechanisms of action. A large number of natural alkaloids, such as paclitaxel, vinblastine and camptothecin have already been successfully developed into chemotherapy agents. Following the success of these natural products, in this review, twenty-six types of isoquinoline alkaloids (a total of 379 alkaloids), including benzyltetrahydroisoquinoline, aporphine, oxoaporphine, isooxoaporphine, dimeric aporphine, bisbenzylisoquinoline, tetrahydroprotoberberine, protoberberine, protopine, dihydrobenzophenanthridine, benzophenanthridine, benzophenanthridine dimer, ipecac, simple isoquinoline, pavine, montanine, erythrina, chelidonine, tropoloisoquinoline, azafluoranthene, phthalideisoquinoline, naphthylisoquinoline, lycorine, crinane, narciclasine, and phenanthridone, were summarized based on their cytotoxic and MDR reversing activities against various cancer cells. Additionally, the structure-activity relationships of different types of isoquinoline alkaloid were also discussed. Interestingly, some aporphine, oxoaporphine, isooxoaporphine, bisbenzylisoquinoline, and protoberberine alkaloids display more potent anticancer activities or anti-MDR effects than positive control against the tested cancer cells and are regarded as attractive targets for discovery new anticancer drugs or lead compounds.