Exploring the ester-exchange reactions of diester-diterpenoid alkaloids in the aconite decoction process by electrospray ionization tandem mass spectrometry

The chemical components in the decoctions of Chinese herbal medicines are not always the same as those in the crude herbs because of the insolubility or instability of some compounds. In this work electrospray ionization tandem mass spectrometry was used to explore the ester-exchange reactions for aconitine-type diester-diterpenoid alkaloids occurring during the process of decocting aconite root. The aconitines were screened in a diverse range of samples, including crude aconite, decoction of crude aconite, residues from decoction of crude aconite, prepared aconite, decoction of prepared aconite, decoction of prepared aconite with added palmitic acid, and decoction of a mixture of mesaconitine and hypaconitine standards with liquorice root. It was found that diester-diterpenoid aconitines were converted into lipo-alkaloids as well as monoester alkaloids by the decoction of aconite.

Benzodiazepine Alkaloids from Marine-Derived Endophytic Fungus Aspergillus ochraceus

A new fungus-derived benzodiazepine analogue, 2-hydroxycircumdatin C (1), and a compound which has been isolated from a natural resource for the first time, but has been previously synthesized, namely (11aS)-2,3-dihydro-7-methoxy-1H-pyrrolo[2,1-c][1,4]benzodiazepine-5,11(10H,11aH)-dione (2), along with five structurally related known alkaloids (3-7), were isolated from Aspergillus ochraceus, an endophytic fungus derived from the marine brown alga Sargassum kjellmanianum. Their structures were established on the basis of spectroscopic methods. The absolute configuration of I was determined through CD evidence. Compound 1 displayed significant DPPH radical-scavenging activity with an IC50 value of 9.9 mu M, which is 8.9-fold more potent than that of butylated hydroxytoluene (BHT), a well-known synthetic positive control.

Dioxopiperazine Alkaloids Produced by the Marine Mangrove Derived Endophytic Fungus Eurotium rubrum

Cultivation of the fungal strain Eurotium rubrum, an endophytic fungus that was isolated from the inner tissue of stems of the mangrove plant Hibiscus tiliaceus, resulted in the isolation of two new dioxopiperazine derivatives, namely, dehydrovariecolorin L (1) and dehydroechinulin (2), together with eight known dioxopiperazine compounds including variecolorin L (3), echinulin (4), isoechinulin A (5), dihydroxyisoechinulin A (6), preechinulin (7), neoechinulin A (8), neoechinulin E (9), and cryptoechinuline D (10). The structures of the isolated compounds were determined by extensive analysis of their spectroscopic data as well as by comparison with literature. Compounds 1, 2, 9, and 10 were investigated for their a,a-diphenyl-beta-picrylhydrazyl (DPPH) radical-scavenging activity. In addition, the new compounds, 1 and 2, were evaluated for their cytotoxic activity against the P-388, HL-60, and A549 cell lines.

Comparative Study of Contents of Four Tropane Alkaloids in Cultural and Wild Anisodus tanguticus

To assess the medicinal value of cultural Anisodus tanguticus,the contents of four bioactive tropane alkaloids,anisodine,anisodamine,scopolamine and atropine,in cultural and wild materials were determined by the HPLC method.The results showed that content of each alkaloid in the aboveground parts of cultural and wild samples was lower than that in roots,and this explained why it was not the whole plant but the root that was used as medicinal materials.The content of each alkaloid in the roots of one-year cultural material was lower than that in the two-year plants.The discrepancy of the total of four alkaloids between one-year and wild plants is not significant.Moreover,the total of four alkaloids,and the contents of anisodine,scopolamine,and atropine in two-year plants were higher than those in wild plant.Thus there is medicinal value in the cultivated A.tanguticus as well as wild A.tanguticus,especially in the two-year cultural A.tanguticus.

Determination of dissociation constants of Strychnos alkaloids from Strychnos nux-vomica L. by capillary electrophoresis

An accurate capillary electrophoresis method was developed for the determination of dissociation constants of five Strychnos alkaloids from Strychnos nux-vomica L. The method relies on measuring the effective mobility of the solute as a function of the buffer pH. The mathematical relationship was strictly derived from the fundamental electrophoresis theory and the dissociation equilibrium of a weak base without any simplifications. Careful optimization of the running buffer permitted base-line resolution of the five structurally similar alkaloids.

Physicochemical characterization of the Strychnos alkaloids by capillary zone electrophoresis

A capillary zone electrophoresis (CZE) method has been developed for investigating the physicochemical characteristics of five Strychnos alkaloids in Strychnos nux-vomica L. Firstly, the dissociation constants of the five Strychnos alkaloids were determined, based on the relation between the effective mobility of the solutes and the buffer pH. The mathematical relationship was strictly deduced from the fundamental electrophoretic theory and the dissociation equilibrium. Secondly, an equation describing the relation between the migration time of alkaloids of similar structure and their molecular weights was developed and used to predict the migration order and to calculate the electrosomotic velocity. The results predicted by the theory agreed with those from experiments.

Absolute configuration assignment and enantiopurity determination of chiral alkaloids and coumarins derived from O- and C-prenyl epoxides

A combination method of ozonolysis and chiral stationary phase (CSP)-GC-MS analysis has been developed to determine the enantiopurity values and absolute configurations of a range of alkaloid and coumarin hemiterpenoids derived from C- and O-prenyl epoxides.

Cytotoxic alkaloids motuporamines A-C: Synthesis and structural verification

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Synthesis of the heterocyclic core of the alkaloids martinelline and martinellic acid

The tricyclic core of martinelline and martinellic acid was rapidly assembled utilising an imino Diels-Alder reaction of an imine derived from cinnamaldehyde with a cyclic enamide. The cycloaddition was completely regioselective though the exo endo selectivity was poor. These diastercoisomers were readily separated by flash chromatography and the relative stereochemistry of the exo-isomer confirmed by single crystal X-ray crystallography. This intermediate was converted to the central core of the aforementioned alkaloids in five additional synthetic operations. (C) 2001 Elsevier Science Ltd. All rights reserved.

Palladium catalysed formal 6-endo-trig approaches to pumiliotoxin alkaloids: interception of the elusive cyclopropyl intermediate

Intramolecular Heck cyclisation of (E)-vinyl bromides leads to indolizidines, related to pumiliotoxin alkaloids, in which the stereochemistry of the trisubstituted double bond undergoes inversion. A cyclopropyl intermediate, which is believed to be responsible for the double bond inversion, has been intercepted by forcing an 'early' beta-hydride elimination on this species. The relative stereochemistry of this cyclopropyl intermediate determines the regioselectivity of the final beta-hydride elimination. In this case all three beta-hydride eliminations were stereochemically permitted, giving rise to a mixture of three isomeric products, differing in the position of a double bond. (Z)-Vinyl bromides were found to be less reactive than (E)-vinyl bromides, but on cyclisation gave the required conjugated diene, with inversion of the vinyl bromide stereochemistry, as the sole reaction product. This methodology will allow rapid stereoselective access to the diene-based pumiliotoxin alkaloids.

Synthesis of unsymmetrical spermine alkaloids of the Homalium group

. Crombie, Leslie; Jones, Raymond C. F.; Haigh, David. Dep. Chem., Univ. Nottingham, Nottingham, UK. Tetrahedron Letters (1986), 27(42), 5147-50. CODEN: TELEAY ISSN: 0040-4039. Journal written in English. CAN 107:96956 AN 1987:496956 CAPLUS (Copyright (C) 2009 ACS on SciFinder (R)) Abstract Spermine alkaloids homaline (I), hopromalinol, hopromine, and hoprominol are prpared by sequential coupling of 4-substituted 5-methyl-1,5-diazacyclooctan-2-ones, available by transamidation from 4-substituted azetidin-2-ones, to 1,4-dichlorobut-2-ene.