Alkaloid isolation spectrometry

Dehydrocancentrine-B, a cherry-red alkaloid isolated from the same source, had the same functional groups as cancentrine (NMR, IR). However, its IR spectrum indicated the presence of an additional double bond in agreement with the molecular formula (C36H32N2O7) obtained by high-resolution mass spectrometry (HRMS). The mass spectrum was very similar to that of cancentrine with the exception that ions from the cularine half of the molecule appeared two mass units lower. Thus there were ions at m/e 361 (C21H15NO5) and m/e 348 (C20H14NO5) arising from fissions a + b and a -l- c, respectively (Scheme 1). This indicated that the extra double bond was in the cularine part of the molecule and must be located at the only available position, namely, C-31—C-32 (12). The NMR spectrum supported the location of the double bond in this position by the presence of a fourth AB system one half of which was visible at S 6.25 (Jab = 7.0 Hz). The location of the substituents and the relative stereochemistry of the alkaloid were shown to be identical with those... 

This is undoubtedly the most important class of L-histidine derivatives only because of pilocarpine s (27) therapeutic uses [8, 23, 24]. Since Byasson s first report of jaborandi alkaloids isolation from the leaves of Pilocarpus spp. (Rutaceae) [8], in 1875, several other imidazole alkaloids have been reported in this genus. The identification of these was facilitated due to recent advances in hyphenated chromatographic techniques such as HPLC—ESI—MS/MS (high performance liquid chromatography with electrospray ionization tandem mass spectrometry). 

Vincristine (VC) and vinblastine (VB) are dimeric catharanthus alkaloids isolated from the plant Catharanthus roseus. A capillary zone electrophoresis (CZE) was conducted for systematic and comprehensive study of the separation and quantification of two dimeric catharanthus alkaloids. Various separation parameters such as buffer concentration and pH, column internal diameter, and applied voltage were studied column, 72 cm (57 cm effective length) x 75 pm I.D. buffer, 0.2 M ammonium acetate solution, pH 6.2 and an applied voltage of 10 kV. Although the separation of VB and VC was the primary focus, the separation parameters determined in this study can be applied to the separation of other alkaloids as well. Separation of other alkaloids in the plant samples was observed under conditions presented in this work. A secondary objective of this study was to develop a method with experimental conditions which could be applied to electrophoresis-mass spectrometry. For this purpose, ammonium acetate buffers, which are more compatible with mass spectrometry than the widely used phosphate buffers, were used exclusively. Also, methanol-water-acetic acid was used as external buffer for the same reason [16]. 

Amongst products isolated from Heliotropium spathulatum (Boraginaceae) were 9 mg of a new alkaloid which gave a positive Ehrlich reaction with p-dimethylaminobenzaldehyde The molecular formula determined by mass spectrometry is CisH2sNOs. What is the structure of the alkaloid given the set of NMR results 54 Reference is useful in providing the solution to this problem. Conditions CDCI3, 9 mg per 0.3 ml, 25 °C, 400 MHz ( //), 100 MHz ( C). (a) HH COSY plot ... 

The alkaloid Nigellicine proved to be the pyridazino[l,2-u]indazolium-l 1-carboxylate (234) and forms yellow crystals (Scheme 77). It was isolated from the widely distributed herbaceous plant Nigella saliva L., which is used as a spice and for the treatment of various diseases (85TL2759). The structure was determined by an X-ray crystal structure analysis. The carboxylate bond distances are essentially equal (123.3 and 125.6 pm). An intramolecular hydrogen bond was found between the carboxylate oxygen atom and the hydroxy group. In mass spectrometry, the molecular peak was found at mjz —246 (20) and the base peak at mjz —202 which corresponds... 

Gelsevirine (2) was first isolated in 1953 from G. sempervirens as a minor component (3). Its structure was later elucidated on the basis of mass spectrometry as well as H-NMR and 13C-NMR studies (4). Gelsevirine has been found to be the predominant alkaloid in G. rankinii (24), and it was claimed that some of the previously reported 1 H-NMR and 13C-NMR data should be revised. Thus the previous assignments of H-16, H-15, H-14a, H-14e, and H-6 for gelsevirine should be changed to H-15, H-14a, H-16, H-6, and H-14e, respectively, from the evidence of the more accurate homonu-clear 2D COSY experiments. Similarly, from the heteronuclear 2D correlation spectrum, the assignments for C-16, C-15, C-6, and 1V-CH3 should be revised to C-15, C-16,1V-CH3, and C-6, respectively. 

Isolation and identification of pyrazine alkaloids (Table III) have been achieved in most cases by a combination of gas chromatography and mass spectrometry (35,36,38,69,97,142). Methyl-, 2,3,6-trimethyl-, and tetramethylpyrazines (23a, 21a, and 22a) from the melon fly are identified by utilizing a solid sampling technique in conjunction with gas chromatography-mass spectroscopy (147). Methylpyrazines show the molecule ion as a base peak. Fragmentation proceeds mainly by the loss of HCN or CH3CN from the molecular ion (141). Eth-... 

Three new alkaloids, euthyroideones A, B and C (11-13) were isolated from the New Zealand bryozoan Euthyroides episcopalis [38]. All three compounds contain the unique heterocyclic pyrido(4,3-h)-l,4-benzothiazine skeleton. The structure of euthyroideone A (11) was determined by X-ray crystallography, NMR spectroscopy and mass spectrometry. Euthyroideone B (12) exhibited modest cytotoxicity against the BSC-1 cell line [38],... 

The antibacterial and cytotoxic bicyclic alkaloid phloeodictine B (473) was isolated from a New Caledonian species of Phloeodictyon and is unusual as it contains a cyclic aminoketal functionality. The structure was proposed on the basis of spectral data [398], A Phloeodictyon sp. from New Caledonia contained the cytotoxic and antibiotic alkaloids, phloeodictines Ci (474) and C2 (475). Their structures were elucidated by mass spectrometry and NMR spectroscopy [399]. 

The four new cyclopeptide alkaloids (19a)—(19d) isolated from the shrub Ceanothus integerrimus contain a para-bridged fourteen-membered-ring nucleus (19), for which the name phencyclopeptine has been proposed.16 The crude alkaloidal extract from Ceanothus sanguineus17 showed the presence of five major components on composite field-desorption mass spectrometry. H.p.l.c., however, yielded six alkaloids, two of which were isomeric and one of which was a new alkaloid (20). The bark of Scutia buxifolia contains five scutianine alkaloids (B, C, D, E, and H) H is new, and is (21).18 Two new cyclopeptides, sativanines A and B, have been identified as (22) and (23) by m.s.-n.m.r. study.19... 

The methods employed for isolation of the alkaloids depend on the nature of the compounds, and specific conditions have frequently been devised for the selective isolation of particular types of compounds. Usually, fresh or dried plant material is extracted with dilute acid solution or with alcohol, and the extract obtained is further fractionated by extraction into organic solvents with variation of pH. Extraction columns (288), membrane processes (425), and ion-exchange materials (288-290) may be particularly useful for subfractionation or isolation procedures. For further identification and isolation of separate compounds, preparative thin-layer chromatography, (288, 291, 292, 426), liquid chromatography (293, 294), or gas chromatography may be used (202, 296, 297). Because some of the products reviewed in this chapter occur naturally in very small amounts, they have not been isolated in crystalline form. Gas chromatography-mass spectrometry (87, 213, 299), mass fragmentography (192), and mass spectrometry-mass spectrometry (301, 359) have proved to be particularly useful techniques for identification of trace alkaloids in complex mixtures. 

In a reinvestigation of the minor alkaloids of A. quebrachoblanco, whose presence had already been indicated by Hesse (59) in 1882 (Vol. II), Biemann et al. (28, 51a) were able to isolate by a combination of alumina and gas chromatography about twenty compounds. The identification or structure determination of fifteen of these by mass spectrometry was described. Six belonged to the aspidospermine group and four of these were the known compounds, aspidospermine (II), deacetylaspido-spermine (VI), V.,-methyldeacetylaspidospermine (XLI), and (— )-pyri-folidine (XLVI). The three last-named had not previously been encountered in nature, VI and XLI having been prepared from aspidospermine (II) and vallesine (XXXVIII) (38, 39, 25). (— )-Pyrifolidine is identical with O-methylaspidocarpine (XLVI) which has been prepared... 

The three alkaloids named in the title (XXXII, XXXIII, and XXXIV) are respectively the A -formyl, -acetyl, and -propionyl derivatives of aspidospermidine (Section II, E). Demethoxypalosine (XXXIV) has been isolated from Aspidosperma limae (40) and A. discolor (40a) and was characterized as an iVa-acyldihydroindole by its UV-spectrum (Table III) and IR-absorption at 5.89 p. A strong band in the IR-spectrum at 13.1 p indicated an unsubstituted benzene ring. The foregoing information was confirmed and the substance was shown to belong to the aspidospermine group by NMR- and mass spectrometry. In the NMR-spectrum (Table IV) the 17-proton absorption is found at 8.13 well downfield from the three-proton multiplet due to the other aromatic protons which is centered at 7.07 8. This shift is due to the proximity of the carbonyl group of the iVa-propionyl group. In the aliphatic part of the spectrum, absorptions which are characteristic of the... 

A classic procedure in the chemical study of alkaloids includes extraction from a plant or animal source, chemical isolation and purification of the active principal, elucidation of the molecular formula by means of chemical degradation, mass spectrometry, infrared, ultraviolet, and nuclear magnetic resonance analyses, and laboratory synthesis of the product. Serious diffi-... 

Another difficulty is the determination of the homogenity of the isolated alkaloids. To illustrate this two extreme examples are given. By different chromatographic methods and because of its spectral properties (NMR, IR, MS), the natural, approximate 1 1 mixture of the spermidine alkaloids inandenin-12-one and inandenin-13-one appeared to be a pure compound. This was supported by the sharp melting point of its hydrochloride (150- 151°C). Only after chemical degradation was the nature of the mixture determined by mass spectrometry. On the other hand, the behavior of the pure crystalline spermine alkaloid aphelandrine was that of a mixture. At least two criteria were in favor of a mixture. In the H-NMR spectrum... 

Maytenine (31) was the first of these so-called simple alkaloids to be isolated and identified structurally by use of mass spectrometry, NMR, and UV spectroscopy (48). Several syntheses of 31 have been published in the past and are summarized in Scheme 4. 

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