Berberine reagent

Benztriazole, derivatives 281 ff 2-(2-Hydroxy-5-niethylphenyl)- 282 2-(2-Hydroxy-3-(l -methylpropyl)-5-tert-butylphenyl- 283 Berberine reagent 44,213 Beryllium cations 144,145,311,312 Besthorn s hydrazone reagent 347 Beta-blockers 74, 299, 301, 426—428 Beta-fronts 126 Beta-radiation 12 Betulae, Extr. 279 Betulic acid 59... 

Scheme 16. Synthesis of polyberbine (66), polycarpine (67), and its analog from proto-berberines. Reagents a, MCPBA, NaHCQ3, CH2C12, -78°C b. MCPBA, NaH, THF.

Experiment 2. Cholinesterase as a sensor on the cell surface A target of the allelochemical may also be a surface sensor-cholinesterase (Fig. 10). If after the staining with Red analogue of Ellman reagent the blue colour is absent in the allelochemical treated microspore, possible target is the enzyme (Roshchina, 2001a,b) as for alkaloid berberine tested. If after the treatment by the test allelochemical, the colour is absent or light, the compound inhibits the enzyme (also see biochemical assay in Chapter 11). 

The free bases are soluble in lipophilic organic solvents, like chloroform. The different solubility for bases and salts is used for isolation and purification. Alkaloids are generally colourless solid materials. Some alkaloids that do not contain oxygen, like coniine, nicotine and sparteine, are liquid, and berberine and chelidonine are intensely yellow. Several alkaloids, e.g. strychnine and quinine, have a very bitter taste. Alkaloids give precipitates with heavy metals like mercury and bismuth. DragendorfPs reagent is used to show the presence of alkaloids. 

B Berberine and the minor alkaloids, such as jatrorrhizine and palmatine, react with a brown-red colour with DRG reagent (vis.). 

Nonsensitized photochemical oxidation of dihydrodibenzo[a,5 ]quinolizinium compounds such as berberine (102) in the presence of nucleophilic reagents affords isoquinoline lactam aldehydes (103) (Scheme 13) <84H(22)10l>. A mechanistic proposal <81H(16)1735> involving the intermediacy of the dihydroberberine (104) was rejected on the basis of the results of direct irradiation of this compound. Participation of singlet oxygen was also excluded. 

Note that some derivatization reagents like the primuline or berberine do not interfere with MALDl-MS recording as the physical linkage is readily broken. Hence, the recording can be performed directly from the derivatized zones. 

With few exceptions (colchicine, berberine) alkaloids are bases, tnrning red litmns paper bine. Many are precipitated by varions reagents, for example Meyers (mercuric chloride and potassinm iodide). Some give more or less characteristic colonr reactions with certain reagents. Most are snsceptible to destruction by heat, some by exposure to air and light. 

Alkaloids, for example, quinine, are widely applied as catalytic reagents in chiral organic syntheses and also in the production of HPLC stationary phases for chiral separations. Cinchona alkaloids also induce the enantioselection of chiral fluoro-compounds analyzed by FNMR spectroscopy [32]. (-)-Brucine and (-)-berberine mixed with silica gel were used for preparation of thin-layer plates to resolve racemic amino acids. Other optically active pure enantiomers of natural compounds are applied for impregnation of TLC plates (-l-)-tartaric acid, L-aspartic acid [33]. (—)-Menthol is used for preparation of diastereomeric derivatives in indirect enantiomeric separation of, for example, 2- and 3-hydroxy acids [34]. 

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