Document Detail


Photochemistry of the alkaloids eudistomin N (6-bromo-nor-harmane) and eudistomin O (8-bromo-nor-harmane) and other bromo-beta-carbolines.
MedLine Citation:
PMID:  15963435     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The UV-absorption, fluorescence excitation and emission spectra of the alkaloids eudistomin N (6-bromo-nor-harmane) and eudistomin O (8-bromo-nor-harmane) were described. In order to perform a comparative analysis, we also studied other bromo-beta-carbolines and the corresponding non-substituted-carboline. Thus, 6-bromo-, 8-bromo-, 6,8-dibromo-, 3,6-dibromo- and 3,6,8-tribromo-derivatives of nor-harmane, harmane and harmine were studied. These studies were performed in EtOH and in EtOH + 1% perchloric acid solutions (pa). Furthermore, fluorescence quantum yields (phi(f)) in acetonitrile and acetonitrile + 1% perchloric acid solutions at 298 K were measured. The HOMO and LUMO energy, the positions (lambda(max)) and oscillator strength (f) of the (1)S(1) <--(1)S(0) band for all the neutral and protonated beta-carbolines studied was calculated and compared with the experimental data. The pK(a) values in aqueous solution for eudistomin N and O (6-bromo- and 8-bromo-nor-harmane), for 6-bromo-, 8-bromo- and 6,8-dibromo-harmane, and for 6-bromo- and 8-bromo-harmine were spectrophotometrically measured (pK((a)(H(2)O))) . The change of the acid-base character of these compounds on going from the ground state (pK(a)) to the first electronic excited singlet state (pK(a)(*)) as DeltapK(a) = pK(a)(*)-pK(a) = 0.625 Deltanu /T, in ethanol solution at 298 K were calculated (DeltapK(a(EtOH))). Proton affinities (PA) for all the compounds studied defined as minus the enthalpy change of the reaction M+H(+)--> MH(+) (gas state) were calculated. Basicity relative to pyridine (DeltaH(rPy)) defined as the enthalpy change of the isodesmic reaction MH(+) + Py--> M + PyH(+) (gas state) was also calculated. The effect of bromine as substituent on the properties of the beta-carboline moiety in nor-harmane, harmane and harmine is discussed.
Authors:
Olga I Tarzi; Rosa Erra-Balsells
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't     Date:  2005-04-09
Journal Detail:
Title:  Journal of photochemistry and photobiology. B, Biology     Volume:  80     ISSN:  1011-1344     ISO Abbreviation:  J. Photochem. Photobiol. B, Biol.     Publication Date:  2005 Jul 
Date Detail:
Created Date:  2005-06-20     Completed Date:  2005-12-01     Revised Date:  2007-07-23    
Medline Journal Info:
Nlm Unique ID:  8804966     Medline TA:  J Photochem Photobiol B     Country:  Switzerland    
Other Details:
Languages:  eng     Pagination:  29-45     Citation Subset:  IM    
Affiliation:
CIHIDECAR-CONICET, Departamento de Química Orgánica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Pabellón II, 3rd Ciudad Universitaria, Argentina.
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MeSH Terms
Descriptor/Qualifier:
Carbolines / chemistry*
Molecular Structure
Photochemistry
Spectrometry, Fluorescence
Spectrophotometry
Structure-Activity Relationship
Ultraviolet Rays
Chemical
Reg. No./Substance:
0/Carbolines; 59444-69-8/eudistomin N; 88704-40-9/eudistomin O

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