dos Reis M. M., Pessine F. B. T., Ferreira M. M. C., “Photochemical behavior, under uva ultraviolet radiation, of b-cyclodextrin included parsol TM 1789 sunscreen”. Prague, Czech Republic, 23-28/08/1998: XXIV European Congress on Molecular Spectroscopy (EUCMOS XXIV), Book of Abstracts, 114 (1998). Poster D115.

EUCMOS XXIV, Prague 1998 (Book of Abstracts)

D115

PHOTOCHEMICAL BEHAVIOR, UNDER UVA ULTRAVIOLET RADIATION
OF b-CYCLODEXTRIN INCLUDED PARSON^TM 1789 SUNSCREEN


D. Naki, M. M. Reis, F. B. T. Pessine  and M. M. C. Ferreira

Department of Physical Chemistry/Institude of Chemistry/UNICAMP
13083-970, Campinas/SP/Brazil, e-mail: marcia@iqm.unicamp.br
 
 

           The  compound  Butyl  methoxy-dibenzoyl-methane,  commercially   available  as  the
trade   name   Parsol   1789   (from  Givaudan-Roure),   is    a   sunscreen  agent   used   for
photoprotection in the UVA  (320-400 nm)  spectral region.   Toxicological  tests have shown
that this substance may cause  cutaneous  and  ocular  irritation,   photo  and  subcutaneous
toxicity  and  also  be  teratogenic  and  mutagenic.   In this way  it is important  to  know   the
photochemical behavior of this substance in different solvents and systems.  So  the stability
of   b-cyclodextrin  (bCD)  encapsulated  Parsol  under  UVA  irradiation was  investigated by
absorption  and  fluorescence  spectroscopy.
           The study of both,  free  and  complexed   Parsol,   was  carried  out  to  check   if  the
inclusion of the sunscreeen molecule  in the cyclodextrin hydrophobic  cavity  could  increase
its  photochemical  stability.    The   samples  were   irradiated  with  UVA  light  and  different
exposition    times    and     in    two    solvents     with    different    polarities    (ethanol    and
isopropylmiristate).    A  significant  increase   in  absorption  and  emission  intensities  under
complexation were  observed indicating that the cromophore group,  which  is responsible for
the  electronic  transitions,   is  not  included  in  the CD  cavity.
           The spectra of keto and enol forms of Parsol, which were overlapped,   were  resolved
by   Self-Modeling   Curve   Resolution  (SMCR),    the  chemometric  method   developed  by
Lawton  and  Sylvestre.   This  method  was  applied  to the  Parsol  spectra  after  they  were
substracted from the solvent  blank.  For absorption  and  fluorescent  data  two spectra were
resolved  and  by  regression  the  concentration  profiles  were  found.
           The   results   show   that   the  complex   has   a   1:2   stoichiometry   (Parsol:CD,  as
expected  from  the  geometries  of  the  involved  species)   determined   by   measuring   the
diffusion coefficient  using  the  Taylor-Aris  technique  and the complexation  did not improve
the sunscreen photochemical stability,   regardless the employed solvents.   However,  it may
decrease the  effects  related to photoallergy/phototoxicity  through  inclusion  of the products
formed  during  the  photolysis.

         This work is a part of the M.Sc. Dissertation of D. Nakai. We are grateful to Natura and
the  American Maize Co.  that  provided  free  samples  of  the  sunscreen  and  cyclodextrin,
respectively.
 
 
 
 

[CAPES, FAPESP, CNPq]
 
 

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