FÃsico-quÃmica interfacial de filmes mistos de fosfolipÃdeos e Ãcido Ãsnico

AUTOR(ES)
DATA DE PUBLICAÇÃO

2004

RESUMO

The usnic acid it comes as a yellow pigment, of strong character hidrophobic, being insoluble in water and glicerol, partially soluble in etanol and easily soluble in ether, acetone, benzene and chloroform. Produced by liquens seeking your defense, the acid Ãsnico is in the shaft liquÃnico, where your concentration seems to be related with the integral amount of aromatic toxicant agents of the atmosphere. Of the classes of composed of low molecular weight, derived of liquens, the acid Ãsnico has been extensivamente studied by virtue of your wide potentiality biological action. Like this, in the extensive study field involving the usnic acid, they stand out the works that look for forms of minimizing your collateral effects: the carriers for liposomes has been one of those study lines. The study of the mechanism of interaction of the usnic acid with liposomes can be made through the physical-chemical analysis of mixed monolayers of phospholipids with acid Ãsnico. In the present work, studies were accomplished aiming at the characterization physical-chemistry interfacial, through the technique of Langmuir, of the properties of the pure usnic acid and when in mixed films with phos[pholips. The technique of Langmuir involves the formation with subsequent compression of fine films formed by molecular monolayers in an interface air-water. Through this technique, isotherms that they relate the molecular area (Ã2/mol.) of the films with the superficial pressures (p) correspondents are obtained. Such isotherms supplied results that indicate that: in pure films of PC (phosphocholine) the usnic acid reduces the collapse pressure, of 45 substantially so much for 24 mN/m, as the molecular area, of 62.5 for 37.5 Ã2/mol.; in films of DPPE, the usnic acid reduces the area of 40.8 for 16.5 Ã2/mol., without altering the collapse pressure; in films of DPPC, the medium molecular area was not altered, although the collapse pressure has suffered an increment of 55 for 68.5 mN/m. In mixed films so much with DPPC as with PC, the usnic acid little influenced the parameters of the obtained isotherms. Like this, for the obtained results, the acid Ãsnico presents a larger adsorption in pure films of DPPC, where it contributes to increase the mechanical resistance of the film in 13.5 mN/m. In pure films of DPPE, the presence of usnic acid promoted the dessorcion of this phospholipids for the aqueous subfase, phenomenon also observed in the pure films of PC, where it also happened reduction of the mechanical resistance of the film in 21 mN/m

ASSUNTO(S)

Ãcido Ãsnico bioquimica fosfolipÃdeos fÃsico-quÃmica

ACESSO AO ARTIGO

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