Resumo

SOTO Z., Adriana M.; VALENCIA U., Gloria C.  e  GIL, Mariluz. SOLVENT EFFECT ON THE PHOTOOXIDATION OF AMODIAQUINE WITH SINGLET MOLECULAR OXYGEN. Vitae [online]. 2007, vol.14, n.2, pp.71-77. ISSN 0121-4004.

The use of Amodiaquine (AQ) in the treatment and prevention of the malaria, cause adverse effects in tissue exposed to the light; previous investigations relate these nocive effects to the capacity of this drug to generate active species of oxygen as singlet molecular oxygen (O₂(¹Δ_g)). This study shows chemical rate constants, k_r, for interaction between AQ and (O₂(¹Δ_g)) measured in several solvents, in the range from 0,12±0,2 x 10⁶ M^-1s^-1 in chloroform to 1,71±0,16 x 10⁶ M^-1s^-1 in methanol, indicating that k_r depends on solvent properties, increasing in solvent of greater polarity. Values for k_r are one and two orders of magnitude smaller respect to k_T (chemical and physical rate constant); these results show that AQ is a good singlet oxygen quencher. Analysis of solvent effects on k_r using the LSER, indicates that k_r increases in solvents with great capacity to stabilize charges and dipoles and hydrogen-bond acceptor (HBA) solvents. This solvent dependence is similar to that observed in aliphatic amines, such as triethylamine. Therefore, the little significance from parameter donor HBA is attributed to the formation of a intramolecular hydrogen bridge between of phenol and the nitrogen of tertiary amine.

Palavras-chave : Amodiaquine; Singlet oxygen; Photooxidation; Solvent effect; LSER.

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