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. 2014 Nov 4:1:963-968.
doi: 10.1016/j.toxrep.2014.10.019. eCollection 2014.

Chloroquine and hydroxychloroquine binding to melanin: Some possible consequences for pathologies

R L Schroeder  1 , J P Gerber  1
Affiliations

Chloroquine and hydroxychloroquine binding to melanin: Some possible consequences for pathologies

R L Schroeder et al. Toxicol Rep. .

Abstract

For many years chloroquine was used as a prophylactic agent against malaria, and more recently as a mild immunosuppressive. However, due to lengthy treatment periods, adverse effects have become apparent, which included retinopathy. The structurally related hydroxychloroquine is less toxic, thought to be owing to a lower tissue accumulation in melanin rich areas. This study primarily focused on quantifying melanin binding between chloroquine and hydroxychloroquine at physiological pH to investigate the potential link between binding and reported toxicity. In addition, for the first time this study quantified the actual extent of adsorption of chloroquine and hydroxychloroquine to melanin and examined the desorption profile of both drugs from melanin to demonstrate the affinity between the pigment and the solutes. The results suggest that there is a difference between the adsorption affinities of chloroquine and hydroxychloroquine, potentially explaining the differences in bioaccumulation in retinal tissue. In addition, both solutes displayed a strong physical attraction to the absorbent.

Keywords: Adsorption; Chloroquine; Desorption; Hydroxychloroquine; Melanin; Sepia.

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Figures

Fig. 1
Fig. 1
(a) Chloroquine and (b) hydroxychloroquine.
Fig. 2
Fig. 2
Equilibration time of chloroquine and hydroxychloroquine at pH 7.4.
Fig. 3
Fig. 3
(a) Adsorption isotherm of chloroquine and hydroxychloroquine for melanin at pH 7 4. (b) Linear form of the Langmuir expression.
Fig. 4
Fig. 4
Desorption profile for chloroquine and hydroxychloroquine on melanin.
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