Photochemical Stability of Biologically Active Compounds. Ix. Characterization of the Spectroscopic Properties of the 4‐aminoquinolines, Chloroquine and Hydroxychloroquine, and of Selected Metabolites by Absorption, Fluorescence and Phosphorescence Measurements

Abstract

The spectroscopic properties of the antimalarials chloroquine, hydroxychloroquineand selected metabolites were investigated by absorption, fluorescence and phosphorescence measurements. The antimalarials exhibit both fluorescence and phosphorescence. Fluorescence dominates for the deprotonated forms of the 4‐aminoquinolines, while phosphorescence dominates when the compounds are protonated. The phosphorescence lifetimes of the 4‐aminoquinolines were measured. Both the protonated and the deprotonated forms have long phosphorescence lifetimes indicating a long‐lived triplet state.

Photophysical Properties and Photobiological Behavior of Amodiaquine, Primaquine and Chloroquine

“…Spectroscopic properties (absorption, fluorescence and phosphorescence spectra) of CQ and hydroxychloroquine were previously reported by Nord et al. (22) and the two findings are in agreement.…”

“…For all the drugs the emission spectra are featureless, and for AQ and PQ they are centered at 480 and 520 nm, respectively; the CQ spectrum shows a main maximum at 380 nm and a shoulder at 475 nm. Spectroscopic properties (absorption, fluorescence and phosphorescence spectra) of CQ and hydroxychloroquine were previously reported by Nord et al (22) and the two findings are in agreement.…”

Photophysics of Bifunctional Ru(II) Complexes Bearing an Aminoquinoline Organic Unit. Potential New Photoprobes and Photoreagents of DNA

“…In acetonitrile the absorption also changes upon addition of an acid (methanesulfonic acid) or a base (piperidine). The acid produces a strong hyperchromic effect on the band at 354 nm due to protonation of the aromatic nitrogen 2 Absorption spectra for (solid circle) [Ru(BPY) 2 POQ−Nmet] 2+ , (solid diamond) [Ru(BPY) 2 acPhen] 2+ , (open circle) [Ru(BPY) 2 Phen] 2+ and (crossed square) Nmet−quinoline in aqueous solution, 1 mM NaH 2 PO 4 (pH 4.5).

3 Changes of the absorption spectrum of the Nmet−quinoline (Figure ) with increasing pH (aqueous solution, 1 mM phosphate buffer): pH, 5, 5.5, 6.5, 7, 7.5, 8, and 9.

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Photophysical Studies on Antimalarial Drugs

“…The capacity to produce singlet oxygen depends on a large yield of a (preferably) long-lived triplet state. Relatively large triplet yields are known to be associated with the monocations of CQ and HQ, for example, because of their lowlying n r * states (6). However, at pH 7.4, these two compounds will exist primarily as dications (pK, = 8.4, pK, = 10.4)(8.9).…”