Radiolytically induced one-electron reduction of artemisinin in H2O/ethanol (1:1 v/v) solution: a pulse radiolysis study.
The aim was to obtain information on the one-electron reduction of the antimalarial natural drug artemisinin (ART). The pulse radiolysis of ART in H(2)O/ethanol (EtOH) (1:1 v/v) solution was studied in the absence and presence of the so-called redox indicators N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD), Fe(CN)6(4-), 1,1'-dimethyl-4,4'-bipyridinium dichloride (methyl viologen, MV(2+)) and Fe(CN)6(3-). In an argon-purged solution, ART reacts with solvated electrons (es(-)) with k=4.4 x 10(9) dm(3) mol(-1) s(-1) generating an absorption band rising in the ultraviolet region similar to the spectrum of the CH3(*)CHOH radical. The species originating from the reaction between ART and es(-) do not show any appreciable reactivity toward Fe(CN)6(4-), TMPD, MV(2+) and Fe(CN)6(3-). The experiments performed in the presence of ART and MV(2+) have provided strong support to the idea that the first species obtained from the addition of the electron, which is believed to occur at the endoperoxide group level, undergoes a rapid (k on the order of 10(8) s(-1) or higher) intramolecular rearrangement to give species, most likely carbon-centred radicals, that show some reactivity towards the methyl viologen radical cation (MV(*+)).
Fuochi
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Instituto per la Sintesi Organica e la Fotoreattivitá, Consiglio Nazionale delle Ricerche, Bologna, Italy.
Marconi
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Mulazzani
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D037621:Artemisinins / Q000737:chemistry / Q000528:radiation effects*; D005609:Free Radicals; D010084:Oxidation-Reduction; D011675:Pulse Radiolysis; D012717:Sesquiterpenes / Q000737:chemistry / Q000528:radiation effects*
D037621:Artemisinins; D005609:Free Radicals; D012717:Sesquiterpenes; C031327:artemisinin