[14] Nevirapine-induced rash is related to the 12-hydroxylation of nevirapine and is presumed to be due to the conversion of 12-hydroxy metabolite to a reactive quinone
methide in skin.
This quinone
methide is used for treatment of rheumatoid arthritis in traditional Chinese medicine [140].
Thus curcumin oxidation forms a large number of intermediary metabolites such as quinone
methide, peroxyl radical, endoperoxide, spiroepoxide, vinylether, and cyclopentadione [146] leading to the formation of bicyclopentadione [147].
The reaction likely proceeds through a [C.sub.3]-[C.sub.4] cyclization of a quinone
methide intermediate arising from elimination of fluoride anion [24].
da Rocha, Addition of Thiols to o-Quinone
Methide: New 2-hydroxy-3- phenylsulfanylmethyl [1,4]naphthoquinones and their Activity Against the Human Malaria Parasite Plasmodium falciparum (3D7), Eur.
Inhibition of NF-kappa B activation through targeting I kappa B kinase by celastrol, a quinone
methide triterpenoid.
Rietjens, "Structure-activity study on the quinone/quinone
methide chemistry of flavonoids,"
While the mechanism of hepatotoxicity remains poorly characterized, NVP metabolites such as 12OH-NVP and quinone
methide have been strongly implicated in the process [17, 18] and evidence for the metabolic activation of NVP through the detection of mercapturates in urine has been previously presented [19].
Meanwhile, the carbenium ion can also present the reaction of rearrangement due to instability, leading to the formation of different unsaturated bonds (--CH=CH and >C=[CH.sub.2]) by the isomerization of the double bond and hydride and/or
methide shifts (Fig.
Evidence for the formation of a quinone
methide during the oxidation of the insect cuticular sclerotizing precursor 1,2-dehydro-N-acetyldopamine.
A wellknown catalysis mechanism includes the formation of a quinone
methide intermediate and subsequent Michael type addition with the formation of a methylene group between aromatic rings [3].
Two cases of poisoning by mercuric
methide. Saint Bartholomew's Hosp Rep 1:141-150.