title: Oxidation reactions of hydroxy naphthoquinones: mechanistic investigation by LC-Q-TOF-MS analysis.
abstract: OBJECTIVE
  The hydroxyl radical ((●)OH)-induced oxidation reactions of isomeric hydroxy naphthoquinones (generally having anti-tumor activities) namely, lawsone and juglone, were carried out and the reaction mechanism was elucidated.
  
  
  METHODS
  The degradation products from the reaction of (●)OH (produced by H(2)O(2)/UV) with lawsone and juglone were analyzed using a liquid chromatography quadrupole-time-of-flight mass spectrometer (LC-Q-TOF-MS). The transient intermediate studies were investigated using picosecond pulse radiolysis technique.
  
  
  RESULTS
  Mono hydroxylated and dihydroxylated adducts of both lawsone and juglone were identified from the product analysis. The isomeric mono-hydroxylated adducts of lawsone were confirmed using survival yield (SY) analysis. The hydroxylated adducts of lawsone also underwent dimerization reaction. The transient spectral analysis using pulse radiolysis studies revealed the formation of hydroxycyclohexadienyl type radical of both lawsone and juglone as the initially formed intermediate.
  
  
  CONCLUSIONS
  The (●)OH-induced reactions of both lawsone and juglone result in the mono and di-hydoxylated derivatives. The demonstration of the various isomeric products using mass spectrometry is a clear proof of the addition probability of (●)OH at different positions of lawsone and juglone, which is generally a difficult task using other analytical techniques.
authors.affiliation: School of Chemical Sciences.
authors.forename: Radhakrishnan
authors.initials: R
authors.lastname: Sreekanth
authors.forename: Sunil Paul M
authors.initials: SP
authors.lastname: Menachery
authors.forename: Usha K
authors.initials: UK
authors.lastname: Aravind
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Marignier
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Belloni
authors.forename: Charuvila T
authors.initials: CT
authors.lastname: Aravindakumar
mesh_terms: D002853:Chromatography, Liquid; D017665:Hydroxyl Radical / Q000737:chemistry / Q000528:radiation effects; D008956:Models, Chemical; D015394:Molecular Structure; D009285:Naphthoquinones / Q000737:chemistry* / Q000528:radiation effects*; D010084:Oxidation-Reduction; D011675:Pulse Radiolysis; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry; D014466:Ultraviolet Rays
chemical_list: D009285:Naphthoquinones; D017665:Hydroxyl Radical; C005090:lawsone; C005134:juglone
keywords: Hydroxy naphthoquinones; mass spectrometry; product analysis; pulse radiolysis; ●OH