title: Evaluation of the 1-methyl-2-phenylindole colorimetric assay for aldehydic lipid peroxidation products in plants: malondialdehyde and 4-hydroxynonenal.
abstract: The 1-methyl-2-phenylindole colorimetric assay is considered specific for malondialdehyde (MDA) and 4-hydroxynonenal (HNE) in mammalian systems, but its specificity in plant tissues is unknown. This study demonstrates that the assay produces a purple/blue chromophore with an absorbance peak at 586 nm for a malondialdehyde standard, while aqueous extractions from Ribes spp. Beta vulgaris, and Lycopersicon esculentum tissues produce an orange chromophore with an absorbance maximum at 450 nm and a large shoulder that extends to 700 nm. No distinctive MDA peak was discernable in plant samples at lambda=586 nm and absorbance was attributed to background interference. The reaction between sucrose and 1-methyl-2-phenylindole produced an orange chromophore with a spectrum similar to those obtained from plant extractions, suggesting that simple sugars are the likely source of background interference. This study demonstrates that the 1-methyl-2-phenylindole colorimetric assay is non-specific for detecting MDA and HNE in plants and its use is cautioned due to interference, particularly from sugars.
authors.affiliation: Plant Conservation Group, School of Contemporary Science, University of Abertay Dundee, Kydd Building, Bell St, Dundee DD1 1HG, UK. jjohnston@hortresarch.co.nz
authors.forename: Jason W
authors.initials: JW
authors.lastname: Johnston
authors.forename: Susan
authors.initials: S
authors.lastname: Horne
authors.forename: Keith
authors.initials: K
authors.lastname: Harding
authors.forename: Erica E
authors.initials: EE
authors.lastname: Benson
mesh_terms: D000447:Aldehydes / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D027461:Beta vulgaris / Q000378:metabolism; D001671:Biochemistry / Q000379:methods; D003124:Colorimetry / Q000379:methods*; D005069:Evaluation Studies as Topic; D006851:Hydrochloric Acid / Q000737:chemistry; D007211:Indoles / Q000494:pharmacology*; D015227:Lipid Peroxidation; D008315:Malondialdehyde / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D008698:Mesylates / Q000737:chemistry; D018384:Oxidative Stress; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism; D031965:Ribes / Q000378:metabolism; D013053:Spectrophotometry
chemical_list: D000447:Aldehydes; D007211:Indoles; D008698:Mesylates; D010940:Plant Proteins; C045880:methanesulfonic acid; D008315:Malondialdehyde; C520322:1-methyl-2-phenylindole; C027576:4-hydroxy-2-nonenal; D006851:Hydrochloric Acid