title: Reduction of 8a-hydroxy-2,2,5,7,8-pentamethyl-6-chromanone.
abstract: Two-electron oxidation of 2,2,5,7,8-pentamethyl-6-chromanol (PH), a model compound of alpha-tocopherol, gives the unstable 8a-hydroxy-2,2,5,7,8-pentamethyl-6-chromanone (POH) which rearranges to form stable 2-(3-hydroxy-3-methylbutyl)-3,5,6-trimethyl-1,4-benzoquinone (PQ). POH and PQ are isomers which have the same oxidation state. The aim of this work was to compare the ease of reduction of POH and PQ at room temperature using a variety of biological and chemical reductants in a reductant:POH (PQ) ratio of 20:1 (or 16:1). Ascorbic acid completely reduced POH to PH in 20 min, but had no effect on PQ after 40 min. Sodium ascorbate did not reduce POH or PQ at all after 40 min. Sodium dithionite reduced POH to PH (85%) in 20 min, but reduced PQ to its hydroquinone, PQH2 (67%) in 40 min. Dithiothreitol produced a slight reduction of POH to PH (21%) but reduced PQ to PQH2 (69%). NADH/FAD reduced POH and PQ to PQH2 (73% and 42%, respectively) in 10 min. It was concluded that POH is easier to reduce than PQ and more likely to form PH as a product, particularly under conditions of mild acidity.
authors.affiliation: Faculty of Pharmacy, The University of Surabaya, Surabaya, Indonesia.
authors.forename: Indrajati
authors.initials: I
authors.lastname: Kohar
authors.forename: Peter T
authors.initials: PT
authors.lastname: Southwell-Keely
mesh_terms: D001205:Ascorbic Acid / Q000494:pharmacology; D016227:Benzoquinones / Q000737:chemistry*; D002839:Chromans / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D004227:Dithionite / Q000494:pharmacology; D004229:Dithiothreitol / Q000494:pharmacology; D008956:Models, Chemical; D009243:NAD / Q000378:metabolism; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D013053:Spectrophotometry; D013997:Time Factors; D024505:Tocopherols / Q000737:chemistry
chemical_list: C476542:8a-hydroxy-2,2,5,7,8-pentamethyl-6-chromanone; D016227:Benzoquinones; D002839:Chromans; D009243:NAD; D004227:Dithionite; C476541:2-(3-hydroxy-3-methylbutyl)-3,5,6-trimethyl-1,4-benzoquinone; D001205:Ascorbic Acid; D024505:Tocopherols; D010100:Oxygen; D004229:Dithiothreitol