title: In vitro antioxidant and radical-scavenging capacities of Citrullus colocynthes (L) and Artemisia absinthium extracts using promethazine hydrochloride radical cation and contemporary assays.
abstract: A new, quick and economical decolorization assay based upon the generation of a radical cation made from promethazine hydrochloride (PMZH) is described for screening of antioxidant activity of plants/herbal extracts. PMZH radical cations, produced through a reaction between PMZH and potassium persulfate (K(2)S(2)O(8)) in phosphoric acid medium, have maximum absorption at 515 nm in their first-order derivative spectrum. Theconcentrations of chromagen and K(2)S(2)O(8) were optimized (final concentration of PMZH and K₂S₂O₈ were 0.166 mM and 0.11 mM, respectively) for better stability and sensitivity of the radical cation produced. Agood linear correlation was found between the percentage inhibition and the increasing amounts of standard antioxidants, with correlation coefficients ranging from 0.989 to 0.999. The newly developed assay was employed to evaluate the antioxidant capacity of Citrullus colocynthes L. and Artemisia absinthium extracts. The proposed assay involved a more stable radical cation and required only 1 h for preparation of a working solution in comparison to the 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation decolorizaion assay, which was reported to be less sensitive at low pH and almost 12-16 h were required for preparation of a working ABTS solution. Other assays employed to evaluate the antioxidant potential andradical-scavenging capacities of the extracts were the ferric-reducing antioxidant power, 2,2'-diphenyl-1-picrylhydrazyl radical scavenging, total phenolic contents assay, total flavonoid contents and metal-chelating activity assays, and the lipid peroxidation value in linoleic acid emulsion systems. The results indicate that boththe plants have potent free radical-scavenging activity and the ability to prevent lipid peroxidation and radical chain reactions.
authors.affiliation: Department of Chemistry, Faculty of Science and Technology, GC University, Lahore-54000, Pakistan. mnasghar2003@yahoo.com
authors.forename: M Nadeem
authors.initials: MN
authors.lastname: Asghar
authors.forename: I Ullah
authors.initials: IU
authors.lastname: Khan
authors.forename: N
authors.initials: N
authors.lastname: Bano
mesh_terms: D000975:Antioxidants / Q000737:chemistry* / Q000302:isolation & purification; D031171:Artemisia absinthium / Q000737:chemistry*; D029773:Citrullus / Q000737:chemistry*; D055808:Drug Discovery / Q000379:methods*; D005419:Flavonoids / Q000032:analysis / Q000737:chemistry / Q000302:isolation & purification; D016166:Free Radical Scavengers / Q000737:chemistry* / Q000302:isolation & purification; D005638:Fruit / Q000737:chemistry; D007194:India; D007202:Indicators and Reagents / Q000737:chemistry; D007502:Iron Chelating Agents / Q000737:chemistry / Q000302:isolation & purification; D008519:Medicine, Traditional; D010154:Pakistan; D010636:Phenols / Q000032:analysis / Q000737:chemistry / Q000302:isolation & purification; D010936:Plant Extracts / Q000737:chemistry* / Q000302:isolation & purification; D018515:Plant Leaves / Q000737:chemistry; D018520:Plant Shoots / Q000737:chemistry; D017680:Potassium Compounds / Q000737:chemistry; D011398:Promethazine / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry; D013053:Spectrophotometry; D013431:Sulfates / Q000737:chemistry
chemical_list: D000975:Antioxidants; D005419:Flavonoids; D016166:Free Radical Scavengers; D007202:Indicators and Reagents; D007502:Iron Chelating Agents; D010636:Phenols; D010936:Plant Extracts; D017680:Potassium Compounds; D012997:Solvents; D013431:Sulfates; C009007:potassium persulfate; D011398:Promethazine