title: Antioxidant properties of indapamide, 5-OH indapamide and hydrochlorothiazide evaluated by oxygen-radical absorbing capacity and electron paramagnetic resonance.
abstract: The aim of these experiments was to investigate the radical scavenging properties of three diuretics: indapamide (IND) and its major metabolite, 5-OH indapamide (5-OH IND), compared to a reference diuretic, hydrochlorothiazide (HTZ). Electron Paramagnetic Resonance (EPR) was used to determine the scavenging abilities of these compounds on enzymatically produced superoxide radical anion, with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) used as a spin-trap. These experiments revealed that IND and specially 5-OH IND were effective superoxide radical anion scavengers at 0.2 mg/ml. In the second part of these studies, allophycocyanin was used as an indicator of free radical mediated protein damage. In the assay, 2,2'-azobis(2-amidinopropane) hydrochloride (AAPH) was used as a peroxyl radical generator, Trolox (a water-soluble analogue of vitamin E) as a control standard, and the loss of allophycocyanin fluorescence was monitored. The antioxidant effects of the diuretics were expressed in oxygen-radical absorbing capacity (ORAC), where one ORAC unit equals the net protection produced by 1 microM Trolox. HTZ showed no protection up to 100 microM final concentration, whereas IND and 5-OH IND showed linear correlation with respect to concentration when expressed in ORAC units: 5-OH IND induced the highest protection against peroxyl radical. The above observations suggested that IND and 5-OH IND are potent radical scavengers, with the metabolite 5-OH IND having a superior antioxidant potency than IND. By contrast, HTZ had no effect. These radical scavenging properties of 5-OH IND may be of clinical interest for vascular protection and may help to protect the heart from oxidative injury.
authors.affiliation: Laboratoire de Physiopathologie et Pharmacologie Cardiovasculaires Expérimentales, Faculté de Médecine, Dijon, France.
authors.forename: C
authors.initials: C
authors.lastname: Vergely
authors.forename: M K
authors.initials: MK
authors.lastname: Walker
authors.forename: M
authors.initials: M
authors.lastname: Zeller
authors.forename: J R
authors.initials: JR
authors.lastname: Rademakers
authors.forename: V
authors.initials: V
authors.lastname: Maupoil
authors.forename: P
authors.initials: P
authors.lastname: Schiavi
authors.forename: D
authors.initials: D
authors.lastname: Guez
authors.forename: L
authors.initials: L
authors.lastname: Rochette
mesh_terms: D000975:Antioxidants / Q000378:metabolism*; D004232:Diuretics / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D006852:Hydrochlorothiazide / Q000378:metabolism*; D007190:Indapamide / Q000031:analogs & derivatives* / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D010545:Peroxides / Q000378:metabolism; D010798:Phycocyanin / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism
chemical_list: D000975:Antioxidants; D004232:Diuretics; D010545:Peroxides; C002497:allophycocyanin; D006852:Hydrochlorothiazide; D010798:Phycocyanin; D013481:Superoxides; C064096:5-hydroxyindapamide; C049375:perhydroxyl radical; D007190:Indapamide; D010100:Oxygen