title: Marine natural products as novel antioxidant prototypes.
abstract: Pure natural products isolated from marine sponges, algae, and cyanobacteria were examined for antioxidant activity using a 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) solution-based chemical assay and a 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) cellular-based assay. The DCFH system detects only antioxidants that penetrate cellular membranes. Potent antioxidants were identified and the results from each system compared. The algal metabolites cymopol (1), avrainvilleol (3), and fragilamide (4), and the invertebrate constituent puupehenone (5) showed strong antioxidant activity in both systems. Several compounds were active in the DPPH assay but significantly less active in the DCFH system. The green algal metabolite 7-hydroxycymopol (2) was isolated from Cymopolia barbataand its structure determined. Compound 2 was significantly less active in the DCFH system than cymopol (1). The sponge metabolites (1S)-(+)-curcuphenol (6), aaptamine (7), isoaaptamine (8), and curcudiol (9) and the cyanobacterial pigment scytonemin (10) showed strong antioxidant activity in the DPPH assay, but were relatively inactive in the DCFH system. Thus, cellular uptake dramatically affects the potential significance of antioxidants discovered using only the DPPH assay. The apparent "proantioxidants" hormothamnione A diacetate (11) and Laurencia monomer diacetate (12) require metabolic activation for antioxidant activity. Significant advantages are achieved using both a solution- and cellular-based assay to discover new antioxidants.
authors.affiliation: National Center for Natural Products Research, Department of Pharmacognosy, School of Pharmacy, University of Mississippi, 38677-1848, USA.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Takamatsu
authors.forename: Tyler W
authors.initials: TW
authors.lastname: Hodges
authors.forename: Ira
authors.initials: I
authors.lastname: Rajbhandari
authors.forename: William H
authors.initials: WH
authors.lastname: Gerwick
authors.forename: Mark T
authors.initials: MT
authors.lastname: Hamann
authors.forename: Dale G
authors.initials: DG
authors.lastname: Nagle
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D001688:Biological Products / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D001713:Biphenyl Compounds; D000458:Cyanobacteria / Q000737:chemistry*; D056890:Eukaryota / Q000737:chemistry*; D007563:Jamaica; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D010851:Picrates; D011161:Porifera / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000975:Antioxidants; D001688:Biological Products; D001713:Biphenyl Compounds; D010851:Picrates; C004931:1,1-diphenyl-2-picrylhydrazyl