title: Antioxidative effects of 6-methoxysorigenin and its derivatives from Rhamnus nakaharai.
abstract: In the search for potential antioxidants, the naphthalenic compounds, 6-methoxysorigenin (2) and its glycosides [i.e. 6-methoxysorigenin-8-O-glucoside (3), alpha-sorinin (4), and 6-methoxysorigenin-8-rutinoside (5)] isolated from Rhamnus nakaharai together with two acylates (peracetate and perpropionate) of 2 were evaluated for antioxidant activities using 2,2-diphenyl-1-picrylhydrazyl (DPPH), metal chelating, and electron spin resonance (ESR) assays as well as anti-lipid peroxidation assay. The results showed that 2 possesses the most potent DPPH radical scavenging, metal chelating, and anti-lipid peroxidation activities with IC50 values of 3.48, 615.90, and 5.95 microg/ml, respectively. The glycosides 3, 4, and 5 showed decreasing antioxidant activity that was related to an increased substitution at 1,8-dihydroxyl with sugar molecules. This suggests the importance of 1,8-dihydroxyl of 2 in the antioxidative effect. The iron chelation result could further explain the main cause of increasing antioxidant activity in 2. The acylates of 2 (2a peracetate and 2b perpropionate), although lacking a free hydroxyl, also exhibited significant anti-lipid peroxidation effect. ESR results further demonstrated that 2 possesses strong antioxidant activities. Taken together, this study shows that 2 is a potent antioxidant and may also be used for designing new iron chelators for clinical applications.
authors.affiliation: Department of Biotechnology, Tajen University, Pingtung, Taiwan.
authors.forename: Lean-Teik
authors.initials: LT
authors.lastname: Ng
authors.forename: Chun-Ching
authors.initials: CC
authors.lastname: Lin
authors.forename: Chai-Ming
authors.initials: CM
authors.lastname: Lu
mesh_terms: D000975:Antioxidants / Q000737:chemistry* / Q000494:pharmacology*; D001713:Biphenyl Compounds / Q000737:chemistry; D002614:Chelating Agents / Q000737:chemistry / Q000494:pharmacology; D002839:Chromans / Q000737:chemistry / Q000494:pharmacology; D004492:Edetic Acid / Q000737:chemistry / Q000494:pharmacology; D006834:Hydrazines / Q000737:chemistry; D015394:Molecular Structure; D009281:Naphthalenes / Q000737:chemistry* / Q000494:pharmacology*; D010851:Picrates; D031955:Rhamnus / Q000737:chemistry*
chemical_list: C520691:6-methoxysorigenin; D000975:Antioxidants; D001713:Biphenyl Compounds; D002614:Chelating Agents; D002839:Chromans; D006834:Hydrazines; D009281:Naphthalenes; D010851:Picrates; D004492:Edetic Acid; C004931:1,1-diphenyl-2-picrylhydrazyl; C010643:6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid