title: Antioxidant activity of (+)-bergenin: a phytoconstituent isolated from the bark of Sacoglottis uchi Huber (Humireaceae).
abstract: (+)-Bergenin (1) was isolated from Sacoglottis uchi, a species of vegetable found in the Amazon region and popularly used for the treatment of several hepatic problems. The structure of 1 was fully characterized using IR, GC-MS and NMR (1D and 2D) analyses. This phytoconstituent has been used as an oriental folk medicine for the treatment of many diseases and shows antihepatotoxic properties. Tests with beta-carotene, DPPH and a heterogeneous Fenton system were carried out, confirming the antioxidant activity of 1. Theoretical calculations were performed to investigate the formation of the radical derivatives of 1 using *H, *OH, *CH(3), and *CCl(3) as initiator radicals. DFT thermodynamic calculations showed that the methoxyl group (O-6-CH(3)) is the most favorable site for radical attack. Frontier molecular orbital analysis showed that nucleophilic radical attack is favored on the aromatic ring of 1 where the LUMO is localized, with antibonding character with respect to the O-6-CH(3) bond. The possibilities of attack at other sites on 1 were investigated in detail in order to understand the regiospecificity of this reaction.
authors.affiliation: Departamento de Química, ICEx-Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil. haabreu@qui.dout.ufmg.br
authors.forename: Heitor A
authors.initials: HA
authors.lastname: De Abreu
authors.forename: Izandina
authors.initials: I
authors.lastname: Aparecida Dos S Lago
authors.forename: Gilmar P
authors.initials: GP
authors.lastname: Souza
authors.forename: Dorila
authors.initials: D
authors.lastname: Piló-Veloso
authors.forename: Hélio A
authors.initials: HA
authors.lastname: Duarte
authors.forename: Antônio Flávio
authors.initials: AF
authors.lastname: de C Alcântara
mesh_terms: D000975:Antioxidants / Q000737:chemistry* / Q000494:pharmacology; D001578:Benzopyrans / Q000737:chemistry* / Q000494:pharmacology; D001713:Biphenyl Compounds / Q000737:chemistry; D003198:Computer Simulation; D008401:Gas Chromatography-Mass Spectrometry; D006834:Hydrazines / Q000737:chemistry; D017665:Hydroxyl Radical / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D029581:Malpighiaceae / Q000737:chemistry*; D015394:Molecular Structure; D010851:Picrates; D024301:Plant Bark / Q000737:chemistry*; D010936:Plant Extracts / Q000494:pharmacology*; D010946:Plants, Medicinal; D013020:South America; D013055:Spectrophotometry, Infrared; D013237:Stereoisomerism; D019207:beta Carotene / Q000737:chemistry
chemical_list: D000975:Antioxidants; D001578:Benzopyrans; D001713:Biphenyl Compounds; D006834:Hydrazines; D010851:Picrates; D010936:Plant Extracts; D019207:beta Carotene; D017665:Hydroxyl Radical; C004931:1,1-diphenyl-2-picrylhydrazyl; C006741:bergenin