title: Identification of two polyphenolic compounds with antioxidant activities in longan pericarp tissues.
abstract: Longan fruits contain a significant amount of polyphenols. In the present study, polyphenols were extracted from longan pericarp tissues, and then two representative polyphenols were separated and purified by polyamide column chromatography, Sephadex LH-20 column chromatography, and silica gel column chromatography. On the basis of 1H NMR, 13C NMR, and electrospray ionization mass spectrometric (ESI-MS) data, the two compounds were identified as 4-O-methylgallic acid and (-)-epicatechin, respectively. In terms of reaction with longan polyphenol oxidase (PPO), (-)-epicatechin was further identified as the PPO substrate that caused longan fruit to brown. The results of antioxidant activity showed that 4-O-methylgallic acid had higher reducing power and 2,2-diphenyl-1-picrylhydrazyl- (DPPH-), hydroxyl radical-, and superoxide radical-scavenging activities than (-)-epicatechin.
authors.affiliation: South China Botanical Garden, The Chinese Academy of Sciences, Guangzhou Leyiju 510650, People's Republic of China.
authors.forename: Jian
authors.initials: J
authors.lastname: Sun
authors.forename: John
authors.initials: J
authors.lastname: Shi
authors.forename: Yueming
authors.initials: Y
authors.lastname: Jiang
authors.forename: Sophia Jun
authors.initials: SJ
authors.lastname: Xue
authors.forename: Xiaoyi
authors.initials: X
authors.lastname: Wei
mesh_terms: D000975:Antioxidants / Q000494:pharmacology*; D002392:Catechin / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology; D004156:Catechol Oxidase / Q000378:metabolism; D005419:Flavonoids / Q000302:isolation & purification* / Q000494:pharmacology*; D005638:Fruit / Q000737:chemistry; D005707:Gallic Acid / Q000031:analogs & derivatives / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology; D009682:Magnetic Resonance Spectroscopy; D010636:Phenols / Q000302:isolation & purification* / Q000494:pharmacology*; D059808:Polyphenols; D029631:Sapindaceae / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D000975:Antioxidants; D005419:Flavonoids; D010636:Phenols; D059808:Polyphenols; C024272:3,5-dihydroxy-4-methoxybenzoic acid; D005707:Gallic Acid; D002392:Catechin; D004156:Catechol Oxidase