title: Isolation and characterization of ellagitannins as the major polyphenolic components of Longan (Dimocarpus longan Lour) seeds.
abstract: Longan (Dimocarpus longan Lour, syn. Euphoria longan Lam.) represents an important fruit in Northern Thailand and has significant economic impact. The fruit is either consumed fresh or as commercially prepared dried and canned products. The canning industry in Thailand produces considerable quantities of waste products, in particular Longan seeds. Because these seeds may be an exploitable source of natural phenolic antioxidants, it was of interest to identify, purify and quantitate the major potential antioxidant phenolics contained therein. The polyphenolic fraction from ground Longan seeds was obtained by extraction with methanol after delipidation with hexane. The hexane extract contained predominantly long-chain fatty acids with major contributions from palmitic (35%) and oleic (28%) acids. The polyphenolic fraction (80.90 g/kg dry weight) was dominated by ellagic acid (25.84 g/kg) and the known ellagitannins corilagin (13.31 g/kg), chebulagic acid (13.06 g/kg), ellagic acid 4-O-α-l-arabinofuranoside (9.93 g/kg), isomallotinic acid (8.56 g/kg) and geraniin (5.79 g/kg). Structure elucidation was performed with mass spectrometry and complete assignment of (1)H and (13)C NMR signals. The methanol extracts exhibited strong antioxidant capacities with an IC(50) of 154 μg/ml for reactive oxygen species attack on salicylic acid and 78 μg/ml for inhibition of xanthine oxidase in the hypoxanthine/xanthine oxidase assay. The extracts were less effective in the 2-deoxyguanosine assay (IC(50)=2.46 mg/ml), indicating that gallates along with ellagic acid and its congeners exert their potential antioxidant effects predominantly by precipitation of proteins such as xanthine oxidase. This was confirmed for the pure compounds gallic acid, methyl gallate, ellagic acid and corilagin.
authors.affiliation: Division of Preventive Oncology, National Center for Tumor Diseases, German Cancer Research Center, Im Neuenheimer Feld 581, 69120 Heidelberg, Germany.
authors.forename: Yuttana
authors.initials: Y
authors.lastname: Sudjaroen
authors.forename: William E
authors.initials: WE
authors.lastname: Hull
authors.forename: Gerhard
authors.initials: G
authors.lastname: Erben
authors.forename: Gerd
authors.initials: G
authors.lastname: Würtele
authors.forename: Supranee
authors.initials: S
authors.lastname: Changbumrung
authors.forename: Cornelia M
authors.initials: CM
authors.lastname: Ulrich
authors.forename: Robert W
authors.initials: RW
authors.lastname: Owen
mesh_terms: D000975:Antioxidants / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D036681:Fluorescence Recovery After Photobleaching; D047348:Hydrolyzable Tannins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D019271:Hypoxanthine / Q000737:chemistry; D050356:Lipid Metabolism; D013058:Mass Spectrometry; D019906:Nuclear Magnetic Resonance, Biomolecular; D010636:Phenols / Q000737:chemistry / Q000302:isolation & purification; D017382:Reactive Oxygen Species / Q000737:chemistry; D020156:Salicylic Acid / Q000737:chemistry; D029631:Sapindaceae / Q000737:chemistry* / Q000378:metabolism; D012639:Seeds / Q000737:chemistry* / Q000378:metabolism; D013785:Thailand; D014969:Xanthine Oxidase / Q000737:chemistry
chemical_list: D000975:Antioxidants; D047348:Hydrolyzable Tannins; D010636:Phenols; D017382:Reactive Oxygen Species; C013515:ellagitannin; D019271:Hypoxanthine; D014969:Xanthine Oxidase; D020156:Salicylic Acid