Analysis and identification of phenolic compounds in dioscorea hispida dennst

Publication Type:
Thesis
Issue Date:
2007
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NO FULL TEXT AVAILABLE ----- Phenolic compounds in the Kloi tuber (Dioscorea hispida Dennst) were extracted with 60% aqueous MeOH, hydrolyzed and fractionated into fractions with an SPE C18 cartridge by using aqueous MeOH (10 - 60%.MeOH). The separate fractions were characterised by Rp HPLC in a gradient mode. Identification of the phenolic compounds in each fraction was performed by ESI-LC-MS in negative ion mode. Total polyphenol content, DPPH assay and FRAP assay of each fraction were also determined. Classes of phenolic compounds found in the extracts were hydroxybenzoic acids, hydroxycinnamic acids and their derivatives. No flavonoids were detected. The compounds caffeic acid, chlorogenic acid, p- hydroxybenzaldehyde and methylprotocatechuate were found in the peel. The identification of the phenolic compounds was achieved by comparison of chromatographic parameters, mass spectrometric data and UV spectra against information obtained for authentic samples of each compound. Only methylprotocatechuate was found in the flesh of Kloi. Most of the identified compounds were in the 20%MeOH fraction. The DPPH value for the 20% MeOH peel and flesh fractions were EC50 1.05 x 102 µg/ml for the peel fraction and EC50 2.04 x 102 µg/ml for the flesh fraction. FRAP values were 3.26 x 102 µmol Fe2+/mg for peel and 2.93 x 102 pmol Fe2+/mg for flesh. The total phenol content of peel was 0.068 ± 0.04 mg GAE/mg and 0.085 ± 0.05 mg GAE/mg for flesh.
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