Abstract:

Two pectin extracts from citrus peel were obtained with hydrochloric acid and ammonium oxalate, and then
their pectin composition, monosaccharide composition and infrared spectral characteristics were analyzed. Moreover, the
antioxidant activities of the two extracts were compared. The results indicated high DE (degree of esterification) in both
extracts. The pectin prepared with hydrochloric acid (PEH) contained more rhamnose (5.4%, molar ratio) and a trace of
mannose, and demonstrated a lower relative molecular mass than the pectin obtained with ammonium oxalate (PEA).
However, PEA contained more mannose (5.3%, molar ratio) and arabinose (24.4%, molar ratio). Both pectins displayed
absorption peaks at 1102, 1018 cm-1 and 1745 cm-1 indicating the existence of uronic acid and CH3O- groups. They were
effective at scavenging superoxide anion radical with scavenging rate of 77.0% and 68.0%, resepctively. In addition, DPPH
radical and hydroxide radicals could be scavenged by both.

Key words: hydrochloric acid, ammonium oxalate, pectin, monosaccharide composition, antioxidant activity