Mucilage chemical profile and antioxidant properties of giant swamp taro tubers.

The yellow (YP) and white (WP) sections of giant swamp taro (GST) contain 40.0 g/kg and 51.5 g/kg (dry wt) respectively of pure mucilage made up of D-glucose (44.95-78.85 %), D-galactose (8.70-25.35 %), D-mannose (3.20-10.45 %), D-arabinose (2.45-5.20 %) and small amounts of glucuronic acid and rhamnose. Arabinogalactan-proteins (5.30-8.83 g/kg) contain mainly arabinose and galactose (in a 1:1 proportion) and also significant amounts of rhamnose, xylose, glucuronic acid and mannose. Antioxidant activity of YP was higher than those of WP while chelating ability and reducing power increased with mucilages content. Generally YP and WP showed better reducing power (1.06 ± 0.35 at 5 mg/mL) than ascorbic acid (0.89 ± 0.22). WP and YP chelated ferrous ions by 20.0-76.0 % and 16.4-71.0 % respectively. Effective concentrations (EC50) of mucilages (WP 1.28 ± 0.05 mg/mL; YP 1.42 ± 0.04 mg/mL) were lower than those of citric acid (1.58 ± 0.04 mg/mL). Generally mucilage from the WP and YP sections are excellent sources of chelating agents.