Chemical compositions and some physical properties of the water and alkali-extracted mucilage from the young fronds of Asplenium australasicum (J. Sm.) Hook

Effect of extraction conditions, including solvent types (water and sodium bicarbonate) and extraction temperatures (25, 50, 70 and 90 °C), on the physicochemical properties of the water and alkali-extracted mucilage from the young fronds of Asplenium australasicum (J. Sm.) Hook was evaluated. It was found that sodium bicarbonate extract generally showed higher yield than water extract, and its yield increased with increasing extraction temperature. Composition analysis revealed that A. australasicum mucilage was composed of mainly carbohydrates in conjunction with some glycoproteins. The weight average molecular size of the carbohydrate fraction of crude mucilage obtained from alkali and water extractions were about 6.30 × 107 and 2.63 × 107, respectively. Sugar composition analysis revealed that A. australasicum young fronds mucilage contained significant amount of uronic acid (14.3–56.6% based on total sugars). For the water extracted mucilage, GlcA is predominant. However, for the sodium bicarbonate extracted mucilage, GalA is predominant. Furthermore, Rha can only be detected in sodium bicarbonate extract. Other major neutral sugars include Gal, Man, Xyl and Fuc. The intrinsic viscosity of the water and alkali-extracted mucilage in deionized water were around 21.12 and 5.92 dL/g, respectively. This information would be useful when considering A. australasicum young fronds mucilage as a new Agro-ingredient.

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