Antioxidant Activities and Functional Properties of Complex Polysaccharide (Mucilage) in Vegetable Fern (Diplazium esculentum)

Diplazium esculentum is a type of edible fern which has long been used in traditional dishes and is also known to contain mucilaginous material in a form of complex polysaccharide called mucilage. This study aimed to determine antioxidant activities and functional properties of mucilage extracted from D. esculentum. Extraction of mucilage from young fronds of D. esculentum was done using three different extraction methods i.e. hot water, alkaline and acidic. All subsequent analyses were done according to the established procedures. The results showed that hot water and alkaline extractions gave a significant (P < 0.05) higher yield (2.6 and 2.5%, respectively) of mucilage as compared to acidic extraction (1.6%). It was also found that mucilage extracted using hot water exhibited a significant higher (P < 0.05) ability to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radicals (scavenging activity = 51.3%), as compared to other mucilage including gum Arabic. Hot water and acidic mucilage were found to be significantly different (P < 0.05) from alkaline mucilage and gum Arabic in terms of antioxidant activity measured via ferric thiocyanate (FTC) analysis with higher percentages of peroxide inhibition (22.7% and 27.4%, respectively). Hot water mucilage was further studied for functional properties. This mucilage exhibited a clear thixotropic flow behaviour with higher viscosity profile and also better emulsion stability (68.0%) at 0.5% concentration, as compared to gum Arabic. These findings suggest that D. esculentum mucilage could be an interesting functional food ingredient with significant antioxidant properties though further study should be done in order to fully understand its potential as one of alternative food hydrocolloids.