Extraction optimization, chemical, structural characterization and antioxidant activity of water-soluble polysaccharides from Feijoa leave

Finding natural, inexpensive and new polysaccharides resources is essential due to the high potential for utilization in the food and medicinal industries. Therefore, the current study was aimed to extraction optimization of polysaccharides from feijoa leaves in order to maximize extraction yield and, evaluate chemical, structural characteristics and antioxidant activity. In this regard, the effects of three independent parameters including extraction temperature (50-90°C), pH of water (3.5-5.5) and extraction time (1-4 h) on the extraction yield were studied. Optimum conditions were obtained at extraction temperature of 68°C, pH of 6.75 and extraction time of 2.96 h. Under optimum conditions, the predicted yield (3.38%) was consistent with the experimental yield (3.35±0.02%). The preliminary chemical characteristics of the polysaccharides extracted from the feijoa leaves were determined under optimum conditions. Based on the results obtained, total carbohydrate content was 54.77%, polyphenols and protein were 0.14 mg GAE and 0.18%, respectively. The FT-IR spectrum demonstrated obvious characteristic peaks of polysaccharides. Feijoa leave polysaccharides mainly consisted of glucose, ribose, mannose, arabinose and galactose. The results of antioxidant activity revealed the good ability of feijoa leave polysaccharides to scavenge DPPH free radicals and to reducing iron ions. Finally, the feijoa leave can be introduced as a natural, inexpensive and new resource for the extraction of polysaccharides with good biological activity for the production of functional foods or medicines.