Preparation, antioxidant activity and in vitro digestion of Manilkara zapota alkali-soluble polysaccharide-Fe (Ⅲ) complex

In this study, alkali-soluble polysaccharide from Manilkara zapota (MZAP) was extracted and polysaccharide-iron complexes MZAP-Fe (III) was synthesized. Structural characterization, antioxidant and digestive properties were used to evaluate the feasibility of MZAP-Fe (III) as an iron supplement. The results showed that when the reaction temperature was 70 ℃, the pH was 9 and the addition of sodium citrate was 0.025 g, MZAP- Fe (Ⅲ) had the highest iron content (14.68 %) and its average molecular weight increased compared to MZAP. The UV and FT-IR results indicated that MZAP- Fe (Ⅲ) was formed by the carboxyl and hydroxyl groups in MZAP with the iron group to form Fe-O bonds. MZAP-Fe (III) maintained high thermal stability over the temperature range of 20°C to 450℃. When the concentration of MZAP- Fe (Ⅲ) was 1.0 mg/mL, hydroxyl radical-scavenging activity and DPPH radical scavenging activity reached 57.03 % and 82.21 %, respectively, and both were significantly higher than the antioxidant activity of MZAP. Moreover, in the simulating human digestion, MZAP- Fe (Ⅲ) was more stable than FeSO₄ and less likely to be destroyed by stomach acid. The present study demonstrated the potential of MZAP-Fe (III) as a novel iron supplement.