Flavonoids from the Zizania latifolia Bracts: Extraction Optimization, Antioxidant Activity and Exploration in Strawberry Preservation

Zizania latifolia bracts are Z. latifolia-based agricultural waste materials, distributed in various parts of the world. In the current study, the Response Surface Method (RSM) was used to optimize the cellulase-assisted extraction of Total Flavonoids from Z. latifolia bracts (TFZB). Then, the in vitro antioxidant capacity and the potential effect on strawberry preservation were assessed. The results showed that the optimal conditions for extracting TFZB was: Solid-to-liquid ratio of 1: 40 g/mL; ethanol concentration of 60% (v/v); cellulase dosage of 0.4% (w/w); incubation time of 2 h. Under these conditions, the yield of TFZB reached 0.49±0.01%. TFZB exerted certain antioxidant capacity. The free radical-scavenging rates against hydroxyl and DPPH radicals were 86±1.32% and 90±1.6% respectively at the concentration of 1.6 mg/mL and TFZB also exerted reducing power on Fe³⁺. Finally, the potential of TFZB on strawberry preservation was investigated from three aspects: Weightlessness rate, rotting rate and Vc content. It was found that the above-mentioned profiles were all improved after the strawberries sprayed with TFZB solution during the storage period. This study suggested that the TFZB may be developed as a novel antioxidant and fruits preservative, providing an evidence for the further utilization of Z. latifolia bracts.