On the Extraction and Antioxidation of Total Flavonoids and Polysaccharides from Pitaya Peel (Hylocereus undatus 'Foo-Lon')

The effects of extraction time, ratio of solid to liquid, ethanol concentration and extraction temperature on the yield of total flavonoids and polysaccharides from pitaya peel were investigated. On the basis of the single-factor test results, an orthogonal experiment of L₉(3⁴) was designed to optimize the extraction process of total flavonoids and polysaccharides. In addition, the antioxidant activity of pitaya peel extract was investigated with experiments with DPPH·, ABTS free radical and ·OH scavenging assay. The optimal extraction conditions of total flavonoids and polysaccharides from pitaya peel were as follows: extraction time 3 h, solid-liquid ratio 1 ∶ 30, ethanol mass fraction 70%, and extraction temperature 70 ℃. Under these conditions, the average contents of total flavonoids and polysaccharides in pitaya peel were 7.87 mg/g and 114.05 mg/g, respectively. The in vitro antioxidant study showed that in the concentration of 373.44 μg/mL, the scavenging effect on DPPH ·, ·OH and ABTS radical was significant, and the maximum scavenging rates of the ascorbic acid were 95.25%, 99.57% and 89.99% while those of the sample were 88.64%, 60.84% and 61.77%, respectively. In conclusion, pitaya peel extract has good antioxidant capacity.