Abstract:

Based on single-factor tests, optimal extraction conditions of hot water extraction and ethanol precipitation of
polysaccharides from dried pitaya flowers (Hylocereus undatus (Haw.) Urilt. et. Rose) were explored by orthogonal array
design. Factors including extraction duration, temperature, solid-solvent ratio and extraction times were selected to maximize
the extraction rate of polysaccharides. The salicylic acid method was used to inspect the hydroxyl radical-scavenging activity
of polysaccharides from pitaya flowers. The results showed that the optimal parameters for extracting polysaccharides from
pitaya flowers were one cycle of extraction at 90 ℃ for 4 h with distilled water at a solid-to-solvent ratio of 1:100 (g/mL) and
after ethanol reflux pretreatment for 1 h. Under the optimal extraction conditions, the extraction rate of polysaccharides after
ethanol precipitation was 9.59 %. The resulting polysaccharide extract was evaluated for solubility and spectral properties
and it was found that its hydroxyl radical-scavenging rate was 50% at 6.4 mg/mL.

Key words: pitaya flower, water-soluble polysaccharide, water extraction, hydroxyl free radicals