Studies On The Stability And Bioactivity Of Purple Pitaya Pigments

This paper taked red-purple pitaya pulp as experimental material, optimized the technology and conditions of extraction and purification of the red-purple pitaya pigments, established analysis conditions of HPLC-MS, discussed some factors effecting pigments stability, and probed into the biological activity of red-purple pitaya pigments, providing technical surports for exploitation and process of red-purple pitaya and pigments. The main results are as following:Through the static adsorption-desorption and dynamic adsorption-desorption experiments, the purification effects of red-purple pitaya pigments were analysed to screen for the suitable macroporous resin. Results showed that S-8 resin was preferable for separation and purification of red-purple pitaya pigments. The optimum adsorption and desorption conditions were that the pH value 3.0, the concentration of pigments 1.0 mg/mL, the flow rate of adsorption 3.0 BV/h, 0.1%Hcl-40% ethanol as eluant, and the flow rate of desorption 1.5 BV/h. In that case, the content of betacyanins in the purified sample was 40.9%.The analysis conditions of red-purple pigments by HPLC-MS were: (1)The mass spectrometer fitted with an electrospray ionisation source operating in the positive ionisation mode. The high voltage of capillary was 3.5 Kv. Nitrogen was used as dry gas at 325℃, a flow rate of 10 L/min, and a pressure of 40 psi. Scaned from 100 m/z to 900 m.z. (2)Column: Waters Atlantis dC18 (250×4.6 mm i.d., 5μm); Mobile phase, A: 0.2% formic acid in water, B: acetonitrile; Temperature:30℃; Injection quatity: 20μL; Flow rate: 1mL/min; Gradient elution condition (min/B%) was: 0/0, 4/0, 7/7, 24/9, 30/9, 35/10, 40/10, 60/15, 70/100; Detection: 280 nm,405 nm, 476 nm and 538 nm. By this method, ten components were determined, which mainly were betacyanins.The degradation of red-purple pitaya pigments was followed first-order reaction kinetics. The degradation prediction model was established through mensurating the changes of residual rate of pigments at different pH values and heating temperatures. The effects of different pH values, heating temperatures, sugar, mental ions, oxidant-reductant and copigments on the stability of pigments were mensurated. The results showed that the red-purple pitaya pigments was instable to heat and alkali, it was the most stable at pH 4.0⁵.0; the sugar concentrations from 0% to 12% which were used in juice processing had no significant effects on the stability of pigment; the metal ions had certain effects on the stability of it, Fe²⁺ could speed up its degradation while Ca²⁺, Mg²⁺, Zn²⁺ could protect the color; Among the copigments, rutin had no significant effects on the stability of pigments, but tannin, tea polyphenols and gallic acid had the protectivecoloration.Red-purple pitaya pigments exhibited a certain scavenging activity against DPPH radicals, hydroxyl radicals and superoxida anions, and the hemi-inhibiting concentration for them was 20.99 mg/L, 142.37 mg/L and 9000 mg/L respectively. The total antioxidant capacity was 32.66 U/mg, which suggeested that red-purple pigments had very powerful antioxidant activity. The proliferation of HL-60 cells was inhibited obviously by pigments. Cultured HL-60 cells using medium that contained different concentrations of pigments for 48 h and 72 h, the highest inhibition rates were 87.25% and 87.53% respectively. Red-purple pitaya pigments also could induced the apoptosis of HL-60 cells, the cells manifested apoptosis at 0.25 mg/mL. When the pigments concentrations were 2.0 mg/mL and 2.5 mg/mL, the cells manifested necrosis.