Studies On Extraction, Purification, Antioxidant And Lipid-regulating Effects Of Pigments From Red Pitaya

Objective1. To optimize the technological conditions for extraction of pigments from redpitaya.2. To optimize the technological conditions for purification of pigments from redpitaya.3. To explore the stability of pigments obtained from red pitaya under differentconditions.4. To explore whether pigments obtained from red pitaya have the antioxidantcapacities in vitro, in vivo and regulating blood lipid effect in vivo.Methods1. The single factor design and response surface methodology were used to optimizethe technological conditions for the preparation of pigment extracts from peel and pulpof red pitaya.2. Macroporous adsorptive resins were used for purification of pigment extracts frompeel and pulp of red pitaya.3. The stability of pigments was studied under the action of light, metal ions, organicacids and carbohydrates.4. Free radical scavenging methods were used to determine the in vitro antioxidantcapacity of pigment extracts obtained from peel and pulp of red pitaya.5. High fat diets were used to set up the experimental hyperlipemia rat model,activities of regulating blood lipid and antioxidation of pigment extracts from peel ofred pitaya were studied in vivo.Results1. The optimal technological conditions for the preparation of pigment extracts were obtained by using response surface methodology. The optimal technological conditions forextracting pigments from peel of red pitaya were as follows: extraction time was51min,ethanol concentration was32%, the ratio of material to solvent was1:45(g/mL) and pH was5.3. And the optimal conditions for extracting pigments from pulp of red pitaya were found:namely extraction time,61min; ethanol concentration,27%; the ratio of material to solvent,1:55(g/mL); pH,5.3.2. HPD100resin was the best in adsorption effect and desorption effect for pigmentsfrom red pitaya. At room temperature,30%and40%ethanol were used as eluent agentsrespectively for peel and pulp of red pitaya, adsorption and desorption flow velocities wereboth10mL/min, the color scale of pigments purified from peel of red pitaya was72.33,and it was5.39times higher as compared with that before purification, and the color scaleof pigments purified from pulp of pitaya was109.62, and it was6.2times higher ascompared with that before purification. Light was not conducive to the stability of pigmentsfrom peel and pulp, Na+, K+, Mg2+, Ca2+, EDTA and glucose had little effects on thestability of pigments. However, Sn2+, citric acid and tartaric acid accelerated thedegradation of pigments.3. The contents of betacyanins in peel and pulp of red pitaya, expressed as betaninequivalents, were22.23±0.21mg/g dried extracts and24.30±0.3mg/g dried extractsrespectively. Seven components of betacyanins were isolated from peel and pulp, they werebetanidin-5-O-β-glucoside(betanin),isobetanidin-5-O-β-glucoside(isobetanin),2,17-bidecarboxy-betanin,unknown betacyanin, betanidin-5-O-(6′-O-malonyl)-β-glucoside (phyllocactin), isobetanidin-5-O-(6′-O-malonyl)-β-glucoside (isophyllocactin),betanidin-5-O-(6′-O-3-hydroxy-butyryl)-β-glucoside.4. Pigment extracts obtained from peel and pulp of red pitaya were showed to havestronger scavenging effects on hydroxyl free radical,1,1-diphenyl-2-picrylhydrazyl(DPPH·) free radical,2,2-azinobs-3-ethylbenzothiazoline-6-sulfonic acid (ABTS+·) freeradical, and have stronger ferric reducing power. But after digestion in vitro, antioxidantactivities of betacyanins were decreased.5. Heating could lower the contents of betacyanins in pigment extracts significantly;microwave irradiation and ultraviolet irradiation had little effects on the contents ofbetacyanins. In the2,2-azinobs-3-ethylbenzothiazoline-6-sulfonic acid (ABTS+·) assay,thermal treatment increased the antioxidant activity of pigment extracts obtained from peelof red pitaya, and decreased the antioxidant capacity of pigment extracts obtained from pulp of red pitaya. In the1,1-diphenyl-2-picrylhydrazyl (DPPH·) radical scavenging assay,microwave irradiation increased, but ultraviolet irradiation decreased the antioxidantactivities of pigment extracts significantly. After microwave irradiation and ultravioletirradiation, the Ferric Reducing Antioxidant Power(FRAP) value of pigment extracts frompeel increased.6. Pigment extracts from red pitaya peel could reduce the contents of the totalcholesterol, triglyceride, low density lipoprotein cholesterol in serum, increase the contentof high density lipoprotein cholesterol in serum, and decrease atherosclerosis indices:AI1and AI2significantly, indicating that betacyanins from peel of red pitaya had effects inprevention and treatment of atherosclerosis. Meanwhile, the pigment extracts couldincrease the activities of superoxide dismutase and glutathione peroxidase, and increase thetotal antioxidant capacity in serum and liver of rats with hyperlipemia.ConclusionsThe pigment extracts from red pitaya should be stored in the dark, and avoid contactwith Sn2+, citric acid and tartaric acid. Heating could accelerate the degradation ofbetacyanins. The pigment extracts from peel of red pitaya have stronger antioxidantcapacities in vitro, but after digestion in vitro, their antioxidant activities decrease. Thepigment extracts from peel of red pitaya could reduce the contents of the total cholesterol,triglyceride in serum of rats with hyperlipemia, decrease the atherosclerosis indices, andincrease activities of superoxide dismutase, glutathione peroxidase and total antioxidantcapacity.