琼北红米色素的精制及抗氧化性研究

Study on purification and antioxidation of Qiongbei red rice pigment

琼北红米具有较高的营养价值和保健功效,富含多种生物活性物质。为更好地探究琼北红米的潜在利用价值,进行红米色素单因素提取试验,采用Box-Behnken响应面试验优化了色素提取工艺,采用大孔吸附树脂对提取的红米色素进行精制,通过傅里叶红外和紫外光谱法对精制红米色素的结构进行分析,研究其抗氧化性。结果表明:红米色素最优提取工艺为提取时间95 min、提取温度50℃、乙醇体积分数75%、料液比1∶20 g·mL^(-1),在此提取条件下红米色素得率为(6.22±0.13) mg·g^(-1);红米色素中原花青素是以(表)儿茶素为结构单元构成的原花青定聚合物;红米色素对DPPH以及ABTS自由基清除能力随浓度的增加而提高,其IC_(50)分别为6.48、7.38μg·mL^(-1)。红米色素是一种天然的抗氧化活性物质,可为提高琼北红米的应用价值提供参考依据。

Red rice has high nutritional value and health care efficacy,and is rich in a variety of bioactive substances.In this experiment,the content of protein,moisture,ash,crude fat,total phenol and flavonoids in Qiongbei red rice was determined.It was preliminarily determined that the red rice pigment extract contained procyanidins by UV-Vis spectroscopy.The effects of extraction time(30,60,90,120,and 150 min),water bath temperature(30,40,50,60,and 70℃),solid-liquid ratio(1∶5,1∶10,1∶15,1∶20,and 1∶25 g·mL^(-1))and ethanol concentration(50%,60%,70%,80%,and 90%)on the yield of red rice pigment were investigated by single factor experiment.The response surface experiment was designed by Box Behnken,and the extraction time,extraction temperature,and ethanol concentration were selected as the investigation factors.Through the analysis of variance,it can be seen that the influence of the three factors on the yield of red rice pigment is C(ethanol concentration)>B(extraction temperature)>A(extraction time),and the influence of the interaction of various factors on the yield of red rice pigment is AB>BC>AC.Through the analysis of design-expert 8.0 software,the best technological conditions of red rice pigment were:extraction time 93.81 min,extraction temperature 49.33℃,ethanol concentration 72.61%.Combined with the actual situation,the process parameters were adjusted as follows:extraction time 95min,extraction temperature 50℃,ethanol concentration 75%,material liquid ratio 1∶20 g·mL^(-1).Validation experiment result showed that the yield of red rice pigment was(6.22±0.13)mg·g^(-1).Among the three resins,the adsorption rate and resolution rate of AB-8 resin were significantly higher than those of HPD300 and NKA-9 resin,and their adsorption rate and resolution rate were 76.47%and 89.74%respectively.The purification conditions were water washing volume 2BV,elution 70%ethanol and elution volume 3BV.The structure of the purified red rice pigment was identified by Fourier transform infrared and ultraviolet spectroscopy.It was proved that the red rice pigment contained proanthocyanidins,and the proanthocyanidins of the red rice pigment were proanthocyanidins polymers composed of(epicatechin)as structural units.The antioxidant experiment showed that the scavenging ability of red rice pigment to DPPH and ABTS free radicals increased with the increase of pigment concentration,and its IC50 values were 6.48 and 7.38μg·mL^(-1) respectively,while the IC_(50) values of Vc were 4.44 and 7.50μg·mL^(-1) respectively,hence,red rice pigment has the same strong antioxidant capacity as Vc and is a natural antioxidant substance.