| Purple corn know as is a kind of herbaceous plant of the genus Cornaceae.It is sown in most parts of China,and it is planted in a similar way with ordinary yellow corn.Purple corn cobs and kernels are rich in anthocyanins.Anthocyanins are natural red pigments with the effects of scavenging free radicals,fighting tumors,and protecting vision.At present,it is mostly extracted from blueberries,grapes,purple sweet potatoes and black rice,it is used as the raw material for natural pigments and health foods.Compared with other anthocyanin-rich resources,purple corn anthocyanin extract has the advantages of high yield,low price,high anthocyanin content and of various types,which can be used as a good source of anthocyanin extraction raw material.In this experiment,purple corn cobs and kernels were used as raw materials,and the conditions during the process were optimized by ultra high pressure extraction method,and they were purified by macroporous resin.By the HPLC method,this paper analyzed and compared the types and contents of anthocyanin aglycones in cob and kernel.At the same time,the HPLC-MS method was used to analyze and compare the anthocyanin species in cob and kernel.The test results are as follows:1.The ultra high pressure method was used to extract the purple corn cob and kernel anthocyanins.The single factor test was carried out by three factors of ultra high pressure,material-to-liquid ratio and dwell time.After optimization of the response surface,the optimum process conditions were determined as follows: The high hydrostatic pressure was 270 MPa,the ratio of material to liquid was 1:35 g/mL,and the dwell time was 2 min.The total anthocyanin content of the cob was(743.158 ± 11.304)mg/100g·DW,and the total anthocyanin content of the kernel was(552.381 ± 9.12)mg/100g·DW.2.The adsorption rate and desorption rate of five macroporous resins(NKA-II,NKA-9,AB-8,HPD-100,D-101)were evaluated,and the adsorption temperature was determined to be 25 °C.The purified resin model was D-101.The dynamic adsorption-desorption conditions are as follows: The upper column volume was 9 BV,the sample concentration was 3.5 mg/mL,the loading flow rate was 1.5 mL/min,the eluent was 70% ethanol-0.02% hydrochloric acid(v/v),the elution flow rate was 1.5 mL/min,and the elution volume was 8 BV,under this condition,the purity of the cob anthocyanin was 29.76%,the purity of the kernel anthocyanin was 22.64%,and the purity of the raw material was increased by about 40 times.3.The HPLC method was used to analyze the types and contents of anthocyanin aglycones for the purple cob and kernel.The results showed that: there were six aglycones in the cob and kernel,which were respectively delphinidin(212.305 ± 4.896)mg/100g·DW,(137.704 ± 2.984)mg/100g·DW,cyanidin(35.246 ± 0.127)mg /100g·DW,(18.214 ± 0.04)mg/100g·DW,petunidin(31.653 ± 0.115)mg/100g·DW,(28.210 ± 0.09)mg/100g·DW,pelargonidin(16.275 ± 0.07)mg /100g·DW,(15.422 ± 0.05)mg/100g·DW,paeonidin(12.716 ± 0.04)mg/100g·DW,(11.809 ± 0.02)mg/100g·DW,malvidin(174.277 ± 3.282)mg/ 100 g·DW,(140.966 ± 2.998)mg/100 g·DW.4.The HPLC-MS method was used to identify the structure of purple corn cob and kernel anthocyanin.The results showed that anthocyanins in cob and kernel contained delphinidin,delphinidin-3-O-glucoside,cyanidin-3-O-glucoside,cyanidin,cyanidin-3-malonylglucose,petunidin,pelargonidin,peonidin-3-O-glucoside,peonidin,malvidin,malvidin-3-O-glucoside were identified more on the cob than on the kernel. |
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