Study On Copigmentation Of Organic Acids And Phenolic Aldehyde On Anthocyanins From Sugarcane

Sugarcane contains abundant anthocyanins,which not only play an important role in food coloring,but also have a potential biological activity.Sugar cane is widely cultivated in China.During sugar production process,bagasse(by-product),accounting for 25% of the quality of sugarcane contains an amount of anthocyanins.Recently,the research on anthocyanins of fruits and vegetables mainly focused on separation,purification and stability,while little research was done on the identification and copigmentation of anthocyanins in sugarcane.In order to enrich the types of sugarcane products,enhance the utilization rate of sugarcane and provide theoretical support for the systematic development and utilization of sugarcane anthocyanins,the effects of different extraction methods on the extraction of anthocyanins from sugarcane were studied.And the optimum extraction conditions were obtained.The effects of organic acid and phenolic aldehyde,as copigments,on the absorption spectra and stability of anthocyanin were studied.The mechanism of early and later copigmentation between copigments and C3 G was also explored.The main conclusions are as follows:The yield of sugarcane anthocyanin was extracted by acid extraction,methanol acetone and acidified methanol acetone.The orthogonal experiment was carried out by acidified methanol acetone.The results showed that the optimum extraction conditions were as follows: solvent composition 20% water,40% acetone and 40% methanol(v/v/v,pH = 1.0),feed ratio 1:10,extraction time 120 min,extraction tempareture 20 °C.The yield of anthocyanin from sugarcane was 125.01 ± 1.77 mg / 100 g DW under the optimum extraction conditions.Ultra-high performance liquid chromatography(UPLC)analysis,combined with electrospray ionisation quadrupole-time-of-flight tandem mass spectrometry(ESI-QTOFMS/MS),showed that sugarcane contained ten anthocyanins and seven of them were identified as cyanidin-3-(succinyl)-glucoside,cyanidin-3-glucoside,cyanidin-3,5-glucoside,peonidin-3-glucoside,cyanidin-3-(malonyl)-glucoside,peonidin-3-(malonyl)-glucoside and cyanidin-3-(cinnamoyl)-glucoside.The effects of the type and concentration of copigments,pH,temperature and storage time on the copigmentation were studied in the simulated system(15% ethanol,v/v,pH3.0).The results showed that ferulic acid,vanillic acid,4-coumaric acid,vanillin and syring aldehyde had a strong effect on copigmentation.The absorbance in solutions increased with the increasing concentrations of the copigments;the absorbance in solutions decreased with the increasing of pH values.A highest absorbance in solutions with ferulic acid,4-coumaric acid and vanillin aldehyde were observed when the temperatures was 20°C.While a highest absorbance in solution with syring aldehyde was observed at 15°C.Among these copigments,ferulic acid and 4-coumaric acid appered stronger effects in the copigmentations.The mechanism of copigmantation between five copigments and C3 G was studied.Comparing the experimental and theoretical values of the thermodynamics parameters of copigmentation and analyzing the interaction between the copigments and C3 G molecules by quantum chemical method,the mechanism of copigmentation was discussed.The ΔG°,ΔH° and ΔS° values of the system were negative for all of these complexes,indicating that these copigmentations were spontaneous and these reactions were exothermic.The ΔGbinding value for ferulic acid and C3 G was highest,indicating that the copigmentation was thermodynamically favored.The trend of ΔE and ΔGbinding is consistent,which indicates that the complex of ferulic acid and C3 G is the most stable.Quantum chemical analysis showed that hydrogen bond and van der Waals force were the main driving force of these reactions.Two kinds of anthocyanin derivatives formed in solutions with ferulic acid and 4-coumaric acid at the last period of copigmentation were identified: cyanidin-3-glucoside-vinylguaiacol and cyanidin-3-glucoside-vinylphenol,respectively.While no anthocyanin derivatives were found in solutions with other three copigments.