Study On Antioxidant Activity And Thermal Stability Of Cyanidin-3-diglucoside-5-glucoside Complexes

Anthocyanin is a nature flavonoid pigment with antioxidant and chemopreventative properties.Acyl groups can influence stability,color and antioxidant activity of anthocyanin.Besides,anthocyanin complex,composed of stoichiometric amounts of anthocyanins,flavonoids and metal ions,can enhance some functional activities of anthocyanin.Cyanidin-3-diglucoside-5-glucoside（CY3D5G）and Delphinidin-3-rutinose-5-glucoside（DP3R5G）were extracted and saponified from red cabbage and eggplant peel respectively.Differences of structures and antioxidant activity between acyled anthocyanins and deacyled anthocyanins were investigated.Anthocyanin complexes,composed of the anthocyanin（CY3D5G）,flavonoids（rutin（L）,kaempferol-4’-glucoside（S））and metal ions(Mg²⁺,Zn²⁺,Fe³⁺,Cu²⁺and Ca²⁺)were established and their stuctures,colors,stablilty as well as antioxidant activity were investigated.The results are shown as follow:（1）Cyanidin derivatives from red cabbage were CY3D5G as a nuclear parent,acyled with one or two acyl groups（caffeic acid,sinapic acid,ferulic acid,cumaric acid）.The delphinidin derivative from eggplant peel was DP3R5G as a nuclear parent,acyled with one p-coumaroyl.CY3D5G and DP3R5G were prepared through saponification.Antioxidant activities（ORAC,FRAP and DPPH assay）of the delphinidin derivative were enhanced by acyl group.In comparision with deacyled cyanidin derivatives,higher antioxidant activity of acyled cyanidin derivatives were determined by FRAP and DPPH assay,while lower antioxidant activity were determined by ORAC assay.（2）The visible spectrum of CY3D5G-Fe³⁺showed a red-shift and a sharp increase of maximum absorption value compared with CY3D5G.Circular dichroisms of CY3D5G/L/S complexes（30 samples）were analysed.Thereinto,CY3D5G-L-Mg²⁺,CY3D5G-L-Zn²⁺,CY3D5G-L-Fe³⁺,CY3D5G-Fe³⁺and CY3D5G-S-Fe³⁺had chiral structure initially,while only CY3D5G-L-Fe³⁺preserved chiral structure after 24h.FT-IR spectrums showed that Fe³⁺affected C-OH stretching vibration and aglycon atomic vibration of sugars in the structure of CY3D5G.（3）Antioxidant activities（ORAC and FRAP assay）of CY3D5G were enhanced by adding flavonoids（L or S）and metal ions.CY3D5G-L-Mg²⁺exhibited the greatest antioxidant activity（ORAC assay）which was 25.66 times higher than CY3D5G.Besides,Mg²⁺and Zn²⁺enhanced cellular antioxidant activity of CY3D5G while Fe³⁺led to an adverse trend.The interaction between CY3D5G-Mg²⁺and L was synergistic,while CY3D5G,CY3D5G-Fe³⁺and CY3D5G-Zn²⁺exerted an additive interaction with L for cellular antioxidant activity.（4）The thermal degration kinetics of CY3D5G complexes were followed the first-order kinetics equation.In addition,thermal stabilities of CY3D5G-Mg²⁺,CY3D5G-L-Mg²⁺and CY3D5G-L-Zn²⁺were better than CY3D5G-L at 70oC.With the increase of temperature,the total chromatism,chroma and hue of CY3D5G complexes were augmented.