Preparation And Activity Study Of Anthocyanin Microcapsules From Lycium Barbarum

Lycium ruthenicum Murr.,a member of the Lycium genus in the Solanaceae family,growing on the desert areas of Qinghai-Tibetan plateau in China,is a unique salt-tolerant and drought-resistant wild plant in Northwest China.The fruit of L.ruthenicum contains a lot of anthocyanins,which has strong coloring power and low toxicity,so it has attracted wide attention because it has more activity and can be used as a potential food color enhancer.However,the stability of anthocyanin is poor,and it is easy to be degraded by pH,light,high temperature,oxygen and metal ions,among which pH and temperature are the most important.In addition,the strong antioxidant capacity of anthocyanins can consume the necessary oxygen in the process of tyrosinase catalytic reaction and inhibit the activity of tyrosinase.Therefore,it is of great practical significance to study the methods suitable for industrial preparation of anthocyanins,to improve the stability of anthocyanins and to study the activity of anthocyanins and their microcapsules.The main contents of this research are as follows:1.In this experiment,anthocyanin microcapsules from L.ruthenicum dried fruits were prepared by freeze-drying method.The effects of hydroxypropyl-β-cyclodextrin(HP-β-CD),chitosan(CS),encapsulation time,pH value and stirring speed on the entrapment rate,tyrosinase inhibitory activity,DPPH radical scavenging activity and ABTS radical scavenging activity of L.ruthenicum anthocyanin microcapsules were investigated.On the basis of single factor,the optimal condition was 66 min of preparation time,0.2 mg/mL of CS concentration and 1.93 mg/mL of HP-β-CD concentration.Under this condition,encapsulation efficiency,tyrosinase inhibitory activity,DPPH radical scavenging activity and ABTS radical scavenging activity of L.ruthenicum dried fruits anthocyanin microcapsules were 84.28 ± 0.34%,50.75 ± 0.78%,54.88 ± 0.67%and 60.35 ± 0.5456%respectively.2.FT-IR and XRD were used to support the formation of L.ruthenicum dried fruits anthocyanin microcapsules.The characteristic absorption peak of anthocyanins of L.ruthenicum did not appear in the FT-IR spectrum of the microcapsule at 1514 cm-1,indicating that the anthocyanins of L.ruthenicum had formed an inclusion complex with CS and HP-β-CD.In the XRD spectrum of anthocyanin microcapsules,all the characteristic peaks of anthocyanins of L.ruthenicum,CS and HP-β-CD had disappeared,which also indicated that the anthocyanin microcapsules had been successfully prepared.3.This study involves the effects of pH,temperatures and simulated oral and gastrointestinal conditions for the stabilities of anthocyanins and microcapsules from L.ruthenicum.Anthocyanin retention rate is regarded as indicator to assay the stabilities of anthocyanins and microcapsules from L.ruthenicum.The results showed that,anthocyanin microcapsules from L.ruthenicum improved the pH stability ranged 4 to 7;anthocyanin microcapsules from L.ruthenicum(0.5～1 mg/mL)increased the thermal stability from 90 to 98 ℃;anthocyanin microcapsules from L.ruthenicum(0.5～3 mg/mL)enhanced the thermal stability from 60 to 98℃;anthocyanin microcapsules from L.ruthenicum presented good release behavior under simulated gastrointestinal conditions compared with unencapsulated anthocyanin.4.This study aimed to research the antioxidant activities,tyrosinase inhibitory capacity and the melanin synthesis inhibitory activity in B16 mouse melanoma cells.The results showed that,compared with anthocyanins from L.ruthenicum,anthocyanin microcapsules have lower 1-diphenyl-2-picrylhydrazyl(DPPH)radical scavenging capacity,2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid(ABTS)radical scavenging capacity,hydroxyl radical scavenging capacity and superoxide radical scavenging capacity respectively,which means it has poorer antioxidant activity;L.ruthenicum dried fruits anthocyanins had inhibitory effect on tyrosinase monophenolase(IC50=1.483 ± 0.058 mg/mL),and the type of inhibition was competitive inhibition(Ki=39.83 ± 1.4 mg/mL),the maximum inhibitory activity of L.dried fruits anthocyanins(3.00 mg/mL)on tyrosinase diphenolase was 42.16± 0.77%,and the type of inhibition was anti-competitive inhibition(Kis=2.387 ± 0.10 mg/mL);microcapsules have poor tyrosinase inhibitory capacity;microcapsules could significantly inhibit the melanin synthesis in B16 mouse melanoma cells.