Extraction And Antioxidant Activity Of Flavonoids From Mulberry

As a health fruit of the same origin of medicine and food,the research of mulberry(Frustus Mori)has been widely concerned at home and abroad.Flavonoids,as one of the main active substances of mulberry,was one of the research hotspots in recent years.In this study,the main components of the growth and maturation process of Dashi,Hongguo,Siji and white pearl were analyzed,and the extraction methods of main flavonoids in mulberry were compared and optimized.A highperformance liquid chromatography tandem mass spectrometry(HPLC-MS/MS)method was established.The contents of seven flavonoids in mulberry were determined by HPLC-MS/MS,and the changes of seven flavonoids in four varieties of mulberry were analyzed.Finally,the antioxidant activity and stability of mulberry flavonoids were studied.The main components of four mulberry varieties were detected and analyzed.The results showed that the contents of soluble sugar and soluble solids in white pearl were the highest among the four varieties,which were 17.2°Brix and 168.33 g/kg,respectively The contents of total amino acids and total flavonoids in mature fruits were the highest,which were 2.28 mg/g and 1.33 mg/g,respectively.The results showed that the contents of citric acid,malic acid,oxalic acid and succinic acid were higher in the green and astringent period;citric acid and malic acid were the main organic acids in the color changing period;citric acid was the main organic acid in the mature period.The analysis of main components among mulberry varieties showed that white pearl was significantly different from the other three red varieties.The results showed that the ethanol extraction method was better than the enzymatic extraction method.Ultrasound assisted extraction could promote the extraction of flavonoids from mulberry.Under the condition of ultrasound,the increase of ethanol extraction method,pectinase,cellulase and complex enzymatic hydrolysis were 1%,9%,11% and 9%,respectively.The optimal extraction parameters were as follows: liquid to material ratio 30:1(m L: g),ethanol volume fraction 60%,ultrasonic time 30 min.The actual content of flavonoids from mulberry was 1.20 mg/g,which was in good agreement with the theoretical prediction.The main flavonoids in mulberry were determined by HPLC-MS/MS method.The results showed that 0.2% formic acid and acetonitrile were used as mobile phases A and B,and the flavonoids were analyzed in positive ion source mode(ESI +).When the flow rate was 0.3 m L/min,the gradient elution procedure could achieve the accurate separation of seven flavonoids,namely catechin,rutin,quercitrin,myricetin,kaempferol and isorhamnetin.The method had the advantages of low detection line and limit of quantitation,high reproducibility and accuracy,and could achieve the accurate separation of seven flavonoids.Qualitative and quantitative analysis of flavonoids in mulberry samples showed that: isorhamnetin and quercetin were the main flavonoids in mulberry,and there were significant differences in flavonoids monomer among different varieties of mulberry.myricetin was not detected in white pearl,kaempferol,catechin and quercetin were not detected in red fruit and Dashi.quercetin was only detected in white pearl.The antioxidant activity and stability of mulberry were studied.Antioxidant test showed that the scavenging ability of different mulberry flavonoids extracts was different at the same concentration.At 0-0.3 mg/m L,the DPPH free radical scavenging rate of Dashi was lower than that of the other three varieties,the ABTS free radical scavenging rate of white pearl was lower than that of the other three varieties,and the-Oh free radical scavenging rate of Siji was lower than that of the other three varieties.The study on the stability of mulberry flavonoids showed that the content of flavonoids in mulberry remained unchanged in 24 hours at low temperature(4? and-20?),and it could be stored in 9 hours at medium high temperature(20?,40?,60?);the optimum p H value of mulberry flavonoids was p H 5-7;ascorbic acid had protective effect on flavonoids,citric acid would destroy the structure of flavonoids,sodium benzoate had no effect on flavonoids.