Phenolic Profiles And Activity Study Of Dimocarpus Longan Lour

Longans?Dimocarpus longan Lour.?belong to the family Sapindaceae,which is widely distributed in the subtropical zones,such as some southeastern Asian countries and southern China.The longan is considered to have various polyphenols and nutritional components that are commonly used in Traditional Chinese Medicine to treat chronic disease,including antioxidant,antihyperlipidaemic,anti-hyperglycaemic,antitumour and anti-inflammatory activities.Currently,the discovery of antioxidants,?-glucosidase inhibitors and?-amylase inhibitors from natural materials,such as food matrices,in the development of physiological functional food or lead compounds for precaution or treatment of chronic disease is a promising topic.Therefore,the aim of the present study was to quantitatively analyse on the phenolic profiles,in vitro antioxidant activities,and?-amylase and?-glucosidase inhibitory capacities of eight different species of longans from southern China which were planted in the area of the middle and upper Yangtze River.These findings may provide a basis for evaluating regional longan resources and the development of longan medicine and food homologous food deep processing.The moisture contents of eight different varieties of longan was determined by the constant weight method,and the moisture contents were found to be above 80%.The cultivar of Shuguan had the highest moisture content,reached 89.23%.The longan pulp was dried by vacuum freeze drying and extracted with 80%methanol.The total polyphenol content?TPC?was measured by the Folin-Ciocalteu colorimetric method,ranged from 1069±55.83 to 1215.81±45.77 g gallica acid equivalents?GAE?/100 g.The total flavonoid content?TFC?was determined by the sodium nitrite-aluminum nitrate colorimetric,varied from 88.65±57.87 to 1028.54±303.82 g rutin equivalents?RE?/100 g.The ultra high performance liquid chromatography-triplet quadrupole tandem mass spectrometry?UHPLC-QqQ-MS/MS?released that the polyphenols of longans have 3 phenolic acids and 9 flavonoids,including quinic acid,gallic acid,phthalic acid,narirutin,naringin,rutin,quercetin,hesperidin,phlorizin,rhoifolin,methyl hesperidin and naringenin.The principal components analysis?PCA?indicate that the cultivars of Rongyu8 and Songfengben have nearly analogous polyphenol compounds.The in vitro antioxidant methods were evaluated by DPPH free radical scavenging ability,ABTS free radical scavenging capacity and ferric reducing ability power?FRAP?.The results of DPPH free radical scavenging capacity indicated that the capacity of the three species of Songfengben,Shuguan and Dongliang was better,there were no difference?P>0.05?,and the IC₅₀values were all 1.012 mg/mL.Dongliang has a good ABTS radical scavenging capacity of 2032.43 g VC equivalents/100 g.There was no difference in the FRAP of the eight varieties of longan at the P>0.05 level.In the evaluation of the inhibitory effect of longan polyphenols on?-amylase and?-glucosidase,Fuwan8 had the best inhibitory effect on?-amylase,reaching 97.56%;there were no difference between the inhibitory effects of?-glucosidase of Songfengben,Dongliang and FD97?P>0.05?.