Effects Of Collecting Stages And Drying Methods On The Phenolic Compounds And Antioxidant Activities Of Sonchus Brachyotus DC.

Sonchus brachyotus DC.belongs to genus sonchus(family compositae),is an edible potherb with high eating quality.It also has medicinal properties,including antioxidant,anti-inflammatory,anti-tumour activity etc.The chemical components of the genus sonchus is complex,including various active ingredients such as flavonoids,terpenoids,coumarins and so on.The current research mainly focuses on sesquiterpene lactones and sesquiterpene lactone glycosides,but there are a few researches about phenolics and antioxidant activity of S.brachyotus.Drying is a common processing method for S.brachyotus,but the effect of different collecting stages and drying methods on phenolics and antioxidant activities is still unclear.The article focused on S.brachyotus,analysed phenolics and antioxidant activities of different polar composition from methanol extracts.Besides,our research detected the content and composition of phenolics and antioxidant activity of S.brachyotus in different collecting stages and drying methods.The result revealed the composition and antioxidant activity of S.brachyotus changing with collecting time,and found an optimum drying method.The research provided a scientific basis for S.brachyotus utilization and exploitation.Main results were as follows:(1)From four different solvent extracts,ethyl acetate extracts had the highest content of total phenolics and flavonoids,and the strongest antioxidant activity.(2)The nine kinds of phenolics detected in S.brachyotus by HPLC were caffeic acid,coumaric,protocatechuic,orientin prime,rutin,quercetin,luteolin,myricetin and chlorogenic acid.(3)The total phenolic and flavonoid content of S.brachyotus increased,and the antioxidant activity enhanced over collecting time from April to August.The sample collected in August had the higest content of total phenolics and flavonoids,and the strongest antioxidant activity.The effect of collecting stages on phenolics composition was analysed.The contents of chlorogenic acid,myricetin,caffeic acid,coumaric acid and quercetin in S.brachyotus collected in August were the highest;the contents of rutin,protocatechuic acid and luteolin were the highst in July;the orientin content was the highest in June.(4)Blanching pretreatment before drying could reduce the losses of phenolics in S.brachyotus.Lyophilization,microwave treatment,hot-air treatment,sun-dried and shade-dried were separately applied to the drying of S.brachyotus.By comparing the phenolic content and antioxidant activity of dried products by five methods,the freeze-drying product had the higest total phenolic and flavonoid content and strongest antioxidant activity,followed by microware drying product.Microware was more suitable methods than lyophilization,based on the comparisons of various factors such as drying cycle,the cost,the effect on active ingredients and so on.(5)There was a significant relationship between the content of phenolic compound and antioxidant activity.