| Coreopsis tinctoria Nutt. is a plant that belongs to the Asteraceae family anddistributes mainly in alpine regions with altitude above3000m in hetian in XinjiangUygur Autonomous Region, now is grown in south and north of Xinjiang. It istraditionally used as tea-like beverage and pharmacological research results showedthat the extractions have obvious activities, such as cytoprotective, reducedhyperglycaemia, against hyperpiesia and hyperlipemia, strengthen blood,anticoagulation and microcirculation, antioxidant acivity. Along with the increasing ofacreage and production, it is necessary to develop the further deep processing to meetmarket demand. On the basis of comparison on volatile components of Coreopsistinctoria Nutt. grown in different areas, the extraction processes on active componentsof Coreopsis tinctoria Nutt. and its antioxidant activity were studied by using differentsolvent extracts in this paper. Moreover it was focused on extraction process with thesubcritical water of Coreopsis tinctoria Nutt.. The main works are as follows:The volatile components of Coreopsis tinctoria Nutt. from different extractmethods were analyzed by GC-MS, and the differences and similarities werecompared between two cultivars by SPME-GC-MS. The data did not indicate a majordifference in components between the two cultivars except in terms of the relativepercent content of the components, but an obvious difference was observed when theessential oils were extracted by using three different methods, namely SubcriticalWater Extraction (SW), Hexane Extraction (HE) and Steam-Distillated (SD). Theanalysis results for volatile components by SPME-GC-MS showed that hydrocarbons(include terpene) were the main composition, and limonene was the most abundantmonoterpene hydrocarbon, followed by-myrcene and-pinene, the relative contentof hydrocarbon compound reached above85%, dihydroactinidiolide was newlydetected in essential oils from the plant. For the essential oils obtained by usingdifferent extraction methods, limonene was also the most abundant components in HEand SD, however,(Z)-9-octadecenoic acid methyl ester was the main component inSW which relative content achieved16.01%. In the SW method revealed the presenceof high quantity of esters, which relative content reached49.82%; and hydrocarbons(include terpene) were still the main compounds in HE and SD, and they account for 40.89%,71.42%, respectively.Secondly, compare the antioxidant activity of different solvent extracts fromCoreopsis tinctoria Nutt.. The sample was extracted by95%ethanol,50%ethanol,acetone and subcritical respectively, which was pre-processed by using with thesupercritical CO2extracted and4different solvent extracts was obtained. Antioxidantactivities of4sample above-mentioned were evaluated by observing their scavengingcapacity about two different kinds of free radicals-DPPH radicals and hydroxylradicals, and the content of flavonoids and polyphenols were analyzed for comparison.The results shown that all those extracts have antioxidant ability, but were weakcompared with a comparison (BHT or rutin, or Trolox, and so on). In DPPH radicalscavenging assay:50%ethanol extracts have the highest scavenging activity andacetone extracts have the weakest scavenging activity, in hydroxyl radicalsscavenging assay: subcritical extracts have the highest scavenging activity andacetone extracts have the weakest scavenging activity, and the results shown that therewas a positive correlation between the contents of flavonoids and polyphenol andantioxidant activity.Thirdly, optimize the subcritical water extraction processes to extract thepolyphenols compounds and flavonoids from Coreopsis tinctoria Nutt.: a processusing water of in different temperatures. The total polyphenols compounds content,total favonoids compounds content and antioxidant activity were determined in allthe extracts obtained. The process performance was evaluated with respect to yield ofboth polyphenols and favonoids in the raw materials. The results suggested thattemperatures can influence the yield of favonoids, as a result, the flavonoids contentdecreased more than180℃, but no influence in the yield of polyphenols. With respectto the antioxidant activity, the extracts obtained from Coreopsis tinctoria Nutt.presented high antioxidant activities.Finally, Random-Centroid Optimization (RCO) methodology has been usd tooptimize the extraction technology of flavonoids and polyphenols from the Coreopsistinctoria Nutt., and subcritical water as a solvent. After two rounds of optimizationexperiments, the optimum extraction conditions were determined namely: extractiontemperature160℃, solid-liquid ratio0.04, extraction time47min. At the conditions, 15.81%of the yield were obtained for flavonoids, and10.04%for polyphenols. Thetotal yields of flavonoids and polyphenols reached25.85%. To isolate and purifyflavonoid of subcritical water extract, fractional extraction was conducted anddifferent polar parts was obtained including non-polar and chloroform, ethyl acetate,n-butanol and water. Then the ethyl acetate parts were isolated by solvent extractioncombining with recrystallization technology, and one main flavonoid was achieved.Furthermore its structure was identified as isokanin-7-O-β-D-galactoside by means ofmelting point determination, TLC, UV, IR,1H-NMR and13C-NMR, and so on. |
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