Studies On Extraction, Seperation Of Total Flavonoids And Dendrobine And Antioxidant Activity Of Total Flavonoids From Dendrobium Nobile Lindl.

Dendrobium, the second largest genus of Orchidaceous, has a broad bioactivities. In this research, Dendrobium nobile Lindl. was picked from Chishui area, Guizhou Province, and used as the raw material. Drying methods, simultaneous extraction and synchronized separation processes of total flavonoids and dendrobine from Dendrobium nobile Lindl. were studied. Moreover, the antioxidant activity of purified total flavonoids was also evaluated. The present study provided theoretical basis and technical support for the effective and rational development and utilization of Dendrobium nobile Lindl.. The main contents and results were as follows:(1) The determination methods of total flavonoids and dendrobine from Dendrobium nobile Lindl. were established by spectrophotometry(NaNO2-Al(NO3)3-NaOH) and HPLC. Results showed that the two methods had favorable stability and repeatability with a high recovery. The contents of total flavonoids and dendrobine in Dendrobium nobile Lindl. were 4.973 mg/g and 2.326 mg/g, respectively.(2) Different drying methods of Dendrobium nobile Lindl. was studied. Taking water content under 12% as index, technological parameters of different drying methods(hot air drying, microwave drying, hot-air combined with microwave drying, combination drying of microwave and hot-air coupling fixation process) were determined. Compared to the effect of different drying methods on functional components content and cost, microwave drying was the most optimal one. The contents of total flavonoids and dendrobine in Dendrobium nobile Lindl. product dried by microwave were 0.407% and 0.180%, respectively. Drying time was 40 min, much shorter than other 3 drying methods. Moreover, the drying cost and equipment investment was the lowest.(3) The simultaneous extraction process of total flavonoids and dendrobine from Dendrobium nobile Lindl. was studied. Ionic liquid was first applied to the extraction of total flavonoids and dendrobine from Dendrobium nobile Lindl. by the ultrasonic and microwave assisted extraction(UMAE) technique. The optimal UMAE conditions obtained by response surface methodology were as follows: 1.0 mol/L [Bmim]BF4 as solvent, solid-liquid ratio of 1:22(W/V), microwave irradiation power of 328 W, extraction time of 185 s. Under the condition, the average yields of total flavonoids and dendrobine were 0.490% and 0.224%, respectively. Compared with heating reflux extraction(HRE), the average yields of them were increased by 14.22% and 23.76%, while the extraction time were reduced from 90 min to 185 s.(4) Macroporous resin was used to separate total flavonoids and dendrobine synchronously, and the recovery of the ionic liquid was also explored. By static and dynamic experiments and adsorption kinetic studies, AB-8 was selected to separate and purify the total flavonoids and dendrobine synchronously, and both of their adsorption isotherms were well fitted to Langmuir equation model. Then the dynamic adsorption and desorption conditions were further optimized, and the results were shown below: at the temperature of 25℃, the sample concentration was 0.392 mg/m L(total flavonoids concentration) and 0.180 mg/mL(dendrobine concentration), loaded at the rate of 1 BV/h, after absorption equilibrium, eluted with gradient concentrations(0, 20%, 50% and 80%) of alcohol each 4 BV, total flavonoids existed in 50% effluent fraction with a 20.89% purity and a recovery of 79.43%, and dendrobine in 80% effluent fraction with a 61.04% purity and a recovery of 86.49%. The ionic liquid was recovered from sample effluent and water eluent with a recovery of 93.67%, then reused to extract total flavonoids and dendrobine, and their yields were 0.483% and 0.223%, respectively. Therefore, the ionic liquid could be reused.(5) The antioxidant activity of purified total flavonoids was studied by three different systems(DPPH·, O2-·and Fe2+). Compared to corresponding positive controls, the purified total flavonoids from Dendrobium nobile Lindl. showed an obvious scavenging capacity to DPPH·and O2-·, and Fe2+-chelation ability in some degree. When the concentration of purified total flavonoids was 1.0 mg/m L, DPPH·scavenging capacity reached 83.01%, O2-·scavenging capacity was 78.64%, while Fe2+-chelation ability was 33.43%. By comparing IC50, the order of antioxidant activity was DPPH·> O2-·> Fe2+. It demonstrated the antioxidant activity of purified total flavonoids from Dendrobium nobile Lindl.