Extraction, Separation, Purification And Structural Characterizations Of Flavonoids In Onion Skin

Allium cepa L liliaceous onion garlic, belonging to liliaceous category, is one kind of biennial herbaceous plants. Abundant of onion skins will be generated from onion processing, while onion skin is rich in bio-flavonoids flavonoids. Research on how to develop and make full use of abundant flavonoid compounds in onion skins is an important practical significance for protecting environ, saving resource, enhancing the added value of agricultural products and increasing farmer’s income.In this paper, purple onion skins were used as experiment material. The flavonoids had been systemically studied on extraction, separation and purfaction from onion, moreover, the structure of purified samples had been further identified, the main results are as follows:1. Flavonoids in onion were extracted by closed microwave extraction methods. In the extraction process, using response surface method to design the experiment process, the optimal technical parameter were as following:microwave power256W, microwave radiation time150S, solid to liquid ratio1:35g mL-1, the volume percentage of ethanol60%. Under this condition, the predicable yield of flavonoids was46.60mg g-1. In verification condition:microwave power250W, microwave radiation time145S, solid to liquid ratio1:35g mL-1, the volume percentage of ethanol60%, actual yield of46.52mg g-1was reached, which is consistent with the theoretical value.2. In the study of separation purification of flavoniods from onion skin, D101macroporous adsorption resin, Sephadex LH-20was used. Compared with the results of adsorption and desorption experiments of three kinds of macroporous, finally D101macroporous were selected as the suitable resin. The adsorption and desorption dynamic experiments results of the D101macroporous resin determined the main purifaction parameters as follow:ratio of diameter and heightl:18, concentration of flavonoids2.0mg mL-1, ethanol concentration70%, injection speed1.5mL min-1, elution rates1.0mL min-1. Under this conditions, the without purification of the onion flavonoid was9.87%, the purity of later was63.16%, it shows that the refining effect of the D101macroporous resin was obvious.3. Using Sephadex LH-20column to further separate flavonoids by D101macroporous resin, the suitable purification condition as follows:30%,50%,70%,90%methanol gradient elution, elution flow0.5mL min-1, two kinds of single components:OF1and OF2were separated from the parts of90%and100%methanol elution. After RRLC/Q-TOFMS analysis, the identified results shows OF1was quercetion, which measured by RP-HPLC, with92.11%purity. OF2was inferred as Quercetin3-p-D-glucoside in present study.