Study On Extraction, Purification And Stability Of Proanthocyanidins From Rhodiola Rosea

Rhodiola rosea is a species which comes from Rhodiola genus of Crassulaceae. As a valuable resource of the medicinal plants, Rhodiola rosea has the superordinary efficiency in health. It contains many kinds of chemical composition with physiological activation, such as salidroside, tyrosol, flavonoids and so on. However, there are only few literatures about proanthocyanidins in Rhodiola rosea at home and abroad. In this paper, the optimum extracting condition and purification method of proanthocyanidins from Rhodiola rosea, and the stability of the purified proanthocyanidins were studied. The study laid theoretical foundation for large-scale industrialization manufacture and purification of proanthocyanidins.The method of analyzing proanthocyanidins of Rhodiola rosea by spectrophotometric determination of the vanillin-hydrochloric acid method was founded. Two different methods were adopted to extract the proanthocyanidins. Through the single factor experiment and the orthogonal experimental design, the optimum extraction conditions of proanthocyanidins from Rhodiola rosea by ethanol circumfluence were showed as follows: extraction solvent was 50% ethanol (v/v), extraction temperature was 80℃, the solid- solvent ratio was 1:25, extraction time was 120 min. The optimum extraction conditions of proanthocyanidins from Rhodiola rosea by ultrasonic-microwave synergistic extraction were obtained as follows: extraction solvent was 50% ethanol (v/v), the solid-solvent ratio was 1:25, the microwave power was 200 W, the microwave time was 50 s, then ultrasonic wave treatment 20 min under the 50℃constant temperature. Under the optimum condition, the extracting ratio of the two methods were 5.43% and 4.72%, respectively.Proanthocyanidins of Rhodiola rosea was refined by macroreticular resins. According to the adsorption and desorption capacity, AB-8 was the best in five kinds of selected macroreticular resins. The adsorption and elution conditions were determined. The results showed that much impurity was removed and the purity of the proanthocyanidins was raised by separation and enriched with AB-8 resin fixed bed. The experiment was successful.The purified proanthocyanidins determined by IR and HPLC, the result showed that proanthocyanidins of Rhodiola rosea was mainly composed of (-)-epigallocatechin-3-O -gallate (EGCG), and it belonged to prodelphinidins.The stability of proanthocyanidins was studied. The results showed that the amount would decrease under the sunlight, the proanthocyanidins was likely stable at low temperature and low pH. The proanthocyanidins was stable against to antiseptic such as sodium benzoate and potassium sorbate. H₂O₂ had obvious effect on the stability of proanthocyanidins, on the contrary, Vc could protect its stability. Among different metal ions, K⁺, Mg²⁺, Na⁺ and Cu²⁺ had little influence on the stability of proanthocyanidins, but Fe³⁺, Sn²⁺ and Al³⁺ could destroy its stability.