Study Of Chemical Composition And Biological Activities Of Rubus Caesius L. In Xin Jiang

Rubus caesius L. is a kind of unique edible Rubus plant in Xinjiang, which is widely distributed in the north of Xinjiang. The study on the chemical constituents and biological activities of Rubus caesius L. are rarely reported. In this paper, the chemical constituents and biological activities of Rubus caesius L.are studied in order to find highly active compounds.First, the ethyl acetate, n-butanol and water fraction of setms and leaves were prepared by organic solvent extraction and fractional extraction. Then these fractions’ flavonoid content and activities(including antioxidant activity, protein tyrosine phosphatase 1B(PTP1B) inhibitory activity and 3T3-L1 preadipocyte inhibitory activity) were determined respectively. The results show that Rubus caesius L. have high flavonoids content. The flavonoids content in stems are higher than in leaves. And the flavonoid content of stems ethyl acetate fraction is highest(685.65 ± 11.43 mg/ml). Rubus caesius L. have high antioxidant activity. The fractions have higher flavonoid content, and their antioxidant capacity are higher relatively. The different fractions of Rubus caesius L. showed inhibitory effect on PTP1 B. And stems water fraction and leaves ethyl acetate fraction have higher PTP1 B inhibitory effect(IC50 0.08±0.01 μg/ml, 0.16±0.06μg/ml respectively), which is lower than the positive control of vitriol acid sodium. The different fractions of Rubus caesius L. showed effective inhibitory effect on 3T3-L1 preadipocyte. The stems water fraction, ethyl acetate fraction, leaves water fraction have high activity, their inhibitory percentage can achieve above 75%.The extraction conditions of flavonoids and polyphenols from the leaves and stems of Rubus caesius L. was optimized by single factor experiments(including different solvents, ethanol concentration, extraction temperature, extraction time and solid-liquid ratio) and an orthogonal array design. The optimal extraction conditions were as follows: 80℃, 70 min, 60 % ethanol, and solid-liquid ratio of 1:90. Under the optimal conditions, the flavonoids content of stems and leaves is 10.51 ± 0.27mg/g and 16.32 ± 0.44mg/g respectively, polyphenol content is 76.28±1.46mg/g and 134.65±5.77mg/g respectively. The flavonoids purification was optimized by screening the different macroporous resin, static adsorption time, ethanol concentration of total flavonoids static analysis, the sample flow rate, sample volume, elution flow rate, elution volume. The optimal process were as follows: flow velocity of sample 1 mL/min, flavonoids concentration of sample 0.32 mg/m L, volume of sample 80 mL until reaching adsorption balance, dynamically eluted with 40 mL 60 % ethanol, and the desorption flow velocity was 1.5 mL/min. After separated and purified by AB-8 resin, the total flavonoids content and total antioxidant capacity significantly were improved. The total flavonoids content of leaves and stems increased 1.4 and 2.4 times, and the ABTS radical scavenging rate increased 1.7 and 2.5 times, and the DPPH radical scavenging rate increased 1.7 and 2.6 times respectively.5 compounds were isolated from ethyl acetate fractions of the leaves and stems were separated by liquid- liquid extraction, column chromatography on silica gel, pressure silica gel column chromatography, Sephadex LH-20 column chromatography, HPLC semi-preparative chromatography. Their strucures were determined by their physical, chemical properties and spectroscopic methods(MS, 1H NMR, 13 C NMR). These compounds were isolated from this plant for the first time, they are isoquercitrin, naringin, hyperoside,(-)-epicatechin 3-O-gallate(ECG), acteoside respectively.These results indicate that the leaves and stems of Rubus caesius L. have high flavonoids content and antioxidant activity, and they are potential resources of natural antioxidants. The different fractions of Rubus caesius L. show inhibitory activity on PTP1 B and 3T3-L1 preadipocyte. After the active compounds are separated, purified and identified, it will provid the scientific basis on development and utilization of antidiabetic plant medicine from Rubus caesius L.