Extraction And Separation Of Active Components From Hemp Leaves And Their Antioxtdant Activity Study

Hemp(Cannabis sativa L.) is annual herbaceous plants and medicine which belongs to the Cannabis sativa species of Cannabis sativa family. Nowadays, the products originating from fiber and seed in hemp were fully utilized, whereas it wastes of resources that quite a lot of hemp leaves have not been utilized. Chemical components from Hemp leaves mainly contain flavonoids, polyphenols, polysaccharides and so on, possess versatile biological activities including antioxidant, anticancer, anti-tumor, antifungal and anti-inflammatory. Therefore, the depth study of active components from Hemp leaves is significant to expand the medicinal source and increase the added value of hemp crops.With Hemp leaves as the raw material, the crude polysaccharides from Hemp leaves was studied the extraction conditions by response surface methodology(RSM), separation and their antioxidant activity in vitro. On this basis, RSM was used to optimize the simultaneous extraction of total flavonoids (TFs) and total phenolics compounds (TPC) from Hemp leaves based on extraction rate and their scavenging capacity against DPPH free radicals. The research results show that the optimum extraction conditions of the crude polysaccharides were as follows:ratio of water to raw material 22:1 (mL/g), extraction time 98 min, extraction temperature 97℃, extraction number 3 times. Under these conditions, the experimental value was 3.38±0.08% closed to the predicted values 3.41%, which is well in close agreement with value predicted by the model. The crude polysaccharides were purified by Sevage method, macroprous resin chromatography and isolated by DEAE-52, Sephadex G-100 column chromatography.Two fraction polysaccharides(HLP-A and HLP-B) were composed of ribose, rhamnose, arabinose, xylose, mannose, glucose and galactose with molecular ratios of 0.44:0.38:0.47:0.40:0.64:1.00:0.56 and 0.03:0.08:0.23:0.10: 1.01:1.00:0.39; their molecular weight distributions were 1626.5 Dal and 54923.2 Dal. Their IR spectrum revealed the characteristic absorption peaks of polysaccharides at 4000-400 cm-1. Antioxidant activity tests were performed with HLPs、HLP-A and HLP-B, and the Vc was positive control. The IC50(mg/mL) of hydroxyl free radicals scavenging were 0.449,0.563 and 0.331; the IC50 (mg/mL) of DPPH free radicals scavenging were 3.82,14.94 and 1.81; the ferric reducing activity power (FRAP) values were 0.941,0.444 and 1.653, when the concentrations of them were 1 mg/mL. For antioxidant activities in vitro, HLP-B had stronger than HLPs and HLP-A in certain antioxidant models.The optimum process conditions for simultaneously increasing the yields of TFs and TPC were found to be extraction at 60℃ for 133 min with an ethanol concentration of 65% and a liguid-to-solid ratio of 30:1 (mL/g). The actual extraction rate and their scavenging capacity of TFs and TPC under the optimized conditions were 2.01 ± 0.22%,1.84 ± 0.32% and 77.63 ± 2.15%, respectively, which is well in close agreement with value predicted by the model.