| Ganoderma lucidum(named as Lingzhi in China), is a species of basidiomycetes which belongs to Polyporaceae of Aphyllophorales, and it is one of the most popular medicinal mushrooms in China, and other Asian countries. Previous literatures showed that Ganoderma lucidum could promote health and longevity for its numerous bioactive components such as polysaccharides, triterpenoids, ergosterols, various proteins, unsaturated fatty acids, vitamins and minerals.Ganoderma lucidum polysaccharides as the primary bioactive components have been demonstrated to possess diverse and potentially significant pharmacological activities such as anti-tumor, immuno-modulatory, anti-viral, and antioxidant functions. Nowadays, more and more polysaccharides products as functional foods have appeared in the market. Since oxidative stress induced by reactive oxygen species(ROS) generated by normal metabolic processes might attribute to some chronic diseases, such as cancer, coronary heart disease, atherosclerosis et al..GLPmay exhibited strong antioxidant properties and might be a resource for natural antioxidants exploration.Now research about GLP is relatively scattered, and it is almost focused on some kind of extraction method or research on property of GLP. Rarely research in different extraction methods of GLP systematically. In view of this, we conducted a more systematically studies of GLP in this paper, including the optimization of GLP extraction by different reinforcement methods, the separation and purification of GLP, the physical and chemical characterization of GLP and antioxidant activity in vitro.The main findings are as follows: ⑴ Extraction optimization of GLP by Ultrasonic assisted extraction(UAE) and Hot water extraction(HWE)The best conditions of HWE of GLP could be concluded that: extraction temperature, 95 ℃, extraction time, 6 h, and ratio of water to raw material, 55:1(mL/g), under these conditions, the yield of GLP was 0.66%, that was 7.6 mg/g. The best conditions of UAE of GLP through the orthogonal experiment could be concluded that: extraction temperature, 80 ℃, extraction time, 40 min, and ratio of water to raw material, 50:1(mL/g), under these conditions, the yield of GLP was 0.76%, that was 7.6 mg/g. ⑵ Extraction optimization of GLP by Ultrasonic assisted enzyme extraction(UAEE) and enzyme extraction(EE)The best conditions of EE for GLP could be concluded that: value of pH, 6.9; extraction time, 86 min; and extraction temperature, 52 ℃. Under these conditions, the experimental value was 1.32%, that was 30.9 mg/g. The optimal conditions ofUAEE for GLP extraction were the following: value of pH, 6.8; extraction time, 50 min; ratio of water to raw material, 50:1(mL/g); and extraction temperature, 54℃. Under these conditions, the experimental value was 3.09%, thatwas 30.9 mg/g, which is well matched with value 3.13% predicted by the model. ⑶Isolation and purification of GLPIsolation and purification of GLPwere deproteinized with Sevag solution and discolored by the addition of activated carbon, after GLPUAE were obtained. GLPUAE was purified by DEAE-52 cellulose chromatography and Sephadex G-100 chromatography to afford 5 fractions that were a neutral polysaccharide F1 and acidic polysaccharides F2, F3, F4 and F5, respectively. The highest content of F1 was collected and was conducted with Sephadex G-100 chromatography after GLPUAE-1 was obtained. ⑷Characterization of GLP by ultrasound assisted and conventional methodsCharacterization of GLPUAE and GLPHWE were compared. HPGPC results showed that the average molecular weight of GLPUAE and GLPHWE were 465.65 KDa and 703.45 KDa, respectively. GLPUAE was composed of mannose, rhamnose, glucose, galactose and arabinose in the molar ratio of 2.58:1.25:11.17:2.5:1, while GLPHWE was composed of the same monosaccharide in the ratio of 3.11:1.11:19.44:2.33:1. FTIR indicated that both GLPUAE and GLPHWE had the typical features bands of the polysaccharides. The results of Periodic acid oxidation and Congo red showed that GLPUAE and GLPHWE had similar glycosidic bond, but had not triple helical structure. ⑸Antioxidant activity of GLP by ultrasound assisted and conventional methodsThe in vitro antioxidant activity of GLPUAE and GLPHWE were compared by testing the scavenging abilities on 1.1-diphenyl-2-picryl-hydrazyl(DPPH), reducing power and hydroxyl radicals, and GLPHWE showed a relatively higher antioxidant activity than GLPUAE. So there had differences in molecular weight, monosaccharide composition and antioxidant activity of polysaccharides by varied extraction methods. Considering the yield of GLPUAE was higher than that GLPHWE, appropriate extraction methods should be chosen by a compromise of yield and antioxidant activity. |
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