br Acknowledgement We gratefully acknowledge

Acknowledgement We gratefully acknowledge the Department of Food Science and Technology, Ferdowsi University of Mashhad for financial support of this work.
Introduction Fungal polysaccharide, a kind of active organic compound, is found in the mycelium, fruiting bodies, and fermentation broth of large medicinal and edible fungi [1]. In recent years, polysaccharides derived from fungi have become an important source of bioactive substances. A polysaccharide from the fungus, Polyporus umbellatus, a polymer of glucose primarily linked by β (1→3) glycosidic bond, has been shown to be capable of decimating tumor cells [2]. Further investigations revealed that the tertiary structure, rather than the primary structure, is the major determinant of the pharmacological activities of this fungal polysaccharide. It has been suggested that a polysaccharide with both β (1→3) and β (1→6) or with both β (1→4) and β (1→6) glycosidic bonds, instead of purely β (1→4) glycosidic bond, is generally more pharmacologically active [3,4]. The structures of polysaccharides from several edible and pharmacologically active fungi have been elucidated. The main chain of lentinan polysaccharide is linked by β (1→3) glycosidic bond, while the side chains branch out at C6. There are three types of side chains, namely, side chains with β (1→6) glycosidic bond only, short side chains with β (1→3) glycosidic bond only and side chains with a non-reducing end [5]. The polysaccharide of fruiting body from the glossy ganoderma, Ganoderma lucidum, is made up of fucose, xylose and mannose at a molar ratio of 1:1:1. The main chain is a polymer of -mannose linked by (1→4) glycosidic bond, and the side chains, which are polymers of fucose and xylose, branch out at C3 of the mannose on the main chain [2]. The insoluble polysaccharide from the Chinese caterpillar fungus, Cordyceps sinensis, is a glucosan with a molecular weight of 632kDa [2], while the acidic tremellan consists of a main chain made up of mannose linked by α (1→3) and side chains that are polymers of glucuronic PF-573228 manufacturer and xylose [6]. However, to our best knowledge, there has been no report on biochemical properties of the polysaccharide from the mycelium of P. umbellatus. The anti-microbial activities of extracts from fermented fungi have been reported for numerous fungal species, such as Cordyceps sinensis[7], Ganodorma lucidum[8], and Lactarius deliciosus[9]. However, very little is known about the anti-microbial activities or pharmacological activities of extracts of fermented mycelium of P. umbellatus. Hence, the objectives of the present investigation were to characterize the biochemical properties of polysaccharides purified from the mycelium and fruiting body of P. umbellatus and test anti-microbial and immune activities of these polysaccharides.
Materials and methods
Results and discussion The elution profile was shown in Fig. 1. UV scan at 260nm and 280nm exhibited no absorption, suggesting that there was no nucleic acids or proteins. HPLC analysis of hydrolysis products of these two polysaccharides (Fig. 2) showed that the polysaccharide from the fruiting body of P. umbellatus consisted of glucose and galactose at a molar ratio of 5.42:1, and the one from mycelium of this fungus was also made up of glucose and galactose but at a molar ratio of 1.57:1. The molecular weights of these two polysaccharides were 679kDa for the one from the fruiting body and 857kDa for mycelium polysaccharide according to the HPLC results (Fig. 3). It has been noted that the anti-tumorogenicity of a polysaccharide is related to its molecular weight, with the minimum molecular weight for anti-tumorogenicity of 10kDa [2]. The molecular weights of the two polysaccharides were greater than 10kDa, suggesting that these two fungal polysaccharides may possess anti-tumor activity. NK and LAK cells play an important role in immune defense. In the present investigation, alterations in the potency of these cells in killing NK-specific target cells (YAC-1 cells), NK-non-specific cells (P815), Lewis lung cancer cells (Lewis) and liver cancer cells (HAC) after dietary treatments with P. umbellatus polysaccharides were examined. The potency in killing P815 cells of NK cells from mice fed with the single formula containing P. umbellatus polysaccharide was 19%, greater than that of the blank group (13.06%) (Table 2). In other words, dietary treatments with the mycelium polysaccharide resulted in a 60% increase in the killing potency of NK cells. But this dose of mycelium polysaccharide had no effect on the killing potency of LAK cells. Dietary treatments with three doses of the mixture formula resulted in greater P815-killing potencies of LAK relative to the control, with the highest dose being the most potent (Table 2). Treatments with polysaccharide mixture increased the potency of LAK cells in killing HAC, Lewis and YAC-1 in a dose-response manner. These results strongly suggest that P. umbellatus polysaccharides, when given alone or in mixture with other fungal polysaccharides, increase the activity of immune cells.