Anti-tumor Activity Of Enzymatic Hydrolysates Of β-1, 3-glucan From Saccharomyces Cerevisiae

β-1,3-glucan from yeast (Saccharomyces cerevisiae) is a biological responsemodifier with high efficiency and low side-effect. However, its application is constrainedbecause of the low solubility. Hydrolysis of yeastβ-1,3-glucan byβ-1,3-glucanase is agreat method to increase the solubility ofβ-1,3-glucan, which will widen its application inmedicine, food and cosmetic industry. Utilizing yeastβ-1,3-glucan as materials, solubleyeastβ-1,3-glucan with large molecular weight was obtained by theβ-1,3-glucanase fromTrichoderma strain LE02 and separated by ultrafiltration, and the antioxidative actixity invotro, and the antitumor and antioxidative actixities in vivo of soluble yeastβ-1,3-glucanwere studied. The main results were as follows:Ⅰ. The enzymatic hydrolysis conditions of yeastβ-1,3-glucan were studied. Yeastβ-1,3-glucan was hydrolyzed by theβ-1,3-glucanase from Trichoderma strain LE02, andeffects of substrate concentration, enzyme amount, reaction temperature and reaction pHon yield of soluble polysaccharides were studied. The optimum conditions of enzymatichydrolysis were 20％substrate with 4 U/mL enzyme were incubated at 55℃in pH4.5buffer for 2 h. The hydrolysates separated through Sephadex G-100 included threefractions: high-molecular-weight polysaccharides (FractionⅠ), oligosaccharides(FractionⅡ), and low-molecular-weight oligosaccharides (FractionⅢ). The ratio ofFractionⅠdecreased while FractionⅢincreased rapidly as theβ-1,3-glucan washydrolyzed. The molecular weight distribution of the hydrolysates hydrolyzed for 2 h wasanalyzed by gel-permeation chromatography (GPC) and over 66.2％fraction had themolecular weight larger than 30 kD.Ⅱ. Yeast glucan hydrolysates were separated by ultrafiltration. Effects of membrane,temperature, pressure and time of the filtration on yield of soluble polysaccharides andmembrane flux were studied. Water soluble glucan I (WSGI) (Mw＞10kD) and WSGII(Mw＜10 kD) were separated and purified when the yeast glucan hydrolysates werefiltrated under 0.2 MPa and 40℃for 90min through the membrane PES-10. The ratio ofthe total sugar content of WSGI (24.23 mg/mL) to that of WSGII (4.52mg/mL) were 5.26.And the percentage of the soluble sugar in WSGI was 94.8％.Ⅲ. Effects of WSGI on hemolysis of rat RBC, rat liver homogenate and MDAformation in rat liver mitochondria in votro were studied. Hemolysis of rat RBC, rat liverhomogenate, MDA formation and swelling of rat liver mitochondria were inhibited in adosage-dependent manner by WSGI in the tested concentration. The results showed that WSGI had antioxidate activity to organelle (mitochondria), cell (red blood) and tissue(liver) of rats.Ⅳ. Antitumor activity and antioxidate activity of WSGI in vivo were studied. Effectsof different administration routines of WSGI, water soluble glucan andcarboxylmethyl-glucan were compared on Tumor inhibition rate, Thymus index, Spleenindex, and the malondialdehyde (MDA), superoxide dismutase (SOD) and glutathioneperoxidase (GSH-PX) were examined. The results showed that WSGI could remarkablyinhibit the growth of S180 in a dosage-dependent manner and the inhibition rate of 200mg/kgod group was 49.84％. The antitumor activity of WSGI by intraperitoneal injectionwas higher than that of by gavage. And the antitumor activity of WSGI was higher thanthat of CMG. WSGI could enhance the bowel index of S180-bearing mice and reducedthe level of MDA and increased the activities of SOD and GSH-Px in liver of mice.WSGI had high antitumor and antioxidant abilities. The antitumor activity of WSPII(Mw＜10 kD) could not be observed.