Study On Polysaccharide Extracted From Ulva Pertusa Kjellm (Chlorophyta) And Its Derivatives

Ulva pertusa has been utilizing for medical purpose for centuries in China. The decocta of algae was traditionally used by local inhabitants to treat sunstroke and urinary diseases. The previous work carried out showed that the water-soluble polysaccharide from U. pertusa has a favorably antihyperlipidemic activity. Based on the literatures, studies were concentrated on subchronic (6 months) toxicity, general pharmacology, derivatives of ulvan, antioxidant activity of different molecular weight ulvans, antioxidant activity and antihyperlipedemia of derivatives.The polysaccharide was prepared by water extraction and ethanol precipitation. Polysaccharide was determined to be mainly composed of uronic acids, rhamnose, xylose, glucose and sulfate with smaller amounts of arabinose, manose and galactose. The predominantly repeating disaccharide units are [β-D-GlcpA-(1->4)-α-L-Rhap 3S] and [α-L-IdopA-(1->4)-α-L-Rhap 3S]. The acute and toxic tests of polysaccharide showed that MTD of KM mice was higher than 4000 mg/kg, and LD50 for female KM mice was 408.7 mg/kg and male animals 432.7 mg/kg, respectively. Subchronic toxicity (6 months) experiment showed that the non-observed effect dose (NOED) of ulvan from U. pertusa is 1200 mg/kg body weight per day. General pharmacology indicated that ulvan had no obvious influence on nerve system of rats and no obvious influence on breath and cardiovascular system of narcosis dogs.Different molecular weight ulvans were obtained by the degradation methods of hydrogen peroxide, and their antioxidant activity in vitro were determined. High sulfate content, acetylated and benzoylated derivatives of ulvan were prepared, and their antioxidant activity and antihyperlipedemia were determined. The results proved that different molecular weight ulvans had different antioxidant activity. Moreover, the antioxidant activity increased with the decreasing of molecular weight. The derivatives of ulvan showed stronger antioxidant activity than ulvan. The antihyperlipedemia animal experiment indicated that ulvan and its derivatives possessed antihyperlipedemic activity. Furthermore, high sulfate content derivative had more pronounced activity than ulvan, but the difference was not considered to be statistically significant. Low and middle dose of high sulfate content ulvan have more pronounced antihyperlipedemic activity than high dose, except on LDL-C, moreover, the middle dose of HSU showed stronger activity on TG (P<0.01) and LDL-C (P<0.01) than ulvan. Low dose of acetylated ulvan showed stronger activity on decreasing TG and LDL-C than high and middle dose. The antihyperlipedemic mechanism of ulvan and its derivatives needed to be further studied.