Abstract
The green seaweed, <i>Monostroma nitidum</i>, is widespread in Japan. In Okinawa Prefecture, the production of seaweed is performed using culture-nets that are seeded artificially. Algae contain a soluble polysaccharide, rhamnan sulfate. To estimate its applicability, the anticoagulant activity of rhamnan sulfate was investigated. Rhamanan sulfate was fractionated by ion-exchange chromatography on a DEAE-sepharose column, and two fractions (A and B) were obtained. Partially hydrolyzed rhamnan sulfates with different molecular mass (C1, C2 and C3) were also prepared. The activated partial thromboplastin time (APTT) test, prothrombin time (PT) and thrombin time (TT) were applied using human plasma and compared with standard heparin (174 units/mg). The native rhamnan sulfate (molecular mass, 630 kDa; sulfuric acid content, 22.7%), fraction A (12.4%) and fraction B (27.8%) showed approximately 73% APTT activity in comparison with that of standard heparin, but fraction C2 (molecular mass, 450 kDa) had a higher activity than that of the standard (107%). On the other hand, in the PT assay, all fractions except fraction C2 and C3 (370 kDa) showed higher activity approximately 120-155% greater than that of standard heparin. The TT activity of rhamnan sulfate depended on the sulfate content, and that of fraction B, which has high sulfuric acid content (27.8%), was 135-173% greater than that of heparin. The sulfate groups of L-rhamnosyl residues and carboxyl group of D-glucuronosyl residue on the trisaccharide side chains of the rhamnan sulfate might interact strongly with the active site of thrombin molecules. The results and discussion suggested that rhamnan sulfate from commercially cultured <i>Monostroma nitidum</i> could be a potential anticoagulant polysaccharide.
Highlights
We isolated agar [1], methylated agar [2], fucoidan [3,4,5,6,7], alginate [5, 8, 9], κ-carrageenan [10], ι-carrageenan [11], rhamnan sulfate [12], ulvan [13] and pyruvated glucogalactan sulfate [14] from some seaweeds grown in Okinawa Islands, Japan
Rhamnan sulfate was hydrolyzed into smaller fragments with different molecular weights by a formic acid solution adjusted to pH 3.5, 2.5 and 1.5; the products were referred to as C1, C2 and C3
Rhamnan sulfate with long molecular mass >550 kDa interacted with thromboplastin and/or prothrombin molecules, resulting in the prolongation of the prothrombin time (PT) time
Summary
We isolated agar [1], methylated agar (agarose) [2], fucoidan [3,4,5,6,7], alginate [5, 8, 9], κ-carrageenan [10], ι-carrageenan [11], rhamnan sulfate [12], ulvan [13] and pyruvated glucogalactan sulfate [14] from some seaweeds grown in Okinawa Islands, Japan. The novel acetyl fucoidan from commercially cultured Cladosiphon okamuranus was isolated and characterized [5, 15, 16]. An acetyl fucoidan exhibits some biological activities, such as antitumor [15] and immune-enhancing abilities [16]. An over-sulfated acetyl fucoidan, the sulfate content of which was 32.8%, showed a significant antitumor activity in vitro [15]. The results suggested that the over-sulfated acetyl fucoidan was applicable as an anticancer drug. Acetyl fucoidan is used as a supplement in the health food, food and cosmetic industries worldwide
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