It has been suggested that oxidative stress is associated with the pathogenesis of osteoarthritis (OA)1. Hyaluronic acid (HA) has been used as therapeutic option for individuals with OA. The chemical structure of HA is quite similar to other polysaccharides such as ulvan. In fact, this sulfated polysaccharide from marine algae has been reported to possess biological activity of potential medicinal value. Ulvan presents many advantages as compared to HA, due to its sulfate groups on its backbone2, which are responsible by anticoagulant and antioxidant effects. In addition, ulvan has a number of unique properties as biocompatibility, biodegradability, and non-toxicity3. The objective of this study was to determine the antioxidant and anticoagulant activities of ulvan and compare its activities to that of HA.
Materials and Methods
Ulvan was extracted from Ulva as referred elsewhere2. HA (Novozymes) is from bacterial origin. The antioxidant activities of ulvan and HA were evaluated as radical scavengers, against nitric oxide and hydroxyl radicals, and their reducing power, as previously described by Subhapradha et al 4. The anticoagulant activity of ulvan was also determined for human plasma with respect to the activated partial thomboplastin time (APTT) and prothrombin time (PT)4.
Ulvan (0.4%, w/V) directly compared with HA at same concentration, presents a much higher antioxidant capacity by scavenging hydroxyl radicals (2 mg Trolox/g of extract). Moreover, the inhibitory effect of ulvan (0.4%, w/V) on nitric oxide radicals was two times superior to HA at same concentration. The reducing power capacity of ulvan (53%) was much higher compared to HA (3%) at same concentration.
The reducing power capacity of ulvan is almost 20 times superior to HA. Ulvan exhibits anticoagulant activity on APTT assay, the clotting time at different concentrations lies between 275 - 58 s, much higher than normal conditions (23 s). However, on PT assay ulvan performed equal to normal conditions.
Discussion and Conclusions
This project demonstrates that ulvan possesses higher antioxidant performance as compared to HA by either ROS or NOS. This fact may justify a potential advantage of ulvan over HA as a bioactive molecule for cell protection in oxidative stress environments, including inflammation contexts. The anticoagulant activity observed for ulvan indicates a different mechanism of action, as compared to gold standard heparin. These results appear to demonstrate non thrombogenicity of ulvan which is highly relevant taking into account its potential application as an injectable biomaterial. The results here reported confirm ulvan as a biocompatible candidate for biomedical applications, including oxidative stress contexts.
1. Ziskoven C et al., Orthopedic Reviews, 2(2):e23, 2010; 2. Pinto AA et al, Carbohydrate Research, 2194-2200, 345, 2010; 3. Pinto AA et al., Phytotherapy Research., 1143-8, 27(8), 2012. 4. Subhapradha N et al. International Journal of Nutrition, Pharmacology, Neurological Diseases. 39-45, 3(1), 2013.