Comparative Study Of Fucoidan On Extraction, Purification And Functional Activities From Five Brown Seaweeds

Fucoidan is a type of complex sulfated polysaccharide, mainly found in thecell-wall matrix of various brown seaweed species. For the past decade fucoidan hasbeen extensively studied due to its numerous biological activities, which haverevealed that fucoidan has great potential in cosmetics, functional foods andpharmaceuticals industries. But fucoidan extracted from different sources has variouscomposition, structure and biological activity. In this study, we compared fucoidanfrom five brown seaweeds on their extraction, purification and functional activities,such as food functional properties, vitro antioxidant activity and inhibitory activity ofPTP1B, which provides a theoretical basis for their development and utilization. Themain results are as follows.1. Optimization of supersonic-assisted extraction of fucoidan from Laminariajaponica using response surface methodology. To optimize the extraction parameters,the weighting values of the seperate yields of crude fucoidan（Yw）, fucose（Yf）andsulfate（Ys） were used by Minitab. Based on Uniform design experiment,3factorsand3levels Box-Behnken central composite experimental were performed toestablish the quadratic polynomial regression equation between the weighting values(Y) and the factors. The optimization condition was that ultrasonic assistant11min,hot water extraction temperature100℃, hot water extraction time2h and the ratio ofsolution to algae power35(mL:g). Under this condition, the relative error aboutprediction to the experimental result was0.0394. Besides the comparison test foundthat ultrasound not only increased the yield of crude fucoidin, lowered alginateextraction rate, but also had little effect on the content of total sugar and sulfate.2. Fucoidans were isolated from five brown algas, Laminaria japonica, Lessonianigrescens, Lessonia trabeculata, Ascophyllum mackaii and Ecklonia maxima (namely LJF, LNF, LTF, AMF, and EMF respectively), using a low-chemical approachassisted by ultrasound. The crude polysaccharide was fractionated on aDEAE-cellulose anion-exchange chromatography column, which yielded twofractions: F1(eluted with1mol/L NaCl) and F2(eluted with2mol/L NaCl). Bycomparative study of chemical analysis, we found that fucoidans from five browseaweeds show a significant difference in fucose, sulfate, molecular weight andmonosaccharide composition.AMF was determined with highest amount of fucoseand sulphates, while LJF with lowest. F1was similar to crude fucoidan inmonosaccharide composition, but F2was significantly different, which has highamount of galatose and except main sugar, has fewer monosaccharides other withlower content. Compared with other brown seaweeds, fucoidan from L. japonica hadhigh molar ratio of fucose and galactose, and F1had similar molecular weight to F2and crude one. Though the fractions were relatively homogeneous, considering thatF1mostly contained two peaks, further purification is needed.3.To explore potential applications of fucoidan as cosmetic and food ingredients,we investigated its functional properties and antioxidant properties. Except LNF andLTF, freeze-dried fucoidan had a higher solubility, and the fluffy, fibrous and irregularshape. EMF had good moisturizing function; the higher values of oil absorptioncapacity exhibited by AMF, LJF and EMF; LJF had higher foaming activity, whileAMF and EMF had better foaming stability; but the low emusifying activity wasamong all samples. Moreover, the functional properties had a high positive correlationwith the total amount of protein, bulk density and sulfate content. Their antioxidantproperties were investigated employing various established in vitro systems. Theresults showed that all fucoidans were antioxidative, however, the antioxidant abilityof them was quite different in vitro. LNF and LTF exhibited a high inhibitory effecton superoxide radical scavenging activity and hydroxyl radical scavenging activity ata low level.Available data presented there may be a combination of several factorsthat have an influence on the antioxidant activities，and the relations of reducingpower to sulfate content and molecular weight were significant.4. A comparative study of fractions from five seaweeds was conducted on their chemical analysis and infrared spectrum. It was found that the main components of F1and F2were similar, but their ratios were quite different. There were many similaritiesbetween the infrared spectrums of fractions from one seaweed, while many significantdifferences were found amond different seaweeds, which may be used to identify thesource of fucoidan.5. The PTP1B inhibition activity of fucoidan from five brown seaweeds wereinvestigated under the single concentration (20μg/ml) and optical absorptiondetection method was used to test the activity of the sample. The results showed thatexcept LNF2, LTF, AMF and EMF, the other samples had a certain degree of activity(inhibition rate>50%), especially fractions from Ecklonia maxima with highestactivity (inhibition rate>95%). The research provides a reference of fucoidan in thetreatment of diabetes and obesity.