Study On Extraction, Purification，and Activity In Vitro Of Fucoidans From Laminaria Japonica And Lessonia Nigrescen Residues

Fucoidan, an important sulfated polysaccharide in brown seaweed, has manybioactivities, such as anti-virus, anticoagulant, antioxidant and immunomodulation.Laminaria japonica and Lessonia Nigrescen are seaweeds which are commonly used asindustrial materials, and their industrial residues contain abundant fucoidan. In this article,industrial residues of Laminaria japonica and Lessonia Nigrescen were used as raw materialto establish an effective preparation technology of fucoidan. Purification and fraction offucoidan as well as its chemical composition, antioxidant activity in vitro and PTP1Binhibition activity were analysed. The results showed as follows:1. Single factor experiment, response surface methodology (RSM) and uniform designwere used to optimize the extraction technology of fucoidan from Laminaria japonica andLessonia Nigrescen residues by establishing mathematical modeling and regression model.Ultrasound assisted extraction was finally chosen as the optimal extraction method, andcomparied with CaCl2solution and hot water extraction on the basis of yield and chemicalcontent. The optimal extraction condition was as follows: ultrasound time70min, hot waterextraction time2h, extraction temperature90℃, solid to liquid ratio80(mL:g), pH=6.2. Under the optimal condition, the extraction rates of LF and NF were4.49%and3.69%,respectively. LF contained higher sulfate content but lower fucose content than that of NF.The monosaccharide composition of LF and NF (LPF and NPF) were purified by HPLC, themolar ratio of fucose and galactose in LPF was1.03:1, and contained high galactose andfucose. In addition, glucose, mannose, glucuronic acid and a small amount of rhamnose andxylose were also detected in LPF. The main monosaccharide of NPF was fucose, rhamnoseand mannose. Galactose, xylose and a small amount of glucose were also found butglucuronic acid was not detected in NPF. Molecular weights of LF and NF were142KDa and136KDa, respectively.3. LF and NF were preliminary purified by calcium chloride and ethanol separately.Ethanol method had lower yield but higher purity of fucoidan when compared with calciumchloride method. The total sugar and fucose contents of LPF and NPF were both higher afterpurification, but the content of the sulfate was reduced.4. LPF and NPF respectively were purified and fractionized by anion exchange columnchromatography. Three fractions were obtained respectively. Their chemical constituents weredifferent as follows: L1riches in higher glucose molar consistency, and also contain mannose,glucuronic acid, galactose and a small amount of rhamnose and xylose. L2contained moregalactose, other monosaccharides were also detected.Galactose and fucose content in L3was higher, however, mannose and xylose were not detected, it showed that the monosaccharidecomposition of L3was relatively simple. The main monosaccharide of N1was fucose. N2contained higher mannose and glucuronic acid, whereas rhamnose was not detected. Themonosaccharide composition of N3was similar to L3.5. The antioxidant activity assays showed that LF and NF both possessed scavenging capacityon hydroxyl radicals and superoxide anion radicals, and reducing power. The superoxideanion radical scavenging concentration (EC50value) of LF and NF were1.564mg/mL and1.506mg/mL, respectively. In vitro, LF exhibited higher antioxidant activity than that of NF.6. Fucoidan and its fractions had PTP1B inhibition activity at20μg/mL. LF and its threefractions all had inhibition activity, the inhibition rates were more than50%. LF inbibitionwas up to89.15%. NF and N1had no activity. N2and N3had better inhibition activities, andthe inhibition of N3was up to95.87%.