Molecular characteristics and antioxidant activity of laminarin extracted from the seaweed species Laminaria hyperborea, using hydrothermal-assisted extraction and a multi-step purification procedure

摘要

The objective of this study was to determine the effect of hydrothermal-assisted extraction (HAE) and a multi-step purification process on the molecular characteristics and antioxidant activity of extracts of laminarin from the brown seaweed Laminaria hyperborea. The HAE with optimised extraction conditions (time - 30 min; temperature - 99.3 degrees C; sample to solvent ratio - 1:21.3 (w/v)) resulted in 368 mg/g laminarin in the Crude Extract. Purification using solvents, molecular weight cut-off filter (MWCO; 10 kDa) and solid-phase extraction (SPE) improved the concentration to 542.6 mg/g, 906.6 mg/g and 862.5 mg/g on dry weight extract basis, respectively (p 0.05). The crude HAE extract had greater antioxidant activity, as determined by 1,1-diphenyl-2-picryl-hydrazyl radical scavenging and ferric reducing antioxidant power assays, than the purified fractions (p 0.05). The identification of a chromatographic peak at 17.66 min (retention time) and FT-IR (Fourier transform infrared) absorption bands at 1420 cm(-1) (carboxyl groups), 2950 cm(-1) (C-H stretch) and at 2410 cm(-1) (transmitting angle peak) was similar between the purified samples and a laminarin standard that was used as a control, confirming the presence of laminarin. The quadruple time of flight mass spectrometry (Q-ToF-MS) confirmed the molecular weight of purified laminarin was in the range of 5.7 kDa-6.2 kDa. HAE under optimised conditions was an effective method to recover biologically active laminarin from L. hyperborea. A multi-step purification, involving solvents and MWCO filters in a sequence could improve the purity of laminarin, however, purification reduced the antioxidant activity compared to the crude HAE extract.