Preparation, characterization, radical scavenging property and antidiabetic potential of laminarioligosaccharides derived from laminarin.

Laminarin is a polysaccharide (dietary fibre), rich in marine brown seaweed. Derived low molecular weight
polysaccharides exhibit various biofunctional properties including antitumor, anti-apoptotic, anti-inflammatory,
antiobese and antioxidant activity. Hence, the present study aimed to hydrolyse laminarin using 0.2 M Hydrochloric
acid (HCl) into laminarioligosaccharides and their characterization and evaluation of antioxidant, antidiabetic
(α-amylase and α-glucosidase inhibition) properties in vitro. Thin layer chromatography (TLC) revealed
the hydrolysis of laminarin up to 7 laminarioligosaccharides, also the hydrolysis pattern was validated by ultraperformance
liquid chromatography (UPLC) and 1H and 13C NMR. Mass spectrometry investigation confirmed
the molecular mass of laminarioligosaccharides. 1H and 13C NMR revealed that the laminarioligosaccharides has
both β(1–6)-linked and β(1–3)-linked glucose. Further, 2 h hydrolysate showed higher reductive capability (20 μg
saccharide equivalent to 7.1 μg quercetin) and total antioxidant activity (20 μg saccharide equivalent to 6.7 μg
vitamin C). The percent inhibition of 2 h hydrolysate was 42.9% (IC50-15.7 μg/mL) in 2,2-diphenyl-1-picrylhydrazyl-
hydrate (DPPH) assay and 27.4% (IC50-28.4 μg/mL) in 2,2′ -azino-bis (3-ethylbenzothiazoline-6-sulfonic
acid (ABTS) assay. Additionally, 2 h laminarioligosaccharides showed maximum inhibition of α-amylase
(30 μg- 32.2% inhibition, IC50-46.6 μg/mL) and α-glucosidase (30 μg- 58.8% inhibition, IC50-25.5 μg/mL) activity.
Thus, HCl hydrolysis of laminarin to laminarioligosaccharides could be a promising method for obtaining
low molecular weight saccharides with enhanced biological activities.