Extraction and Yield Optimisation of Fucose, Glucans and Associated Antioxidant Activities from Laminaria digitata by Applying Response Surface Methodology to High Intensity Ultrasound-Assisted Extraction.

Marco Garcia-Vaquero,John O’Doherty,Gaurav Rajauria,Brijesh Tiwari,Torres Sweeney

doi:10.3390/md16080257

Abstract

The objectives of this study were to employ response surface methodology (RSM) to investigate and optimize the effect of ultrasound-assisted extraction (UAE) variables, temperature, time and amplitude on the yields of polysaccharides (fucose and total glucans) and antioxidant activities (ferric reducing antioxidant power (FRAP) and 1,1-diphenyl-2-picryl-hydrazyl radical scavenging activity (DPPH)) from Laminaria digitata, and to explore the suitability of applying the optimum UAE conditions for L. digitata to other brown macroalgae (L. hyperborea and Ascophyllum nodosum). The RSM with three-factor, four-level Box-Behnken Design (BBD) was used to study and optimize the extraction variables. A second order polynomial model fitted well to the experimental data with R2 values of 0.79, 0.66, 0.64, 0.73 for fucose, total glucans, FRAP and DPPH, respectively. The UAE parameters studied had a significant influence on the levels of fucose, FRAP and DPPH. The optimised UAE conditions (temperature = 76 °C, time = 10 min and amplitude = 100%) achieved yields of fucose (1060.7 ± 70.6 mg/100 g dried seaweed (ds)), total glucans (968.6 ± 13.3 mg/100 g ds), FRAP (8.7 ± 0.5 µM trolox/mg freeze-dried extract (fde)) and DPPH (11.0 ± 0.2%) in L. digitata. Polysaccharide rich extracts were also attained from L. hyperborea and A. nodosum with variable results when utilizing the optimum UAE conditions for L. digitata.

Highlights

Macroalgae are a diverse group of organisms capable of adapting to the extreme marine environmental conditions by producing multiple bioactive compounds
There was considerable variation in the results obtained across the different parameters with ranges for: fucose (900.6 to 1257.7 mg/100 g ds), total glucans
The highest yields of fucose (1257.7 mg/100 g ds) were obtained at an ultrasonic amplitude of 70%, at 80 ◦ C for 30 min, while total glucans were maximum (1014.4 mg/100 g ds) using higher amplitudes (100%) and lower temperature and time during Ultrasound-assisted extraction (UAE) (60 ◦ C for 10 min)

Summary

Introduction

Macroalgae are a diverse group of organisms capable of adapting to the extreme marine environmental conditions by producing multiple bioactive compounds. Marine macroalgae are considered a rich source of micro- and macronutrients with antioxidant activities, i.e., minerals, carotenoids, phenolic compounds, proteins and polysaccharides [1]. Macroalgal polysaccharides, fucoidan and laminarin have a wide range of biological activities such as antioxidant, immunostimulatory and anti-microbial both in vitro and in vivo [2,3]. Mar. Drugs 2018, 16, 257 α-L-fucopyranose residues [4]. Drugs 2018, 16, 257 α-L-fucopyranose residues [4] These polysaccharides are an integral part of the cell walls of brown macroalgae, playing a crucial role in the protection of seaweeds against environmental challenges [5]

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Conclusion