Abstract
Aqueous extracts from Ascophyllum nodosum brown edible seaweeds were obtained after continuous ultrasound-assisted extraction. The effect of sonication time (from 2 to 6 min), sonication amplitude (from 80 to 100%) and solvent-solid ratio (from 20 to 40 g water g−1 dried seaweed) on the extracts features was studied employing a Box-Behnken experimental design. Extracts were characterised by polyphenols, carbohydrate and uronic acid content. Response surface method (by means of a quadratic model) was successfully employed to relate chemical composition of extracts and operation conditions. Optimal experimental conditions were established to obtain maximal polyphenols content and several polyphenols-carbohydrates ratios together with the conditions that minimise energy consumption per extracted polyphenols amount relationship. Antioxidant capacities of extracts were measured employing different methods (DPPH, FRAP and ABTS). Positive linear correlations between antioxidant activity and total polyphenols content were established.
Highlights
High seaweeds content of polysaccharides, polyunsaturated fatty acids, minerals, fibre, vitamins and antioxidant bioactive molecules (Pereira 2011) put algae in the spotlight to be used in several applications such as medicine, Nowadays, the algae-based refinery concept is promoted
The significant effect on the uronic acids content (UA) was contributed by the linear terms A and S and interaction terms AS and time-liquid–solid ratio (tS). These results indicated that liquid–solid ratio, as well as their interactions with amplitude and time, played a prominent role in the Ultrasound-assisted extraction (UAE) of polyphenols, carbohydrates and uronic acids, while sonication amplitude and time residence played secondary roles
Kadam et al (2015b) working with dried A. nodosum (40 °C for 12 h) and employing longer extraction times than those employed in this work, HCl solvent concentration and ultrasound amplitude determined that maximal total polyphenol content (TPC) of 143.0 mgGE gDS−1 (14.3 g GE L−1) expressed in gallic acid equivalents was accompanied with maximal CHOs extraction of 86.6 mgGE gDS−1 (8.7 gGE L−1) and UA of 117.4 mgGE gDS−1 (11.7 g GE L−1) operating at the highest sonication power and acidic concentration and the longest times
Summary
High seaweeds content of polysaccharides, polyunsaturated fatty acids, minerals, fibre, vitamins and antioxidant bioactive molecules (Pereira 2011) put algae in the spotlight to be used in several applications such as medicine, Nowadays, the algae-based refinery concept is promoted. Brown seaweeds are resource for several industries since they have high contents of polyphenols, fucoidans and alginate (Holdt and Kraan 2011). These nutraceuticals have recently gained relevance for their beneficial health applications since they have shown antioxidant (Koivikko et al 2005), anticoagulant, antitumor, anti-inflammatory (Cumashi et al 2007) and anti-viral properties (Damonte et al 2012).
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