Abstract
The use of green marine seaweed Ulva spp. as foods, feed supplements, and functional ingredients has gained increasing interest. Microwave-assisted extraction technology was employed to improve the extraction yield and composition of Ulva pertusa polysaccharides. The antioxidant activity of ulvan was also evaluated. The impacts of four independent variables, i.e., extraction time (X1, 30 to 60 min), power (X2, 500 to 700 W), water-to-raw-material ratio (X3, 40 to 70), and pH (X4, 5 to 7) were evaluated. The chemical structure of different polysaccharides fractions was investigated via FT-IR and the determination of their antioxidant activities. A response surface methodology based on a Box–Behnken design (BBD) was used to optimize the extraction conditions as follows: extraction time of 43.63 min, power level of 600 W, water-to-raw-material ratio of 55.45, pH of 6.57, and maximum yield of 41.91%, with a desired value of 0.381. Ulvan exerted a strong antioxidant effect against 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and showed reducing power in vitro. Ulvan protected RAW 264.7 cells against H2O2-induced oxidative stress by upregulating the expression and enhancing the activity of oxidative enzymes such as superoxide dismutase (SOD) and superoxide dismutase (CAT). The results suggest that the polysaccharides from U. pertusa might be promising bioactive compounds for commercial use.
Highlights
The genus Ulva (Chlorophyta) is a cosmopolitan, abundant, and fast-growing green macroalgae forming natural beds in shallow waters throughout the world [1]
A response surface methodology based on a Box–Behnken design (BBD) was used to optimize the extraction conditions as follows: extraction time of 43.63 min, power level of 600 W, water-to-raw-material ratio of 55.45, pH of 6.57, and maximum yield of 41.91%, with a desired value of 0.381
The yield of ulvan affected by the different ratios between water and raw materials is shown in Figure 1c, whereas the other extraction variables were as follows: 600 W power, pH of 6, and extraction time of 45 min
Summary
The genus Ulva (Chlorophyta) is a cosmopolitan, abundant, and fast-growing green macroalgae forming natural beds in shallow waters throughout the world [1]. Ulvan has been demonstrated to play an important role as an antitumor [6] and antihyperlipidemic [7] substance in living organisms and induces a defense mechanism in crops [8]. It is one of the important antioxidant compounds, whose antioxidant properties are mainly attributed to its scavenging activity against superoxide and hydroxyl radicals, its chelating ability, singlet and triplet oxygen quenching activity, and reducing
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