# Assessment of the Resource Potential of Baltic Sea Macroalgae
## 3 Results
### Studying of the Antioxidant Properties of Macroalgae  
A solution of a known antioxidant, ascorbic acid, was used as a reference substance when evaluating the results of determining antioxidant properties. Table 8 shows the results of the antioxidant activity determination for algae extract samples.  
_Furcellaria_ samples had the highest antioxidant activity of all the macroalgae alcoholic extracts tested. The IC50, or concentration of half-maximal binding of the DPPH radical, for this genus of algae was 90.38 mg/mL. The IC50 value for 33 _Cladophora_ macroalgae samples was 136.61 mg/m; for the species _Ulva_ sp., the concentration of half-maximal binding of the DPPH radical was 314.74 mg/mL. The samples of macroalgae _Polysiphonia_ had the lowest antioxidant activity as the IC50 value was 1069.21 mg/mL.  
\begin{table}
\begin{tabular}{l c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multirow{2}{*}{**Source**} & \multicolumn{5}{c}{**Content, \%**} \\ \cline{3-6}  & & **C** & **H** & **N** & **S** & **O (Calc.) 1** \\ \hline _Furcellaria_ & & 37.52 \(\pm\) 1.12 & 5.82 \(\pm\) 0.17 & 3.60 \(\pm\) 0.10 & 3.00 \(\pm\) 0.09 & 50.05 \(\pm\) 1.50 \\ _Polysiphonia_ & Experimental & 33.80 \(\pm\) 1.01 & 5.05 \(\pm\) 0.14 & 3.65 \(\pm\) 0.11 & 2.38 \(\pm\) 0.07 & 55.12 \(\pm\) 1.65 \\ _Ulva_ & research & 32.08 \(\pm\) 0.96 & 5.15 \(\pm\) 0.15 & 2.06 \(\pm\) 0.06 & 1.94 \(\pm\) 0.06 & 58.77 \(\pm\) 1.76 \\ _Cladophora_ & & 31.33 \(\pm\) 0.93 & 4.96 \(\pm\) 0.14 & 2.26 \(\pm\) 0.06 & 1.75 \(\pm\) 0.05 & 59.70 \(\pm\) 1.79 \\ _Coniferous wood_ & [65] & 48.56 & 11.84 & 0.7 & 0.06 & 38.85 \\ Poplar & [65] & 51.60 & 6.00 & 0.60 & 0.02 & 41.70 \\ Rice hulls & 49.40 & 6.20 & 0.30 & 0.40 & 43.70 \\ Cotton stalk & [66] & 49.80 & 5.70 & 0.69 & 0.22 & 43.10 \\ Corn stalk & & 49.30 & 6.00 & 0.70 & 0.11 & 43.60 \\ \hline \hline \end{tabular}  
* \({}^{1}\)—this value was obtained by calculation.  
\end{table}
Table 6: Elemental analysis of algae biomass.  
\begin{table}
\begin{tabular}{l c} \hline \hline
**Algae Species** & **Ash Content, \% (wt.)** \\ \hline _Furcellaria_ & 7.80 \(\pm\) 0.23 \\ _Polysiphonia_ & 20.04 \(\pm\) 0.60 \\ _Ulva_ & 24.21 \(\pm\) 0.72 \\ _Cladophora_ & 28.30 \(\pm\) 0.85 \\ \hline \hline \end{tabular}
\end{table}
Table 7: The ash content assessment of macroalgae biomass.  
The alcohol extracts of the studied macroalgae species did not possess significant antioxidant properties. Further research into the selection of other types of solvents should be conducted using samples of the biomass of algae from the genus _Furellaria_, which demonstrated to have the highest antioxidant activity among other types of algae (Table 8).  
The antioxidant activity of the isolated lipids was also assessed by scavenging 2-2-diphenyl-1-picrylhydrazyl (DPPH) free radicals. Lipids isolated from samples of macroalgae of the species _Ulva_ sp. had the highest antioxidant activity: the IC50 for this genus of algae was 0.0026 mg/mL. The concentration of half-maximal DPPH radical binding in the lipid samples of _Cladophora_ macroalgae was 0.0167 mg/mL. Lipids isolated from samples of macroalgae of the genus _Furellaria_ had the lowest ability to bind DPPH radicals, at 0.0739 (Table 8). However, the lipid content in samples of algae from the genus _Furellaria_ was 4.3%, compared to 2.3-2.8% percent in other types of algae, which compensated for the moderate antioxidant activity of fats and made the biomass of this algae species the most promising source of antioxidants.  
It was discovered that extracts of isolated carbohydrates and proteins lacked 2-2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging antioxidant activity due to negative DPPH radical scavenging effect values.