# Microalgae as Potential Sources of Bioactive Compounds for Functional Foods and Pharmaceuticals
## 3 Results and Discussion
### Evaluation of Bioactivities of Microalgal Extracts
#### 3.1.1 Antioxidant Activity
\begin{table}
\begin{tabular}{c c c c} \hline
**Microalga/Positive Control** & **Extract** & **DPPH Scavenging Activity (\%)** & **IC\({}_{50}\) (mg/mL)** \\ \hline \multirow{3}{*}{_Porphyridium_ sp. (POC)} & W & 87.5 \(\pm\) 10.0 & 0.535 \(\pm\) 0.001 d \\  & ET & 59.1 \(\pm\) 1.0 & 0.566 \(\pm\) 0.001 d \\  & EA & 105 \(\pm\) 3 & 0.524 \(\pm\) 0.001 d \\ \hline \multirow{3}{*}{_Nannochloropsis_ sp. (NANNO)} & W & 51.0 \(\pm\) 5.2 & n.d. \\  & ET & 80.3 \(\pm\) 2.3 & 0.539 \(\pm\) 0.030 d \\  & EA & 81.7 \(\pm\) 2.2 & 0.990 \(\pm\) 0.024 b \\ \hline \multirow{3}{*}{_Tetraselmis striata_ CTP4 (TCTP4)} & W & 23.2 \(\pm\) 3.7 & n.d. \\  & ET & 58.1 \(\pm\) 1.5 & 1.17 \(\pm\) 0.01 a \\  & EA & 37.8 \(\pm\) 3.2 & n.d. \\ \hline \multirow{3}{*}{_Tisochrysis lutea_ (TIL)} & W & 42.2 \(\pm\) 3.3 & n.d. \\  & ET & 41.6 \(\pm\) 0.2 & n.d. \\  & EA & 97.8 \(\pm\) 2.1 & 0.794 \(\pm\) 0.001 c \\ \hline \multirow{3}{*}{_Phaeodactylum tricornutum_ (PHA)} & W & 26.8 \(\pm\) 2.2 & n.d. \\  & ET & 61.8 \(\pm\) 1.3 & 0.575 \(\pm\) 0.004 d \\  & EA & 94.9 \(\pm\) 3.3 & 0.452 \(\pm\) 0.002 d \\ \hline \multirow{3}{*}{_Skeletonema_ sp. (SKE)} & W & 24.1 \(\pm\) 3.1 & n.d. \\  & ET & 71.1 \(\pm\) 1.2 & 0.478 \(\pm\) 0.054 d \\ \cline{1-1}  & EA & 73.3 \(\pm\) 7.25 & 0.447 \(\pm\) 0.060 d \\ \hline \multirow{3}{*}{Spirulina (SPR)} & ET & 71.5 \(\pm\) 0.3 & 0.923 \(\pm\) 0.001 b \\ \cline{1-1}  & ET & 66.8 \(\pm\) 1.0 & 1.14 \(\pm\) 0.01 a \\ \hline \multirow{2}{*}{_Tetraselmis chui_ (TCH)} & ET & 103 \(\pm\) 58 & 0.408 \(\pm\) 0.007 d \\ \hline \multirow{2}{*}{_Haematococcus pluvialis_ (HPL)} & - & 94.1 \(\pm\) 2.8 & n.d. \\ \hline \end{tabular}  
* Positive control, BHT, 0.1 mg/mL. n.d. = not determined. \(N=3\). Presented values are mean with standard deviation. Extracts labelled with different superscript letters are significantly different (\(p<0.05\)).  
\end{table} 
Table 1: DPPH radical scavenging activity (IC\({}_{50}\): mg/mL) of water (W), ethanol (ET) and ethyl acetate (EA) extracts of different microalgae species at 1 mg/mL. The IC\({}_{50}\) values of both freshly prepared extracts were slightly higher than the ones used in the first screening, possibly due to differences in microalgal biomass batches. Nonetheless, fractionation led to an enrichment of the active compound(s) in the obtained fractions as these presented lower IC\({}_{50}\) than the crude extract, especially the hexane fractions. This suggests that the compounds with metal-chelating capacity are from the same polarity family since non-polar solvents tend to extract non-polar compounds due to their mutual solubility. Hexane is known to have higher recovery of cellular non-polar compounds such as terpen, including neutral lipids, essential oils, and alkanes [40]. Both _Porphyidium_ sp. [41] and _Skeletonema_ sp. [42] are reported to produce significant amounts of long-chain polyunsaturated fatty acids (with special focus on eicosapentaenoic acid and arachidonic acid), fluorescent phycobiliproteins, carotenoids (zeaxanthin,tocopherol, fucoxanthin, etc) and vitamins during their metabolic processes, which are believed to be at least partially responsible for the microalgal metal chelating activity. Exopolysaccharideacharides also appear to play a role in metal chelating of these species, although probably not being present in the hexane fraction due to their polar nature [43]. Currently both _Porphyidium_ sp. [44] and _Skeletonema_ sp. [45] are acknowledged as Generally Recognized as Safe by the Food and Drug Administration and are also being investigated as bioremediation agents of heavy  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**MicroaIga**} & \multirow{2}{*}{**Extract**} & \multirow{2}{*}{**\% Cu\({}^{2+}\) CA**} & \multicolumn{2}{c}{**IC\({}_{50}\) (mg/mL) for**} & \multirow{2}{*}{**\% Fe\({}^{2+}\) CA**} & \multicolumn{2}{c}{**IC\({}_{50}\) (mg/mL) for**} \\  & & & & **Cu\({}^{2+}\)CA** & & **Fe\({}^{2+}\)CA** \\ \hline \multirow{3}{*}{_Porphyidium_ sp.