# Microalgae as Potential Sources of Bioactive Compounds for Functional Foods and Pharmaceuticals
## 3 Results and Discussion
### Evaluation of Bioactivities of Microalgal Extracts
#### 3.1.2 Calcium Chelating Activity  
Similar to the results from redox-metal chelation assays, in the calcium chelating assay the extracts with highest chelating capacity were POC ET (IC\({}_{50}\) = 0.0519 mg/mL) and SKE ET (IC\({}_{50}\) = 0.0638 mg/mL), followed by EA extracts of the same species with 0.150 mg/mL and 0.0906 mg/mL, respectively (Table 4).  
Fractionation was performed on POC ET and SKE ET extracts, based on their low IC\({}_{50}\) values (Table 5). As new extract had to be prepared for the fractionation, this was also analyzed.  
The IC\({}_{50}\) values of the freshly prepared extracts were higher than the ones obtained in the initial screening, and this may be due to differences in the industrially grown microalgal biomass composition. The hexane fractions of ethanol extracts from _Porphyridium_ sp. and _Skeletonema_ sp. presented the highest chelating activity of calcium when compared to the other fractions and crude extract. This means that chelating compounds were concentrated in the hexane fractions, suggesting that the compounds with calcium-chelating capacity are from the same polarity family, since non-polar solvents tend to extract non-polar compounds (such as fatty acids, carotenoids, and sterols, among others). It has been reported that compounds with amino, carboxyl, and phosphoric groups may be responsible for the calcium-binding activity of compounds due to simultaneously providing an atom with a non-bonding free electron pair (nitrogen, oxygen or phosphorus) and a suitable binding site [49]. Our findings suggest that both hexane fractions may be sources of calcium chelating compounds, and could play a significant role in neuroprotective mechanisms as  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Microalgal Extract** & **Fractionating Solvent** & **\% Cu2\({}^{\star}\) CA** & **IC\({}_{50}\) (mg/mL) for Cu2\({}^{\star}\)CA** & **\% Fe2\({}^{\star}\) CA** & **IC\({}_{50}\) (mg/mL) for Fe2\({}^{\star}\)CA** \\ \hline _Porphyridium_ sp. & Crude ET extract & 74.1 \(\pm\) 0.6 & 0.272 \(\pm\) 0.010  & 77.4 \(\pm\) 0.1 & 0.047 \(\pm\) 0.002  \\ \cline{2-5}  (POC ET) & H & 81.2 \(\pm\) 0.1 & 0.046 \(\pm\) 0.004  & 85.2 \(\pm\) 0.3 & 0.026 \(\pm\) 0.001  \\ \cline{2-5}  & DCM & 61.1 \(\pm\) 1.1 & 0.648 \(\pm\) 0.043  & 61.1 \(\pm\) 1.0 & n.d. \\ \cline{2-5}  & EA & 46.6 \(\pm\) 1.2 & 0.912 \(\pm\) 0.023  & 46.6 \(\pm\) 1.2 & 0.384 \(\pm\) 0.019  \\ \hline _Skeletonema_ sp. & Crude ET extract & 83.4 \(\pm\) 0.4 & 0.240 \(\pm\)0.010  & 83.5 \(\pm\) 1.6 & 0.055 \(\pm\) 0.002  \\ \cline{2-5}  & H & 92.6 \(\pm\) 0.3 & 0.036 \(\pm\) 0.001  & 97.9 \(\pm\) 0.3 & 0.024 \(\pm\) 0.001  \\ \cline{2-5}  & DCM & 61.4 \(\pm\) 0.1 & 0.725 \(\pm\) 0.038  & 61.4 \(\pm\) 0.1 & 0.386 \(\pm\) 0.015  \\ \cline{2-5}  & EA & 51.0 \(\pm\) 0.1 & 0.917 \(\pm\) 0.056  & 51.0 \(\pm\) 0.1 & 0.246 \(\pm\) 0.018  \\ \hline \hline \end{tabular}  
* n.d. = not determined. Presented values are mean with standard deviation and extracts with different superscript letters are significantly different from each other (\(p<0.05\)). \(n=3\).  
\end{table}
Table 3: Redox-metal chelating activity (CA) for copper (Cu2\({}^{\star}\)) and iron (Fe2\({}^{\star}\)) of hexane (H), dichloromethane (DCM) and ethyl acetate (EA) fractions of ethanol extracts from _Porphyridium_ sp. and _Skeletonema_ sp. tested at 1 mg/mL (%) and IC\({}_{50}\) (mg/mL).  
evidence suggests that an intracellular calcium overload is linked to the neurobiology of neurodegenerative diseases (NDs) like Alzheimer's [50; 51]. Therefore, extracts/compounds with calcium-chelating capacity may assist in rebalancing calcium overload and reestablish calcium homeostasis, therefore providing a neuroprotective effect [50].