## 3 Results and Discussion
### In Vitro Antioxidant Capacity of Obtained Extracts  
The _in vitro_ antioxidant capacity of the obtained extracts was assessed with the TPC and ABTS assays, and the results are summarised in Table 2. Among the various techniques, \begin{table}
\begin{tabular}{l l l l l l} \hline \hline
**Method** & **Extraction Conditions** & \begin{tabular}{c} **PC** \\ **(mg/g)** \\ \end{tabular} & \
\begin{tabular}{c} **APC** \\ **(mg/g)** \\ \end{tabular} & **Purity** & **Reference** \\ \hline \multicolumn{5}{l}{Results of this study:} \\ \multicolumn{5}{l}{Maceration} & 1 cycle, 250 rpm, 2 h, 25 °C, 0.1 M phosphate buffer pH 7 & 30.7 \(\pm\) 0.3 \({}^{\text{a}}\) & 13.2 \(\pm\) 0.5 \({}^{\text{a}}\) & 1.350 \({}^{\text{a}}\) \\ \multicolumn{5}{l}{Homogeniser} & 1 cycle, 12,000 rpm, 30 min, 25 °C, 0.1 M phosphate buffer pH 7 & 36.5 \(\pm\) 0.6 \({}^{\text{c}}\) & 30.9 \(\pm\) 0.2 \({}^{\text{b}}\) & 0.846 \({}^{\text{b}}\) \\ \multicolumn{5}{l}{Freeze-thaw} & 3 cycles, \(-\) 18 °C 4 h, thawing at 25 °C, 0.1 M phosphate buffer & 31.3 \(\pm\) 0.1 \({}^{\text{b}}\) & 11.2 \(\pm\) 0.5 \({}^{\text{c}}\) & 1.093 \({}^{\text{c}}\) \\ \multicolumn{5}{l}{Optimal} & \multicolumn{5}{l}{Maceration 3 cycles, 250 rpm, 25 °C, 0.1 M phosphate buffer pH 7} & 55.9\(\pm\) 0.4 \({}^{\text{d}}\) & 24.9 \(\pm\) 0.2 \({}^{\text{d}}\) & 1.12 \({}^{\text{d}}\) \\ \multicolumn{5}{l}{Results of previous reports:} \\ \multicolumn{5}{l}{Maceration} & 60 min, 950 rpm and 30 °C, 1625, DW & 28.93 & & [41] \\ \multicolumn{5}{l}{} & 18 h, 800 rpm, 28 °C, DW & 38.3 & & [47] \\ \multicolumn{5}{l}{} & 18 h, 37 °C, 0.1 M sodium phosphate buffer pH 7.0 & 74.3 & & [48] \\ \multicolumn{5}{l}{Homogeniser} & 30 min, 12,000 rpm, 30 °C, DW & 32.2 & & [41] \\ \multicolumn{5}{l}{} & 15 min, 25 °C, 1.5% CaCl\({}_{2}\) (\(w/w\)) & 67.6 & & [49] \\ \multicolumn{5}{l}{\(6\) min, 2500\(\times\) 27 °C, 0.1 M phosphate buffer (pH 6.8)} & 53.8 & & [39] \\ \multicolumn{5}{l}{Freeze-thaw} & Liquid N, 25 min, thawed at 30 °C, 15 min, 3 times per cycle, DW & 26.64 & & [41] \\ \multicolumn{5}{l}{4 cycles (4 h, \(-\) 40 °C, 1 h at 27 °C), 0.1 M phosphate buffer pH 6.8} & 73.73 & & [39] \\ \multicolumn{5}{l}{2 cycles, 0.1 M phosphate buffer pH 6.8} & 92.6 & & [42] \\ \multicolumn{5}{l}{4 cycles (4 h at \(-\) 40°C and 1.5 h of thawing at ambient} & 41.9 & & [50] \\ \multicolumn{5}{l}{temperature} & \multicolumn{5}{l}{DW} \\ \hline \hline \end{tabular}
\begin{tabular}{l} rpm: rotations per minute; DW: distilled water. Different lowercase letters among columns indicate statistically significant differences (\(p<0.05\)).  
\end{table} 
Table 1: Comparison of yields among this study’s various techniques and optimal conditions with previous reports. Values of PC and APC are expressed as mg/g of biomass (mean \(\pm\) standard deviation, n = 3). the extract from homogenisation extraction had the highest antioxidant activity, with 35.7 \(\pm\) 1.9 mg of GAE/G OF BIOMASS for TPC and 48.9 \(\pm\) 2.1 mg of TE/g of biomass for TEACABTS. As expected, the highest values overall were observed for the sample extracted under the optimal conditions reported in the previous section. The high values for homogenisation can probably be attributed to the co-extraction of chlorophylls and PBP. Indeed, upon spectrophotometric measurement, the total chlorophyll content in the extract from homogenization was 5.59 \(\pm\) 0.01 mg/g of biomass, with 1.9 and 2.6 mg/g of biomass being attributed to chlorophyll A and B, respectively, whereas in all other cases it was negligible. Chlorophylls, as the major photosynthetic pigments in multiple microalgae, have been widely studied, but their antioxidant, antibacterial, and antitumor properties in medicinal applications are, to date, not well understood [51]. Nevertheless, spirulina's antioxidant effects are widely reported, with extracts frequently presenting effective alkoxyl, superoxide, and hydrogen peroxide radical scavenging properties or potent lipid peroxidation inhibition, as summarised in reviews [43; 52; 53].