*2.4. Total Phenolic Content (TPC) of Tested Cyanobacteria*

Folin–Ciocalteu technique [36] has been employed. For assessment of the total phenolic content of each cyanobacterial strain extract, the Gallic acid (0–500 mg L−1) was used to construct a standard calibration curve. The absorbance of the sample was tested to a blank at 760 nm. Gallic acid equivalent (GAE)/g extract was used to measure total phenolic content (TPC).

#### *2.5. Total Flavonoids Content (T.F.C.s) of Tested Cyanobacteria*

Total flavonoid contents were measured for the tested cyanobacterial strains using a colorimetric method [37]. Five hundred microliters of the cyanobacterial extract were dissolved in 2 mL methanol and then mixed with 3 mL of water, 100 μL of potassium acetate (1 M), and 100 μL of aluminum chloride. After that, the samples were left in the dark for 30 min. The mixture's absorbance was measured at 415 nm. The total flavonoid content was calculated using a standard curve as (mg/concentration of Quercetin Equivalent (QE) obtained from calibration curve) mg Q.C.E./g of extract.
