## 3 Results and Discussion
### Some Chemical and Phytochemical Components
Flavonols (rutin, quercetin, naringin, myricetin, and kaempferol) had the highest antioxidant activity among flavonoids. Quercetin has the highest antioxidant capacity against water-soluble and fat-soluble free radicals. [PERSON]. [86], shows that it has even higher antioxidant activity than vitamins C and E.  
Another class of biologically active flavonoids are catechins. In addition to their high antioxidant activity, they are characterized by various therapeutic effects: they reduce the accumulation of atherosclerotic plaques, have anti-cancer effects, and reduce the risk of heart attack and stroke. The brown algae _E. crinita_ were rich in quercetin and catechin. _Chlorella_ spp. had a higher content of naringin and kaempferol compared to _U. intestinalis_ and _C. linum_, and _A. platensis_ (grown in a bioreactor). Some authors report that the least diversity in flavonoid components found in the cyanobacterium _A. platensis_, in which only the flavone apigenin is present [87]. Polyphenols (especially flavonoids) prevent oxidative damage caused by free radicals through ingestion activity, play a crucial role in preventing degenerative neuropathies or diabetes, and have anti-inflammatory and antiviral functions. Phenolic acids are also responsible for antimicrobial, anti-inflammatory, antiviral, and anti-cancer effects. They act as antioxidants by preventing radical formation [88]. The composition and the amount of phenolic acids in the studied algae are presented in Figure 4.  
Figure 3: Content of flavonoids determined by HPLC method, mg/100 g. 1. _A. platensis_ (convection dried); 2. _A. platensis_ (lyophilized); 3. _U. intestinalis_; 4. _C. linum_; 5. _E. crinita_; 6. _Chlorella_ spp. The amount of chlorogenic acid was highest in _A. platensis_ grown in a bioreactor 31.13 mg/ 100 g and lowest in _Cladophora_ ssp. 4.94 mg/100 g. In the brown seaweed _E. crimita_ and freshwater algae _Chlorella_ spp., chlorogenic acid was not detected. The presence of 3\(A\), dihydroxybenzoic acid was found in _U. intestinalis_ and in _E. crimita_, where it is about 2.5 times higher than in _U. intestinalis_. Other macroalgae for which the presence of this acid has been reported are _Neopyropia tenera_ (formerly _Porphyna tenera_) (Rhodophyta) and _Undaria pinmattifida_ (Phaeophyceae)--690 and 211 ng\(\cdot\)g\({}^{-1}\), respectively [89]. _E. crimita_ had the highest values for vanillic acid (14.73 mg/100 g), and in the other samples, it was almost twice lower. All tested samples contained neochlorogenic acid (Figure 4), excluding conventionally dried _A. platensis_, but the lyophilized one demonstrated high values; therefore, the lyophilization process allowed the preservation of the neochlorogenic acid. The case of chlorogenic acid was just the opposite, lyophilization reduced its values, in _E. crimita_ and _Chlorella_ spp. chlorogenic acid was not detected. Of the acids studied, [PERSON] et al. reported a _p_-coumaric acid content of 920 ng/g in _Arthospira_ (Cyanobacteria), 770 ng/g for _Porphyridium_ (Rhodophyta) and 7000 ng/g for _Tetraselmiss_ (Chlorophyta) [87]. In addition to phenolic acids and rutin, algae contain pigments such as chlorophyll and carotenoids. Chlorophyll is a major photosynthetic pigment and natural dye. The values for the content of chlorophyll \(a\) and \(b\) in freshwater algae _Chlorella_ spp., _A. platensis_ (lyophilized and conventionally dried) as well as _U. intestinalis_ and _E. crimita_ (lyophilized feedstock) are presented in Table 8. Chlorophyll \(b\) dominated in all samples compared to chlorophyll \(a\), with one exception--lyophilized _U. intestinalis_, where chlorophyll \(b\) values were many times lower than those of the other samples. The highest values of chlorophyll \(b\) were found in _A. platensis_--4843 g/g dw. Chlorophyll values were between 589 and 4237 g/g dw (Table 8).