Cyanobacteria as the Source of Antioxidants

*Rashi Tyagi, Pankaj Kumar Singh and Archana Tiwari*

### **Abstract**

The present-day scenario in the health sector calls for alternative medicine sources with no risk of resistance, effective in the mode of action, and eco-friendly. Cyanobacteria are microbial factories for a wide range of products. They are reservoirs of bioactive compounds which have the potential to act as precursors of novel drug molecules. A plethora of algae have been documented for their therapeutic abilities in treating diseases. A plethora of antioxidative compounds along with enzymes are present in cyanobacteria, possessing applications in nutraceuticals and cosmeceuticals, which is quite evident from the products available in the market. This chapter highlights the significant leads in the area of cyanobacteria-based antioxidants. A sustainable approach to envisaging cyanobacteria as competent antioxidants can open new doors in prevention, treatment, and control of a plethora of diseases.

**Keywords:** algae, antioxidants, cyanobacteria, cosmeceuticals, nutraceuticals

### **1. Introduction**

Cyanobacteria exist in various habitats that are exposed to various adverse environmental variables, such as ultraviolet light, salinity, climate, and food supplements. Algae are multicellular creatures found in freshwater, saltwater, and marine environments. They synthesize a wide range of metabolites to acclimate to these demanding environments quickly [1]. Cyanobacteria's antioxidants can be used in the pharmaceutical and medical fields. The search for safe antioxidants derived from natural sources is currently generating interest on a global scale. Algae could biogenically create, consume, collect, and develop a wide variety of metabolites [2]. The agricultural, medicinal, pharmaceutical, food, nutritional, cosmetic, and other industries employ algae. In the absence of light, they can also grow under heterotrophic conditions by utilizing an organic carbon substrate as an energy source [3].

The existence of several proterozoic oil deposits is related to cyanobacterial activity. Additionally, they are significant suppliers of nitrogen fertilizer for growing rice and beans. Throughout the planet's history, cyanobacteria also played a major role in determining ecological change and evolution. Many cyanobacteria produce the oxygen atmosphere on which we rely. Before it, the atmosphere's chemistry was significantly different and unsuitable for modern species.

The nascent, most diversified, and wide cluster of photosynthetic prokaryotes known as cyanobacteria (blue-green algae) exhibits similarities to green plant life

in oxygenic photosynthesis and to Gram-negative bacteria in the cellular organization [4]. Almost all terrestrial and aquatic freshwater and marine habitats support the growth and colonization of blue-green algae, which adapt to diverse ecological circumstances [5]. Microalgae exist as a standard source of bioactive chemicals and have been used in various pharmacological applications due to their richness in primary and secondary metabolites [6]. Bioactive substances are physiologically active molecules that can either benefit or harm a living thing, tissue, or cell when present in small amounts [7].

Proteins called antioxidant enzymes to play a catalytic role in converting reactive oxygen species (ROS) and their byproducts into stable, harmless compounds, making them the most effective protection against oxidative stress-related cell damage. Antioxidant enzymes can stabilize or inactivate free radicals before damaging cellular components. They work by lowering the free radicals' energy or by sacrificing part of their electrons for its use, making the radicals more stable. To lessen the harm by free radicals, they may also halt the oxidative chain reaction. Over the last 10 years, numerous studies have been conducted on the advantages of antioxidant enzymes. Antioxidants protect cells against the harm caused by free ions, even when their concentration is lower than the substance being oxidized [8]. However, various harmful side effects, including cancer and liver damage, are associated with these synthetic antioxidants. As a result, scientists are looking for natural antioxidants that may be used in place of synthetic antioxidants in the food and pharmaceutical industries that are safe and efficient [9]. Our body's capacity to lower the risk of free radicalrelated health issues is made more tangible by minimizing exposure to free radicals and increasing the intake of foods or supplements rich in antioxidant enzymes [8]. Therefore, antioxidant enzymes are vitally essential for preserving the best possible cellular and systemic health and well-being. Free radicals are included in the highly reactive oxygen-containing molecules known as reactive oxygen species (ROS). The hydroxyl radical, superoxide anion radical, hydrogen peroxide, singlet oxygen, nitric oxide, and chlorine ions radicals, and other lipid peroxides are examples of ROS. All have the potential to interact with cellular membranes, phospholipids, nucleic acids, proteins, enzymes, and other tiny molecules to cause cellular harm [8].

Algae's numerous bioactive chemicals are being examined. PUFA, sterols, terpenoids, carotenoids, and alkaloids are just a few functional chemical components found in the diverse group of organisms known as algae. These have been shown to protect against various diseases, including cancer [9].

### **2. Algae antioxidants**

Algae are photoautotroph organisms. There is no damage to the structure, and it can produce the substances they need to defend itself against oxidation. They are a rich source of powerful antioxidants that can shield our bodies from the harmful effects of oxygen species created during regular bodily metabolism. Carotenoids and vitamin E (gamma-tocopherol) are two types of powerful fat-soluble antioxidants found in algae, whereas vitamins, phycobiliproteins (PBPs), and polyphenols are adequate water-soluble antioxidants [9].

As naturally obtained bioactive compounds with a wide variety of biological potencies, such as antibacterial, antiviral, antioxidant, and anti-inflammatory, cyanobacteria have attracted much attention [1]. Antioxidants and phycobiliproteins (PBPs), which are cyanobacteria's distinctive photosynthetic pigments, are thought

#### *Cyanobacteria as the Source of Antioxidants DOI: http://dx.doi.org/10.5772/intechopen.110598*

to be abundant in cyanobacteria. In particular, these pigments have been exploited as organic coloring replacements in nutritive, cosmetic, and pharmaceutical products. Due to their fluorescent qualities, PBPs are also utilized in the branch of immunology [2]. Phycobiliproteins are highly effective fluorescent substances due to their distinctive characteristics of high molar absorbance coefficients, high fluorescence quantum yield, big stokes shift, high oligomer stability, and high photostability [10]. The primary endogenous damage to the biological system is caused by free radicals generated during oxidative stress. This kind of damage is frequently linked to several degenerative diseases and disorders, including cancer, cardiovascular disease, aging, and immune function loss. Free radicals are the main factor in lipid oxidation, the process by which food degrades and finally loses its properties to sense it through sensory organs and edibility, in addition to harming live cells [11]. Many individuals use antioxidants in the form of commercial food additives, which are produced synthetically and may contain significant amounts of preservatives, to combat the effects of oxidative stress [12]. However, most antioxidant sources identified to date compete with conventional meals and commodities.

Most biologically active compounds in algae, including pigments like carotene, astaxanthin, lutein, zeaxanthin, and phycobiliproteins [13], exhibit both antiinflammatory and antioxidant properties [14]. One of the key factors driving the hunt for bioactive substances like anti-inflammatory kinetic molecules from natural sources such as microalgae is the rising demand for medications with few adverse effects. The cell that showed anti-inflammatory action will accumulate metabolites from the various microalgae. Several research has already shown the chemical makeup, structural details, and biosynthesis routes of the bioactive substances displaying anti-inflammatory chemicals produced by microalgae [15]. Proteins, phycobiliproteins, flavonoids, carotenoids like astaxanthin and lutein, and the fatty acids DHA, EPA, and SPs produced by metabolically active microalgae species are all present examples of substances with anti-inflammatory properties [2]. To be a valuable target product, these bioactive compounds must fulfill two requirements: (1) they must accumulate in relatively large amounts in cultures grown under standard test conditions throughout commercial production, and (2) they should continuously be overexpressed as an algal reaction to unpleasant development surroundings or when exposed to the synthetic or actual pressure. This can be achieved by differing the circumstances, like changing the physicochemical boundaries and the retention of supplements, as well as changes in temperature, pH, light quality, and irradiance [16]. The species of algae and the growing circumstances significantly impact the generation of anti-inflammatory chemicals [14]. Only a peptide from *P. tricornutum* with anti-inflammatory characteristics made it to market. Carotenoids, an algae stain, are discovered to positively influence immune response modulations and anti-inflammatory cellular response pathways [2]. *H. pluvialis* microalgae produce the carotenoid astaxanthin, which has strong anti-inflammatory properties [14]. One extremophilic microalga, *D. salina*, is used in industry to create a valuable substance with anti-inflammatory properties [17]. Microalgae-produced compounds have also been shown to have antioxidant as well as anti-inflammatory activity. Microalgal anti-inflammatory compounds known as sugars have also demonstrated antioxidant potential. Several excellent reviews have been published recently to discuss their uses and advantages for human health [2]. The antioxidant microalgae sugars extracted from *Porphyridium* [18] and *Rhodella* [19] are two excellent patterns.

Cyanobacteria inherently produce ROS throughout the photosynthetic activity. These species are created by abiotic causes such as ultraviolet radiation, osmotic disturbances, desiccation, and heat. Multiple strategies are needed for cyanobacteria

**Figure 1.** *ROS removing bioactive compounds.*

to avoid the inhibitory effects of harsh conditions. By reducing the amount of energy lost during the photosynthetic process, they can reduce the generation of ROS. One approach uses the carotenoid zeaxanthin to non-photochemically quench (NPQ ) excitation energy through photosystem II [20]. Cyanobacteria remove ROS using various bioactive compounds, as mentioned in **Figure 1**, and their genetic relationship can be elucidated using various methods of molecular phylogenetics [21]. Although peroxidases and catalases accelerate the removal of peroxides (such as H2O2 and R-O-O-H)13, SORs and SODs eliminate superoxide free radicals (O2). These O2 molecules are produced by photosynthetic and respiratory electron transport chains12, as well as extracellular processes on the cell surface. This promotes various processes like a ferrous deposition, cell signaling, and growth; however, if O2 is allowed to accumulate inside the cell, it reacts with solvent-exposed 4Fe-4S clusters in proteins, including those needed for amino acid biosynthesis17 and photosynthesis18, resulting in Fenton reactants, which can eventually cause cell death. Therefore, SODs and SORs are discovered in all three branches – Eukarya, Archaea, and Bacteria [21].

Some of the important antioxidants found in algal species are listed below in **Table 1**.


*Cyanobacteria as the Source of Antioxidants DOI: http://dx.doi.org/10.5772/intechopen.110598*


**Table 1.**

*Antioxidants from algae.*
