# Microalgae as Potential Sources of Bioactive Compounds for Functional Foods and Pharmaceuticals
## 1 Introduction  
Non-communicable diseases (NCDs) are a concerning phenomena worldwide as they have an increasingly high prevalence and are considered to be the leading cause of death worldwide (71% of all deaths), besides accounting for about 80% of all premature deaths and increasing the likelihood of developing other diseases. The main NCDs are cardiovascular diseases (such as heart attacks and strokes), cancers, chronic respiratory diseases, diabetes, and mental and neurological conditions [1]. Oxidative stress and inflammation are considered key factors for the development of NCDs, playing either a central or a secondary role but always an important one. Reactive oxygen species (ROS) and free radicals are the main oxidative stress effectors, which are linked to cell injury (damaging of membranes, lipids, proteins, lipoproteins, and DNA) and can cause a variety of diseases and disorders (cancer, arteriosclerosis, myocardial infarction, diabetes, inflammatory diseases, central nervous system problems, and cell aging) and acute pathologies if not managed and strictly controlled [2]. Oxidative stress can also cause chronic inflammation due to various mechanisms, mainly due to modifications of DNA andproteins and overall ROS-induced damage, all leading to the signaling and activation of the inflammatory pathway [3]. Inflammatory response involves complex interactions between blood cells, immune cells (e.g., macrophages), and molecular mediators like cytokines (such as IL-6 or TNF-\(\alpha\)); acute phase proteins and chemokines promote the migration of neutrophils and macrophages to the site of inflammation by increasing vasodilitation and angiogenesis [1]. When inflammation is prolonged over time, chronic inflammation sets in, and dysregulated inflammation has been identified in the genesis of almost all types of human diseases or disorders such as cancer, neurodegenerative disorders, multiple sclerosis, diabetes, atherosclerosis, arthritis, and cardiovascular diseases [4; 5]. Deregulation of metal homeostasis is another component that contributes to illness development, especially in neurodegenerative diseases, as the accumulation of hazardous redox metals in the body can result in neuron degeneration, cell damage, loss, and death [6]. Redox-active metals have been linked to oxidative stress due to the Fenton and Haber-Weiss reactions, which produce reactive oxygen and nitrogen species, further increasing oxidative stress [7], which is especially dramatic considering that the brain is the organ with highest oxygen consumption [8]. Many of the traditionally therapeutic drugs that are currently used in the treatment of NCDs have severe side-effects as they are used for a broad spectrum of diseases and frequently possess low selectivity, which often leads to damage of healthy cells [9]. Therefore, the pursuit for new, more natural and targeted therapeutic approaches is constantly increasing, and several novel sources of bioactive compounds have been under investigation, such as microalgae [10]. Additionally, the use of natural products and/or extracts as sources of bioactive compounds for functional foods or pharmaceuticals production may help to reduce the need for synthetic pharmaceutical (e.g., antibiotics and anti-inflammatories), decreasing antibiotic resistance issues and the environmental contamination of ground and surface waters due to ineffective removal in wastewater treatment plants [11; 12]. Microalgae produce high-value bioactive compounds (e.g., carotenoids, polyunsaturated fatty acids [PUFAs], phenolic compounds, terpenes and sulphated polysaccharides) with health benefits such as antimicrobial, anti-inflammatory, anti-aging, aggregative, vasoconstrdicting, anti-tumoral, hypocholesterolemia, antioxidant, immunosuppressive and antiviral properties [13; 14].