# Microalgae as Potential Sources of Bioactive Compounds for Functional Foods and Pharmaceuticals
## 1 Introduction
Apart from known bioactive compounds, microalgae biomass, as an untapped resource, could provide novel bioactive compounds with one-of-a-kind structural architecture and anti-inflammatory activity, which might be applied in both the pharmaceutical and food industries [10; 15]. Microalgae also have several other characteristics that make them appealing for biotechnological applications, including high growth rate, ease of cultivation, production scalability, possibility of genetic manipulation, low maintenance costs, being a relatively unexploited resource, and the ability to induce the production of target compounds by changing culture conditions [16; 17]. The fact that all the microalgae species used in this study have been industrially cultivated is a significant advantage as their growth conditions have already been optimized, guaranteeing both the environmental and supply sustainability of the biomass, which are key features for the development of marine biotechnological processes [15]. As these microalgae are already used for other purposes (such as food, animal feed, and cosmetics) and have the potential for many other uses such as pharmaceuticals, fertilizers, wastewater treatment, and biofuel production, they can also be integrated into a circular economy [18]. Microalgae are known to be very resilient and are able to induce a wide range of defense mechanisms to obtain a competitive edge or boost survival, namely by producing secondary metabolites with unique structures, which are not found in any terrestrial species [19; 20]. These secondary metabolites act in the human body, with reported antioxidant [21; 22], metal chelating [23], anti-cholesterol [24], antimicrobial, immunomodulatory [25], anti-inflammatory [26; 27], anti-proliferative [28], and acetylcholinesterasecholinesterase inhibitory activities [29], among others. This propensity of creating bioactive molecules, which have potential for the treatment and prevention of various diseases (diabetes, cancer,hypertension, neurological diseases, dyslipidemia, cardiovascular diseases, obesity, among others), has put microalgae in the biotechnological spotlight for applications in a variety of fields, such as human nutrition, pharmaceutical, and medicinal goods [30]. One of the main fields of investigation concerning microalgae is their huge biological potential in disease treatment and prevention, however, there still is a clear need for more research regarding the already reported compounds and their activity in the treatment and prevention of various diseases, as well as a continuous search for novel, unreported metabolites. The purpose of this study was to assess bioactive properties of different industrially produced microalgal and to find potential sources of biologically active substances that might assist in the treatment of different human ailments. The selected species include different genera covering different classes, namely: Chlorophyceae (_Tetraselmis chui_, _Tetraselmis striata_ CTP4, _Haematococcus pluvialis_); Prymnesiophyceae (_Tisoclrysis lutea_); Baclliapophyceae (_Phaeodactylum tricornutum_, _Skeletonema_ sp. ); Eustigmatophyceae (_Nannochloropsis_ sp. ); Porphyridiophyceae (_Porphyridiium_ sp. ); and Cyanophyceae (Spirulina), thus ensuring that the extracts produced include a wide diversity of chemical structures. The results reported here will enhance the current knowledge on industrially produced microalgae and the identification of small molecules from microalgal origin with the ability to promote the treatment of inflammation, oxidative stress, cancer, and neurological diseases and, as such, will help to further improve microalgal biotechnology by providing different industrial applications for this biomass using a circular economy concept.