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marine drugs Review Diverse Applications of Marine Macroalgae Adriana Leandro 1, Leonel Pereira 1 and Ana M. M. Gonçalves 1,2,* 1 MARE (Marine and Environmental Sciences Centre), Department of Life Sciences, Faculty of Sciences and Technology, University of Coimbra, 3004-517 Coimbra, Portugal; [email protected] (A.L.); [email protected] (L.P.) 2 Department of Biology and CESAM, University of Aveiro, 3810-193 Aveiro, Portugal * Correspondence: [email protected]; Tel.: +351-239-240-700 (ext. 262-286) Received: 27 November 2019; Accepted: 22 December 2019; Published: 24 December 2019 Abstract: The aim of this paper is to review the multiplicity of the current uses of marine macroalgae. Seaweeds are already used in many products and for different purposes, from food products to medicine. They are a natural resource that can provide a number of compounds with beneficial bioactivities like antioxidant, anti-inflammatory, anti-aging effects, among others. Despite studies directed in prospecting for their properties and the commodities already marketed, they could, surely, be even more researched and sustainably explored. Keywords: macroalgae/seaweed; natural resources; health; food; feed; agriculture 1. Marine Macroalgae Diversity and Ecology The marine environment is home for many diverse organisms such as algae, molluscs, sponges, corals, tunicates. Currently, oceans are already considered the “lungs of the Earth” due to Cyanobacteria and other algae that live in seawater. In fact, these beings provide up to 80% of the atmospheric oxygen, which we rely on to breathe. Cyanobacteria are blue colored, aquatic, photosynthetic, and because they are bacteria, they usually are unicellular, but they often grow in colonies large enough to be seen. Cyanobacteria are prokaryotic organisms while algae are eukaryotic organisms. Algae are almost ubiquitous, between microscopic and macroscopic species, they can be found in every wet environment in land, in fresh water or in oceans [1]. In this review, the focus is the marine macroalgae or seaweeds, which are multicellular, macroscopic, eukaryotic, and autotrophic organisms. They are taxonomically organized in three large and distinct groups, based on the color of the thallus: Chlorophyta (green algae), Rhodophyta (red algae), and Ochrophyta— Phaeophyceae (brown algae). All of them accumulate starch in the interior of their cells as energy store, and other different polysaccharides of large molecular chain. The green algae produce ulvan and contain carotene and xanthophylls and chlorophylls a and b (what sustains the idea that they are the ancestors of the plants) as pigments. The red algae (most common in hot seas) have chlorophylls a and d and carotenoids and their staining is due to the presence of phycoerythrin (pigment) in their cells. In the brown algae are found the pigments fucoxanthin, chlorophylls a and c and carotenoids and, as reserve substances, oils, and polysaccharides (such as laminarin) [2,3]. Like plants in terrestrial land, seaweeds have similar ecological roles but in aquatic territory. Some macroalgae species may serve as bioindicators of the quality of water and some can do bioremediation by bioabsorption and bioaccumulation [4–6]. As other vegetables, seaweeds are primary producers, the base of the marine food chain, sustaining several benthic animal communities [7]. They also compete for light, nutrients, and space, in addition to the need of carbon dioxide and water to develop. Inclusively algae and plants produce the same storage compounds and use similar defence strategies against predators and parasites [2]. They have also Mar. Drugs 2020, 18, 17; doi:10.3390/md18010017 www.mdpi.com/journal/marinedrugs Mar. Drugs 2020, 18, 17 2 of 15 Mar. 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Value of the ofthe seaweed seaweed market market worldwide worldwide in 2017 in 2017 and and 2024 2024 (in (inbillion billion U.S. U.S. dollars) dollars) [10 []10. ]. 2. Marine Macroalgae Applications 2. Marine Macroalgae Applications 2.1. Human Food 2.1. Human Food Asian countries, especially China and Japan, are known for being large seaweed consumers Asian countries, especially China and Japan, are known for being large seaweed consumers for for many centuries. The first records show that the harvesting of macroalgae, such as Laminaria many centuries. The first records show that the harvesting of macroalgae, such as Laminaria spp., spp., Undaria pinnatifida, Sargassum fusiforme (formerly Hizikia fusiforme) (commonly known as kombu, Undaria pinnatifida, Sargassum fusiforme (formerly Hizikia fusiforme) (commonly known as kombu, wakame, and hiziki, respectively), for human consumption was already carried out by people in China, wakame, and hiziki, respectively), for human consumption was already carried out by people in at least from 500 B.C. [7]. While in Europe it occurred a thousand years later [9]. China, at least from 500 B.C. [7]. While in Europe it occurred a thousand years later [9]. More than 600 species of edible seaweeds are categorized. Now it is recognized that edibles More than 600 species of edible seaweeds are categorized. Now it is recognized that edibles seaweeds have great nutritional content as they are a low caloric food, but rich in vitamins, minerals, seaweeds have great nutritional content as they are a low caloric food, but rich in vitamins, minerals, and dietary fibers [7,9]. Their nutritive value may vary depending on the geographic location, season and dietary fibers [7,9]. Their nutritive value may vary depending on the geographic location, season of the year, growth stage, part of the seaweed harvested, etc [11]. Thus, to assure the nutritional value of the year, growth stage, part of the seaweed harvested, etc [11]. Thus, to assure the nutritional value of seaweeds, they need to be evaluated before being used as supplements. of seaweeds, they need to be evaluated before being used as supplements. Seaweeds draw from the sea an incomparable wealth of mineral elements, macro elements, Seaweeds draw from the sea an incomparable