Recent studies demonstrate the high nutritional value of seaweeds and the powerful properties that seaweeds’ bioactive compounds provide. Species of class Phaeophyceae, phylum Rhodophyta and Chlorophyta possess unique compounds with several properties that are potential allies of our health, which make them valuable compounds to be involved in biotechnological applications.
1. Introduction
Seaweeds are considered a nutrient-rich food as they are a good source of minerals, vitamins (A, B
1, B
2, B
9, B
12, C, D, E, and K), essential minerals (calcium, iron, iodine, magnesium, phosphorus, potassium, zinc, copper, manganese, selenium, and fluoride), dietary fibers
[1][2][3][4][1,2,3,4], protein, essential amino acids and polyphenols, which exhibit antioxidant and anti-inflammatory properties
[5]. Seaweeds possess a low lipid content, nonetheless enriched in polyunsaturated fatty acids. This characteristic makes them even more attractive, as they are a healthy, nutritive and low-caloric food
[2]. Seaweeds were consumed as whole food since ancient times, and they still have great economic importance.
Saccharina spp. with
Porphyra spp. and
Undaria pinnatifida (Phaeophyceae) are the three algae mainly consumed in Asian meals
[6].
Seaweed bioactive compounds are also employed in biomedical and pharmaceutical industries as they possess antitumoral activity against some type of cancer cell lines, but they do not affect negatively healthy cells, as it happens with current antitumoral treatments
[7][8][7,8]. Phycocolloids, which derive from brown and red algae, are used in the food industry (gelling agents), pharmaceuticals (dressings, coatings of medicaments) and biotechnology (culture medium, the Petri dishes). They are also found in cosmetics (body lotions, soaps, shampoos, toothpaste)
[9]. Marine algae have been traditionally used in animal feed and in agriculture and production of biodiesel.
Seaweeds are classified as brown, red or green algae, and for each group are present diverse bioactive compounds with multiple properties which may be exploited for biotechnological applications. Phaeophyceae (brown algae) have been consumed as whole food for a long time in Asian countries; however, scientists have only recently gained an understanding of the reasons behind the positive effects that seaweed bioactive compounds have on our health. Brown algae possess fucoidans that are already available in the market as nutraceutical products, since they exhibit antibacterial
[10], antiviral
[11] anti-inflammatory, anticoagulant, and antithrombotic effects
[12]. Rhodophyta (red algae) extracts are widely exploited in medical and pharmaceutical sectors, particularly carrageenans and agar. Agar is used in biomedicine as suspension component in drug solutions and in prescription products, but also as anticoagulant agents
[13]. Carrageenans can be exploited for the production of antitumoral therapies, due to their antitumor immunity activation
[7]. Chlorophyta (green algae) are rich in ulvan, a sulphate polysaccharide commonly used in biomedicine, cosmetic and pharmaceutical industries but also as emulsifiers, stabilizers, and thickeners in food products
[14].
The human health benefits from seaweeds can be through direct and indirect way: through the consumption of the whole seaweed or the uptake by assumption of food supplement or natural drugs (direct health benefits) or by using seaweeds in agriculture as natural fertilizers, in order to have a nutrient soil and healthy cultivation without the presence of chemicals contained in traditional fertilizers. Thus, the use of seaweeds as biofertilizers will enhance the plants and soil conditions
[15][16][17][15,16,17], giving positive effects to our health after agriculture products consumption (indirect health benefits).
2. Main Bioactive Compounds of Seaweeds
Seaweeds are rich in several bioactive compounds such as polyphenols, sterols, alkaloids, flavonoids, tannins, proteins with essential amino-acids, polyunsaturated fatty acids, etc.
[13]. These bioactive compounds provide not only protection to seaweeds, but also a high nutritional value and several benefits for humans. For example, polysaccharides from seaweeds have a positive effect on intestinal tract, but contrary to fibres, they are free of calories
[2]. Agar and carrageenan, extracted from red algae, and alginates, extracted from brown algae, are commonly employed in food and pharmaceutical products as stabilizers
[18].
Due to their beneficial properties, these biological compounds extracted from marine algae have been received attention from researchers. These compounds might be employed for creation of novel and functional food but also for pharmaceutical and biomedical applications
[19].
3. The Health Benefits of Seaweed Bioactive Compounds
Seaweeds bioactive compounds are exploited in several biotechnological applications (Table 1). Due to their properties, these compounds can contribute to the development of biomedicine and modern pharmacy, in order to achieve new formulation based on components from natural origin. The consumption of seaweeds by food or trough natural drugs will contribute to the occurrence of a healthier lifestyle. Nutraceutical, biomedical and pharmaceutical applications that involve seaweeds’ bioactive compounds are further showed.
Table 1. Main compounds of seaweeds involved in biotechnological applications.
Seaweed
|
Main Bioactive Compound
|
Property
|
Biotechnological Application
|
Reference
|
Phaeaophyceae
|
Laminaria hyperborea
|
Alginate
|
Biodegradability, biocompatibility, non-toxic behaviour
|
Cosmetics, pharmaceutical and food industries as stabilizers
|
[18][20][18,40]
|
Ascophyllum nodosum
|
Ecklonia radiata
|
Durvillaea sp.
|
Lessonia sp.
|
Sargassum sp.
|
Scytothalia dorycarpa
|
Cystophora subfarcinata
|
Sargassum linearifolium
|
Macrocystis pyrifera
|
Alginate
|
Biodegradability, biocompatibility, non-toxic behaviour
|
Cosmetics as a thickening agent
|
[21][36]
|
Phlorotannins
|
Antioxidant activity
|
Cosmetics for preventing skin aging
|
[22][90]
|
Ecklonia cava
|
Phlorotannins
|
Anticancer, antioxidant, anti-inflammatory, antiviral activities and antihypertensive effects.
|
Pharmaceutical and nutraceutical industries
|
[23][24][49[25],50,53]
|
Eisenia arborea
|
Phlorotannins
|
Antiallergic effects
|
Pharmaceutical industry
|
[26][62]
|
Eisenia bicyclis
|
Phlorotannins
|
Antidiabetic, antioxidant, antitumor, anti-inflammatory, and anticancer activities
|
Pharmaceutical and medical industries
|
[27][61]
|
Ecklonia kurome
|
Ecklonia stolonifera
|
Pelvetia siliquosa
|
Ishige okamurae
|
Fucus vesiculosus
|
Phlorotannins
|
Anti-inflammatory and antioxidant properties
|
Cosmetics, to produce make-up and sunscreens
|
[28][91]
|
Fucus evanescens
|
Fucoidans
|
Anticoagulant activity
|
Potential substitute to heparin
|
[29][30][92,93]
|
Laminaria cichorioides
|
Rhodophyta
|
Chondrus pinnulatus
|
λ-carrageenan and κ-carrageenan
|
High viscosity in drinks; antitumoral property
|
Food industry (production of drinks, e.g., milk and chocolate) and pharmaceutical industry
|
[7][31][7,73]
|
Chondrus armatus
|
Chondrus yendoi
|
Kappaphycus striatum
|
κ-carrageenan
|
Antitumoral activity against human nasopharynx carcinoma, human gastric carcinoma, and cervical cancer cell lines
|
Pharmaceutical industry
|
[32][94]
|
Kappaphycus alvarezii
|
κ-carrageenan and agar
|
Antioxidant properties
|
Cosmetics and nutraceutical industry
|
[33][34][68,95]
|
Gracilaria edulis
|
Agar
Phenolic, flavonoid, and alkaloid compounds
|
Antidiabetic, antioxidant, antimicrobial, anticoagulant, anti-inflammatory, and antitumoral activities; hypoglycaemic activity
|
Pharmaceutical industry
|
[35][36][37][38][74,96,97,98]
|
Laurencia catarinensis
|
Halogenated metabolites
|
Antitumoral activity
|
Pharmaceutical industry
|
[39][99]
|
Laurencia obtuse
|
Diterpene and sesquiterpene
|
Actions against different cancer cell lines (KB, HepG2 and MCF-7)
|
Pharmaceutical industry
|
[39][99]
|
Griffithsia sp.
|
Griffith (Protein)
|
Antiviral activity against MERS-CoV-2 virus and SARS-CoV-2 glycoprotein
|
Pharmaceutical industry
|
[40][41][100,101]
|
Chlorophyta
|
Caulerpa racemosa
|
Phenolic compounds and flavonoids
|
Antioxidant, scavenging, anti-proliferative activities of cancer line cells
|
Pharmaceutical and nutraceutical industries
|
[42][43][102,103]
|
Ulva lactuca
|
Ulvan
|
Antioxidant activity, antimicrobial and photocatalytic activities
|
Food industry (the whole body is used as salad) and industrial industry (production of biogas and biodiesel)
|
[44][43][45][][47][83,103,10446,105,106]
|
Ulva rigida
|
Ulvan
|
Antigenotoxic activity in human lymphocytes; hypoglycaemic effect in vivo experiment
|
Pharmaceutical industry
|
[48][49][107,108]
|
Ulva fasciata
|
Ulvan
|
Antioxidant and good mechanical properties; antiviral property
|
Industrial industry to develop bioplastics; pharmaceutical industry
|
[50][51][109,110]
|
4. Seaweeds Extracts in Industrial Applications
Seaweeds biological compounds are widely exploited in several industrial applications (Table 4). For example, these compounds have been explored for the production of biogas and biodiesel, which can be an alternative and efficient fuel to replace the use of fossil fuels. The SP ulvan extracted from the green seaweed possesses attractive physicochemical properties and biological activities, resulting in its applications in different innovative applications
[52][53][171,172].
Ulvan extracted from
Ulva lactuca (Chlorophyta) has been tested for production of biogas
[45][104] and biodiesel
[46][105]. Moreover, the optical, structural, thermal, and antioxidant properties make ulvan a potential contribute for new packaging material for food
[54][173]. Ulvan from
Ulva fasciata (Chlorophyta) was extracted and utilized to create edible films for food application. The films presented good mechanical and physicochemical properties adapted for containing food. The water vapour permeability in the pack decreased, preserving better the food. Moreover, ulvan from
Ulva fasciata presents strong antioxidant activity
[50][109], making this polysaccharide a perfect candidate for the production of novel, sustainable and eco-friendly bioplastics.